Abstract:
In one embodiment, a method of fabricating a lead comprises: providing a lead body comprising a plurality of conductive wires; providing a flex film connector structure, the flex film connector structure comprising a plurality of conductive pads on a first portion of the flex film connector structure, a plurality of contacts on a second portion of the flex film connectors, and a plurality of traces electrically connecting the plurality of conductive pads with the plurality of contacts; placing the first portion of the flex film connector adjacent to a cross-section of one end of the lead body; electrically coupling the plurality of conductive pads of the flex film connector structure to the plurality of conductive wires at the one end of the lead body; and wrapping the second portion of the flex film connector structure about the lead body to form a plurality of electrical contacts.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. application Ser. No. 12/361,807, filed Jan. 29, 2009, pending, which claims the benefit of U.S. Provisional Application No. 61/025,369, filed Feb. 1, 2008, the disclosures of which are fully incorporated herein by reference for all purposes. 
     
    
     TECHNICAL FIELD 
       [0002]    The present application is generally related to a design for electrode and/or terminal contacts of a stimulation lead, a stimulation system, and a method of fabrication of a stimulation lead. 
       BACKGROUND 
       [0003]    Neurostimulation systems are devices that generate electrical pulses and deliver the pulses to nerve tissue to treat a variety of disorders. Spinal cord stimulation (SCS) is an example of neurostimulation in which electrical pulses are delivered to nerve tissue in the spine, typically for the purpose of treating chronic pain. While a precise understanding of the interaction between the applied electrical energy and the nervous tissue is not fully appreciated, it is known that application of an electrical field to spinal nervous tissue can effectively mask certain types of pain transmitted from regions of the body associated with the stimulated nerve tissue. Specifically, applying electrical energy to the spinal cord associated with regions of the body afflicted with chronic pain can induce “paresthesia” (a subjective sensation of numbness or tingling) in the afflicted bodily regions. Thereby, paresthesia can effectively mask the transmission of non-acute pain sensations to the brain. 
         [0004]    Neurostimulation systems generally include a pulse generator and one or several leads. The pulse generator is typically implemented using a metallic housing that encloses circuitry for generating the electrical pulses. The pulse generator is usually implanted within a subcutaneous pocket created under the skin by a physician. The leads are used to conduct the electrical pulses from the implant site of the pulse generator to the targeted nerve tissue. The leads typically include a lead body of an insulative polymer material with embedded wire conductors extending through the lead body. Electrodes on a distal end of the lead body are coupled to the conductors to deliver the electrical pulses to the nerve tissue. 
         [0005]    Leads are typically adapted to couple with electrical connectors enclosed within a header structure of the implantable pulse generator. “Terminal” contacts are fabricated on a proximal end of the lead to facilitate the electrical coupling. The terminal contacts are usually fabricated in substantially the same manner as the fabrication of electrodes on a distal end of the lead. Typically, an aperture is made in the lead body to expose a conductive wire within the lead body, a conductive connector is disposed within the aperture, and a metal ring is swaged or crimped around the lead body and is placed in electrical contact with the conductive connector. 
       SUMMARY 
       [0006]    In one embodiment, a method of fabricating a lead comprises: providing a lead body comprising a plurality of conductive wires; providing a flex film connector structure, the flex film connector structure comprising a plurality of conductive pads on a first portion of the flex film connector structure, a plurality of contacts on a second portion of the flex film connectors, and a plurality of traces electrically connecting the plurality of conductive pads with the plurality of contacts; placing the first portion of the flex film connector adjacent to a cross-section of one end of the lead body; electrically coupling the plurality of conductive pads of the flex film connector structure to the plurality of conductive wires at the one end of the lead body; and wrapping the second portion of the flex film connector structure about the lead body to form a plurality of electrical contacts. 
         [0007]    The foregoing has outlined rather broadly certain features and/or technical advantages in order that the detailed description that follows may be better understood. Additional features and/or advantages will be described hereinafter which form the subject of the claims. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the appended claims. The novel features, both as to organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  depicts a flex film connector according to one representative embodiment. 
           [0009]      FIG. 2  depicts one end of a stimulation lead according to one representative embodiment. 
           [0010]      FIGS. 3A and 3B  depict respective flowcharts for fabricating a flex film connector according to some representative embodiments. 
           [0011]      FIG. 4  depicts a flowchart for fabrication of a stimulation lead according to one representative embodiment. 
           [0012]      FIG. 5  depicts a stimulation system according to one representative embodiment. 
           [0013]      FIG. 6  depicts an annular portion of a flex film connector according to one representative embodiment. 
           [0014]      FIG. 7  depicts a rectangular portion of a flex film connector according to one representative embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    Some representative embodiments are directed to a stimulation lead that comprises a flex film with conductive bands to couple with the electrical connectors of an implantable pulse generator. By employing electrical contacts formed on a flex film substrate, the spacing between electrical contacts can be relatively close. Accordingly, a smaller header design can be employed and, hence, a smaller implantable pulse generator can be achieved. In other embodiments, the stimulation electrodes adapted to provide electrical pulses to tissue of a patient are formed on a flex film substrate. The use of a flex film design for terminals and/or electrodes may allow the lead fabrication process to occur in a more efficient manner. 
         [0016]      FIG. 1  depicts flex film connector  100  that comprises a plurality of electrical contacts  101  according to one representative embodiment. Flex film connector  100  is preferably implemented by providing metal contacts  101 , traces  102 , and pads  103  adjacent to insulative substrate  104 . Insulative substrate  104  preferably comprises annular portion  105  and rectangular portion  106 . The insulative backing may be formed of urethane material, polyimide material, or preferably polyetheretherketone (PEEK) material, liquid crystal polymer (LCP) material, polyetherketoneketone (PEKK) material, as examples. The various metal components can be disposed on the insulative backing using any suitable number of techniques. For example, a continuous metal film may be bonded to the insulative backing and the various metal components can be defined by etching away metal between the discrete components using a programmable YAG laser system. Photolithographic and metallization fabrication processes can also be utilized to define and deposit the various metal components onto insulative substrate  104 . In another alternative embodiment, micro-printing is employed to deposit the conductive material. 
         [0017]    As shown in  FIG. 1 , flex film connector  100  comprises annular structure  105  on which a plurality of pads  103  are formed, deposited, bonded, or otherwise provided. Annular structure  105  is approximately sized according to the cross-section of a stimulation lead body to which flex film connector  100  will be attached. Pads  103  on annular structure  105  are preferably arranged according to the same pattern as the conductive wires within the stimulation lead. In some embodiments, the size of pads  103  is relatively large as compared to the size of the wire conductors to provide an amount of tolerance for variability of the position of the conductive wires within a lead. In one embodiment, a hole or slit (not shown) may be provided in each pad  103 . A respective wire of the lead body may be exposed and threaded through the hole or slit in each pad  103 . The respective wire can then be welded or soldered to pad  103  to facilitate the electrical connection. 
         [0018]    Each pad  103  is, in turn, electrically coupled to a respective metal contact  101  by a corresponding trace  102  (only one trace  102  is annotated in  FIG. 1  for the sake of clarity). In the embodiment shown in  FIG. 1 , each contact  101  is separated into two portions on the left and right sides of rectangular portion  106  of insulative substrate  104 . One side of each contact  101  is intended to be electrically coupled to the other side when flex film connector  100  is attached to the stimulation lead. 
         [0019]      FIG. 2  depicts flex film connector  100  coupled to stimulation lead  200 . Annular structure  105  is disposed at the proximal end of the stimulation lead. Pads  103  are preferably electrically coupled to the conductive wires (not shown) within stimulation lead  200 . The remaining portion of flex film connector  100  is wrapped around the body of stimulation lead  200  such that contacts  101  substantially circumscribe the lead body. Although flex film connector  100  as shown in  FIG. 1  is only adapted to provide eight terminal contacts, any suitable number (e.g., sixteen or thirty-two) of terminal contacts may be employed according to alternative embodiments. 
         [0020]      FIG. 3A  depicts a flowchart for fabricating flex film connector  100  according to one representative embodiment. In  301 , a rectangle or other suitable portion of conductive material is provided. Although the following discussion only refers to fabrication of a single flex film connector  100 , multiple flex film connectors  100  can be fabricated in parallel on suitably sized portion of conductive material according to some representative embodiments. The conductive material can be gold, conductive composite materials, medical grade stainless steel, platinum iridium, and/or the like. The thickness of the conductive material is selected to allow the conductive material to be relatively flexible. As an example, a suitable thickness for stainless steel would be about 25.4 microns (1 mil). 
         [0021]    In  302 , a thin coating of urethane (or a similar polymer) is spin coated on one side of the conductive material for the purpose of achieving a surface with greater adhesive qualities. In  303 , a urethane film (or any other suitable polymer) is applied to the same side as the spin coat and is laminated to the conductive material. 
         [0022]    In  304 , contacts  101 , traces  102 , and pads  103  are created by scribing their respective forms in the conductive material using a suitable laser (e.g., a programmable YAG laser system). Specifically, the programmable YAG laser system traces its output beam along the contour defined between the various metal components. The application of the laser energy separates the desired metal components from the extraneous material. In  305 , the extraneous metal material is optionally removed or peeled away from the insulative backing, leaving contacts  101 , traces  102 , and pads  103  in place. 
         [0023]    In  306 , a thin top coat of insulative material is applied to portions of the assembly. For example, a spin coat of an insulative material can be applied over annular structure  105  and/or traces  102 . Contacts  101  are left exposed, since contacts  101  are intended to make electrical contact within the header of an implantable pulse generator. 
         [0024]    In  307 , electrical connections are made for the purpose of exposing portions of pads  103  on the posterior side of flex film connector  100  to permit electrical coupling with the lead wires of a stimulation lead (see the description of the flowchart of  FIG. 4  below). Selected portions of the insulative material could be removed to expose portions of pads  103 . A CO 2  laser, a YAG laser, other suitable laser could be utilized for this purpose. Alternatively, conductive material could be fabricated on the backside of flex film connector and typical via processing can be used to facilitate the subsequent electrical coupling with the conductors of the lead. 
         [0025]      FIG. 3B  depicts a flowchart for fabricating flex film connector  100  according to one representative embodiment. In  351 , a flexible substrate is provided. The substrate can be formed of urethane material, polyimide material, or preferably polyetheretherketone (PEEK) material, liquid crystal polymer (LCP) material, polyetherketoneketone (PEKK) material, as examples. In  352 , a conductive base layer is provided to facilitate subsequent provision of the metal that will be utilized to form the traces, pads, and contacts. 
         [0026]    A resist layer is provided ( 353 ) and the resist layer is patterned ( 354 ). The patterned resist layer is exposed to radiation at an appropriate wavelength ( 355 ). The exposed portions of the resist layers are removed ( 356 ). In the removed areas, pads, traces, and contacts are formed using a suitable metallization process ( 357 ). The remaining portion of the resist layer is removed ( 358 ) and the remaining conductive base layer is removed ( 359 ) leaving the substrate with electrically isolated sets of pads, traces, and contacts on the substrate. An insulative coating is preferably provided over the traces and pads ( 360 ). Posterior portions of the pads are exposed for subsequent electrical coupling to conductive wires of a stimulation lead ( 361 ). 
         [0027]      FIG. 4  depicts a flowchart for fabricating a stimulation lead according to one representative embodiment. In  401 , a stimulation lead body is provided. Any known or later developed stimulation lead body can be provided. An example of a lead body that can be employed according to one representative embodiment is described in U.S. Patent Application Publication No. 20050027339, entitled “System and method for providing a medical lead body,” which is incorporated herein by reference. The lead body may comprise a single layer of conductive wires or multiple layers. If the stimulation lead comprises multiple layers of conductive wires, annular portion  105  would be modified to arrange pads  103  in a pattern corresponding to the cross-sectional arrangement of conductive wires in the lead body. The conductive wires within the lead body may be disposed in a linear arrangement, a helical manner, or any other suitable pattern along the longitudinal length of the lead body. 
         [0028]    In  402 , annular portion  105  of flex film connector  100  is placed over the proximal or distal face of the stimulation lead such that pads  103  are placed immediately adjacent to the respective ends of the conductive wires within the stimulation lead. In  403 , pads  103  are mechanically and electrically coupled to the conductive wires. Laser welding, resistive welding, conductive epoxy bonding, or any other suitable technique may be employed. 
         [0029]    In  404 , rectangular portion  106  of flex film connector  100  is wrapped about the lead body. In  405 , the rectangular portion  106  of flex film connection  100  is suitable coupled or bonded to the lead body, e.g., glued thereto, to mechanically retain flex film connector  100  in an annular manner about the lead body. In another embodiment, respective distal portions of contacts  101  could be welded to each other about the lead body. 
         [0030]    Electrical contacts are preferably fabricated on the other end of the stimulation lead. The same techniques can be used to create the other electrical contacts using another flex film connector  100 . Alternatively, a conventional or other process may be utilized to fabricate the other electrical contacts. An example of a conventional electrode contact fabrication technique is described in U.S. Pat. No. 6,216,045, entitled “Implantable lead and method of manufacturing,” which is incorporated herein by reference. The electrical contacts on the other end of the stimulation lead could also be disposed on a paddle structure or other structure suitable for stimulation of tissue of a patient. 
         [0031]      FIG. 5  depicts stimulation system  500  according to one representative embodiment. As shown in  FIG. 5 , lead  200  is coupled to one of apertures in header  510  of implantable pulse generator (IPG)  550 . Each aperture is designed to hold electrical connectors or connections that couple to terminal contacts  101  of a respective lead  200  or an extension lead. The size of header  510  may be significantly reduced, since the density of contacts  101  of lead  200  is relatively high. Accordingly, the overall size of IPG  550  can be reduced. The electrical connectors in each aperture electrically couple to internal components contained within the sealed portion  520  of IPG  550 . The sealed portion  520  contains the pulse generating circuitry, communication circuitry, control circuitry, and battery (not shown) within an enclosure to protect the components after implantation within a patient. The control circuitry controls the pulse generating circuitry to apply varying pulses to the patient via electrodes  530  of lead  200  according to multiple parameters (e.g., amplitude, pulse width, frequency, etc.). As previously mentioned, electrodes  530  could be also fabricated using a flex film connector  100  according to some representative embodiments. The parameters are set by an external programming device (not shown) via wireless communication with IPG  550 . 
         [0032]      FIG. 6  depicts another annular portion  600  suitable for a flex film connector  100  according to another representative embodiment. As shown in  FIG. 6 , annular portion  600  comprises aperture  601  in the insulative substrate. In one embodiment, when annular portion  600  is electrically coupled to the conductive wires of a stimulation lead, a cap structure could be pressed against annular portion  600  and a portion of the cap structure inserted through the aperture  601  and into the stylet lumen of the stimulation lead. Suitable adhesive could be employed to facilitate mechanical coupling. In such a manner, the cap structure could be utilized to provide mechanical protection of annular portion  600 . 
         [0033]      FIG. 7  depicts rectangular portion  700  suitable for a flex film connector  100  according to another representative embodiment. As shown in  FIG. 700 , rectangular portion  700  is asymmetric with all of the contacts  101  on one side of portion  700 . Depending upon the implementation of the internal electrical connectors of the header of the implantable pulse generator, contacts  101  need not necessarily completely circumscribe the lead body. For example, the length of contacts  101  could be selected to traverse one-half of the circumference of the lead body (if desired). 
         [0034]    In another embodiment, flex film connector  100  could be adapted to implement the electrode contacts of a stimulation lead. Flex film connector  100  would preferably size contacts  101  to function as electrodes in such a manner to permit operation according to appropriate current density constraints. Also, the spacing of contacts  101  would be adapted to permit effective electrode selection to permit optimization of stimulation therapies upon implantation of the stimulation lead as is known in the art. In other embodiments, contacts  101  could be adapted to provide directional electrodes, i.e., individual contacts  101  would only occupy a limited radial range along the circumference of a stimulation lead. For example, contacts  101  could follow the electrode designs or patterns shown in U.S. Pat. No. 7,047,084, which is incorporated herein by reference. In another embodiment, flex film connector  100  could be used to provide the terminals for a lead extension in lieu of a stimulation lead. 
         [0035]    Although certain embodiments have been discussed for use in providing an SCS therapy for patients, electrode contacts and/or terminal contacts can be employed for any type of stimulation system according to other embodiments. Stimulation leads having terminal contacts according to some representative embodiments may be used for cardiac applications, peripheral nerve stimulation or peripheral nerve field stimulation, deep brain or cortical stimulation, gastric pacing, and/or the like as other examples. 
         [0036]    Although certain representative embodiments and advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate when reading the present application, other processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the described embodiments may be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.