Patent Publication Number: US-2022219005-A1

Title: Redundant traces for flexible circuits used in an energy delivery device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of application Ser. No. 16/556,701, filed Aug. 30, 2019, which claims the benefit of U.S. Provisional Application No. 62/725,679, filed Aug. 31, 2018, the content of each of which is fully incorporated by reference herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The invention generally relates to flexible circuits for an energy delivery device used to treat tissue with electromagnetic energy. 
     BACKGROUND 
     Certain types of energy delivery devices are capable of treating a patient&#39;s tissue with electromagnetic energy. These energy delivery devices, which emit electromagnetic energy in different regions of the electromagnetic spectrum for tissue treatment, may be used to treat a multitude of diverse skin conditions. For example, the energy delivery device may non-ablatively and non-invasively treat a skin condition or other type of tissue condition. 
     One variety of these energy delivery devices emits high frequency electromagnetic energy in the radio-frequency (RF) band of the electromagnetic spectrum. The high frequency energy may be used to treat skin tissue by passing high frequency energy through a surface of the skin, while actively cooling the skin to prevent damage to the skin&#39;s epidermal layer closer to the skin surface. The high frequency energy heats tissue beneath the epidermis to a temperature sufficient to denature collagen, which causes the collagen to contract and shrink and, thereby, tighten the tissue. Treatment with high frequency energy also causes a mild inflammation. The inflammatory response of the tissue causes new collagen to be generated over time (between three days and six months following treatment), which results in further tissue contraction. 
     Typically, energy delivery devices include a treatment tip that is placed in contact with, or proximate to, the patient&#39;s skin surface and that emits electromagnetic energy that penetrates through the skin surface and into the tissue beneath the skin surface. The non-patient side of the energy delivery device, such as an electrode for high frequency energy, in the treatment tip may be sprayed with a coolant or cryogen spray. Heat is conducted from the warmer tissue to the cooler treatment tip, which cools tissue to a shallow depth beneath the skin surface. A controller may trigger the coolant spray based upon an evaluation of the temperature readings received as feedback from temperature sensors in the treatment tip. 
     The cryogen spray may be used to pre-cool superficial tissue before delivering the electromagnetic energy. When the electromagnetic energy is delivered, the superficial tissue that has been cooled is protected from thermal effects. The target tissue that has not been cooled or that has received nominal cooling will warm up to therapeutic temperatures resulting in the desired therapeutic effect. The amount or duration of pre-cooling can be used to select the depth of the protected zone of untreated superficial tissue. After the delivery of electromagnetic energy has concluded, the cryogen spray may also be employed to prevent or reduce heat originating from treated tissue from conducting upward and heating the more superficial tissue that was cooled before treatment with the electromagnetic energy. 
     The electrode and temperature sensors may be arranged on a flexible circuit inside the treatment tip. The temperature sensors are used to measure the temperature at the interface between the flexible circuit and the patient&#39;s skin. The flexible circuit may include a polyimide layer and traces containing a conductive material that provide conductive paths routed over the polyimide layer to and from the electrode and temperature sensors. In the assembly of the treatment tip, the flexible circuit is folded about a rigid support member with the electrode facing a window in the tip housing. During patient treatment, the flexible circuit experiences repeated flexure when the tip is pressed against the patient&#39;s skin numerous times. The repeated flexure may cause traces to crack and fail, especially at creases at which the flexible circuit is folded and that may experience locally-high stress. Trace failure results in the premature failure of the entire treatment tip. For example, trace failure may interrupt the ability to receive readings from the temperature sensors. 
     Improved flexible circuits for an energy delivery device used to treat tissue with electromagnetic energy are needed. 
     SUMMARY 
     In an embodiment, an apparatus includes an energy delivery device with a flexible circuit. The flexible circuit includes an electronic component and a trace connected with the electronic component. The trace has a plurality of sections that provide parallel current paths over a portion of the trace. 
     In an embodiment, an apparatus includes an energy delivery device with a flexible circuit. The flexible circuit includes an energy delivery device including a flexible circuit, the flexible circuit including an electronic component and a plurality of traces connected with a terminal of the electronic component to provide parallel current paths to the terminal of the electronic component. 
     In embodiments of the invention, two or more redundant electrically-conductive traces, or traces with two or more redundant electrically-conductive sections or segments, may be routed to each side of one or more thermal sensors (e.g., thermistors) on a treatment tip, which may be attached to or integral with a handpiece. The treatment tip and handpiece may be used as an energy delivery device to apply electromagnetic energy to a patient. The traces, or the segments of the traces, may provide electrical redundancy in the event of trace fracture or failure and, therefore, enhanced reliability. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above and the detailed description of the embodiments given below, serve to explain the principles of the invention. In the drawings, like reference numerals are used to indicate like parts in the various views. 
         FIG. 1  is a diagrammatic view of a treatment system with a handpiece, a treatment tip, a console, and a generator. 
         FIG. 2  is a perspective view of an assembly consisting of an embodiment of the handpiece and treatment tip for use with the treatment system of  FIG. 1 . 
         FIG. 3  is an exploded view of the assembly of  FIG. 2 . 
         FIG. 4  is an exploded view of the treatment tip of  FIGS. 2, 3  in which the flexible circuit is shown in a folded condition. 
         FIG. 5  is a rear view of the treatment tip of  FIGS. 2, 3  showing an electrode and temperature sensors on the flexible circuit. 
         FIG. 6  is a rear view in which the flexible circuit of  FIG. 4  is shown in an unfolded condition. 
         FIG. 7  is an enlarged view of a portion of  FIG. 6 . 
         FIG. 8  is a rear view of an assembled treatment tip showing an electrode and temperature sensors on a flexible circuit in accordance with alternative embodiments. 
         FIG. 9  is an enlarged view similar to  FIG. 7  showing a portion of the flexible circuit of  FIG. 8  in an unfolded condition. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings,  FIGS. 1-7  disclose a treatment apparatus  10  that generally includes a handpiece  12 , a treatment tip  14  that may be coupled in a removable and releasable manner with the handpiece  12 , a console generally indicated by reference numeral  16 , and a system controller  18 . The system controller  18 , which is incorporated into the console  16 , orchestrates the global operation of the different individual components of the treatment apparatus  10 . Under the control of the system controller  18  and any operator interaction with the system controller  18  at the console  16  and with controls at the handpiece  12 , the treatment apparatus  10  is adapted to deliver electromagnetic energy in a high frequency band of the electromagnetic spectrum to a region of a patient&#39;s tissue. The electromagnetic energy, which may be delivered non-invasively and non-ablatively, heats the tissue to a targeted temperature range over a tissue depth. The elevation in temperature may produce for example, changes in collagen fibers that achieve a desired treatment result, such as removing or reducing wrinkles and otherwise tightening the skin to thereby improve the appearance of a patient  20  receiving the treatment. 
     The treatment tip  14  may provide, either alone or in combination with the handpiece  12 , an energy delivery member that includes a treatment electrode  24 . In a representative embodiment, the treatment electrode  24  may be arranged on a flexible circuit  74  that includes an electrically-insulating substrate  30  composed of a non-conductive dielectric material and a region  28  composed of an electrical conductor carried on the electrically-insulating substrate  30 . The electrically-insulating substrate  30  may have a contact side  32  that is placed in contact with a patient&#39;s skin surface and a non-contact side  34  that is opposite from the contact side  32 . The conductor region  28  of the treatment electrode  24  is physically carried on the non-contact side  34  of the substrate  30  and is therefore separated by the substrate  30  from the skin surface during treatment. 
     The substrate  30  of the flexible circuit  74  may include a thin flexible base polymer film with thin conductive leads or traces  49 . Some of the leads  49  may electrically couple the conductor region  28  with one or more contact pads  57 . The base polymer film of substrate  30  may be, for example, polyimide or another material with a relatively high electrical resistivity and a relatively high thermal conductivity. The traces  49  and contact pads  57  may contain copper or another conductor characterized by a relatively high electrical conductivity. The traces  49  and contact pads  57  may be formed by depositing a layer of the conductor on the substrate  30  and patterning the conductor layer with lithography and etching processes. Instead of the representative single conductor region  28 , the conductor region  28  providing the treatment electrode  24  may be segmented into plural individual electrodes that can be individually powered to sequentially deliver electromagnetic energy to the tissue. 
     The treatment electrode  24  is electrically coupled through the traces  49  and contact pads  57  by a set of insulated and shielded conductors  22  that extend from the handpiece  12  to the generator  26  at the console  16 . The generator  26  is configured to generate the electromagnetic energy used in the treatment to impart a therapeutic effect by heating target tissue beneath the patient&#39;s skin surface. The generator  26 , which may have the form of a high frequency power supply, is equipped with an electrical circuit operative to generate high frequency electrical current, typically in the radio-frequency (RF) band of the electromagnetic spectrum. The electrical circuit in the generator  26  converts a line alternating current voltage into drive signals for the treatment electrode  24 . The drive signals have parameters (e.g., energy content and duty cycle) appropriate for the amount of power and the mode of operation that have been selected by the treating clinician. In alternative embodiments, the treatment apparatus  10  may be configured to deliver energy in the infrared band, microwave band, or another high frequency band of the electromagnetic spectrum, rather than within the RF band, to the patient&#39;s tissue. 
     The system controller  18  may include at least one processor  23  coupled to a non-transitory memory  25 . The at least one processor  23  may represent one or more microprocessors, and the memory  25  may represent the random access memory (RAM) comprising the main storage of system controller  18 , as well as any supplemental levels of memory, e.g., cache memories, non-volatile or backup memories (e.g., programmable or flash memories), read-only memories, etc. In addition, memory  25  may be considered to include memory storage physically located elsewhere in system controller  18 , e.g., any cache memory in a processor  23 , as well as any storage capacity used as a virtual memory, e.g., as stored on a mass storage device  27  or another computer (not shown) coupled to system controller  18  via a network. 
     The system controller  18  also typically receives a number of inputs and outputs for communicating information externally. For interface with a user or operator, system controller  18  typically includes one or more user input devices (e.g., a keyboard, a mouse, a trackball, a joystick, a touch screen, a keypad, a stylus, discrete buttons, and/or a microphone, among others) in the form of a user interface  29 . The user interface  29  may be used to deliver instructions to the system controller  18  to adjust the generator  26  and to establish treatment settings based upon operator input at the handpiece  12 . System controller  18  may also include a display  31  (e.g., a LED or LCD display panel, among others). 
     System controller  18  operates under the control of an operating system  33 , and executes or otherwise relies upon various computer software applications, components, programs, objects, modules, data structures, etc. In general, the routines executed by the system controller  18  to operate the treatment apparatus  10 , whether implemented as part of an operating system or a specific application, component, program, object, module or sequence of instructions, will be referred to herein as “computer program code.” The computer program code typically comprises one or more instructions that are resident at various times in various memory and storage devices in a computer, and that, when read and executed by one or more processors in a computer, causes that computer to perform the steps necessary to execute steps or elements embodying the various aspects of the embodiments of the invention. 
     The system controller  18  includes digital and/or analog circuitry that interfaces the processor  23  with the generator  26  for regulating the power delivered from the generator  26  to the treatment electrode  24 . Generator software  35  resides as an application (i.e., program code) in the memory  25  and is executed by the processor  23  in order to issue commands that control the operation of the generator  26 . The system controller  18  includes digital and/or analog circuitry that interfaces the processor  23  with a cryogen supply  65 , such as a system configured to deliver pressurized cryogen to a control valve (not shown) at the handpiece  12  and to control the control valve for regulating the cryogen delivered to the treatment electrode  24 . Cryogen software  37  resides as an application (i.e., program code) in the memory  25  and is executed by the processor  23  in order to issue commands that control the operation of the cryogen supply  65  and control valve. Other types of cooling, such as conductive cooling, may be employed, and cooling, while preferable, may be optional. 
     During a tissue treatment involving the treatment electrode  24 , the substrate  30  is arranged between the conductor region  28  and the skin surface of the patient. Electromagnetic energy may be transmitted in a transcutaneous manner from the conductor region  28  through the thickness of substrate  30  and across the surface area of the portion to the tissue by capacitively coupling with the tissue of the patient  20 . 
     As best shown in  FIG. 4 , the treatment tip  14  includes temperature sensors  44 , such as thermistors, that are located on the non-contact side  34  of the substrate  30  that is not in contact with the patient&#39;s skin surface. Typically, the temperature sensors  44  are arranged about the perimeter of the conductor region  28  of the treatment electrode  24 . Temperature sensors  44  are constructed to detect the temperature of the treatment electrode  24  and/or treatment tip  14 , which may be representative of the temperature of the treated tissue. The measured temperature reflects the temperature of the treated tissue and may be used as feedback in a control loop controlling energy delivery and/or cooling of the skin surface. The treatment tip  14  may also include pressure sensors (not shown) for detecting physical contact between the treatment electrode  24  and the skin surface of the patient  20 . 
     An activation button  36 , which is accessible to the operator from the exterior of the handpiece  12 , is configured to be actuated to close a switch in a normally open circuit with the generator  26 . The closed circuit energizes the treatment electrode  24 . Actuation of the activation button  36  triggers delivery of the high frequency energy over a short timed delivery cycle to the target tissue. After a fixed amount of time has elapsed, the delivery of high frequency energy from the treatment electrode  24  to the tissue at the treatment site is discontinued. In a stamping mode of operation, the handpiece  12  is manipulated to position the treatment tip  14  near a different treatment site on the skin surface and another cycle of high frequency energy is delivered to the patient&#39;s tissue. This process may be repeated for an arbitrary number of treatment sites. 
     High frequency electrical current flowing between the treatment electrode  24  and the patient  20  is concentrated at the skin surface and the underlying tissue across the contacting surface area of the portion of the treatment electrode  24 . Capacitive coupling of the high frequency electromagnetic energy relies on energy transfer from the conductor region  28  through the dielectric material of the substrate  30  to create an electric field across the surface area where the treatment electrode  24  contacts the patient&#39;s body. The time-varying electric field induces electrical currents within the surrounding tissue beneath the skin surface. 
     Because of the natural resistance of tissue to electrical current flow, volumetric heating results within the tissue. The volumetric heating delivers a therapeutic effect to the tissue near the treatment site. For example, heating to a temperature of 50° C. or higher may contract collagen, which may result in tissue tightening or another aesthetic effect to improve the patient&#39;s appearance. The heating depth in the tissue is based upon the size and geometry of the treatment electrode  24  and, contingent upon the selection and configuration of the treatment tip  14 , can be controlled to extend from a few hundred micrometers beneath the skin surface to several millimeters. 
     A non-therapeutic passive return electrode  38  may be used to electrically couple the patient  20  with the generator  26 . During patient treatment, the high frequency current flows from the treatment electrode  24  through the treated tissue and the intervening bulk of the patient  20  to the return electrode  38  and then to the generator  26  through conductors inside a return cable  40  to define a closed circuit or current path  42 . The return electrode  38  is physically attached by, for example, an adhesive bond to a site on the body surface of the patient  20 , such as the patient&#39;s back. 
     The surface area of the return electrode  38  in contact with the patient  20  may be relatively large in comparison with the surface area of the treatment electrode  24 . Consequently, at the tissue adjacent to the return electrode  38 , the current density flowing from the patient  20  to the return electrode  38  is relatively low in comparison with the current density flowing from the treatment electrode  24  to the patient  20 . Because negligible heating is produced at its attachment site to the patient, a non-therapeutic effect is created in the tissue adjacent to the return electrode  38 . 
     Although the treatment electrode  24  and the return electrode  38  are representatively configured for the delivery of monopolar high frequency energy, the treatment electrode  24  may be configured to deliver bipolar high frequency energy. The modifications to the treatment apparatus  10  required to deliver bipolar high frequency energy are familiar to a person having ordinary skill in the art. For example, the return electrode  38  may be eliminated from the treatment apparatus  10  and a bipolar type of treatment electrode substituted for the monopolar treatment electrode  24 . 
     With continued reference to  FIGS. 1-7 , the handpiece  12  is constructed from a housing  46  that includes a body  48 , a cover  50  assembled by conventional fasteners with the body  48 , and an electrical/fluid interface  52  for the treatment tip  14 . The housing  46  may be fabricated by an injection molding process using a suitable polymer resin as a construction material. The body  48  and cover  50  constitute shell halves that are integrally fastened together as an assembly. The housing  46  encloses an interior cavity  54  bounded on one side by an interior surface of the body  48  and bounded on the other side by an interior surface of the cover  50 . After the body  48  and cover  50  are assembled, the handpiece  12  has a smoothly contoured shape suitable for gripping and manipulation by an operator. The operator maneuvers the treatment tip  14  and treatment electrode  24  to a location proximate to the skin surface and, typically, to place the treatment electrode  24  in proximity with the skin surface. 
     The housing  46  includes a nose  56  and a window  58  in the nose  56  that is sized for the insertion and removal of the treatment tip  14 . The electrical/fluid interface  52  is disposed between the window  58  and the interior cavity  54  enclosed inside the housing  46 . The treatment tip  14  is sized to be inserted through the window  58  and configured to be physically engaged with the handpiece  12 , as described below. In the engaged state, the contact pads carried on the substrate  30  of the treatment electrode  24  establish respective electrical connections with complementary electrical contacts  60  ( FIG. 3 ), such as pogo pins, carried by the electrical/fluid interface  52  of the handpiece  12 . These electrical contacts  60  are electrically coupled with one or more of the conductors  22  that extend from the handpiece  12  to the generator  26  and system controller  18 . 
     The handpiece  12  may include a control panel  62  and a display  64  that may be carried by the cover  50 . The control panel  62  may include various controls, such as controls  69 ,  70  used to respectively increase and reduce the treatment setting and controls  71 ,  72  that respectively enable and disable the controls  69 ,  70 . The display  64  may be used to display information including, but not limited to, energy delivered, tissue impedance, duration, and feedback on procedure technique. The availability of the information displayed on the display  64  may conveniently eliminate the need to display identical information at the console  16  or may duplicate information displayed at the console  16 . By displaying information at the handpiece  12 , the operator can focus on the procedure without diverting his attention to glance at information displayed by the display on the console  16 . In one embodiment, the display  64  may constitute a thin, flat liquid crystal display (LCD) comprised of a light source or reflector and an arbitrary number of color or monochrome pixels arrayed in front of the light source or reflector. A driver circuit (not shown) is provided to control the operation of the display  64 . 
     The treatment tip  14  includes a rigid outer shell  66  and a nipple  34  that is coupled with the open rearward end of the outer shell  66  to surround an interior cavity. A fluid delivery member  41  is configured to deliver a spray of a cryogen or similar coolant from a nozzle  39  onto the electrode  24 . Extending rearwardly from a central fluid coupling member  32  is a conduit  45  having a lumen defining a fluid path that conveys a flow of the coolant to the nozzle  39 . The coolant is pumped from a coolant supply ( FIG. 1 ) through tubing that is mechanically coupled with a fitting  47  formed on the nipple  34  and hydraulically coupled with the lumen of the conduit  45 . 
     The electrode  24  is exposed through a window  51  defined in a forward open end of the outer shell  66 . The rearward end of the support member  53  includes a flange  55  used to couple the support member  53  to the nipple  34 . The flexible substrate is wrapped or folded about the support member  53  such that the contact pads  57  are exposed through slots  59  defined in the nipple  34 . A support arm  67  bridges the window  51  for lending mechanical support to the flexible substrate  30 . 
     The treatment tip  14  includes openings  68  defined on diametrically opposite sides of the outer shell  66 . The openings  68  are used to temporarily secure the treatment tip  14  with the handpiece  12  in advance of a patient treatment procedure. The handpiece  12  includes a control valve used to deliver a cryogen spray to the treatment electrode  24  for controlling the temperature of the treatment electrode  24 . A line  63  connects the control valve with a cryogen supply  65 . 
     One purpose of the cryogen spray is to pre-cool the patient&#39;s epidermis, before powering the treatment electrode  24 , by heat transfer between the treatment electrode  24  and the skin surface. The cooling creates a reverse thermal gradient in the tissue such that the temperature of the tissue at and near the skin surface is cooler than the temperature of the tissue deeper within the epidermis or dermis. As a result, the high frequency energy delivered to the tissue fails to heat all or a portion of the patient&#39;s epidermis to a temperature sufficient to cause significant epidermal thermal damage. Depths of tissue that are not significantly cooled by pre-cooling will warm up to therapeutic temperatures, which cause a desired therapeutic effect. The amount and/or duration of pre-cooling may be used to select the protected depth of untreated tissue. The cryogen delivered by the control valve may also be used to cool portions of the tissue during and/or after heating by the high frequency energy transferred from the treatment electrode  24 . Post-cooling may prevent or reduce heat delivered deeper into the tissue from conducting upward and heating shallower tissue regions, such as the epidermis, to temperatures which could thermally damage shallower tissue regions even though external energy delivery to the targeted tissue has ceased. 
     Various duty cycles of cooling and heating that rely on cooling and high frequency energy transfer from the treatment electrode  24  are utilized contingent upon the type of treatment and the desired type of therapeutic effect. The cooling and heating duty cycles may be controlled and coordinated by operation of the system controller  18  and control valve. Suitable cryogens include low boiling point fluids, but are not limited to, R134a (1,1,1,2-tetrafluoroethane) refrigerant, liquid nitrogen, HFO-1234ze (1,3,3,3-tetrafluoropropene) refrigerant, and R152a (1,1-difluoroethane) refrigerant. Heat can be extracted from the treatment electrode  24  by virtue of evaporative cooling of the cryogen, which lowers the temperature of the treatment electrode  24 . 
     With specific reference to  FIGS. 5-7 , the flexible circuit  74  in the treatment tip  14  includes the treatment electrode  24  arranged on the electrically-insulating substrate  30  and the temperature sensors  44  that are surface mounted to the electrically-insulating substrate  30 . The flexible circuit  74  is a non-rigid variety of printed circuit board that includes the traces  49 . The temperature sensors  44  are electrically coupled by conductive traces  49  with the contact pads  57 , which are used to supply direct current (DC) voltages from the system controller  18  through the electrical wiring to the temperature sensors  44 . 
     Each of the temperature sensors  44  has terminals that are each attached or connected to attachment pads  43  to provide a mechanical connection with the electrically-insulating substrate  30  and an electrical connection with one of the traces  49  that terminates at each attachment pad  43 . For example, package leads from the temperature sensor  44  may provide terminals in which one of the terminals is attached to one of a pair of attachment pads  43  and the other of the terminals is attached to the other of the pair of attachment pads  43 . Each trace  49  is routed from its respective attachment pad  43  to one of the contact pads  57  arranged on one of the flaps of the flexible circuit  74 . 
     Each of the traces  49  is split over a portion of its length into multiple sections  49   a  that supply parallel current paths for communicating with the associated temperature sensor  44 . The trace sections  49   a  are arranged adjacent to each other along the length of the traces  49 . A crease or fold line  73  created when the flexible circuit  74  is wrapped about the support member  53  is diagrammatically indicated by the dashed rectangle in  FIG. 6 . The trace sections  49   a  cross the fold line  73  when the flexible circuit  74  is folded over the support member during assembly of the treatment tip  14  such that the trace sections  49   a  separate on one side of the fold line and converge back together on an opposite side of the fold line  73 . The respective longitudinal axes of the trace sections  49   a  of the traces  49  may be oriented to intersect the fold line  73  at a right angle (i.e., perpendicular to the fold line  73 ) or substantially at a right angle (i.e., transverse to the fold line  73 ). The trace sections  49   a  are separated by a central open slit or slot of a given length. The width of the slot and/or the width of the trace sections  49   a  may be selected to enhance the resistance to cracking and crack propagation. The fold line  73  extends across the open slot transverse to its length. 
     The redundancy in the current paths provided by the trace sections  49   a  of each trace  49  furnishes a mechanism by which one of the trace sections  49   a  of the trace  49  may fail due to, for example, the propagation of a crack generated by flexure and electrically open, while the other of the trace sections  49   a  of the trace  49  maintains a closed circuit. Differences in the local stresses in the folded flexible circuit  74 , among other factors, may cause differences in the failure rate of the different trace sections  49   a  over the operational lifetime of the treatment tip  14 . 
     The number of individual trace sections  49   a  in the representative embodiment is two (2), although more than two trace sections  49   a  may be incorporated into each trace  49  to provide more than two parallel and redundant current paths in the traces  49  leading to and from the sides of the associated temperature sensor  44  (e.g., the positive and negative terminals of a thermistor). The aspect ratio (e.g., width and thickness) of the traces  49  may be selected to provide additional resistance to crack propagation and to lessen the failure probability due to cracking. In some embodiments, the number of trace sections  49   a  may be at least two (2), or at least three (3), or at least four (4), or at least five (5), or at most five (5), or at most four (4), or at most three (3), or at most two (2) per trace  49 . In some embodiments, each trace  49  may include two (2), or three (3), or four (4), or five (5) trace sections  49   a.    
     With reference to  FIGS. 8, 9  and in accordance with embodiments of the invention, each attachment pad  43  may be connected with multiple traces  49  that extend from the attachment pad  43  to one of the contact pads  57  arranged on the flaps of the flexible circuit  74 . The multiple traces  49  provide redundancy in the circuit path similar to the trace sections  49   a  ( FIGS. 6, 7 ). The traces  49  are routed to cross the fold line  73  ( FIG. 6 ) when the treatment tip  14  is assembled and, in particular, may have longitudinal axes that are oriented to intersect the fold line at a right angle (i.e., perpendicular to the fold line  73 ) or substantially at a right angle (i.e., transverse to the fold line  73 ). Each of the traces  49  connected with one of the attachment pads  43  extend along its full length from the associated attachment pad  43  to the associate contact pad  57  such that the parallel current paths are separated over their entire length and lack trace sections. 
     References herein to terms such as “vertical,” “horizontal,” etc. are made by way of example, and not by way of limitation, to establish a frame of reference. It is understood that various other frames of reference may be employed for describing the invention without departing from the spirit and scope of the invention. It is also understood that features of the invention are not necessarily shown to scale in the drawings. Furthermore, to the extent that the terms “composed of”, “includes”, “having”, “has”, “with”, or variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive and open-ended in a manner similar to the term “comprising.” 
     References herein to terms modified by language of approximation, such as “about”, “approximately”, and “substantially”, are not to be limited to the precise value specified. The language of approximation may correspond to the precision of an instrument used to measure the value and, unless otherwise dependent on the precision of the instrument, may indicate +/−10% of the stated value(s). 
     A feature “connected” or “coupled” to or with another element may be directly connected or coupled to the other element or, instead, one or more intervening elements may be present. A feature may be “directly connected” or “directly coupled” to another element if intervening elements are absent. A feature may be “indirectly connected” or “indirectly coupled” to another element if at least one intervening element is present. 
     While the invention has been illustrated by a description of various embodiments and while these embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Thus, the invention in its broader aspects is therefore not limited to the specific details, representative apparatus and method, and illustrative example shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicant&#39;s general inventive concept.