Patent Publication Number: US-2022212016-A1

Title: Connectors For High Density Neural Interfaces

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority and benefit from U.S. Provisional Application No. 62/838,550, filed Apr. 25, 2019, entitled “CONNECTORS FOR HIGH DENSITY NEURAL INTERFACES,” the entire contents of which are incorporated herein by reference for all purposes. 
    
    
     FIELD 
     The present disclosure relates to implantable neuromodulation devices and methods of fabrication, and in particular to connectors for high density neural interfaces and methods of microfabricating the connectors. 
     BACKGROUND 
     Normal neural activity is an intricate balance of electrical and chemical signals, which can be disrupted by a variety of insults (genetic, chemical or physical trauma) to the nervous system, causing cognitive, motor and sensory impairments. Similar to the way a cardiac pacemaker or defibrillator corrects heartbeat abnormalities, neuromodulation therapies help to reestablish normal neural balance. In particular instances, neuromodulation therapies utilize medical device technologies to enhance or suppress activity of the nervous system for the treatment of disease. These technologies include implantable as well as non-implantable neuromodulation devices and systems that deliver electrical, chemical or other agents to reversibly modify brain and nerve cell activity. The most common neuromodulation therapy is spinal cord stimulation to treat chronic neuropathic pain, in addition to chronic pain relief, some examples of neuromodulation therapies include deep brain stimulation for essential tremor, Parkinson&#39;s disease, dystonia, epilepsy and psychiatric disorders such as depression, obsessive compulsive disorder and Tourette syndrome; sacral nerve stimulation for pelvic disorders and incontinence, vagus nerve stimulation for rheumatoid arthritis; gastric and colonic stimulation for gastrointestinal disorders such as dysmotility or obesity; vagus nerve stimulation for epilepsy, obesity or depression; carotid artery stimulation for hypertension, and spinal cord stimulation for ischemic disorders such as angina and peripheral vascular disease. 
     Neuromodulation devices and systems tend to have a similar form factor, derived from their predecessors, e.g. the pacemaker or defibrillator. Such neuromodulation devices and systems typically consist of an implant comprising a neurostimulator having electronics connected to a lead assembly that delivers electrical pulses to electrodes interfaced with nerves or nerve bundles via an electrode assembly. The lead assembly is typically formed of a conductive material and takes the form of an insulated wire (e.g., a dedicated channel) connected to the electrodes via a first connector on one end (e.g., a distal end) and the electronics of the neurostimulator via a second connector on another end (e.g., a proximal end). In some instances (e.g., deep implants), the lead assembly comprises additional conductors and connectors such as extension wires or a cable connected via connectors between the electrodes and the electronics of the neurostimulator. 
     Conventional neuromodulation devices include between four and sixteen electrodes, and thus typically include four to sixteen channels or wires connected respectively to the electrodes at the distal end and the electronics of the neurostimulator at the proximal end. However, there is a need for high density neural interfaces that include greater than sixteen electrodes to interface with larger tissue volumes, to recruit smaller populations of neurons for recording, or to provide more targeted therapy by tailoring the electrical stimulation parameters and activated tissue volume. Increasing the density or number of electrodes can increase the number of channels or wires needed to connect the electrodes and the electronics of the neurostimulator. In order to implement high channel or wire counts, there is a need for reliable electrical connections that can maintain contact and electrical isolation in a subject body (e.g., a patient body) for many years. Typically, a lead assembly containing a high channel or wire count needs to be permanently connected to the electronics. However, this is not ideal because the electronics need to be replaced every few years to upgrade them or to replace batteries, and surgeons have a strong preference not to remove the lead assembly from the neural tissue due to the risk to the patient. Therefore, there is a need for reliable and non-permanent connectors for lead assemblies having high density neural interfaces. 
     BRIEF SUMMARY 
     In various embodiments, a lead assembly is provided that comprises: a cable comprising a proximal end, a distal end, and first conductive traces; a connector comprising a core and a supporting structure wrapped around at least a portion of the core, where: the connector is located at the proximal end of the cable; the supporting structure comprises a first layer of dielectric material and a second layer of dielectric material; the first layer of dielectric material is a high temperature liquid crystal polymer; the second layer of dielectric material is a low temperature liquid crystal polymer that is reflowed to attach the supporting structure to the core; second conductive traces are buried between the first layer of dielectric material and the second layer of dielectric material; the second conductive traces terminate at conductive contacts formed on a surface of the first layer of dielectric material; and the connector has a predetermined shape or profile, which facilitates alignment and insertion of the connector into a header; and an electrode assembly located at the distal end of the cable, the electrode assembly comprising electrodes electrically connected to the conductive contacts via the first conductive traces and the second conductive traces. 
     In some embodiments, the connector further comprises multiple sectors extending along the surface of the first dielectric layer, and one or more contacts of the conductive contacts are arranged in each sector of the multiple sectors. 
     In some embodiments, the conductive contacts are arranged as split annular rings positioned around an axis of the connector and exposed on the surface of the first dielectric layer, and a first portion of the split annular rings is disposed in a first sector of the multiple sectors and a second portion of the split annular rings is disposed in a second sector of the multiple sectors. 
     In some embodiments, the predetermined shape or profile is a “D”-shaped profile, the contacts are arranged as split rings on the surface of the first layer of dielectric material in the curved portion of the “D”-shaped profile, and the flat portion of the “D”-shaped profile is an indexing feature for keying during insertion of the connector into the header. 
     In some embodiments, the predetermined shape or profile is a notched profile, the contacts are arranged as split rings on the surface of the first layer of dielectric material in a curved portion of the notched profile, and a notch of the notched profile is an indexing feature for keying during insertion of the connector into the header. 
     In some embodiments, a first portion of the split annular rings is disposed in a first sector of the multiple sectors and a second portion of the split annular rings is disposed in a second sector of the multiple sectors. Optionally, each split annular ring is spaced apart from one another on the surface by a region of the first layer of the dielectric material. Optionally, a width of the region of the first layer of the dielectric material that separates each split annular ring is between 0.1 mm to 10 mm. 
     In some embodiments, the predetermined shape or profile is a square shaped profile having quadruple planar sectors, and one or more contacts of the contacts are arranged in each sector of the quadruple planar sectors. Optionally, the connector further comprises one or more additional contacts with impedance, resistive, or ohmic fiducials to provide orientation queues of the contacts. 
     In some embodiments, the connector further comprises a scaling feature, which is a section of the predetermined shape or profile at a distal end of the connector, and the sealing feature comprises a different material, texture, or stiffness from the core and the supporting structure to engage a scaling surface of the header. 
     In some embodiments, the connector further comprises a retention feature for mechanical retention or connection with a corresponding feature in the header to retain insertion of the connector in the header. 
     In various embodiments, a header and lead assembly is provided comprising: a connector comprising a core and a first supporting structure wrapped around at least a portion of the core, where: the first supporting structure comprises a first layer of dielectric material and a second layer of dielectric material; the first layer of dielectric material is a high temperature liquid crystal polymer; the second layer of dielectric material is a low temperature liquid crystal polymer that is reflowed to attach the first supporting structure to the core; first conductive traces are buried between the first layer of dielectric material and the second layer of dielectric material; the first conductive traces terminate at first conductive contacts formed on a surface of the first dielectric layer; and the connector has a first predetermined shape or profile; a header comprising a second supporting structure, where: the second supporting structure comprises one or more layers of polymer; second conductive traces are buried between the one or more layers of polymer; the second conductive traces terminate at second conductive contacts formed on a surface of the one or more layers of polymer; and the header has a second predetermined shape or profile structured to receive the first predetermined shape or profile of the connector; and a clip structured to hold the first conductive contacts in electrical contact with the second conductive contacts. 
     In some embodiments, the clip is one or more clip springs or spring-fibers arranged into a comb or rib-cage arrangement on an outside of the second supporting structure, and the clip springs or spring-fibers have a spring force that exerts a clasping pressure on the second supporting structure to electrically connect the header to the connector. 
     In some embodiments, the one or more layers of polymer have a thickness of from 0.5 μm to 250 μm, which allows for the spring force of the clip to be distributed across all of the first conductive contacts and the second conductive contacts. 
     In some embodiments, the header and lead assembly further comprises a cable comprising a proximal end, a distal end, and third conductive traces, where the connector is located at the proximal end of the cable. 
     In some embodiments, the header and lead assembly further comprises an electrode assembly located at the distal end of the cable, the electrode assembly comprising electrodes electrically connected to the second conductive traces via the third conductive traces, the first conductive traces, the first conductive contacts, and the second conductive contacts. 
     In some embodiments, the connector further comprises multiple sectors extending along the surface of the first layer of dielectric material, and one or more contacts of the first conductive contacts are arranged in each sector of the multiple sectors. 
     In some embodiments, the first conductive contacts are arranged as split rows positioned in columns and exposed on the surface of the first layer of dielectric material, and a first portion of the split rows is disposed in a first sector of the multiple sectors and a second portion of the split rows is disposed in a second sector of the multiple sectors. Optionally, the first sector is located on a first side of the connector and the second sector is located on a second side of the connector. 
     In some embodiments, the first predetermined shape or profile is a blade shape with the first supporting structure folded over the core, and the first conductive contacts face outward on the surface of the first layer of dielectric material. 
     In some embodiments, the second predetermined shape or profile is a “U”-shape, and the second conductive contacts face inward on the surface of the one or more layers of polymer. 
     In various embodiments, a lead assembly is provided comprising: a first cable comprising a proximal end and a distal end; a second cable comprising a proximal end and a distal end; a connection assembly comprising: a first connector comprising a core and a first supporting structure wrapped around at least a portion of the core, where: the first connector is located at the proximal end of the first cable; the first supporting structure comprises a first layer of dielectric material and a second layer of dielectric material; the first layer of dielectric material is a high temperature liquid crystal polymer; the second layer of dielectric material is a low temperature liquid crystal polymer that is reflowed to attach the first supporting structure to the core; first conductive traces are buried between the first layer of dielectric material and the second layer of dielectric material; and the first conductive traces terminate at first conductive contacts formed on a surface of the first layer of dielectric material; a second connector comprising a second supporting structure, where: the second connector is located at the distal end of the second cable; the second supporting structure comprises a one or more layers of polymer; second conductive traces are buried between the one or more layers of polymer; and the second conductive traces terminate at second conductive contacts formed on a surface of the one or more layers of polymer; and one or more attachment features that hold the first connector in physical contact with the second connector such that the first conductive contacts are in electrical contact with the second conductive contacts. 
     In some embodiments, the connection assembly further comprises a housing comprising: a first half portion, a second half portion, a proximal port, and a distal port, wherein the first cable is inserted into the connection assembly through the distal port, the second cable is inserted into the connection assembly through the proximal port, and the first half portion is attached to the second half portion with the one or more attachment features. 
     In some embodiments, the first half portion comprises alignment pins, a seal, and a first compliant pad, the second half comprises the one or more attachment features and a second compliant pad, and the first compliant pad and the second compliant pad assist the one or more attachment features in holding the first connector in physical contact with the second connector. 
     In some embodiments, the first connector further comprises first alignment holes that fit over the alignment pins, and the second connector further comprises second alignment holes that fit over the alignment pins. 
     In some embodiments, the one or more layers of polymer have a thickness of from 0.5 μm to 250 μm, which allows for a spring force of the first compliant pad and second compliant pad to be distributed across all of the first conductive contacts and the second conductive contacts. 
     In some embodiments, the first cable further comprises third conductive traces, and the second cable further comprises fourth conductive traces. Optionally, the lead assembly further comprises an electrode assembly located at the distal end of the first cable, the electrode assembly comprising electrodes electrically connected to the fourth conductive traces via the third conductive traces, the first conductive traces, the first conductive contacts, the second conductive contacts, and the second conductive traces. 
     In some embodiments, the first connector further comprises multiple sectors extending along the surface of the first layer of dielectric material, and one or more contacts of the first conductive contacts are arranged in each sector of the multiple sectors. 
     In some embodiments, the first conductive contacts are arranged as split rows positioned in columns and exposed on the surface of the first layer of dielectric material, and a first portion of the split rows is disposed in a first sector of the multiple sectors and a second portion of the split rows is disposed in a second sector of the multiple sectors. 
     In some embodiments, the first sector is located on a first side of the connector and the second sector is located on a second side of the connector. In some embodiments, the first connector comprises a first predetermined shape or profile, which is a blade shape with the first supporting structure folded over the core, and the first conductive contacts face outward on the surface of the first layer of dielectric material. 
     In some embodiments, the second connector comprises a second predetermined shape or profile, which is a “U”-shape, and the second conductive contacts face inward on the surface of the one or more layers of polymer. 
     In various embodiments, a lead assembly is provided comprising: a high density cable comprising a proximal end and a distal end; a low density cable comprising a proximal end and a distal end; and a connector comprising: a package comprising a housing, one or more multiplexor chips, distal feedthroughs connected to distal channel inputs of the one or more multiplexor chips, and proximal feedthroughs connected to proximal channel inputs of the one or more multiplexor chips; and a connection assembly comprising a supporting structure, wherein: the connector is located at the proximal end of the high density cable and the distal end of the low density cable; the supporting structure comprises a first layer of dielectric material and a second layer of dielectric material; the first layer of dielectric material is a low temperature liquid crystal polymer that is reflowed to attach the supporting structure to the package; the second layer of dielectric material is a high temperature liquid crystal polymer; distal conductive traces are buried between the first layer of dielectric material and the second layer of dielectric material; proximal conductive traces are buried between the first layer of dielectric material and the second layer of dielectric material; the distal conductive traces connected to the high density cable, and the distal conductive traces terminate at distal conductive contacts formed on a surface of the second layer of dielectric material; the proximal conductive traces connected to the low density cable, and the proximal conductive traces terminate at proximal conductive contacts formed on the surface of the second layer of dielectric material; the distal conductive contacts are electrically connected to the distal feedthroughs; and the proximal conductive contacts are electrically connected to the proximal feedthroughs. 
     In some embodiments, the high density cable further comprises first conductive traces, and the low density cable further comprises second conductive traces. Optionally, the lead assembly further comprises an electrode assembly located at the distal end of the high density cable, the electrode assembly comprising electrodes electrically connected to the second conductive traces via the first conductive traces, the distal conductive traces, the distal conductive contacts, the distal feedthroughs, the one or more multiplexor chips, the proximal feedthroughs, the proximal conductive contacts, and the proximal conductive traces. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be better understood in view of the following non-limiting figures, in which: 
         FIG. 1  shows a neuromodulation system in accordance with various embodiments; 
         FIGS. 2A and 2B  show a lead assembly in accordance with various embodiments; 
         FIGS. 3A-3H  show multi-sector connectors in accordance with various embodiments; 
         FIGS. 4A-4D  show a top view, a bottom view, and cross-sectional side views illustrating a design and method of fabricating multi-sector connectors in accordance with various embodiments; 
         FIG. 5A  shows a header and lead assembly in accordance with various embodiments; 
         FIGS. 5B-5C  show rib-cage connectors in accordance with various embodiments; 
         FIGS. 6A-6D  show a top view, a bottom view, and cross-sectional side views illustrating a design and method of fabricating a header in accordance with various embodiments; 
         FIGS. 6E-6H  show a top view, a bottom view, and cross-sectional side views illustrating a design and method of fabricating a connector in accordance with various embodiments; 
         FIG. 7A  shows a neuromodulation system in accordance with various embodiments; 
         FIGS. 7B-7F  show a connection assembly in accordance with various embodiments; 
         FIGS. 8A-8F  show a top view, a bottom view, and cross-sectional side views illustrating a design and method of fabricating a first portion of a connection assembly in accordance with various embodiments; 
         FIGS. 9A-9E  show a top view, a bottom view, and cross-sectional side views illustrating a design and method of fabricating a second portion of a connection assembly in accordance with various embodiments; 
         FIG. 10A  shows a neuromodulation system in accordance with various embodiments; 
         FIGS. 10B-10D  show multiplexor connector in accordance with various embodiments; and 
         FIGS. 11A-11D  show a top view, a bottom view, and cross-sectional side views illustrating a design and method of fabricating a header in accordance with various embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     I. Introduction 
     The following disclosure describes connectors for high density neural interfaces and methods of microfabricating the connectors. In some embodiments, a connector is located at a proximal end of the lead assembly and used to connect the lead assembly with the neurostimulator. In other embodiments, one or more connectors are located at the proximal end and/or distal end of one or more lead bodies and used to connect one or more lead bodies thereby extending an overall length of the lead assembly. In yet other embodiments, a connector is located at the proximal end or distal end of one or more lead bodies and used to connect a multiplexer chip to the lead assembly. As used herein, the term “proximal” or “proximal end” refers to a first end of the main body, while the term “distal” or “distal end” refers to a second end opposing the first end. For example, the proximal end may be an end of the main body, which is closest to the user, and the distal end may be an end of the main body, which is furthest from the user. 
     The connectors may be fabricated using microfabricating techniques. In certain embodiments, the connector is fabricated as a monolithic structure. As used herein, the phrase “monolithic” refers to a device fabricated using a same layer of base material. As used herein, the phrase “microfabrication” refers to the process of fabricating miniature structures on micrometer scales and smaller. The major concepts and principles of microfabrication are microlithography, doping, thin films, etching, bonding, and polishing. As used herein, the phrase “thin films” refers to a layer of material ranging from fractions of a nanometer (monolayer) to several micrometers in thickness (e.g., between a few nanometers to about 100 μm). Thin films may be deposited by applying a very thin film of material (e.g., between a few nanometers to about 100 μm) onto a substrate surface to be coated, or onto a previously deposited layer of thin film. In various embodiments, a thin film connector is provided comprising a base polymer body (e.g., a supporting structure) and at least one conductive trace formed on the base polymer body. As used herein, the term “high density neural interface(s)” refers to a neural interface that comprises at least sixteen electrodes (i.e., recording, sensing, stimulating, other types of electrodes, or combinations thereof). 
     Neuromodulation devices such as deep brain and spinal cord stimulators electrically interface with neural tissue and treat various neurological conditions through electrical stimulation. As described herein, conventional neuromodulation devices use between four and sixteen electrodes and comprise a neurostimulator and lead assembly containing the electrodes. The neuromodulation devices with high density neural interfaces (i.e., at least sixteen electrodes), deep brain stimulation, cortical brain stimulation, spine stimulation, etc. often are limited in contact count by lead density, connector density/pitch/size, or complexity (e.g., having a lead split to multiple connectors). However, higher density arrays are desired due to the ability to more closely focus energy during therapy in order to increase clinical effectiveness, reduce side effects due to errant charge, and increase battery life by using charge more efficiently. 
     To address these limitations and problems, connectors of various embodiments disclosed herein enable connections with high density neural interfaces and are capable of being physically disconnected between the neurostimulator and the electrode assembly. One illustrative embodiment of the present disclosure is directed to a connector that includes a core and a supporting structure wrapped around at least a portion of the core. The connector may be located at a proximal end of a cable (e.g., a lead) of a lead assembly. The supporting structure comprises a first layer of dielectric material and a second layer of dielectric material. The first layer of dielectric material may be a high temperature liquid crystal polymer, and the second layer of dielectric material may be a low temperature liquid crystal polymer that is reflowed to attach the supporting structure to the core. Conductive traces are buried between the first layer of dielectric material and the second layer of dielectric material, and the conductive traces terminate at conductive contacts formed on a surface of the first layer of dielectric material. The connector has a predetermined shape or profile, which facilitates alignment and insertion of the connector into a header of a neurostimulator. 
     In other embodiments, a lead assembly is provided that comprises a cable comprising a proximal end, a distal end, and first conductive traces; and a connector comprising a core and a supporting structure wrapped around at least a portion of the core. The connector is located at the proximal end of the cable; the supporting structure comprises a first layer of dielectric material and a second layer of dielectric material; the first layer of dielectric material is a high temperature liquid crystal polymer; the second layer of dielectric material is a low temperature liquid crystal polymer that is reflowed to attach the supporting structure to the core; second conductive traces are buried between the first layer of dielectric material and the second layer of dielectric material; the second conductive traces terminate at conductive contacts formed on a surface of the first layer of dielectric material; and the connector has a predetermined shape or profile, which facilitates alignment and insertion of the connector into a header. The lead assembly further comprises an electrode assembly located at the distal end of the cable, the electrode assembly comprising electrodes electrically connected to the conductive contacts via the first conductive traces and the second conductive traces. 
     In other embodiments, a header and lead assembly is provided that comprises a connector comprising a core and a first supporting structure wrapped around at least a portion of the core. The first supporting structure comprises a first layer of dielectric material and a second layer of dielectric material; the first layer of dielectric material is a high temperature liquid crystal polymer; the second layer of dielectric material is a low temperature liquid crystal polymer that is reflowed to attach the first supporting structure to the core; first conductive traces are buried between the first layer of dielectric material and the second layer of dielectric material; the first conductive traces terminate at first conductive contacts formed on a surface of the first dielectric layer; and the connector has a first predetermined shape or profile. The header and lead assembly further comprises a header comprising a second supporting structure. The second supporting structure comprises one or more layers of polymer; second conductive traces are buried between the one or more layers of polymer, the second conductive traces terminate at second conductive contacts formed on a surface of the one or more layers of polymer; and the header has a second predetermined shape or profile structured to receive the first predetermined shape or profile of the connector. The header and lead assembly further comprises a clip structured to hold the first conductive contacts in electrical contact with the second conductive contacts. 
     In other embodiments, a lead assembly is provided that comprises a first cable comprising a proximal end and a distal end; a second cable comprising a proximal end and a distal end; and a connection assembly comprising: a first connector comprising a core and a first supporting structure wrapped around at least a portion of the core. The first connector is located at the proximal end of the first cable; the first supporting structure comprises a first layer of dielectric material and a second layer of dielectric material; the first layer of dielectric material is a high temperature liquid crystal polymer; the second layer of dielectric material is a low temperature liquid crystal polymer that is reflowed to attach the first supporting structure to the core; first conductive traces are buried between the first layer of dielectric material and the second layer of dielectric material; and the first conductive traces terminate at first conductive contacts formed on a surface of the first layer of dielectric material. The connection assembly further comprises a second connector comprising a second supporting structure. The second connector is located at the distal end of the second cable; the second supporting structure comprises a one or more layers of polymer; second conductive traces are buried between the one or more layers of polymer, and the second conductive traces terminate at second conductive contacts formed on a surface of the one or more layers of polymer. The connection assembly further comprises one or more attachment features that hold the first connector in physical contact with the second connector such that the first conductive contacts are in electrical contact with the second conductive contacts. 
     In other embodiments, a lead assembly is provided that comprises a high density cable comprising a proximal end and a distal end; a low density cable comprising a proximal end and a distal end; and a connector. The connector comprises a package comprising a housing, one or more multiplexor chips, distal feedthroughs connected to distal channel inputs of the one or more multiplexor chips, and proximal feedthroughs connected to proximal channel inputs of the one or more multiplexor chips; and a connection assembly comprising a supporting structure. The connector is located at the proximal end of the high density cable and the distal end of the low density cable; the supporting structure comprises a first layer of dielectric material and a second layer of dielectric material; the first layer of dielectric material is a low temperature liquid crystal polymer that is reflowed to attach the supporting structure to the package; the second layer of dielectric material is a high temperature liquid crystal polymer; distal conductive traces are buried between the first layer of dielectric material and the second layer of dielectric material; proximal conductive traces are buried between the first layer of dielectric material and the second layer of dielectric material; the distal conductive traces connected to the high density cable, and the distal conductive traces terminate at distal conductive contacts formed on a surface of the second layer of dielectric material; the proximal conductive traces connected to the low density cable, and the proximal conductive traces terminate at proximal conductive contacts formed on the surface of the second layer of dielectric material; the distal conductive contacts are electrically connected to the distal feedthroughs; and the proximal conductive contacts are electrically connected to the proximal feedthroughs. 
     Advantageously, these approaches provide a connector, which has increased contact points, a smaller footprint, and greater design flexibility. More specifically, these approaches enable connectors with reliable, non-permanent connections between a lead assembly and a neurostimulator. This solution is scalable to connecting many electrodes (e.g., greater than sixteen) using a multiplexer chip, and thus enabling several therapeutic opportunities for neurostimulation. Furthermore even for applications where multiple electrodes are not required, various embodiments can be miniaturized to make the implant minimally invasive, additionally may make invasive anatomies to become accessible (or navigable) due to the miniaturization. It should be understood that although deep brain neurostimulation and vagus nerve or artery/nerve plexus device applications are provided as examples of some embodiments, this solution is applicable to all leads and devices that need electrodes/sensors that need to be attached to a neurostimulator. 
     II. Neuromodulation Devices and Systems with a Lead Assembly 
       FIG. 1  shows a neuromodulation system  100  in accordance with some aspects of the present invention. In various embodiments, the neuromodulation system  100  includes an implantable neurostimulator  105  and a lead assembly  110 . The implantable neurostimulator  105  (e.g., an implantable pulse generator (IPG)) may include a housing  115 , a feedthrough assembly or header  120 , a power source  125 , an antenna  130 , and an electronics module  135  (e.g., a computing system). The housing  115  may be comprised of materials that are biocompatible such as bioceramics or bioglasses for radio frequency transparency, or metals such as titanium. In accordance with some aspects of the present invention, the size and shape of the housing  115  may be selected such that the neurostimulator  105  can be implanted within a patient. In the example shown in  FIG. 1 , the feedthrough assembly or header  120  is attached to a hole  137  in a surface of the housing  115  such that the housing  115  is hermetically sealed. The feedthrough assembly or header  120  may include one or more contacts  140  (i.e., electrically conductive elements, pins, wires, tabs, pads, etc.) mounted within the housing  115  or a cap extending from an interior to an exterior of the housing  115 . The one or more contacts  140  are arranged to match and make electrical contact with one or more contacts of a connector of the lead assembly  110 . In various embodiments, the contacts  140  may be made with a hemisphere on contact (point contact) or with a cylinder on contact (line contact). In some embodiments, the contacts  140  are spring-loaded normal to the outer contact surfaces of the contacts of the connector. The power source  125  may be within the housing  11 S and connected (e.g., electrically connected) to the electronics module  135  to power and operate the components of the electronics module  135 . The antenna  130  may be connected (e.g., electrically connected) to the electronics module  135  for wireless communication with external devices via, for example, radiofrequency (RF) telemetry. 
     In some embodiments, the electronics module  135  may be connected (e.g., electrically connected) to interior ends of the feedthrough assembly  120  such that the electronics module  135  is able to apply a signal or electrical current to conductive traces of the lead assembly  110  connected to the feedthrough assembly  120 . The electronics module  135  may include discrete and/or integrated electronic circuit components that implement analog and/or digital circuits capable of producing the functions attributed to the neuromodulation devices or systems such as applying or delivering neural stimulation to a patient. In various embodiments, the electronics module  135  may include software and/or electronic circuit components such as a pulse generator  142  that generates a signal to deliver a voltage, current, optical, or ultrasonic stimulation to a nerve or artery/nerve plexus via electrodes, a controller  145  that determines or senses electrical activity and physiological responses via the electrodes and sensors, controls stimulation parameters of the pulse generator  140  (e.g., control stimulation parameters based on feedback from the physiological responses), and/or causes delivery of the stimulation via the pulse generator  140  and electrodes, and a memory  150  with program instructions operable on by the pulse generator  140  and the controller  145  to perform one or more processes for applying or delivering neural stimulation. 
     In various embodiments, the lead assembly  110  includes one or more cables or lead bodies  155 , one or more electrode assemblies  160  having one or more electrodes  165  (optionally one or more sensors), and one or more connectors  170 ,  170 ′,  170 ″. In some embodiments, the lead assembly  110  is a monolithic structure. In various embodiments, the one or more connectors  170 ,  170 ′,  170 ″ include a main body having a supporting structure and one or more of conductive traces formed on the supporting structure. The supporting structure may be comprised of one or more layers of dielectric material. Each trace from the one or more conductive traces terminates at a bond pad  175 ,  175 ′,  175 ″ exposed on a surface of the supporting structure. In some embodiments, the connector  170  is located at a proximal end of the lead assembly  110  and used to connect the lead assembly  110  with the neurostimulator  105 . In other embodiments, one or more connectors  170 ′ are located at the proximal end and/or distal end of one or more lead bodies  155  and used to connect the one or more lead bodies  155  thereby extending an overall length of the lead assembly. In yet other embodiments, a connector  170 ″ is located at the proximal end or distal end of one or more lead bodies  155  and used to connect a multiplexer chip  180  to the lead assembly  110 . 
     The one or more cables  155  may include one or more conductive traces  182  formed on a supporting structure  185 . The one or more conductive traces  180  allow for electrical coupling of the electronics module  135  to the electrodes  165  and/or sensors of the electrode assemblies  160  via the one or more connectors  170 . In some embodiments, the one or more of conductive traces  182  and supporting structure  185  are the same conductive traces and supporting structure as the one or more conductive traces and supporting structure (monolithic) of the one or more connectors  170 . In other embodiments, the one or more of conductive traces  182  and supporting structure  185  are different conductive traces and supporting structure from the one or more conductive traces and supporting structure (different structures but electrically connected) of the one or more connectors  170 ,  170 ′,  170 ″. As described herein in detail, the supporting structures may be formed with a dielectric material such as a polymer having suitable dielectric, flexibility and biocompatibility characteristics. Polyurethane, polycarbonate, silicone, polyethylene, fluoropolymer and/or other medical polymers, copolymers and combinations or blends may be used. The conductive material for the traces may be any suitable conductor such as stainless steel, silver, copper or other conductive materials, which may have separate coatings or sheathing for anticorrosive, insulative and/or protective reasons. 
     The electrode assemblies  160  may include the electrodes  165  and/or sensors fabricated using various shapes and patterns to create certain types of electrode assemblies (e.g., book electrodes, split cuff electrodes, spiral cuff electrodes, epidural electrodes, helical electrodes, probe electrodes, linear electrodes, neural probe, paddle electrodes, intraneural electrodes, etc.). In various embodiments, the electrode assemblies  160  include a base material that provides support for microelectronic structures including the electrodes  165 , a wiring layer, optional contacts, etc. In some embodiments, the base material is the supporting structure  185 . The wiring layer may be embedded within or located on a surface of the supporting structure  185 . The wiring layer may be used to electrically connect the electrodes  165  with the one or more conductive traces  180  directly or indirectly via a lead conductor. The term “directly”, as used herein, may be defined as being without something in between. The term “indirectly”, as used herein, may be defined as having something in between. In some embodiments, the electrodes  165  may make electrical contact with the wiring layer by using the contacts. 
     III. Multi-Sector Connectors and Methods of Manufacture 
       FIGS. 2A and 2B  show a lead assembly  200  (e.g., the lead assembly  110  described with respect to  FIG. 1 ) in accordance with aspects of the present disclosure. In various embodiments, the lead assembly  200  comprises a cable  205  having a proximal end  210  and a distal end  215 . The cable  205  may comprise a supporting structure  220  and a plurality of conductive traces  225  formed on a portion of the supporting structure  220 . As used herein, the term “formed on” refers to a structure or feature that is formed on a surface of another structure or feature, a structure or feature that is formed within another structure or feature, or a structure or feature that is formed both on and within another structure or feature. In some embodiments, the supporting structure  220  extends from the proximal end  210  to the distal end  215 . In some embodiments, the supporting structure  220  may be made of one or more layers of dielectric material (i.e., an insulator). The dielectric material may be selected from the group of electrically flexible nonconductive materials consisting of organic or inorganic polymers, polyimide-epoxy, epoxy-fiberglass, and the like. In certain embodiments, the dielectric material is a polymer of imide monomers (i.e., a polyimide), a liquid crystal polymer (LCP) such as KevlarQ®, parylene, polyether ether ketone (PEEK), or combinations thereof. In other embodiments, the supporting structure  220  may be made of one or more layers of dielectric material formed on a substrate. The substrate may be made from any type of metallic or non-metallic material. 
     In various embodiments, the one or more conductive traces  225  are a plurality of traces, for example, two or more conductive traces or from two to twenty-four conductive traces. The plurality of conductive traces  225  are comprised of one or more layers of conductive material. The conductive material selected for the one or more conductive traces  225  should have good electrical conductivity and may include pure metals, metal alloys, combinations of metals and dielectrics, and the like. For example, the conductive material may be platinum (Pt), platinum/iridium (Pt/Ir), titanium (Ti), gold/titanium (Au/Ti), or any alloy thereof. In some embodiments, it is also desirable that the conductive material selected for the one or more conductive traces  225  have thermal expansion characteristics or a coefficient of thermal expansion (CTE) that is approximately equal to that of CTE of the supporting structure  220 . Matching the CTE of components that contact one another is desirable because it eliminates the development of thermal stresses, which may occur during fabrication and the operation of the cable, and thus eliminates a known cause of mechanical failure in the components. As used herein, the terms “substantially,” “approximately” and “about” are defined as being largely but not necessarily wholly what is specified (and include wholly what is specified) as understood by one of ordinary skill in the art. In any disclosed embodiment, the term “substantially,” “approximately,” or “about” may be substituted with “within [a percentage] of” what is specified, where the percentage includes 0.1, 1, 5, and 10 percent. 
     As shown in  FIG. 2A , the lead assembly  200  may further comprise an electrode assembly  230  formed on a supporting structure  235 . The supporting structure  235  may provide support for microelectronic structures including one or more electrodes  240 , a wiring layer  245 , and optional contact(s)(not shown). The electrode assembly  230  may be located at the distal end  215  of the lead assembly  200 . The one or more electrodes  240  are in electrical connection with one or more conductive traces of the plurality of conductive traces  225 , for example, via the wiring layer  245  and optionally the contact(s). In various embodiments, the supporting structure  220  of at least one cable  205  and the supporting structure  235  of the electrode assembly  230  are the same structure (i.e., the supporting structure is continuous), which thus creates a monolithic cable. In alternative embodiments, the supporting structure  220  of at least one cable  205  and the supporting structure  235  of the electrode assembly  230  are different structures but are connected such that there is an electrical connection between the plurality of conductive traces  225 , wiring layer  245 , and the one or more electrodes  240 . 
     As shown in  FIG. 2A , the lead assembly  200  may further comprise a connector  255  formed of a core  260  and an inlaid supporting structure  270  with a predetermined shape or profile  272 . In some embodiments, the core  260  is comprised of one or more layers of material such as polyimide, liquid crystal polymer, parylene, polyether ether ketone, polyurethane, metal, or a combination thereof. In certain embodiments, the one or more layers of material of the core  260  are a TPU. The core  260  may be formed by molding or extrusion with high melting temperature TPU (e.g. Lubrizol Pellethane® 2363-75D, 205C). In some embodiments, the supporting structure  270  is comprised of one or more layers of dielectric material (i.e., an insulator). The layers of dielectric material of the supporting structure  270  may be formed in a FPCB process with metallization layers (e.g., vias or wiring layers) for interconnection. In other embodiments, the supporting structure  270  is made of one or more layers of dielectric material and a coating of a thin layer of a polymer such as TPU. The dielectric material of the supporting structure  270  may be selected from the group of electrically flexible nonconductive materials consisting of organic or inorganic polymers, polyimide-epoxy, epoxy-fiberglass, and the like. In certain embodiments, the dielectric material is a polymer of imide monomers (i.e., a polyimide), a liquid crystal polymer (LCP) such as Kevlar®, parylene, polyether ether ketone (PEEK), or combinations thereof. 
     In some embodiments, one or more conductive traces  275  and one or more contacts  280  (i.e., electrically conductive elements, pins, wires, tabs, pads, etc.) are formed on the supporting structure  270 . The conductive traces  275  and contacts  280  may be comprised of one or more layers of conductive material for electrical conductivity. The conductive material selected for the conductive traces  275  and contacts  280  should have good electrical conductivity and may include pure metals, metal alloys, combinations of metals and dielectrics, and the like. For example, the conductive material may be platinum (Pt), platinum/iridium (Pt/Ir), titanium (Ti), gold/titanium (Au/Ti), or any alloy thereof. In some embodiments, it is also desirable that the conductive material selected for the conductive traces  275  and contacts  280  have a CTE that is approximately equal to that of a CTE of the supporting structure  270 . In some embodiments, the supporting structure  220  of the cable  205  and the supporting structure  270  of the connector  255  are the same structure (i.e., the supporting structure is continuous), which thus creates a monolithic cable. In alternative embodiments, the supporting structure  220  of the cable  205  and the supporting structure  270  of the connector  255  are different structures but are connected such that there is an electrical connection between the plurality of conductive traces  225 , wiring layer  245 , the one or more electrodes  240 , the one or more conductive traces  275 , and the contacts  280 . 
     In various embodiments, the connector  255  may further comprise multiple sectors  285  (e.g., faces of the connector) extending along the outer surface of the supporting structure  270 , and one or more contacts  280  are arranged in each sector of the multiple sectors  285  (see, e.g.,  FIG. 2B ). In some embodiments, the one or more conductive traces  275  are a plurality of traces, for example, two or more conductive traces or from two to twenty-four conductive traces. In some embodiments, the one or more contacts  280  are a plurality of contacts, for example, two or more conductive traces or from two to twenty-four contacts. In some embodiments, at least one trace of the conductive traces  275  terminates at a contact  280  exposed on the outside surface the supporting structure  270  within a sector  285 . In alternative embodiments, each trace from the one or more conductive traces  275  terminates at a contact  280  exposed on the outside surface the supporting structure  270  within a sector  285 . As should be understood, in some embodiments, each electrode from the one or more electrodes  240  is electrically connected via a corresponding wiring layer  245 , optional contact, conductive trace  225 , and conductive trace  275 , to a respective contact  280 . In other words, each electrode may be electrically connected to a different contact (a one to one relationship). In alternative embodiments, a multiplexer chip may be used such that one or more electrodes from the one or more electrodes  240  is electrically connected via wiring layer  245 , optional contact, a conductive trace  225 , and conductive trace  275 , to a single contact  280 . In other words, each electrode may be electrically connected to a same or different contact (a many to one relationship). 
     The one or more conductive traces  275  may be deposited onto a layer of the supporting structure  270  in a sector  285  by using thin film deposition techniques well known to those skilled in the art such as by sputter deposition, chemical vapor deposition, metal organic chemical vapor deposition, electroplating, electroless plating, and the like. In some embodiments, the thickness of the one or more conductive traces  275  is dependent on the particular impedance desired for conductor, in order to ensure excellent signal integrity (e.g., electrical signal integrity for stimulation or recording). For example, if a conductor having a relatively high impedance is desired, a small thickness of conductive material should be deposited onto a layer of the supporting structure  270 . If, however, a signal plane having a relatively low impedance is desired, a greater thickness of electrically conductive material should be deposited onto a layer of the supporting structure  270 . In certain embodiments, each of the one or more conductive traces  275  has a thickness (t). In some embodiments, the thickness (t) is from 0.5 μm to 25 μm or from 5 μm to 10 μm, for example about 5 μm or about 8 μm. In some embodiments, each of the one or more conductive traces  275  has a length (l) of about 1 mm to 100 mm or 1 cm to 3 cm, e.g., about 15 mm. In some embodiments, each of the one or more conductive traces  275  has a width (w) from 2.0 μm to 500 μm, for example about 30 μm or about 50 μm. 
     As shown in  FIGS. 3A-3F , the connector  300  (e.g., the connector  255  as discussed with respect to  FIG. 2 ) may be formed of a core  305  and an inlaid supporting structure  310  at the proximal end  315  of a cable  320  with a predetermined shape or profile  325 . The predetermined shape or profile  325  acts essentially as a key to assist with alignment in insertion of the connector  300  into a header of the neurostimulator. The header includes a predetermined shape or profile (not shown) to match the predetermined shape or profile  325 , which facilitates alignment and insertion of the connector  300  into the header. In some embodiments, the predetermined shape or profile  325  includes an indexing feature  330  that ensures the connector  300  is inserted into the header in a correct manner such that the contacts  335  of the connector  300  match with preselected contacts of the header. As should be understood, the use of an index assures the ultimate connection of each electrode to a specific input port of the electronic module of the neurostimulator such that the controller is guaranteed which electrode it is either activating for stimulation or receiving a signal from during recording. 
       FIGS. 3A and 3B  shows the connector  300  has a “D”-shaped profile  325 , which includes the contacts  335  arranged as split rings on the surface of the supporting structure  310  in the curved portion of the “D”-shaped profile, and the flat portion of the “D”-shaped profile is an indexing feature  330  for keying during insertion of the connector  300  into a header. In some embodiments, the curved portion of the “D”-shaped profile comprises multiple (e.g., dual) sectors  340  of contacts  335 .  FIGS. 3C, 3D, and 3E  show the connector  300  has a notched profile, which includes the contacts  335  arranged as split rings on the surface of the supporting structure  310  in the curved portion of the notched profile, and a notch of the notched profile is an indexing feature  330  for keying during insertion of the connector  300  into a header. The notched profile may increase accuracy of the keying and increases a surface area of the connector  300  for additional sectors  340  of contacts  335  (and may limit overlap in tolerancing of rotational control). In various embodiments, the contacts  335  are formed from split annular rings of conductive material positioned around an axis  342  of the connector  300  and exposed on the surface  345  of the supporting structure  310 . Each split annular ring may be spaced apart from one another on the surface  345  of the supporting structure  310  by a region  355  of a top layer of the dielectric material. A width or pitch (p) of the region  355  of the top layer of the dielectric material that separates each split annular ring may be between 0.1 mm to 10 mm, for example about 2.0 mm. In some embodiments, each portion of the split annular ring connects to a single trace from the conductive traces  360 . In other embodiments, each portion of the split annular ring connects to two or more traces from the conductive traces  360 . For example, a first portion (e.g., a left side portion) of the split annular ring in a sector  340 (A) may be connected with a first trace and a second portion (e.g., a right side portion) of the split annular ring in a sector  340 (B) may be connected with a second trace. Alternatively, a multiplexer chip may be used to drive signals and thus the portions of the split annular ring may be connected to multiple traces from the conductive traces  360 . In various embodiments, eight split annular rings are positioned around the axis  342  of connector  30  and exposed on the surface  345 ; however, it should be understood that more or less than eight split annular rings can be positioned on the supporting structure  310 . For example, the supporting structure may have an increased surface area to accommodate more annular rings or contacts  335  and enhance design flexibility for the connector  300 . Additionally, the annular ring may have two splits (to isolate two contact regions); however, it should be understood that more or less than two splits can be used. For example, the annular rings may have an increased number of splits (3, 4, 5, 6, etc.) to enhance design flexibility for the connector  300 . 
       FIG. 3F  shows the connector  300  has a square shaped profile  325  having quadruple planar sectors  340  of contacts  335 . A used herein “planar” means relating to or in the form of a plane. In this embodiments, the four sides of contacts  335  provides for accurate alignment and high density contacts. However, while the connector  300  is keyed to the square sides, there is no indexing of the four sides of the connector  300 . The absence of the indexing feature may increase usability by health care providers who can insert the connector in any orientation. The orientation may be determined empirically by software of the controller and will adapt to any of the four possible orientations. In certain embodiments, extra contacts  335  could be added with impedance, resistive, or ohmic fiducials to provide orientation queues to the controller of the neurostimulator. In various embodiments, the contacts  335  are formed from separate pads of conductive material positioned around the axis  342  of the connector  300  and exposed on the surface  345  of the supporting structure  310 . Each pad may be spaced apart from one another on the surface  345  of the supporting structure  310  by a region  355  of a top layer of the dielectric material. A width or pitch (p) of the region  355  of the top layer of the dielectric material that separates each pad may be between 0.1 mm to 10 mm, for example about 2.0 mm. In some embodiments, each pad connects to a single trace from the conductive traces  360 . In other embodiments, each pad connects to two or more traces from the conductive traces  360 . For example, a first pad in a sector  340 (A) may be connected with a first trace and a second pad in a sector  340 (B) may be connected with a second trace. Alternatively, a multiplexer chip may be used to drive signals and thus pads may be connected to multiple traces from the conductive traces  360 . In various embodiments, eight pads are positioned in each sector  340  around the axis  342  of connector  300  and exposed on the surface  345 ; however, it should be understood that more or less than eight pads can be positioned on the supporting structure  310  in each sector  340 . For example, the supporting structure  310  may have an increased surface area to accommodate more pads or contacts  335  and enhance design flexibility for the connector  300 . 
     As shown in  FIGS. 3A-3G , the connector  300  (e.g., the connector  255  as discussed with respect to  FIG. 2 ) may further comprise a scaling feature  365 . In various embodiments, the sealing feature  365  is a section of the profile  325  at the distal end  370  of the connector  300 . In some embodiments, the sealing feature  365  includes the core  305  and/or the inlaid supporting structure  310  having a different material, texture, or stiffness such that the sealing feature  365  is structurally configured to engage with a scaling surface of the header of the neurostimulator. In other embodiments, the scaling feature  365  includes an additional layer of material over and/or within the core  305  and/or the inlaid supporting structure  310  (e.g., a polymer material) that is of a different material, texture, or stiffness from that of the core  305  and/or the inlaid supporting structure  310 . As shown in  FIGS. 3A-3H , the connector  300  may further comprise a retention feature  375  proximal to the sealing feature  365  for mechanical retention or connection with a corresponding feature in the header to retain insertion of the connector  300  in the header and maintain a seal between the scaling feature  365  and sealing surface of the header. In some embodiments, the retention feature  375  is an annular ring of material such as metal or polymer formed on the supporting structure, and the corresponding feature of the header is a set screw or engagement hook. 
     As shown in  FIGS. 4A  (frontside) and  4 B (backside), the connector  400  (e.g., the connector  255  as discussed with respect to  FIG. 2 ) may be formed of a core  405  and an inlaid supporting structure  410  with a predetermined layout  415  of contacts  420  and conductive traces  425 . As shown in  FIG. 4C  (cross-section of the connector  400  along X-X from  FIGS. 4A and 4B ), the supporting structure  410  may comprise a first layer of dielectric material  430  and a second layer of dielectric material  435  with the conductive traces  425  buried between the first layer of dielectric material  430  and the second layer of dielectric material  435 . In some embodiments, the first layer of dielectric material  430  comprises at least one contact via  440  for each contact  420 . The contact via  440  may comprise a conductive material for electrically connecting each contact  420  to at least one trace of the conductive traces  425  such that each trace of the conductive traces  425  terminates at a contact  420 . The contact via  440  may be connected to the at least one trace of the conductive traces  425  directly or indirectly by way of a wiring layer (not shown). In some embodiments, the conductive material is lined on at least a portion of the walls of the via hole. In other embodiments, the conductive material fills the via hole. 
     In various embodiments, the connector  400  may be formed with a predetermined shape or profile  445  (e.g., a “D”-shaped profile as shown in  FIG. 4D ). The predetermined shape or profile  445  acts essentially as a key to assist with alignment in insertion of the connector  400  into a header of the neurostimulator. In some embodiments, the predetermined shape or profile  445  includes an indexing feature  450  that ensures the connector  400  is inserted into the header in a correct manner such that the contacts  420  of the connector  400  match with preselected contacts of the header. As shown in  FIG. 4D , the predetermined shape or profile  445  comprises the one or more layers of dielectric material  430 / 435  at least partially wrapped around the core  405 . The first layer of dielectric material  430  may define an outer diameter (d) of the predetermined shape or profile  445  and the second layer of dielectric material  435  may define an inner diameter (d′) of the predetermined shape or profile  445 . The core  405  may at least partially fill the interior of predetermined shape or profile  445  defined by the inner diameter (d′). The core  405  may be comprised of one or more layers of material such that the core  405  has a Shore durometer of greater than 70D. In some embodiments, the one or more layers of material of the core  405  are polyimide, liquid crystal polymer, parylene, polyether ether ketone, polyurethane, metal, or a combination thereof. In certain embodiments, the one or more layers of material of the core  405  is a TPU. Although the connector  400  is shown in  FIG. 4D  and described with respect to a “D”-shaped profile, it should be understood that other shapes for the connector have been contemplated, for example, spherical cubed, torus, ellipsoid, etc. 
     Once the core  405  and the supporting structure  410  are shaped, the core  405  and the supporting structure  410  may then be baked to thermoform the core  405  and supporting structure  410  into a final shape, for example a column with a “D”-shaped profile, as shown in  FIG. 4D . The core  405  and the supporting structure  410  may be reflowed at 130° C.-150° C. (e.g., 137° C.) using the second layer of dielectric material  435  as an adhesive to attach the core  405  to the supporting structure  410 . In some embodiments, the first layer of dielectric material  430  is a first type of polymer material, e.g., a high temperature liquid crystal polymer, that acts as an overlay for insulation, and the second layer of dielectric material  435  is a second type of polymer material, e.g., a low temperature liquid crystal polymer, that acts as an adhesive for bonding the supporting structure  410  to the core  405 , as shown in  FIGS. 4C and 4D . As used herein, “a high temperature liquid crystal polymer” refers to a liquid crystal polymer with a high melting temperature of greater than 300° C. As used herein, “a low temperature liquid crystal polymer” refers to a liquid crystal polymer with a low melting temperature of less than 300° C. 
     As shown in  FIGS. 4A, 4B, and 4D , in some embodiments, the contacts  420  may be split annular rings positioned around an axis  455  of the predetermined shape or profile  445  and exposed on the surface  460  of the predetermined shape or profile  445 . For example, the contacts  420  may be raised above a surface of the supporting structure  410  (e.g., a top surface of the contacts  420  protrudes above a top surface of the supporting structure  410 ) and comprise an anti-abrasive finish. In some embodiments, the contacts  420  are raised above a surface of the supporting structure  410  by a predetermined distance. In certain embodiments, the predetermined distance is from 0.05 mm to 1.0 mm, for example about 0.5 mm. Each split annular ring may be spaced apart from one another on the surface  460  of the cylindrical tube  445  by a region  465  of the first layer of the dielectric material  430 . A width or pitch (p) of the region  465  of the first layer of the dielectric material  550  that separates each split annular ring may be between 1.0 mm to 10 mm, for example about 2 mm. In some embodiments, each contact  420  of a split annular ring connects to a single trace of the conductive traces  425 . In other embodiments, each contact  420  of a split annular ring connects to two or more traces from the conductive traces  420 . For example, a left side of the split annular ring may be connected with a first trace and a right side of the annular ring may be connected with a second trace. Alternatively, a multiplexer chip may be used to drive signals and thus the split annular ring may be connected to multiple traces from the conductive traces  425 . In various embodiments, eight annular rings are positioned around the axis  455  of the cylindrical tube  445  and exposed on the surface  460 ; however, it should be understood that more or less than eight split annular rings can be positioned on the cylindrical tube  445 . For example, the cylindrical tube  445  can have more or less split annular rings (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, etc.) to enhance design flexibility for the connector  400 . 
     IV. Rib-Cage Connectors and Methods of Manufacture 
       FIG. 5A  shows a header and lead assembly  500  (e.g., the header  120  and the lead assembly  110  described with respect to  FIG. 1 ) in accordance with aspects of the present disclosure. In various embodiments, the header and lead assembly  500  comprises a header  505 , a cable  510  having a proximal end  515  and a distal end  520 , and a connector  525  disposed at the proximal end  515  of the cable  510 . The header and lead assembly  50 ) is structured to electrically connect the electronics module of the neurostimulator to electrodes via at least the header  505 , the connector  525  and the cable  510 . The cable  510  may comprise a supporting structure  527  and a plurality of conductive traces  528  formed on a portion of the supporting structure  527 . In some embodiments, the supporting structure  527  is made of one or more layers of dielectric material (i.e., an insulator). The dielectric material may be selected from the group of electrically flexible nonconductive materials consisting of organic or inorganic polymers, polyimide-epoxy, epoxy-fiberglass, and the like. In certain embodiments, the dielectric material is a polymer of imide monomers (i.e., a polyimide), a liquid crystal polymer (LCP) such as Kevlar®, parylene, polyether ether ketone (PEEK), or combinations thereof. In other embodiments, the supporting structure  527  is made of one or more layers of dielectric material formed on a substrate. The substrate may be made from any type of metallic or non-metallic material. 
     In various embodiments, the one or more conductive traces  528  are a plurality of traces, for example, two or more conductive traces or from two to twenty-four conductive traces. The plurality of conductive traces  528  are comprised of one or more layers of conductive material. The conductive material selected for the one or more conductive traces  528  should have good electrical conductivity and may include pure metals, metal alloys, combinations of metals and dielectrics, and the like. For example, the conductive material may be platinum (Pt), platinum/iridium (Pt/Ir), titanium (Ti), gold/titanium (Au/Ti), or any alloy thereof. In some embodiments, it is also desirable that the conductive material selected for the one or more conductive traces  528  have a CTE that is approximately equal to that of the CTE of the supporting structure  527 . 
     As shown in  FIG. 5A , the header and lead assembly  500  may further comprise an electrode assembly  530  formed on a supporting structure  532 . The supporting structure  532  may provide support for microelectronic structures including one or more electrodes  533 , a wiring layer  535 , and optional contact(s) (not shown). The electrode assembly  530  may be located at the distal end  520  of the cable  510 . The one or more electrodes  533  are in electrical connection with one or more conductive traces of the plurality of conductive traces  528 , for example, via the wiring layer  535  and optionally the contact(s). In various embodiments, the supporting structure  527  of the cable  510  and the supporting structure  532  of the electrode assembly  530  are the same structure (i.e., the supporting structure is continuous), which thus creates a monolithic structure. In alternative embodiments, the supporting structure  527  of the cable  510  and the supporting structure  532  of the electrode assembly  530  are different structures but are connected such that there is an electrical connection between the plurality of conductive traces  528 , wiring layer  535 , and the one or more electrodes  533 . 
     In various embodiments, the header  505  comprises a supporting structure  537 . In some embodiments, the supporting structure  537  is a thin-film comprising one or more layers of dielectric material (i.e., an insulator) that are shaped or folded such that the header  505  has a predetermined shape or profile, for example in a “U” shape (see, e.g.,  FIGS. 5A, 5B, and 5C ). In some embodiments, the one or more layers of dielectric material are one or more layers of polymer. The predetermined shape or profile of the header  505  is structured to receive the predetermined shape or profile (e.g., a blade profile) of the connector  525 . In some embodiments, the predetermined shape or profile of the header  505  is structured to wrap around at least a portion of predetermined shape or profile of the connector  525 . In certain embodiments, a thickness (g) of the supporting structure  537  is from 0.5 μm to 250 μm or from 1 μm to 100 μm, for example about 50 μm or about 100 μm. The dielectric material may be selected from the group of electrically flexible nonconductive materials consisting of organic or inorganic polymers, polyimide-epoxy, epoxy-fiberglass, and the like. In certain embodiments, the dielectric material is a polymer of imide monomers (i.e., a polyimide), a liquid crystal polymer (LCP) such as Kevlar®, parylene, polyether ether ketone (PEEK), or combinations thereof. 
     In some embodiments, one or more conductive traces  538  and one or more contacts  540  (i.e., electrically conductive elements, pins, wires, tabs, pads, etc.) are formed on the supporting structure  537  (see, e.g.,  FIG. 5A ). The one or more conductive traces  538  and one or more contacts  540  are structured to electrically connect the header  505  to the electronics module of the neurostimulator. The conductive traces  538  and contacts  540  may be comprised of one or more layers of conductive material for electrical conductivity. The conductive material selected for the conductive traces  538  and contacts  540  should have good electrical conductivity and may include pure metals, metal alloys, combinations of metals and dielectrics, and the like. For example, the conductive material may be platinum (Pt), platinum/iridium (Pt/Ir), titanium (Ti), gold/titanium (Au/Ti), or any alloy thereof. In some embodiments, it is also desirable that the conductive material selected for the conductive traces  538  and contacts  540  have a CTE that is approximately equal to that of a CTE of the supporting structure  537 . 
     In various embodiments, the header  505  further comprises a clip  545  structured to maintain electrical contact between the contacts  540  and corresponding contacts  550  of the connector  525  (see, e.g.,  FIGS. 5B and 5C ). In some embodiments, the clip  545  is one or more clip springs or spring-fibers  555  arranged into a comb or rib-cage arrangement on the outside of the supporting structure  537 . The clip springs or spring-fibers  555  have a spring force that exerts a clasping pressure on the supporting structure  537  to connect the header  505  to the connector  525 , as shown in  FIGS. 5B and 5C . The thin-film thickness (g) of the supporting structure  537  allows for the spring force of the clip  545  to be distributed across all electrical connections of contacts  540  and corresponding contacts  550  as well as for compliance during insertion of the connector  525  into the header  505 . In some embodiments, the clip  545  is held open during insertion of the connector  525  with pull-pins (e.g., pins that may be removed once the connector  525  is inserted into the header  505 ). In other embodiments, the supporting structure  537  is sufficiently stiff or durable such that the clip  545  is at least partially held open during insertion of the connector  525 . For example, a distance that the clip  545  is held open by the supporting structure  530  is no greater than an overall thickness of the connector  525  such that a tight fit is maintained between the header  505  and the connector  525 . 
     In various embodiments, the connector  525  comprises a core  560  and an inlaid supporting structure  565  with a predetermined shape or profile  567  (see, e.g.,  FIG. 5A ). In some embodiments, the core  560  is comprised of one or more layers of material such as polyimide, liquid crystal polymer, parylene, polyether ether ketone, polyurethane, metal, or a combination thereof. In certain embodiments, the one or more layers of material of the core  560  are a TPU. The core  560  may be formed by molding or extrusion with high melting temperature TPU (e.g. Lubrizol Pellethane® 2363-75D, 205C). In some embodiments, the supporting structure  565  is comprised of one or more layers of dielectric material (i.e., an insulator). The layers of dielectric material of the supporting structure  565  may be formed in a FPCB process with metallization layers (e.g., vias or wiring layers) for interconnection. In other embodiments, the supporting structure  565  is made of one or more layers of dielectric material and a coating of a thin layer of a polymer such as TPU. The dielectric material of the supporting structure  565  may be selected from the group of electrically flexible nonconductive materials consisting of organic or inorganic polymers, polyimide-epoxy, epoxy-fiberglass, and the like. In certain embodiments, the dielectric material is a polymer of imide monomers (i.e., a polyimide), a liquid crystal polymer (LCP) such as Kevlar®, parylene, polyether ether ketone (PEEK), or combinations thereof. 
     In some embodiments, one or more conductive traces  570  and one or more contacts  550  (i.e., electrically conductive elements, pins, wires, tabs, pads, etc.) are formed on the supporting structure  565  (see, e.g.,  FIG. 5A ). The conductive traces  570  and contacts  550  may be comprised of one or more layers of conductive material for electrical conductivity. The conductive material selected for the conductive traces  570  and contacts  550  should have good electrical conductivity and may include pure metals, metal alloys, combinations of metals and dielectrics, and the like. For example, the conductive material may be platinum (Pt), platinum/iridium (Pt/Ir), titanium (Ti), gold/titanium (Au/Ti), or any alloy thereof. In some embodiments, it is also desirable that the conductive material selected for the conductive traces  570  and contacts  550  have a CTE that is approximately equal to that of a CTE of the supporting structure  565 . In some embodiments, the supporting structure  527  of the cable  510  and the supporting structure  565  of the connector  525  are the same structure (i.e., the supporting structure is continuous), which thus creates a monolithic cable. In alternative embodiments, the supporting structure  527  of the cable  510  and the supporting structure  565  of the connector  525  are different structures but are connected such that there is an electrical connection between the conductive traces  528 , wiring layer  535 , the electrodes  533 , the conductive traces  570 , and the contacts  550 . 
     In various embodiments, the one or more conductive traces  570  are a plurality of traces, for example, two or more conductive traces or from two to twenty-four conductive traces. In some embodiments, at least one trace of the one or more conductive traces  570  terminates at a contact  550  exposed on the outside surface the supporting structure  565 . In alternative embodiments, each trace from the one or more conductive traces  570  terminates at a contact  550  exposed on the outside surface the supporting structure  565 . As should be understood, in some embodiments, each electrode from the electrodes  533  is electrically connected via a corresponding wiring layer  535 , optional contact, conductive trace  527 , and conductive trace  570 , to a respective contact  550 . In other words, each electrode may be electrically connected to a different contact (a one to one relationship). In alternative embodiments, a multiplexer chip may be used such that one or more electrodes from the electrodes  533  is electrically connected via wiring layer  535 , optional contact, a conductive trace  527 , and conductive trace  570 , to a single contact  550 . In other words, each electrode may be electrically connected to a same or different contact (a many to one relationship). 
     The one or more conductive traces  570  may be deposited onto a layer of the supporting structure  565  by using thin film deposition techniques well known to those skilled in the art such as by sputter deposition, chemical vapor deposition, metal organic chemical vapor deposition, electroplating, electroless plating, and the like. In some embodiments, the thickness of the one or more conductive traces  570  is dependent on the particular impedance desired for conductor, in order to ensure excellent signal integrity (e.g., electrical signal integrity for stimulation or recording). For example, if a conductor having a relatively high impedance is desired, a small thickness of conductive material should be deposited onto a layer of the supporting structure  565 . If, however, a signal plane having a relatively low impedance is desired, a greater thickness of electrically conductive material should be deposited onto a layer of the supporting structure  565 . In certain embodiments, each of the one or more conductive traces  570  has a thickness (t). In some embodiments, the thickness (t) is from 0.5 μm to 25 μm or from 5 μm to 10 μm, for example about 5 μm or about 8 μm. In some embodiments, each of the one or more conductive traces  570  has a length (l) of about 1 mm to 100 μm or 1 cm to 3 cm, e.g., about 15 mm. In some embodiments, each of the one or more conductive traces  570  has a width (w) from 2.0 μm to 500 μm, for example about 30 μm or about 50 μm. 
     As shown in  FIGS. 5A, 5B, and 5C , the connector  525  may be formed with the predetermined shape or profile  567 . The predetermined shape or profile  567  acts essentially as a key to assist with alignment in insertion of the connector  525  into the header  505 . In some embodiments, the predetermined shape or profile  567  is a blade with the inlaid supporting structure  565  folded over the core  560  creating a first planar sector  577  of contacts  575  positioned on a first side of the blade and a second planar sector  578  of contacts  575  positioned on a second side of the blade (see, e.g.,  FIG. 5C ). In various embodiments, the contacts  575  are formed from split rows of conductive material positioned in columns and exposed on the surface  579  of the supporting structure  565 . Each split row may be spaced apart from one another on the surface  579  of the supporting structure  565  by a region  580  of a top layer of the dielectric material. A width or pitch (p) of the region  580  of the top layer of the dielectric material that separates each split row may be between 0.1 mm to 10 mm, for example about 1.0 mm. In some embodiments, each portion of the split row connects to a single trace from the conductive traces  570 . In other embodiments, each portion of the split row connects to two or more traces from the conductive traces  570 . For example, a left side portion of the split row in first planar sector  577  may be connected with a first trace and a right side portion of the split row in the second planar sector  578  may be connected with a second trace. Alternatively, a multiplexer chip may be used to drive signals and thus the portions of the split row may be connected to multiple traces from the conductive traces  570 . In various embodiments, thirty-two split rows are positioned on the supporting structure  565  of the connector  525  and exposed on the surface  579 ; however, it should be understood that more or less than thirty-two split rows may be positioned on the supporting structure  565 . For example, the supporting structure  565  may have an increased surface area to accommodate more rows of contacts  575  and enhance design flexibility for the connector  525 . Additionally, the rows may have one split (to isolate columns of contact regions); however, it should be understood that more than one split can be used. For example, the rows may have an increased number of splits (2, 3, 4, 5, 6, etc.) to enhance design flexibility for the second connector  525 . 
     As shown in  FIGS. 6A  (frontside),  6 B (backside), and  6 C, a header  600  (e.g., the header  505  as discussed with respect to  FIGS. 5A-5C ) may be formed of a supporting structure  605  with a predetermined layout  610  of contacts  615  and conductive traces  620 . In some embodiments, the supporting structure  605  is made of one or more layers of dielectric material formed on an optional substrate. The substrate may be made from any type of metallic or non-metallic material such as polyimide, liquid crystal polymer, parylene, polyether ether ketone, polyurethane, TPU, metal, or a combination thereof. As shown in  FIG. 6C  (cross-section of the connector  600  along X-X from  FIGS. 6A and 6B ), the supporting structure  605  may comprise a first layer of dielectric material  630  and a second layer of dielectric material  635  with the conductive traces  620  buried between the first layer of dielectric material  630  and the second layer of dielectric material  635 . In some embodiments, the first layer of dielectric material  630  comprises at least one contact via  640  for each contact  615 . The contact via  640  may comprise a conductive material for electrically connecting each contact  615  to at least one trace of the conductive traces  620  such that each trace of the conductive traces  620  terminates at a contact  615 . The contact via  640  may be connected to the at least one trace of the conductive traces  620  directly or indirectly by way of a wiring layer (not shown). In some embodiments, the conductive material is lined on at least a portion of the walls of the via hole. In other embodiments, the conductive material fills the via hole. 
     In various embodiments, the contacts  615  are provided as split rows positioned in columns on sectors or faces of the supporting structure  605  (see, e.g.,  FIGS. 6A and 6B ). In some embodiments, a first portion of the split rows is disposed in a first sector of the sectors and a second portion of the split rows is disposed in a second sector of the sectors. The first sector may be located on a first side of the header  600  and the second sector may be located on a second side of the header  600 . In some embodiments, the contacts  615  are exposed on the surface  645  of the supporting structure  605  (see, e.g.,  FIGS. 6C and 6D ). For example, the contacts  615  may be raised above a surface of the supporting structure  605  (e.g., a top surface of the contacts  615  protrudes above a top surface of the supporting structure  605 ) and comprise an anti-abrasive finish. In certain embodiments, the contacts  615  are raised above the surface  645  of the supporting structure  605  by a predetermined distance. The predetermined distance is from 0.05 mm to 1.0 mm, for example about 0.5 mm. Moreover, each split row may be spaced apart from one another on the surface  645  of the supporting structure by a region  650  of the first layer of the dielectric material  630  (see, e.g.,  FIGS. 6A and 6B ). A width or pitch (p) of the region  650  of the first layer of the dielectric material  630  that separates each split row may be between 1.0 mm to 10 mm, for example about 1 mm. In some embodiments, each contact  615  of a split row connects to a single trace of the conductive traces  620 . In other embodiments, each contact  615  of a split row connects to two or more traces from the conductive traces  620 . For example, a left side of the split row may be connected with a first trace and a right side of the split row may be connected with a second trace. Alternatively, a multiplexer chip may be used to drive signals and thus the split row may be connected to multiple traces from the conductive traces  620 . In various embodiments, thirty-two split rows are positioned on the supporting structure  605  and exposed on the surface  645 ; however, it should be understood that more or less than thirty-two split rows can be positioned on the supporting structure  605 . For example, the supporting structure  605  can accommodate more or less split rows (10, 24, 30, 42, 48, 50 etc.) to enhance design flexibility for the first connector  600 . 
     As shown in  FIG. 6D , the supporting structure  605  may be shaped or folded such that the contacts  615  face inwardly. The supporting structure  605  may then be baked to thermoform the supporting structure  605  into a final shape, for example in a “U” shape. In some embodiments, the first layer of dielectric material  630  is a first type of polymer material, e.g., a high temperature liquid crystal polymer or a low temperature liquid crystal polymer, that acts as an overlay for insulation, and the second layer of dielectric material  635  is a second type of polymer material, e.g., a high temperature liquid crystal polymer or a low temperature liquid crystal polymer, that acts as an overlay for insulation. Although the header  600  is shown in  FIG. 6D  and described with respect to a “U” shape, it should be understood that other shapes for the header have been contemplated, for example, spherical cubed, torus, ellipsoid, etc. 
     As shown in  FIGS. 6E  (frontside) and  6 F (backside), the connector  655  (e.g., the connector  525  as discussed with respect to  FIGS. 5A, 5B, and 5C ) may be formed of a core  660  and an inlaid supporting structure  665  with a predetermined layout  667  of contacts  670  and conductive traces  675 . As shown in  FIG. 6G  (cross-section of the connector  655  along X-X from  FIGS. 6E and 6F ), the supporting structure  665  may comprise a first layer of dielectric material  680  and a second layer of dielectric material  685  with the conductive traces  675  buried between the first layer of dielectric material  680  and the second layer of dielectric material  685 . In some embodiments, the first layer of dielectric material  680  comprises at least one contact via  687  for each contact  670 . The contact via  687  may comprise a conductive material for electrically connecting each contact  670  to at least one trace of the conductive traces  675  such that each trace of the conductive traces  675  terminates at a contact  670 . The contact via  687  may be connected to the at least one trace of the conductive traces  675  directly or indirectly by way of a wiring layer (not shown). In some embodiments, the conductive material is lined on at least a portion of the walls of the via hole. In other embodiments, the conductive material fills the via hole. 
     In various embodiments, the contacts  670  are provided as split rows positioned in columns on sectors or faces of the supporting structure  665  (see, e.g.,  FIGS. 6E and 6F ). In some embodiments, a first portion of the split rows is disposed in a first sector of the sectors and a second portion of the split rows is disposed in a second sector of the sectors. The first sector may be located on a first side of the connector  655  and the second sector is located on a second side of the connector  655 . In some embodiments, the contacts  670  are exposed on the surface  690  of the supporting structure  665  (see, e.g.,  FIG. 6G ). For example, the contacts  670  may be raised above a surface of the supporting structure  665  (e.g., a top surface of the contacts  670  protrudes above a top surface of the supporting structure  665 ) and comprise an anti-abrasive finish. In certain embodiments, the contacts  670  are raised above the surface  690  of the supporting structure  665  by a predetermined distance. The predetermined distance is from 0.05 mm to 1.0 mm, for example about 0.5 mm. Moreover, each split row may be spaced apart from one another on the surface  690  of the supporting structure by a region  692  of the first layer of the dielectric material  680  (see, e.g.,  FIG. 6E ). A width or pitch (p) of the region  692  of the first layer of the dielectric material  680  that separates each split row may be between 1.0 mm to 10 mm, for example about 1 mm. In some embodiments, each contact  670  of a split row connects to a single trace of the conductive traces  675 . In other embodiments, each contact  670  of a split row connects to two or more traces from the conductive traces  675 . For example, a left side of the split row may be connected with a first trace and a right side of the split row may be connected with a second trace. Alternatively, a multiplexer chip may be used to drive signals and thus the split row may be connected to multiple traces from the conductive traces  675 . In various embodiments, thirty-two split rows are positioned on the supporting structure  665  and exposed on the surface  690 ; however, it should be understood that more or less than thirty-two split rows can be positioned on the supporting structure  665 . For example, the supporting structure  665  can accommodate more or less split rows (10, 24, 30, 42, 48, 50 etc.) to enhance design flexibility for the connector  655 . 
     As shown in  FIG. 6H , the supporting structure  665  may be shaped or folded on the core  660  (e.g., an injection molded core) such that the contacts  670  face outwardly. In various embodiments, the core  660  and the supporting structure  665  may be formed with a predetermined shape or profile  695  (e.g., a blade as shown in  FIG. 6H ). The predetermined shape or profile  695  acts essentially as a key to assist with alignment in insertion of the second connector  655  into the header  600 . As shown in  FIG. 6H , the shape or profile  695  comprises the one or more layers of dielectric material  680 / 685  at least partially wrapped around the core  660 , e.g., a “U” shaped wrapping. The first layer of dielectric material  680  may define an outer width (n) of the shape or profile  695  and the second layer of dielectric material  685  may define an inner width (n′) of the shape or profile  695 . The shape or profile  695  may further comprise the core  660  that at least partially fills a space interior of the shape or profile  695  defined by the inner width (n′) of the shape or profile  695 . The core  660  may be comprised of one or more layers of material such that the core  660  has a Shore durometer of greater than 70D. In some embodiments, the one or more layers of material of the core  660  is polyimide, liquid crystal polymer, parylene, polyether ether ketone, polyurethane, metal, or a combination thereof. In certain embodiments, the one or more layers of material of the core  660  is a TPU. Although the connector  655  is shown in  FIG. 6H  and described with respect to a blade shape, it should be understood that other shapes for the connector have been contemplated, for example, spherical cubed, torus, ellipsoid, etc. 
     Once the core  660  and the supporting structure  665  are shaped, the core  660  and the supporting structure  665  may then be inserted into a heat shrink tube (e.g., FEP Lay-Flat™ Heat Shrink) and baked to thermoform the core  660  and supporting structure  665  into a final shape, for example a blade, as shown in  FIG. 6H . The core  660  and the supporting structure  665  may be reflowed at 130° C.-150° C. (e.g., 137° C.) using the second layer of dielectric material  685  as an adhesive to attach the core  660  to the supporting structure  665 . In some embodiments, the first layer of dielectric material  680  is a first type of polymer material, e.g., a high temperature liquid crystal polymer, that acts as an overlay for insulation, and the second layer of dielectric material  685  is a second type of polymer material, e.g., a low temperature liquid crystal polymer, that acts as an adhesive for bonding the supporting structure  665  to the core  660 , as shown in  FIG. 6H . 
     V. Extension Connectors and Methods of Manufacture 
       FIG. 7A  shows a neuromodulation system  700  (e.g., the neuromodulation system  100  described with respect to  FIG. 1 ) in accordance with aspects of the present disclosure. In various embodiments, the neuromodulation system  700  comprises an implantable neurostimulator  705  and a lead assembly  707 . The lead assembly  707  includes two or more cables  710 , a proximal end  711 , and a distal end  712 . Each cable  710  may comprise a supporting structure  715  and a plurality of conductive traces  720  formed on a portion of the supporting structure  715 . In some embodiments, the supporting structure  715  is made of one or more layers of dielectric material (i.e., an insulator). The dielectric material may be selected from the group of electrically flexible nonconductive materials consisting of organic or inorganic polymers, polyimide-epoxy, epoxy-fiberglass, and the like. In certain embodiments, the dielectric material is a polymer of imide monomers (i.e., a polyimide), a liquid crystal polymer (LCP) such as Kevlar®, parylene, polyether ether ketone (PEEK), or combinations thereof. In other embodiments, the supporting structure  715  is made of one or more layers of dielectric material formed on a substrate. The substrate may be made from any type of metallic or non-metallic material. 
     In various embodiments, the one or more conductive traces  720  are a plurality of traces, for example, two or more conductive traces or from two to twenty-four conductive traces. The plurality of conductive traces  720  are comprised of one or more layers of conductive material. The conductive material selected for the one or more conductive traces  720  should have good electrical conductivity and may include pure metals, metal alloys, combinations of metals and dielectrics, and the like. For example, the conductive material may be platinum (Pt), platinum/iridium (Pt/Ir), titanium (Ti), gold/titanium (Au/Ti), or any alloy thereof. In some embodiments, it is also desirable that the conductive material selected for the one or more conductive traces  720  have a CTE that is approximately equal to that of the CTE of the supporting structure  715 . 
     As shown in  FIG. 7A , the lead assembly  707  may further comprise an electrode assembly  725  formed on a supporting structure  727 . The supporting structure  727  may provide support for microelectronic structures including one or more electrodes  730 , a wiring layer  732 , and optional contact(s) (not shown). The electrode assembly  707  may be located at the distal end  712  of the lead assembly  707 . The one or more electrodes  730  are in electrical connection with one or more conductive traces of the plurality of conductive traces  720 , for example, via the wiring layer  732  and optionally the contact(s). In various embodiments, the supporting structure  715  of at least one cable  710  and the supporting structure  727  of the electrode assembly  725  are the same structure (i.e., the supporting structure is continuous), which thus creates a monolithic structure. In alternative embodiments, the supporting structure  715  of at least one cable  710  and the supporting structure  727  of the electrode assembly  725  are different structures but are connected such that there is an electrical connection between the plurality of conductive traces  720 , wiring layer  732 , and the one or more electrodes  730 . 
     As shown in  FIG. 7A , the lead assembly  707  may further comprise one or more extension devices  735  for connecting the two or more cables  710 . Each extension device  735  comprises a housing  737  and a connection assembly  740 . In various embodiments, the housing  737  comprises a first half portion  742  (e.g., a bottom half), a second half portion  743  (e.g., a top half), a distal port  744 , and a proximal port  745 , as shown in  FIG. 7B . The first half portion  742  and the second half portion  743  may be formed of a polymer material. The polymer material may be imide monomers (i.e., a polyimide), a liquid crystal polymer (LCP) such as Kevlar®, parylene, polyether ether ketone (PEEK), or combinations thereof. The distal port  744  may be structured to receive a first cable of the two or more cables  710 , and the proximal port  745  may structure to receive a second cable of the two or more cables  710 . In some embodiments, the distal port  744  and/or the proximal port  745  are disposed within the first half portion  742  (e.g., a scalable through-hole in a side of the first portion  742 ). In other embodiments, the distal port  744  and/or the proximal port  745  are disposed within the second half portion  743  (e.g., a scalable through-hole in a side of the second portion  743 ). In other embodiments, the distal port  744  and/or the proximal port  745  are disposed in a space between the first half portion  742  and the second half portion  743  (e.g., in a scalable slot between the two halves). The distal port  744  and/or the proximal port  745  may be sealed by mating the through-hole or slot with other components such as a sealing ring. 
     In some embodiments, the first half portion  742  comprises one or more alignment pins  746 , a seal  747 , and a first compliant pad  748 , as shown in  FIGS. 7B and 7C . The second half portion  743  comprises an optional seal  750 , a second compliant pad  752 , and one or more attachment features  755  (e.g., screws) for attaching the first half portion  742  and the second half portion  743 , as shown in  FIGS. 7B and 7C . The alignment pins  746  may be made of a polymer, metal, or combination thereof, and are structured to align the connection assembly  740  within the housing  737 , as described in further detail herein with reference to  FIG. 7D . The seals  747  and  750  may be made of polyurethane, polycarbonate, silicone, polyethylene, fluoropolymer and/or other medical polymers, copolymers and combinations or blends thereof. The first compliant pad  748  and the second compliant pad  752  may be foam compression pads structured to assist in compression or maintaining electrical contact within the connector, as described in further detail herein with reference to  FIG. 7D . The foam compression pads may be made of polyurethane, polycarbonate, silicone, polyethylene, fluoropolymer and/or other medical polymers, copolymers and combinations or blends thereof. In some embodiments, the one or more attachment features  755  attach the first half portion  742  and the second half portion  743  as well as compressing the seal  747 , optionally seal  750 , the first compliant pad  748 , and the second compliant pad  752  within the housing  737 . 
       FIGS. 7D and 7E  show a connection assembly  740  in accordance with aspects of the present disclosure. In various embodiments, the connection assembly  740  comprises a first connector  760  and a second connector  765 . The first connector  760  may be disposed at an end (e.g., a distal end) of the first cable of the two or more cables  710 . The second connector  765  may be disposed at an end (e.g., the proximal end) of the second cable of the two or more cables  710 . The connection assembly  740  is structured to electrically connect the first cable to the second cable, and thus extend an overall length of the lead assembly  707 . In various embodiments, the fist connector  760  comprises a supporting structure  767 . In some embodiments, the supporting structure  767  is a thin-film comprising one or more layers of dielectric material (i.e., an insulator) that are shaped or folded, for example in a “U” shape (see, e.g.,  FIG. 7E ). In some embodiments, the one or more layers of dielectric material are one or more layers of polymer. In certain embodiments, a thickness (g) of the supporting structure  767  is from 0.5 μm to 250 μm or from 1 μm to 100 μm, for example about 50 μm or about 100 μm. The dielectric material may be selected from the group of electrically flexible nonconductive materials consisting of organic or inorganic polymers, polyimide-epoxy, epoxy-fiberglass, and the like. In certain embodiments, the dielectric material is a polymer of imide monomers (i.e., a polyimide), a liquid crystal polymer (LCP) such as Kevlar®, parylene, polyether ether ketone (PEEK), or combinations thereof. 
     In some embodiments, one or more conductive traces  768  and one or more contacts  769  (i.e., electrically conductive elements, pins, wires, tabs, pads, etc.) are formed on the supporting structure  767  (see, e.g.,  FIG. 7E ). The conductive traces  768  and contacts  769  may be comprised of one or more layers of conductive material for electrical conductivity. The conductive material selected for the conductive traces  768  and contacts  769  should have good electrical conductivity and may include pure metals, metal alloys, combinations of metals and dielectrics, and the like. For example, the conductive material may be platinum (Pt), platinum/iridium (Pt/Ir), titanium (Ti), gold/titanium (Au/Ti), or any alloy thereof. In some embodiments, it is also desirable that the conductive material selected for the conductive traces  768  and contacts  769  have a CTE that is approximately equal to that of a CTE of the supporting structure  767 . In some embodiments, the supporting structure  715  of the first cable  710  and the supporting structure  767  of the first connector  760  are the same structure (i.e., the supporting structure is continuous), which thus creates a monolithic cable. In alternative embodiments, the supporting structure  715  of the first cable  710  and the supporting structure  767  of the first connector  760  are different structures but are connected such that there is an electrical connection between the conductive traces  720 , wiring layer  732 , the electrodes  730 , the conductive traces  768 , and the contacts  769 . 
     In various embodiments, the second connector  765  comprises a core  770  and an inlaid supporting structure  772  with a predetermined shape or profile  773  (see, e.g.,  FIG. 7F ). In some embodiments, the core  770  is comprised of one or more layers of material such as polyimide, liquid crystal polymer, parylene, polyether ether ketone, polyurethane, metal, or a combination thereof. In certain embodiments, the one or more layers of material of the core  770  are a TPU. The core  770  may be formed by molding or extrusion with high melting temperature TPU (e.g. Lubrizol Pellethane® 2363-75D, 205C). In some embodiments, the supporting structure  772  is comprised of one or more layers of dielectric material (i.e., an insulator). The layers of dielectric material of the supporting structure  772  may be formed in a FPCB process with metallization layers (e.g., vias or wiring layers) for interconnection. In other embodiments, the supporting structure  772  is made of one or more layers of dielectric material and a coating of a thin layer of a polymer such as TPU. The dielectric material of the supporting structure  772  may be selected from the group of electrically flexible nonconductive materials consisting of organic or inorganic polymers, polyimide-epoxy, epoxy-fiberglass, and the like. In certain embodiments, the dielectric material is a polymer of imide monomers (i.e., a polyimide), a liquid crystal polymer (LCP) such as Kevlar®, parylene, polyether ether ketone (PEEK), or combinations thereof. 
     In some embodiments, one or more conductive traces  774  and one or more contacts  775  (i.e., electrically conductive elements, pins, wires, tabs, pads, etc.) are formed on the supporting structure  772  (see, e.g.,  FIG. 7F ). The conductive traces  774  and contacts  775  may be comprised of one or more layers of conductive material for electrical conductivity. The conductive material selected for the conductive traces  774  and contacts  775  should have good electrical conductivity and may include pure metals, metal alloys, combinations of metals and dielectrics, and the like. For example, the conductive material may be platinum (Pt), platinum/iridium (Pt/Ir), titanium (Ti), gold/titanium (Au/Ti), or any alloy thereof. In some embodiments, it is also desirable that the conductive material selected for the conductive traces  774  and contacts  775  have a CTE that is approximately equal to that of a CTE of the supporting structure  772 . In some embodiments, the supporting structure  715  of the second cable  710  and the supporting structure  772  of the second connector  765  are the same structure (i.e., the supporting structure is continuous), which thus creates a monolithic cable. In alternative embodiments, the supporting structure  715  of the second cable  710  and the supporting structure  772  of the second connector  765  are different structures but are connected such that there is an electrical connection between the conductive traces  720 , wiring layer  732 , the electrodes  730 , the conductive traces  773 , and the contacts  775 . 
     In various embodiments, the one or more conductive traces  774  are a plurality of traces, for example, two or more conductive traces or from two to twenty-four conductive traces. In some embodiments, at least one trace of the one or more conductive traces  774  terminates at a contact  775  exposed on the outside surface the supporting structure  772 . In alternative embodiments, each trace from the one or more conductive traces  774  terminates at a contact  775  exposed on the outside surface the supporting structure  772 . As should be understood, in some embodiments, each electrode from the electrodes  730  is electrically connected via a corresponding wiring layer  732 , optional contact, conductive trace  720 , and conductive trace  774 , to a respective contact  775 . In other words, each electrode may be electrically connected to a different contact (a one to one relationship). In alternative embodiments, a multiplexer chip may be used such that one or more electrodes from the electrodes  730  is electrically connected via wiring layer  732 , optional contact, a conductive trace  720 , and conductive trace  774 , to a single contact  775 . In other words, each electrode may be electrically connected to a same or different contact (a many to one relationship). 
     The one or more conductive traces  774  may be deposited onto a layer of the supporting structure  772  by using thin film deposition techniques well known to those skilled in the art such as by sputter deposition, chemical vapor deposition, metal organic chemical vapor deposition, electroplating, electroless plating, and the like. In some embodiments, the thickness of the one or more conductive traces  774  is dependent on the particular impedance desired for conductor, in order to ensure excellent signal integrity (e.g., electrical signal integrity for stimulation or recording). For example, if a conductor having a relatively high impedance is desired, a small thickness of conductive material should be deposited onto a layer of the supporting structure  772 . If, however, a signal plane having a relatively low impedance is desired, a greater thickness of electrically conductive material should be deposited onto a layer of the supporting structure  772 . In certain embodiments, each of the one or more conductive traces  774  has a thickness (t). In some embodiments, the thickness (t) is from 0.5 μm to 25 μm or from 5 μm to 10 μm, for example about 5 μm or about 8 μm. In some embodiments, each of the one or more conductive traces  774  has a length (l) of about 1 mm to 100 mm or 1 cm to 3 cm, e.g., about 15 mm. In some embodiments, each of the one or more conductive traces  774  has a width (w) from 2.0 μm to 500 μm, for example about 30 μm or about 50 μm. 
     As shown in  FIGS. 7D and 7F , the second connector  765  may be formed with the predetermined shape or profile  773 . The predetermined shape or profile  773  acts essentially as a key to assist with alignment in insertion of the second connector  765  into the first connector  760 . In some embodiments, the predetermined shape or profile  773  is a blade with the inlaid supporting structure  772  folded over the core  770  creating a first planar sector  777  of contacts  775  positioned on a first side of the blade and a second planar sector  778  of contacts  775  positioned on a second side of the blade. In various embodiments, the contacts  775  are formed from split rows of conductive material positioned in columns and exposed on the surface  779  of the supporting structure  772 . Each split row may be spaced apart from one another on the surface  779  of the supporting structure  772  by a region  780  of a top layer of the dielectric material. A width or pitch (p) of the region  780  of the top layer of the dielectric material that separates each split row may be between 0.1 mm to 10 mm, for example about 1.0 mm. In some embodiments, each portion of the split row connects to a single trace from the conductive traces  774 . In other embodiments, each portion of the split row connects to two or more traces from the conductive traces  774 . For example, a left side portion of the split row in first planar sector  777  may be connected with a first trace and a right side portion of the split row in the second planar sector  778  may be connected with a second trace. Alternatively, a multiplexer chip may be used to drive signals and thus the portions of the split row may be connected to multiple traces from the conductive traces  774 . In various embodiments, thirty-two split rows are positioned on the supporting structure  772  of the second connector  765  and exposed on the surface  779 ; however, it should be understood that more or less than thirty-two split rows may be positioned on the supporting structure  772 . For example, the supporting structure  772  may have an increased surface area to accommodate more rows of contacts  775  and enhance design flexibility for the second connector  765 . Additionally, the rows may have one split (to isolate columns of contact regions); however, it should be understood that more than one split can be used. For example, the rows may have an increased number of splits (2, 3, 4, 5, 6, etc.) to enhance design flexibility for the second connector  765 . 
     In various embodiments, the fist connector  760  further comprises one or more alignment holes  782  and the second connector  765  further comprises one or more alignment holes  783  (see, e.g.,  FIG. 7D ). The alignment holes  782  and  783  are structured to align and assist with maintaining electrical contact between the contacts  769  of the first connector  760  and corresponding contacts  775  of the second connector  765 . In some embodiments, the one or more attachment features  755  hold the first connector  760  in physical contact with the second connector  765  such that the contacts  769  are in electrical contact with the contacts  775 . For example, the alignment holes  782  and  783  fit over the alignment pins  746 , and thus hold the contacts  769  and corresponding contacts  775  in alignment. Moreover, the first compliant pad  748  and the second compliant pad  752  have a spring force that exerts a clasping pressure on the supporting structure  767  to electrically connect the first connector  760  with the second connector  765 , as shown in  FIG. 7C . The thin-film thickness (g) of the supporting structure  767  allows for the spring force of first compliant pad  748  and the second compliant pad  752  to be distributed across all electrical connections of contacts  769  and corresponding contacts  775  as well as for compliance during closing of the housing  737 . 
     As shown in  FIGS. 8A, 8B, and 8C , a first connector  800  (e.g., the connector  760  as discussed with respect to  FIGS. 7A-7G ) may be formed of a supporting structure  805  with a predetermined layout  810  of contacts  815  and conductive traces  820 . In some embodiments, the supporting structure  805  is made of one or more layers of dielectric material formed on a substrate. The substrate may be made from any type of metallic or non-metallic material such as polyimide, liquid crystal polymer, parylene, polyether ether ketone, polyurethane, TPU, metal, or a combination thereof. As shown in  FIG. 8C  (cross-section of the connector  800  along X-X from  FIGS. 8A and 8B ), the supporting structure  805  may comprise a first layer of dielectric material  830  and a second layer of dielectric material  835  with the conductive traces  820  buried between the first layer of dielectric material  830  and the second layer of dielectric material  835 . In some embodiments, the first layer of dielectric material  830  comprises at least one contact via  840  for each contact  815 . The contact via  840  may comprise a conductive material for electrically connecting each contact  815  to at least one trace of the conductive traces  820  such that each trace of the conductive traces  820  terminates at a contact  815 . The contact via  840  may be connected to the at least one trace of the conductive traces  820  directly or indirectly by way of a wiring layer (not shown). In some embodiments, the conductive material is lined on at least a portion of the walls of the via hole. In other embodiments, the conductive material fills the via hole. 
     In various embodiments, the contacts  815  are provided as split rows positioned in columns on sectors or faces of the supporting structure  805  (see, e.g.,  FIGS. 8A and 8B ). In some embodiments, the contacts  815  are exposed on the surface  845  of the supporting structure  805  (see, e.g.,  FIG. 8C ). For example, the contacts  815  may be raised above a surface of the supporting structure  805  (e.g., a top surface of the contacts  815  protrudes above a top surface of the supporting structure  805 ) and comprise an anti-abrasive finish. In certain embodiments, the contacts  815  are raised above the surface  845  of the supporting structure  805  by a predetermined distance. The predetermined distance is from 0.05 mm to 1.0 mm, for example about 0.5 mm. Moreover, each split row may be spaced apart from one another on the surface  845  of the supporting structure by a region  849  of the first layer of the dielectric material  830 . A width or pitch (p) of the region  849  of the first layer of the dielectric material  830  that separates each split row may be between 1.0 mm to 10 mm, for example about 1 mm. In some embodiments, each contact  815  of a split row connects to a single trace of the conductive traces  820 . In other embodiments, each contact  815  of a split row connects to two or more traces from the conductive traces  820 . For example, a left side of the split row may be connected with a first trace and a right side of the split row may be connected with a second trace. Alternatively, a multiplexer chip may be used to drive signals and thus the split row may be connected to multiple traces from the conductive traces  820 . In various embodiments, thirty-two split rows are positioned on the supporting structure  805  and exposed on the surface  845 ; however, it should be understood that more or less than thirty-two split rows can be positioned on the supporting structure  805 . For example, the supporting structure  805  can accommodate more or less split rows (10, 24, 30, 42, 48, 50 etc.) to enhance design flexibility for the first connector  800 . 
     As shown in  FIG. 8D , the supporting structure  805  may be shaped or folded such that the contacts  815  face inwardly. The supporting structure  805  may then be baked to thermoform the supporting structure  805  into a final shape, for example in a “U” shape. As shown in  FIG. 8E , the supporting structure  805  may then be inserted into a pre-defined jacket  855  through a slot opening  850 . In some embodiments, the jacket  855  is formed of a polymer material such as silicone. As shown in  FIG. 8F , the supporting structure  805  and jacket  855  are reflowed at 130° C.-150° C. (e.g.,  137 C) using the second layer of dielectric material  835  or optionally the substrate  825  as an adhesive to attach the supporting structure  805  to the jacket  855 . In some embodiments, the first layer of dielectric material  830  is a first type of polymer material, e.g., a high temperature liquid crystal polymer, that acts as an overlay for insulation, and the second layer of dielectric material  835  is a second type of polymer material, e.g., a low temperature liquid crystal polymer, that acts as the adhesive for bonding the supporting structure  805  to the jacket  855 . In other embodiments, the first layer of dielectric material  830  and the second layer of dielectric material  835  are a first type of polymer material, e.g., a high temperature liquid crystal polymer, that acts as an overlay for insulation, and the substrate  825  is a second type of polymer material, e.g., a low temperature liquid crystal polymer, that acts as an adhesive for bonding the supporting structure  805  to the jacket  855 , as shown in  FIG. 8F . Although the first connector  800  is shown in  FIG. 8D  and described with respect to a “U” shape, it should be understood that other shapes for the connector have been contemplated, for example, spherical cubed, torus, ellipsoid, etc. 
     As shown in  FIGS. 9A and 98 , the second connector  900  (e.g., the connector  765  as discussed with respect to  FIGS. 7A-7G ) may be formed of a core  905  and an inlaid supporting structure  910  with a predetermined layout  915  of contacts  920  and conductive traces  925 . As shown in  FIG. 9C  (cross-section of the second connector  900  along X-X from  FIGS. 9A and 9B ), the supporting structure  910  may comprise a first layer of dielectric material  930  and a second layer of dielectric material  935  with the conductive traces  925  buried between the first layer of dielectric material  930  and the second layer of dielectric material  935 . In some embodiments, the first layer of dielectric material  930  comprises at least one contact via  940  for each contact  920 . The contact via  940  may comprise a conductive material for electrically connecting each contact  920  to at least one trace of the conductive traces  925  such that each trace of the conductive traces  925  terminates at a contact  920 . The contact via  940  may be connected to the at least one trace of the conductive traces  925  directly or indirectly by way of a wiring layer (not shown). In some embodiments, the conductive material is lined on at least a portion of the walls of the via hole. In other embodiments, the conductive material fills the via hole. 
     In various embodiments, the contacts  920  are provided as split rows positioned in columns on sectors or faces of the supporting structure  910  (see, e.g.,  FIGS. 9A and 9B ). In some embodiments, the contacts  920  are exposed on the surface  945  of the supporting structure  910  (see, e.g.,  FIG. 9C ). For example, the contacts  920  may be raised above a surface of the supporting structure  910  (e.g., a top surface of the contacts  920  protrudes above a top surface of the supporting structure  910 ) and comprise an anti-abrasive finish. In certain embodiments, the contacts  920  are raised above the surface  945  of the supporting structure  910  by a predetermined distance. The predetermined distance is from 0.05 mm to 1.0 mm, for example about 0.5 mm. Moreover, each split row may be spaced apart from one another on the surface  945  of the supporting structure by a region  950  of the first layer of the dielectric material  930 . A width or pitch (p) of the region  950  of the first layer of the dielectric material  930  that separates each split row may be between 1.0 mm to 10 mm, for example about 1 mm. In some embodiments, each contact  920  of a split row connects to a single trace of the conductive traces  925 . In other embodiments, each contact  920  of a split row connects to two or more traces from the conductive traces  925 . For example, a left side of the split row may be connected with a first trace and a right side of the split row may be connected with a second trace. Alternatively, a multiplexer chip may be used to drive signals and thus the split row may be connected to multiple traces from the conductive traces  925 . In various embodiments, thirty-two split rows are positioned on the supporting structure  910  and exposed on the surface  945 ; however, it should be understood that more or less than thirty-two split rows can be positioned on the supporting structure  910 . For example, the supporting structure  910  can accommodate more or less split rows (10, 24, 30, 42, 48, 50 etc.) to enhance design flexibility for the second connector  900 . 
     As shown in  FIG. 9D , the supporting structure  910  may be shaped or folded on the core  905  (e.g., an injection molded core) such that the contacts  920  face outwardly. In various embodiments, the core  905  and the supporting structure  910  may be formed with a predetermined shape or profile  955  (e.g., a blade as shown in  FIG. 9D ). The predetermined shape or profile  955  acts essentially as a key to assist with alignment in insertion of the second connector  900  into the first connector  800 . As shown in  FIG. 9D , the shape or profile  955  comprises the one or more layers of dielectric material  930 / 935  at least partially wrapped around the core  905 , e.g., a “U” shaped wrapping. The first layer of dielectric material  930  may define an outer width (n) of the shape or profile  955  and the second layer of dielectric material  935  may define an inner width (n′) of the shape or profile  945 . The shape or profile  955  may further comprise the core  905  that at least partially fills a space interior of the shape or profile  955  defined by the inner width (n′) of the shape or profile  955 . The core  905  may be comprised of one or more layers of material such that the core  905  has a Shore durometer of greater than 70D. In some embodiments, the one or more layers of material of the core  905  is polyimide, liquid crystal polymer, parylene, polyether ether ketone, polyurethane, metal, or a combination thereof. In certain embodiments, the one or more layers of material of the core  905  is a TPU. Although the second connector  900  is shown in  FIG. 9D  and described with respect to a blade shape, it should be understood that other shapes for the connector have been contemplated, for example, spherical cubed, torus, ellipsoid, etc. 
     Once the core  905  and the supporting structure  910  are shaped, the core  905  and the supporting structure  910  may then be inserted into a heat shrink tube  960  (e.g., FEP Lay-Flat-m Heat Shrink) and baked to thermoform the core  905  and supporting structure  910  into a final shape, for example a blade, as shown in  FIG. 9D . The core  905  and the supporting structure  910  may be reflowed at 130° C.-150° C. (e.g., 137° C.) using the second layer of dielectric material  935  as an adhesive to attach the core  905  to the supporting structure  910 . In some embodiments, the first layer of dielectric material  930  is a first type of polymer material, e.g., a high temperature liquid crystal polymer, that acts as an overlay for insulation, and the second layer of dielectric material  935  is a second type of polymer material, e.g., a low temperature liquid crystal polymer, that acts as an adhesive for bonding the supporting structure  910  to the core  905 , as shown in  FIG. 9E . 
     VI. Multiplexor Connectors and Methods of Manufacture 
       FIG. 10A  shows a neuromodulation system  1000  (e.g., the neuromodulation system  100  described with respect to  FIG. 1 ) in accordance with aspects of the present disclosure. In various embodiments, the neuromodulation system  1000  comprises an implantable neurostimulator  1005  and a lead assembly  1007 . The lead assembly  1007  includes two or more cables  1010 , a proximal end  1011 , and a distal end  1012 . In some embodiments, the two or more cables  1010  comprise a high density cable and a low density cable. As used herein, “a high density cable” is a cable with more conductive traces than the “low density cable”. For example, the “high density cable” may have at least sixteen conductive traces, and the “low density cable” may have anywhere from one to fifteen conductive traces. Each cable  1010  may comprise a supporting structure  1015  and a plurality of conductive traces  1020  formed on a portion of the supporting structure  1015 . In some embodiments, the supporting structure  1015  is made of one or more layers of dielectric material (i.e., an insulator). The dielectric material may be selected from the group of electrically flexible nonconductive materials consisting of organic or inorganic polymers, polyimide-epoxy, epoxy-fiberglass, and the like. In certain embodiments, the dielectric material is a polymer of imide monomers (i.e., a polyimide), a liquid crystal polymer (LCP) such as Kevlar®, parylene, polyether ether ketone (PEEK), or combinations thereof. In other embodiments, the supporting structure  1015  is made of one or more layers of dielectric material formed on a substrate. The substrate may be made from any type of metallic or non-metallic material. 
     In various embodiments, the one or more conductive traces  1020  are a plurality of traces, for example, two or more conductive traces or from two to twenty-four conductive traces. The plurality of conductive traces  1020  are comprised of one or more layers of conductive material. The conductive material selected for the one or more conductive traces  1020  should have good electrical conductivity and may include pure metals, metal alloys, combinations of metals and dielectrics, and the like. For example, the conductive material may be platinum (Pt), platinum/iridium (Pt/Ir), titanium (Ti), gold/titanium (Au/Ti), or any alloy thereof. In some embodiments, it is also desirable that the conductive material selected for the one or more conductive traces  1020  have a CTE that is approximately equal to that of the CTE of the supporting structure  1015 . 
     As shown in  FIG. 10A , the lead assembly  1007  may further comprise an electrode assembly  1025  formed on a supporting structure  1027 . The supporting structure  1027  may provide support for microelectronic structures including one or more electrodes  1030 , a wiring layer  1032 , and optional contact(s)(not shown). The electrode assembly  1025  may be located at the distal end  1012  of the lead assembly  1007 . The one or more electrodes  1030  are in electrical connection with one or more conductive traces of the plurality of conductive traces  1020 , for example, via the wiring layer  1032  and optionally the contact(s). In various embodiments, the supporting structure  1015  of at least one cable  1010  and the supporting structure  1027  of the electrode assembly  1025  are the same structure (i.e., the supporting structure is continuous), which thus creates a monolithic structure. In alternative embodiments, the supporting structure  1015  of at least one cable  1010  and the supporting structure  1027  of the electrode assembly  1025  are different structures but are connected such that there is an electrical connection between the plurality of conductive traces  1020 , wiring layer  1032 , and the one or more electrodes  1030 . 
     As shown in  FIGS. 10A and 10B  the lead assembly  1007  may further comprise one or more connectors  1035  for connecting the two or more cables  1010  to one or more multiplexor chips  1040 . Each connector  1035  comprises a package  1037 , the one or more multiplexor chips  1040 , and a connection assembly  1042 . In various embodiments, the package  1037  comprises a housing  1043 , the one or more multiplexor chips  1040 , distal feedthroughs  1045 , and proximal feedthroughs  1046 , as shown in  FIG. 10B . In some embodiments, the multiplexer chips  1040  and other active/passive electronic components are hermetically scaled within the package  1037  with distal feedthroughs  1045  and proximal feedthroughs  1046  (e.g., vertical feedthroughs). The distal feedthroughs  1045  are contact vias comprising a conductive material for electrically connecting the conductive traces or channels  1020 ′ from a high density distal cable  1010 ′ (e.g., the cable connected to the electrode assembly) to distal channel inputs  1048  of the multiplexor chips  1040 , respectively, as shown in  FIGS. 10B and 10C . The proximal feedthroughs  1046  are contact vias comprising a conductive material for electrically connecting the conductive traces or channels  1020 ″ from a low density proximal cable  1010 ″ (e.g., the cable connected to the neurostimulator) to proximal channel inputs  1049  of the multiplexor chips  1040 , respectively, as shown in  FIGS. 10B and 10C . As shown in  FIG. 10C , a multiplexor chip  1040  may be used in the package  1037  to reduce the channel count of the high density distal cable  1010 ′ from a greater number (e.g., 16, 32, 40, etc.) to a lower channel count (e.g., 4, 8, 12, etc.) of the low density cable  1010 ″. The channel count of the high density distal cable  1010 ′ and/or the low density proximal cable  1010 ″ may be expanded by adding more multiplexor ships  1040  to the package  1037  or more connectors  1035  to the lead assembly  1007 . 
     In various embodiments, the connection assembly  1042  comprises a supporting structure  1050 , as shown in  FIG. 10D . In some embodiments, the supporting structure  1050  is comprised of one or more layers of dielectric material (i.e., an insulator). The layers of dielectric material of the supporting structure  1050  may be formed in a FPCB process with metallization layers (e.g., vias or wiring layers) for interconnection. In other embodiments, the supporting structure  1050  is made of one or more layers of dielectric material and a coating of a thin layer of a polymer such as TPU. The dielectric material of the supporting structure  1050  may be selected from the group of electrically flexible nonconductive materials consisting of organic or inorganic polymers, polyimide-epoxy, epoxy-fiberglass, and the like. In certain embodiments, the dielectric material is a polymer of imide monomers (i.e., a polyimide), a liquid crystal polymer (LCP) such as Kevlar®, parylene, polyether ether ketone (PEEK), or combinations thereof. 
     In some embodiments, distal conductive traces  1055  and distal contacts  1060  (i.e., electrically conductive elements, pins, wires, tabs, pads, etc.) are formed on the supporting structure  1050  (see, e.g.,  FIG. 10D ). In some embodiments, proximal conductive traces  1065  and proximal contacts  1070  (i.e., electrically conductive elements, pins, wires, tabs, pads, etc.) are formed on the supporting structure  1050  (see, e.g.,  FIG. 10D ). The conductive traces  1055 / 1065  and contacts  1060 / 1070  may be comprised of one or more layers of conductive material for electrical conductivity. The conductive material selected for the conductive traces  1055 / 1065  and contacts  1060 / 1070  should have good electrical conductivity and may include pure metals, metal alloys, combinations of metals and dielectrics, and the like. For example, the conductive material may be platinum (Pt), platinum/iridium (P/Ir), titanium (Ti), gold/titanium (Au/Ti), or any alloy thereof. In some embodiments, it is also desirable that the conductive material selected for the conductive traces  1055 / 1065  and contacts  1060 / 1070  have a CTE that is approximately equal to that of a CTE of the supporting structure  1050 . In some embodiments, the supporting structure  1015 ′ of the distal cable  1010 ′ and the supporting structure  1050  of the connection assembly  1042  are the same structure (i.e., the supporting structure is continuous), which thus creates a monolithic cable. In alternative embodiments, the supporting structure  1015 ′ of the distal cable  1010 ′ and the supporting structure  1050  of the connection assembly  1042  are different structures but are connected such that there is an electrical connection between the conductive traces  1020 ′, the conductive traces  1055 , and the contacts  1060 . In some embodiments, the supporting structure  1015 ″ of the proximal cable  1010 ″ and the supporting structure  1050  of the connection assembly  1042  are the same structure (i.e., the supporting structure is continuous), which thus creates a monolithic cable. In alternative embodiments, the supporting structure  1015  of the proximal cable  1010 ″ and the supporting structure  1050  of the connection assembly  1042  are different structures but are connected such that there is an electrical connection between the conductive traces  1020 ″, the conductive traces  1065 , and the contacts  1070 . 
     In various embodiments, each trace from the one or more conductive traces  1055  terminates at a contact  1060  exposed on the outside surface of the supporting structure  1050 . Each contact from the one or more contacts  1060  is electrically connected to a distal feedthrough  1045 . As should be understood, each electrode from the electrodes  1030  is electrically connected via at least corresponding wiring layer  1032 , optional contact, conductive trace  1020 ′, conductive trace  1055 , contact  1060 , and distal feedthrough  1045  to a respective distal channel input  1048 . In other words, each electrode may be electrically connected to the multiplexer chip  1040 . Additionally, each trace from the one or more conductive traces  1065  terminates at a contact  1070  exposed on the outside surface the supporting structure  1050 . Each contact from the one or more contacts  1070  is electrically connected to a proximal feedthrough  1046 . As should be understood, the neurostimulator (e.g., the electronics module) is electrically connected via at least conductive trace  1020 ″, conductive trace  1065 , contact  1070 , and proximal feedthrough  1046  to a respective proximal channel input  1049 . In other words, the neurostimulator may be electrically connected to the multiplexer chip  1040 . Consequently, a high density number of electrodes  1030  may be connected via the multiplexer chip  1040  to a neurostimulator with a reduced or limited number of channels for sending and receiving input to and from the electrodes  1030 . 
     The one or more conductive traces  1055 / 1065  may be deposited onto a layer of the supporting structure  1050  by using thin film deposition techniques well known to those skilled in the art such as by sputter deposition, chemical vapor deposition, metal organic chemical vapor deposition, electroplating, electroless plating, and the like. In some embodiments, the thickness of the one or more conductive traces  1055 / 1065  is dependent on the particular impedance desired for conductor, in order to ensure excellent signal integrity (e.g., electrical signal integrity for stimulation or recording). For example, if a conductor having a relatively high impedance is desired, a small thickness of conductive material should be deposited onto a layer of the supporting structure  1050 . If, however, a signal plane having a relatively low impedance is desired, a greater thickness of electrically conductive material should be deposited onto a layer of the supporting structure  1050 . In certain embodiments, each of the one or more conductive traces  1055 / 1065  has a thickness (t). In some embodiments, the thickness (t) is from 0.5 μm to 25 μm or from 5 μm to 10 μm, for example about 5 μm or about 8 μm. In some embodiments, each of the one or more conductive traces  1055 / 1065  has a length (l) of about 1 mm to 100 mm or 1 cm to 3 cm, e.g., about 15 mm. In some embodiments, each of the one or more conductive traces  1055 / 1065  has a width (w) from 2.0 μm to 500 μm, for example about 30 μm or about 50 μm. 
     As shown in  FIGS. 11A and 11B , a connection assembly  1100  (e.g., the connection assembly  1042  as discussed with respect to  FIGS. 10A-10D ) may be formed of a supporting structure  1105  with a predetermined layout  1110  of distal contacts  1115 , distal conductive traces  1120 , proximal contacts  1125 , and proximal conductive traces  1130 . As shown in  FIG. 11C  (cross-section of the connection assembly  1100  along X-X from  FIGS. 11A and 11B ), the supporting structure  1105  may comprise a first layer of dielectric material  1135  and a second layer of dielectric material  1140  with the distal contacts  1115 , the distal conductive traces  1120 , the proximal contacts  1125 , and the proximal conductive traces  1130  disposed between the first layer of dielectric material  1135  and the second layer of dielectric material  1140 . For example, a pre-cut first layer of dielectric material  1135  may be formed over the second layer of dielectric material  1140  such that at least a portion of each of the distal contacts  1115  and the proximal contacts are exposed after reflow of the first layer of dielectric material  1135 . The distal contacts  1115  and proximal contacts  1125  are provided on the second layer of dielectric material  1140  in the predetermined layout  1110  to provide electrical contact with the distal feedthroughs (not shown) and proximal feedthroughs  1150  of a multiplexer chip package  1155 , respectively. 
     Once the distal contacts  1115 , distal conductive traces  1120 , proximal contacts  1125 , and proximal conductive traces  1130  are formed on the supporting structure  1105  and the first layer of dielectric material  1135  is positioned over the second layer of dielectric material  1140 , the supporting structure  1105  and the multiplexer chip package  1155  may then baked to thermoform the supporting structure  1105  into a final shape attached to the multiplexer chip package  1055 , as shown in  FIG. 11D . The supporting structure  1105  may be reflowed at 130° C.-150° C. (e.g., 137° C.) using the first layer of dielectric material  1135  as an adhesive to attach the supporting structure  1105  to the multiplexer chip package  1055 . During bonding, each of the distal feedthroughs  1115  and proximal feedthroughs  1050  is compressed against respective distal contacts  1115  and proximal contacts  1125  to form the electrical connection. Under heat and pressure, the first layer of dielectric material  1135  melts, deforms and reflows to seal the gaps. In some embodiments, the first layer of dielectric material  1135  is a first type of polymer material, e.g., a low temperature liquid crystal polymer, that acts as an adhesive for bonding the supporting structure  1105  to the core, and the second layer of dielectric material  1140  is a second type of polymer material, e.g., a high temperature liquid crystal polymer, that acts as an overlay for insulation, as shown in  FIG. 11D . 
     Advantageously, the low temperature liquid crystal polymer is used for adhesiveless bonding and encapsulation, to eliminate the needs of conductive paste or solder. Moreover, the use of low temperature liquid crystal polymer adhesiveless bonding is also a long-term solution to prevent degradation of adhesive and electrical crosstalk. 
     While the connectors have been described at some length and with some particularity with respect to a specific design and/or performance need, it is not intended that the connectors be limited to any such particular design and/or performance need. Instead, it should be understood the connectors described herein are exemplary embodiments, and that the connectors are to be construed with the broadest sense to include variations of the specific design and/or performance need described herein, as well as other variations that are well known to those of skill in the art. In particular, the shape and location of components and layers in the connectors may be adjusted or modified to meet specific design and/or performance needs. Furthermore, it is to be understood that other structures have been omitted from the description of the connectors for clarity. The omitted structures may include insulating layers, interconnect components, passive devices, etc. 
     While the invention has been described in detail, modifications within the spirit and scope of the invention will be readily apparent to the skilled artisan. It should be understood that aspects of the invention and portions of various embodiments and various features recited above and/or in the appended claims may be combined or interchanged either in whole or in part. In the foregoing descriptions of the various embodiments, those embodiments which refer to another embodiment may be appropriately combined with other embodiments as will be appreciated by the skilled artisan. Furthermore, the skilled artisan will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention.