Branched Proximal Connector for High-Density Neural Interfaces

Abstract

The present disclosure relates to a branched proximal connector for a high-density neural interface and a method of microfabricating the branched proximal connector. Specifically, aspects of the present disclosure are directed to a branched connector that includes a base having a support structure and a body of a plurality of conductive traces formed on the base, and a plurality of plugs extending from the body. Each of the plurality of plugs includes: an end of the support structure, which consists of one or more layers of dielectric material; and a subset of the conductive traces from the plurality of conductive traces. Each trace from the subset of conductive traces terminates at a bonding pad exposed on a surface of the end of the support structure.

Description

[0001] Priority Claim

[0002] This application claims the benefit of priority of U.S. Provisional Application No. 62 / 768,562, filed on Nov. 16, 2018, the entire content of which is incorporated herein by reference for all purposes. Field of the Invention

[0003] The present disclosure relates to implantable neuromodulation devices and manufacturing methods, and more particularly, to a branched proximal connector for a high-density neural interface and a method of microfabricating the branched proximal connector. Background Art

[0004] Normal neural activity is a complex balance of electrical and chemical signals, which can be disrupted by various injuries (genetic, chemical, or physical trauma) to the nervous system, resulting in cognitive, motor, and sensory impairments. Similar to the way a cardiac pacemaker or defibrillator corrects abnormal heartbeats, neuromodulation therapies help to restore normal neural balance. In certain cases, neuromodulation therapies utilize medical device technologies to enhance or inhibit the activity of the nervous system to treat diseases. These technologies include implantable and non-implantable neuromodulation devices and systems that deliver electrical, chemical, or other agents to reversibly alter brain and nerve cell activity. The most common neuromodulation therapy is spinal cord stimulation for treating chronic neuropathic pain. In addition to chronic pain relief, some examples of neuromodulation therapies include: deep brain stimulation for essential tremor, Parkinson'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 motility disorders 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).

[0005] Neuromodulation devices and systems tend to have a similar form factor derived from their predecessors (e.g., pacemakers or defibrillators). Such neuromodulation devices and systems typically consist of an implant that includes a nerve stimulator having electronics connected to a lead assembly that delivers electrical pulses to electrodes that interface with a nerve or nerve bundle 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) that is connected to the electrodes via a first connector at one end (e.g., the distal end) and to the electronics of the nerve stimulator via a second connector at the other end (e.g., the proximal end). In some cases (e.g., deep implants), the lead assembly includes additional conductors and connectors, such as extension wires or cables, connected between the electrodes and the electronics of the nerve stimulator via connectors.

[0006] Conventional neuromodulation devices include between four and sixteen electrodes and thus typically include four to sixteen channels or wires that are connected to the electrodes at the distal end and to the electronics of the nerve stimulator at the proximal end, respectively. However, there is a need for high-density neural interfaces that include more than sixteen electrodes to interface with a larger tissue volume, recruit smaller populations of neurons for recording, or provide more targeted therapy by customizing the electrical stimulation parameters and the tissue volume activated. Increasing the density or number of electrodes increases the number of channels or wires required to connect the electrodes to the electronics of the nerve stimulator. To achieve a high number of channels or wires, a reliable electrical connection is needed that can maintain contact and electrical isolation in the body of the subject (e.g., the patient's body) for many years. Typically, lead assemblies that include a high number of channels or wires need to be permanently connected to the electronics. However, this is not desirable because the electronics need to be replaced every few years to upgrade them or replace the battery, and because of the risk to the patient, surgeons have a strong preference not to remove the lead assembly from the nerve tissue. Thus, there is a need for a reliable and non-permanent connector for lead assemblies having a high-density neural interface. Summary of the Invention

[0007] In various embodiments, a branch connector is provided that includes: a body including a base of a support structure and a plurality of conductive traces formed on the base, wherein the base of the support structure consists of one or more layers of dielectric material; and a plurality of plugs extending from the body. Each plug of the plurality of plugs includes: an end of the support structure, consisting of the one or more layers of dielectric material; and a subset of conductive traces from the plurality of conductive traces, wherein each trace from the subset of conductive traces terminates at a bond pad exposed on a surface of the end of the support structure.

[0008] In some embodiments, the dielectric material is polyimide, liquid crystal polymer, parylene, polyether ether ketone, or a combination thereof. In some embodiments, the plurality of conductive traces is composed of one or more layers of conductive material, and the conductive material is platinum (Pt), platinum / iridium (Pt / Ir), titanium (Ti), gold / titanium (Au / Ti), or any alloy thereof.

[0009] In some embodiments, the coefficient of thermal expansion of the plurality of conductive traces is approximately equal to the coefficient of thermal expansion of the support structure.

[0010] In some embodiments, the base of the support structure and each end of the support structure are integral. Optionally, each end of the support structure is planar. Optionally, each end of the support structure is a cylindrical tube.

[0011] In some embodiments, the one or more layers of dielectric material include a first layer of dielectric material and a second layer of dielectric material, and a subset of the conductive traces is buried between the first layer of dielectric material and the second layer of dielectric material.

[0012] In some embodiments, each bonding pad is a split annular ring positioned around the axis of the cylindrical tube and exposed on the surface of the cylindrical tube. Optionally, each split annular ring is spaced apart from each other on the surface of the cylindrical tube by a region of the first layer of dielectric material. Optionally, the width of the region of the first layer of dielectric material separating each split annular ring is between 1.0 mm and 10 mm.

[0013] In some embodiments, the cylindrical tube includes: (i) the one or more layers of dielectric material, wherein the first layer of dielectric material defines the outer diameter of the cylindrical tube, and the second layer of dielectric material defines the inner diameter of the tube; and (ii) a core that at least partially fills the interior of the cylindrical tube defined by the inner diameter of the cylindrical tube. Optionally, the one or more layers of dielectric material at least partially wind around the core. Optionally, the one or more layers of dielectric material are formed as a split cylindrical tube that winds around the core, and the split cylindrical tube includes a gap for the split having a predetermined width. Optionally, the predetermined width is between 0.1 mm and 10 mm.

[0014] In some embodiments, the first layer of dielectric material includes at least one via for each bonding pad, and the via includes a conductive material for electrically connecting each bonding pad to at least one trace in the subset of conductive traces such that each trace from the subset of conductive traces terminates at the bonding pad.

[0015] In some embodiments, the first layer of dielectric material is a high-temperature liquid crystal polymer, and the second layer of dielectric material is a low-temperature liquid crystal polymer.

[0016] In some embodiments, the core is composed of one or more layers of material such that the core has a Shore hardness greater than 70D. Optionally, the one or more layers of material of the core are polyimide, liquid crystal polymer, parylene, polyether ether ketone, polyurethane, metal, or a combination thereof. Optionally, the one or more layers of material of the core are thermoset or thermoplastic polyurethane.

[0017] In various embodiments, an integral thin film lead assembly is provided, comprising: a cable including a proximal end, a distal end, a support structure extending from the proximal end to the distal end, and a plurality of conductive traces formed on a portion of the support structure, wherein the support structure is composed of one or more layers of dielectric material; an electrode assembly formed on the support structure at the distal end of the cable, wherein the electrode assembly includes one or more electrodes electrically connected to one or more of the plurality of conductive traces; and a branch connector formed on the support structure at the proximal end of the cable, wherein the branch connector includes: (i) a body including the support structure and the plurality of conductive traces, and (ii) a plurality of plugs extending from the body, each of the plurality of plugs including the support structure and a subset of the conductive traces from the plurality of conductive traces, wherein each trace from the subset of conductive traces terminates at a bonding pad exposed on a surface of the support structure.

[0018] In some embodiments, the dielectric material is polyimide, liquid crystal polymer, parylene, polyether ether ketone, or a combination thereof. In some embodiments, the plurality of conductive traces are composed of one or more layers of conductive material, and the conductive material is platinum (Pt), platinum / iridium (Pt / Ir), titanium (Ti), gold / titanium (Au / Ti), or any alloy thereof. Optionally, the support structure of each plug is planar. Optionally, the support structure of each plug is a cylindrical tube.

[0019] In some embodiments, the support structure of each plug includes a first layer of dielectric material and a second layer of dielectric material, and the subset of conductive traces is buried between the first layer of dielectric material and the second layer of dielectric material. In some embodiments, each bonding pad is a split annular ring positioned around the axis of the cylindrical tube and exposed on the surface of the cylindrical tube. Optionally, each split annular ring is spaced apart from each other on the surface of the cylindrical tube by a region of the first layer of dielectric material.

[0020] In some embodiments, the cylindrical tube includes: (i) the one or more layers of dielectric material, wherein the first layer of dielectric material defines the outer diameter of the cylindrical tube, and the second layer of dielectric material defines the inner diameter of the tube; and (ii) a core at least partially filling the interior of the cylindrical tube defined by the inner diameter of the cylindrical tube. Optionally, the one or more layers of dielectric material at least partially wind around the core.

[0021] In some embodiments, the one or more layers of dielectric material are formed as a split cylindrical tube that wraps around the core, and the split cylindrical tube includes a gap for the split having a predetermined width.

[0022] In some embodiments, the first layer of dielectric material includes at least one via for each bonding pad, and the via includes a conductive material for electrically connecting each bonding pad to at least one trace in a subset of conductive traces such that each trace from the subset of conductive traces terminates at a bonding pad. In some embodiments, the first layer of dielectric material is a high-temperature liquid crystal polymer, and the second layer of dielectric material is a low-temperature liquid crystal polymer. Optionally, the core is composed of one or more layers of material such that the core has a Shore hardness greater than 70D.

[0023] In various embodiments, a thin-film lead assembly is provided that includes: a cable including a proximal end, a distal end, a first support structure extending from the proximal end to the distal end, and a plurality of conductive traces formed on a portion of the first support structure; an electrode assembly formed on the first support structure at the distal end of the cable, wherein the electrode assembly includes one or more electrodes electrically connected to one or more of the plurality of conductive traces; and a branch connector that includes: (i) a body including a second support structure and a plurality of conductive connector traces, and (ii) a plurality of plugs extending from the body, each of the plurality of plugs including a second support structure and a subset of conductive connection traces from the plurality of conductive connection traces, wherein each trace from the subset of conductive connection traces terminates at a bonding pad exposed on a surface of the second support structure, and wherein the plurality of conductive connector traces of the branch connector are in electrical contact with the plurality of conductive traces of the cable, respectively.

[0024] In some embodiments, the second support structure is composed of one or more layers of dielectric material, and the dielectric material is polyimide, liquid crystal polymer, parylene, polyether ether ketone, or a combination thereof. In some embodiments, the plurality of conductive connector traces are composed of one or more layers of conductive material, and the conductive material is platinum (Pt), platinum / iridium (Pt / Ir), titanium (Ti), gold / titanium (Au / Ti), or any alloy thereof. Optionally, the second support structure of each plug is planar. Optionally, the second support structure of each plug is a cylindrical tube.

[0025] In some embodiments, the second support structure of each plug includes a first layer of dielectric material and a second layer of dielectric material, and a subset of conductive connection traces is buried between the first layer of dielectric material and the second layer of dielectric material. In some embodiments, each bonding pad is a split annular ring positioned around the axis of the cylindrical tube and exposed on the surface of the cylindrical tube. Optionally, each split annular ring is spaced apart from each other on the surface of the cylindrical tube by a region of the first layer of dielectric material.

[0026] In some embodiments, the cylindrical tube includes: (i) the one or more layers of dielectric material, wherein the first layer of dielectric material defines the outer diameter of the cylindrical tube, and the second layer of dielectric material defines the inner diameter of the tube; and (ii) a core that at least partially fills the interior of the cylindrical tube defined by the inner diameter of the cylindrical tube.

[0027] In some embodiments, the one or more layers of dielectric material at least partially wind around the core. Optionally, the one or more layers of dielectric material are formed as a split cylindrical tube that winds around the core, and the split cylindrical tube includes a gap for the split having a predetermined width. Optionally, the first layer of dielectric material includes at least one via for each bonding pad, and the via includes a conductive material for electrically connecting each bonding pad to at least one of the traces in the subset of conductive connection traces such that each trace from the subset of conductive connection traces terminates at a bonding pad.

[0028] In some embodiments, the first layer of dielectric material is a high-temperature liquid crystal polymer, and the second layer of dielectric material is a low-temperature liquid crystal polymer. Optionally, the core is composed of one or more layers of material such that the core has a Shore hardness greater than 70D.

[0029] In various embodiments, a neuromodulation system is provided that includes: a neurostimulator including an electronic module; a cable including a support structure and a plurality of conductive traces formed on a portion of the support structure, wherein the support structure is composed of one or more layers of dielectric material; an electrode assembly formed on the support structure, wherein the electrode assembly includes one or more electrodes electrically connected to one or more of the plurality of conductive traces; and a branch connector formed on the support structure at the proximal end of the cable, wherein the branch connector includes: (i) a body including the support structure and the plurality of conductive traces, and (ii) a plurality of plugs extending from the body, each of the plurality of plugs including a support structure and a subset of conductive traces from the plurality of conductive traces, wherein the branch connector electrically connects each subset of conductive traces from the plurality of conductive traces to the electronic module.

[0030] In some embodiments, each trace from a subset of conductive traces terminates at a bonding pad exposed on a surface of a support structure. Optionally, the dielectric material is polyimide, liquid crystal polymer, parylene, polyether ether ketone, or a combination thereof. In some embodiments, the plurality of conductive traces consists of one or more layers of conductive material, and the conductive material is platinum (Pt), platinum / iridium (Pt / Ir), titanium (Ti), gold / titanium (Au / Ti), or any alloy thereof. Optionally, the support structure of each plug is planar. Optionally, the support structure of each plug is a cylindrical tube.

[0031] In some embodiments, the support structure of each plug includes a first layer of dielectric material and a second layer of dielectric material, and the subset of conductive traces is buried between the first layer of dielectric material and the second layer of dielectric material. Optionally, each bonding pad is a split annular ring positioned around an axis of the cylindrical tube and exposed on a surface of the cylindrical tube. Optionally, each split annular ring is spaced apart from each other on the surface of the cylindrical tube by a region of the first layer of dielectric material.

[0032] In some embodiments, the cylindrical tube includes: (i) the one or more layers of dielectric material, wherein the first layer of dielectric material defines an outer diameter of the cylindrical tube, and the second layer of dielectric material defines an inner diameter of the tube; and (ii) a core that at least partially fills an interior of the cylindrical tube defined by the inner diameter of the cylindrical tube. Optionally, the one or more layers of dielectric material at least partially wind around the core.

[0033] In some embodiments, the one or more layers of dielectric material are formed as a split cylindrical tube that winds around the core, and the split cylindrical tube includes a gap for the split having a predetermined width.

[0034] In some embodiments, the first layer of dielectric material includes at least one via for each bonding pad, and the via includes a conductive material for electrically connecting each bonding pad to at least one trace in the subset of conductive traces such that each trace from the subset of conductive traces terminates at the bonding pad.

[0035] In some embodiments, the first layer of dielectric material is a high-temperature liquid crystal polymer, and the second layer of dielectric material is a low-temperature liquid crystal polymer. Optionally, the core consists of one or more layers of material such that the core has a Shore hardness greater than 70D.

[0036] In various embodiments, a method of manufacturing a branched connector is provided, which includes: obtaining a flexible printed circuit board structure, the flexible printed circuit board structure including: (i) a body including a support structure and a plurality of conductive traces, and (ii) a plurality of plugs extending from the body, each of the plurality of plugs including a support structure and a subset of the conductive traces from the plurality of conductive traces, wherein each trace from the subset of conductive traces terminates at a bonding pad exposed on a surface of the support structure, and wherein the support structure includes a first polymer layer and a second polymer layer, and the subset of conductive traces is buried between the first polymer layer and the second polymer layer; winding each of the plurality of plugs around a mandrel at least partially such that each of the plurality of plugs assumes a cylindrical tube shape; placing a heat shrink tube over each of the plurality of plugs and the mandrel to form a first intermediate structure; heating the first intermediate structure to cause each heat shrink tube to shrink and form a second intermediate structure; removing the mandrel from the second intermediate structure such that each of the plurality of plugs has a lumen; injecting a polymer into the lumen of the second intermediate structure to form a third intermediate structure; heating the third intermediate structure to form a branched connector having a plurality of cylindrical plugs; and removing the heat shrink tube from the branched connector having the plurality of cylindrical plugs. Each of the plurality of cylindrical plugs includes a first polymer layer and a second polymer layer that at least partially wind around a core made of a polymer.

[0037] In some embodiments, the first polymer layer is polyimide, liquid crystal polymer, parylene, polyether ether ketone, or a combination thereof. In some embodiments, the second polymer layer is polyimide, liquid crystal polymer, parylene, polyether ether ketone, or a combination thereof. In some embodiments, the plurality of conductive traces and the subset of conductive traces are composed of one or more layers of conductive material, and the conductive material is platinum (Pt), platinum / iridium (Pt / Ir), titanium (Ti), gold / titanium (Au / Ti), or any alloy thereof.

[0038] In some embodiments, each end portion is wound around a mandrel or a polymer tube at least partially such that the plurality of cylindrical ends are a plurality of split cylindrical ends, and each of the plurality of split cylindrical ends includes a gap for the split having a predetermined width.

[0039] In some embodiments, the method further includes forming a third polymer layer on the second polymer layer in a region between the body portion and the plurality of ends. In some embodiments, the third polymer layer is silicone.

[0040] In various embodiments, a method of manufacturing a branched connector is provided, which includes: obtaining a flexible printed circuit board structure that includes: (i) a body including a support structure and a plurality of conductive traces, and (ii) a plurality of plugs extending from the body, each of the plurality of plugs including a support structure and a subset of conductive traces from the plurality of conductive traces, wherein each trace from the subset of conductive traces terminates at a bonding pad exposed on a surface of the support structure, and wherein the support structure includes a first polymer layer and a second polymer layer, and the subset of conductive traces is buried between the first polymer layer and the second polymer layer; wrapping each of the plurality of plugs at least partially around a polymer tube such that each of the plurality of plugs assumes a cylindrical tube shape; placing a heat shrink tube over each of the plurality of plugs and the polymer tube to form a first intermediate structure; heating the first intermediate structure having the heat shrink tube to form a branched connector having a plurality of cylindrical plugs; and removing the heat shrink tube from the branched connector having the plurality of cylindrical plugs. Heating embeds each of the plurality of plugs into the polymer tube respectively, and each of the plurality of cylindrical plugs includes a first polymer layer and a second polymer layer that at least partially wrap a core made of the polymer tube.

[0041] In some embodiments, the first polymer layer is polyimide, liquid crystal polymer, parylene, polyether ether ketone, or a combination thereof. In some embodiments, the second polymer layer is polyimide, liquid crystal polymer, parylene, polyether ether ketone, or a combination thereof.

[0042] In some embodiments, the plurality of conductive traces and the subset of conductive traces are composed of one or more layers of conductive material, and the conductive material is platinum (Pt), platinum / iridium (Pt / Ir), titanium (Ti), gold / titanium (Au / Ti), or any alloy thereof.

[0043] In some embodiments, each end portion is respectively partially wrapped around a mandrel or a polymer tube such that the plurality of cylindrical ends are a plurality of split cylindrical ends, and each of the plurality of split cylindrical ends includes a gap for the split having a predetermined width.

[0044] In some embodiments, the method further includes forming a third polymer layer on the second polymer layer in a region between the body portion and the plurality of ends. In some embodiments, the third polymer layer is silicone. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The present invention will be better understood from the following non - limiting drawings, in which:

[0046] Figure 1 shows a neuromodulation system according to various embodiments;

[0047] Figure 2 Shows a lead assembly according to various embodiments;

[0048] Figure 3 Shows a branch connector according to various embodiments;

[0049] Figure 4A Shows an enlarged view of a branch connector according to various embodiments;

[0050] Figure 4B Shows a cross-section of a branch connector according to various embodiments;

[0051] Figures 5A - 5G Shows an alternative lead assembly according to various embodiments;

[0052] Figures 6A - 6M Shows a cross-sectional side view and a top view, which show a method of manufacturing a flexible printed circuit board according to various embodiments;

[0053] Figures 7A - 7H Shows a top view, which shows a method of manufacturing a branch connector according to various embodiments; and

[0054] Figures 8A - 8E Shows a top view, which shows an alternative method of manufacturing a branch connector according to various embodiments. Detailed Description

[0055] I. Introduction

[0056] The following disclosure describes a branched proximal connector for a high-density neural interface and a method of microfabricating the branched proximal connector. As used herein, the phrase "branch" refers to a lateral extension or subdivision extending from a body. As used herein, the term "proximal" or "proximally" refers to the first end of the body, while the term "distal" or "distally" refers to the second end opposite the first end. For example, the proximal end may be the end of the body closest to the user, and the distal end may be the end of the body farthest from the user. The branched proximal connector can be fabricated using microfabrication techniques. In some embodiments, the branched connector is fabricated as a monolithic structure. As used herein, the phrase "monolithic" refers to a device fabricated using a single layer of substrate material. As used herein, the phrase "microfabrication" refers to a process of fabricating microstructures at the micron scale and smaller scales. The main concepts and principles of microfabrication are photolithography, doping, thin films, etching, bonding, and polishing. As used herein, the phrase "thin film" refers to a layer of material having a thickness in the range of a fraction of a nanometer (single layer) to several microns (e.g., between a few nanometers and about 100 μm). A thin film can be deposited by applying a very thin film of material (e.g., between a few nanometers and about 100 μm) onto the surface of a substrate to be coated or onto a previously deposited thin film layer. In various embodiments, a thin film connector is provided that includes a substrate polymer body (e.g., a support structure) and at least one conductive trace formed on the substrate polymer body. As used herein, the term "(a) high-density neural interface" refers to a neural interface that includes at least sixteen electrodes (i.e., recording electrodes, sensing electrodes, stimulating electrodes, other types of electrodes, or combinations thereof).

[0057] Neuromodulation devices such as deep brain and spinal cord stimulators electrically interface with neural tissue and treat various neurological disorders through electrical stimulation. As described herein, conventional neuromodulation devices use between four and sixteen electrodes and include a neural stimulator and a lead assembly that includes the electrodes. There is a need for high-density lead assemblies that can significantly increase the number of electrodes in order to interface with a larger tissue volume, recruit smaller populations of neurons for recording, or provide more targeted therapy by customizing electrical stimulation parameters and the volume of tissue activated. Conventional neuromodulation devices use up to eight channels per lead assembly in the axial orientation. Partly due to the lack of compatible connector technology, these devices are typically limited to no more than eight channels per lead assembly. Conventional neuromodulation devices that can accommodate more than eight channels per lead assembly are limited by the requirement for permanent connections to limit the sensitivity of the connectors to disconnection and breakage.

[0058] To address these limitations and problems, the branch proximal connectors of the various embodiments disclosed herein implement connections to high-density neural interfaces and are capable of being physically disconnected between a neural stimulator and a lead assembly. An illustrative embodiment of the present disclosure is directed to a branch connector that includes a body and a plurality of plugs extending from the body. The body has a base of a support structure and a plurality of conductive traces formed on the base. The base of the support structure is composed of one or more layers of dielectric material. Each of the plurality of plugs includes: an end of the support structure, composed of one or more layers of dielectric material; and a subset of conductive traces from the plurality of conductive traces. Each trace from the subset of conductive traces terminates at a bonding pad exposed on a surface of the end of the support structure.

[0059] In another embodiment, an integral thin-film lead assembly is provided that includes a cable having a proximal end, a distal end, a support structure extending from the proximal end to the distal end, and a plurality of conductive traces formed on a portion of the support structure. The support structure is composed of one or more layers of dielectric material. The integral thin-film lead assembly further includes an electrode assembly formed on the support structure at the distal end of the cable. The electrode assembly includes one or more electrodes electrically connected to one or more of the plurality of conductive traces. The integral thin-film lead assembly further includes a branch connector formed on the support structure at the proximal end of the cable. The branch connector includes: (i) a body including the support structure and the plurality of conductive traces, and (ii) a plurality of plugs extending from the body, each of the plurality of plugs including a support structure and a subset of conductive traces from the plurality of conductive traces, wherein each trace from the subset of conductive traces terminates at a bonding pad exposed on a surface of the support structure.

[0060] In another embodiment, a thin-film lead assembly is provided that includes a cable having a proximal end, a distal end, a first support structure extending from the proximal end to the distal end, and a plurality of conductive traces formed on a portion of the first support structure. The thin-film lead assembly further includes an electrode assembly formed on the first support structure at the distal end of the cable. The electrode assembly includes one or more electrodes electrically connected to one or more of the plurality of conductive traces. The thin-film lead assembly further includes a branch connector that includes: (i) a body including a second support structure and a plurality of conductive connector traces, and (ii) a plurality of plugs extending from the body, each of the plurality of plugs including a second support structure and a subset of conductive connection traces from the plurality of conductive connection traces. Each trace from the subset of conductive connection traces terminates at a bonding pad exposed on a surface of the second support structure. The plurality of conductive connector traces of the branch connector are in electrical contact with the plurality of conductive traces of the cable, respectively.

[0061] In another embodiment, a neuromodulation system is provided that includes: a nerve stimulator including an electronic module; a cable including a support structure and a plurality of conductive traces formed on a portion of the support structure, wherein the support structure is composed of one or more layers of dielectric material; an electrode assembly formed on the support structure, wherein the electrode assembly includes one or more electrodes electrically connected to one or more of the plurality of conductive traces; and a branch connector formed on the support structure at a proximal end of the cable. The branch connector includes: (i) a body including the support structure and the plurality of conductive traces, and (ii) a plurality of plugs extending from the body, each of the plurality of plugs including a support structure and a subset of the conductive traces from the plurality of conductive traces. The branch connector electrically connects each subset of the conductive traces from the plurality of conductive traces to the electronic module.

[0062] To further address these limitations and problems, a method of fabricating a branch connector for various embodiments disclosed herein includes process steps for creating a branch structure that results in increased contact points, a smaller footprint, and greater design flexibility. One illustrative embodiment of the present disclosure is directed to a method of fabricating a branch connector that includes forming a first polymer layer on a substrate. The first polymer layer includes a body portion and a plurality of ends extending from the body portion, and the body portion and the plurality of ends are coplanar. The method further includes forming a plurality of conductive traces in a first pattern on the body portion. The first pattern maintains a first predetermined distance between each of the plurality of traces. The method further includes forming a subset of the conductive traces in a second pattern on each of the plurality of ends. The second pattern maintains a second predetermined distance between each of the traces in the subset of traces and electrically connects each of the traces in the subset of traces to each of the plurality of traces. The method further includes depositing a second polymer layer on the first polymer layer, the plurality of conductive traces, and each subset of the conductive traces. The method further includes forming at least one contact via in the first polymer layer of each of the plurality of ends such that the at least one contact via is in electrical contact with at least one of the traces in the subset of the conductive traces. The method further includes: forming at least one bonding pad on the first polymer layer of each of the plurality of ends such that the at least one bonding pad is in electrical contact with the at least one contact via; and cutting the branch connector from the first polymer layer and the second polymer. The branch connector includes the body portion and the plurality of ends extending from the body portion.

[0063] Advantageously, these solutions provide a bifurcated connector having increased contact points, smaller footprint, and greater design flexibility. More specifically, these solutions implement a bifurcated connector having a reliable, non-permanent connection between a lead assembly and a nerve stimulator. This solution can be extended to connect multiple electrodes (e.g., more than sixteen) using multi-flex chips, thus enabling several therapeutic opportunities for nerve stimulation. Additionally, even for applications that do not require multiple electrodes, the various embodiments can be miniaturized to make the implant minimally invasive. Further, due to the miniaturization, the various embodiments can make the invasive anatomy accessible (or manipulable). It should be understood that although deep brain nerve stimulation 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 require an electrode / sensor that needs to be attached to a nerve stimulator.

[0064] II. Nerve Modulation Devices and Systems with Lead Assemblies

[0065] Figure 1 FIG. 100 shows a nerve modulation system 100 in accordance with some aspects of the present invention. In various embodiments, the nerve modulation system 100 includes an implantable nerve stimulator 105 and a lead assembly 110. The implantable nerve stimulator 105 (e.g., an implantable pulse generator (IPG)) may include a housing 115, a feedthrough assembly 120, a power source 125, an antenna 130, and an electronic module 135 (e.g., a computing system). The housing 115 may be composed of a biocompatible material such as a metal (such as titanium) or a bioceramic or bioglass for radiofrequency transparency. In accordance with some aspects of the present invention, the size and shape of the housing 115 may be selected such that the nerve stimulator 105 can be implanted within a patient. In Figure 1 the example shown, the feedthrough assembly 120 is attached to a hole in the surface of the housing 115 such that the housing 115 is hermetically sealed. The feedthrough assembly 120 may include one or more contacts (i.e., conductive elements, pins, wires, connectors, pads, etc.) mounted within the housing 115 or a cap extending from the interior of the housing 115 to the exterior of the housing 115. The power source 125 may be within the housing 115 and connected (e.g., electrically connected) to the electronic module 135 to power and operate the components of the electronic module 135. The antenna 130 may be connected (e.g., electrically connected) to the electronic module 135 for wireless communication with an external device via, for example, radiofrequency (RF) telemetry.

[0066] In some embodiments, the electronic module 135 may be connected (e.g., electrically connected) to the inner end of the feedthrough assembly 120 such that the electronic module 135 can apply a signal or current to the conductive traces of the lead assembly 110 connected to the feedthrough assembly 120. The electronic module 135 may include discrete and / or integrated electronic circuit components that implement analog and / or digital circuits capable of performing functions attributed to a neuromodulation device or system, such as applying or delivering nerve stimulation to a patient. In various embodiments, the electronic module 135 may include software and / or electronic circuit components, such as: a pulse generator 140 that generates signals to deliver voltage stimulation, current stimulation, optical stimulation, or ultrasound stimulation to a nerve or artery / nerve plexus via an electrode; a controller 145 that determines or senses electrical activity and physiological responses via the electrode and sensor, controls the stimulation parameters of the pulse generator 140 (e.g., controls the stimulation parameters based on feedback from the physiological response), and / or causes the delivery of stimulation via the pulse generator 140 and the electrode; and a memory 150 having program instructions that can be operated by the pulse generator 140 and the controller 145 to execute one or more processes for applying or delivering nerve stimulation.

[0067] In various embodiments, the lead assembly 110 includes a cable or lead body 155, one or more electrode assemblies 160 having one or more electrodes 165 (optionally, one or more sensors), and a branch connector 170. In some embodiments, the lead assembly 110 is a monolithic structure. In various embodiments, the branch connector 170 includes: a body 175 having a base with a support structure 177 and one or more conductive traces 180 formed on the base; and a plurality of plugs 182 extending from the body. The base of the support structure may be composed of one or more layers of dielectric material. Each of the plurality of plugs includes: an end of the support structure, composed of one or more layers of dielectric material; and a subset of conductive traces 185 from the one or more conductive traces. Each trace from the subset of conductive traces terminates at a bonding pad exposed on the surface of the end of the support structure.

[0068] The cable 155 may include one or more conductive traces 190 formed on a support structure 195. The one or more conductive traces 190 allow the electronic module 135 to be electrically coupled to the electrodes 165 of the electrode assembly 160 and / or sensors via the branch connector 170. In some embodiments, the one or more conductive traces 180 are the same conductive traces as the one or more conductive traces 190 (integral traces). In additional embodiments, the one or more conductive traces 180 are different conductive traces from the one or more conductive traces 190 (different structures but electrically connected). As described in detail herein, the support structure 177 / 195 may be formed of a dielectric material (such as a polymer) having suitable dielectric, flexible, and biocompatible properties. Polyurethane, polycarbonate, silicone, polyethylene, fluoropolymer, and / or other medical polymers, copolymers, and combinations or mixtures may be used. The conductive material for the traces 180 / 190 may be any suitable conductor (such as stainless steel, silver, copper, or other conductive materials), which may have a separate coating or sheath for anti-corrosion, insulation, and / or protection reasons.

[0069] The electrode assembly 160 may include electrodes 165 and / or sensors (e.g., book electrodes, split cuff electrodes, spiral cuff electrodes, epidural electrodes, helical electrodes, probe electrodes, linear electrodes, nerve probes, paddle electrodes, intraneural electrodes, etc.) fabricated using various shapes and patterns to create a particular type of electrode assembly. In various embodiments, the electrode assembly 160 includes a substrate material that provides support to a microelectronic structure including the electrodes 165, a wiring layer, optional contacts, etc. In some embodiments, the substrate material is the support structure 195. The wiring layer may be embedded within the support structure 195 or located on the surface of the support structure 195. The wiring layer may be used to electrically connect the electrodes 165 to the one or more conductive traces 190 directly or indirectly via lead conductors. As used herein, the term "directly" may be defined as nothing therebetween. As used herein, the term "indirectly" may be defined as something therebetween. In some embodiments, the electrodes 165 may be in electrical contact with the wiring layer by using contacts.

[0070] III. Branch Connector

[0071] Figure 2 Shown is a lead assembly 200 according to aspects of the present disclosure (e.g., with respect to Figure 1The described lead assembly 110). In various embodiments, the lead assembly 200 includes a cable 205 having a proximal end 210 and a distal end 215. The cable 205 may include a support structure 220 and a plurality of conductive traces 225 formed on a portion of the support structure 220. As used herein, the term "formed on" refers to a structure or feature formed on the surface of another structure or feature, a structure or feature formed within another structure or feature, or a structure or feature that is both formed on and within another structure or feature. In some embodiments, the support structure 220 extends from the proximal end 210 to the distal end 215. In some embodiments, the support structure 220 may be made of one or more layers of dielectric material (i.e., insulator). The dielectric material may be selected from the group of flexible non-conductive materials consisting of organic or inorganic polymers, polyimide-epoxy resins, epoxy-fiberglass, etc. In certain embodiments, the dielectric material is a polymer of imide monomers (i.e., polyimide), liquid crystal polymer (LCP) (such as ), parylene, polyetheretherketone (PEEK), or a combination thereof. In additional embodiments, the support structure 220 may be made of one or more layers of dielectric material formed on a substrate. The substrate may be made of any type of metal or non-metal material.

[0072] In various embodiments, one or more of the conductive traces 225 are multiple traces, such as two or more conductive traces or from two to twenty-four conductive traces. The multiple conductive traces 225 are composed of one or more layers of conductive material. The conductive material selected for one or more of the conductive traces 225 should have good electrical conductivity and may include pure metals, metal alloys, combinations of metals and dielectrics, etc. For example, the conductive material may be platinum (Pt), platinum / iridium (Pt / Ir), titanium (Ti), gold / titanium (Au / Ti), or any of their alloys. In some embodiments, it is also desirable for the conductive material selected for one or more of the conductive traces 225 to have a thermal expansion characteristic or coefficient of thermal expansion (CTE) that is approximately equal to the CTE of the support structure 220. It is desirable to match the CTEs of components that contact each other because it eliminates the development of thermal stresses that may occur during the manufacture and operation of the cable, thus eliminating a known cause of mechanical failure in the components.

[0073] As Figure 2As shown, the lead assembly 200 may further include an electrode assembly 230 formed on a support structure 235. The support structure 235 may provide support to a microelectronic structure including one or more electrodes 240, a wiring layer 245, and optional contacts (not shown). The electrode assembly 230 may be located at the distal end 215 of the lead assembly 200. One or more electrodes 240 are electrically connected to one or more of the conductive traces 225, for example via the wiring layer 245 and optional contacts. In various embodiments, the support structure 220 of the cable 205 and the support structure 235 of the electrode assembly 230 are the same structure (i.e., the support structure is continuous from the proximal end 210 to the distal end 215), which thus creates a monolithic cable. In alternative embodiments, the support structure 220 of the cable 205 and the support structure 235 of the electrode assembly 230 are different structures, but are connected such that there is an electrical connection between the conductive traces 225, the wiring layer 245, and one or more electrodes 240.

[0074] As Figure 2 shown, the lead assembly 200 may further include a branch connector 255 formed on a support structure 260. The branch connector 255 may include a body 265 that includes a base 270 of the support structure 260 and one or more conductive traces 275 formed on the base 270. The base 270 of the support structure 260 may be composed of one or more layers of dielectric material. In some embodiments, the support structure 260 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 flexible non-conductive materials consisting of organic or inorganic polymers, polyimide-epoxy resins, epoxy-fiberglass, etc. In certain embodiments, the dielectric material is a polymer of an imide monomer (i.e., polyimide), a liquid crystal polymer (LCP) (such as ), parylene, polyetheretherketone (PEEK), or a combination thereof. In additional embodiments, the support structure 260 may be made of one or more layers of dielectric material formed on a substrate. The substrate may be made of any type of metal or non-metal material. In various embodiments, the support structure 220 of the cable 205 and the support structure 260 of the branch connector 255 are the same structure (i.e., the support structure is continuous from the proximal end 210 to the distal end 215), which thus creates a monolithic cable. In alternative embodiments, the support structure 220 of the cable 205 and the support structure 260 of the branch connector 255 are different structures, but are connected such that there is an electrical connection between the conductive traces 225, the wiring layer 245, one or more electrodes 240, and one or more conductive traces 275.

[0075] In various embodiments, one or more conductive traces 275 are multiple traces, such as two or more conductive traces or from two to twenty-four conductive traces. The multiple conductive traces 275 are composed of one or more layers of conductive material. The conductive material selected for one or more conductive traces 275 should have good electrical conductivity and can include pure metals, metal alloys, combinations of metals and dielectrics, etc. For example, the conductive material can 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 one or more conductive traces 275 has a thermal expansion characteristic or coefficient of thermal expansion (CTE) that is approximately equal to the CTE of the support structure 260. It is desirable to match the CTEs of components that contact each other because it eliminates the development of thermal stresses that can occur during the manufacture and 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 mostly but not necessarily completely what is specified (and include exactly what is specified), as understood by a person of ordinary skill in the art. In any disclosed embodiment, the terms "substantially", "approximately", or "about" can be replaced with "within [a certain percentage] of" what is specified, where the percentage includes 0.1%, 1%, 5%, and 10%.

[0076] The branch connector 255 may also include a plurality of plugs 280 extending from the body 265. In some embodiments, at least one of the plurality of plugs 280 includes: an end 285 of the support structure 260, composed of one or more layers of dielectric material; and a subset 290 of conductive traces from the plurality of conductive traces 275. The base 270 of the support structure 260 and each end 285 of the support structure 260 may be integral. At least one trace from the subset 290 of conductive traces may terminate at a bonding pad 295 exposed on the surface of the end 285 of the support structure. In an alternative embodiment, each of the plurality of plugs 280 includes: an end 285 of the support structure 260, composed of one or more layers of dielectric material; and a subset 290 of conductive traces from the plurality of conductive traces 275. Each trace from the subset 290 of conductive traces may terminate at a bonding pad 295 exposed on the surface of the end 285 of the support structure. As should be understood, in some embodiments, each electrode from one or more electrodes 240 is electrically connected to a corresponding bonding pad via the corresponding wiring layer 245, optional contacts, conductive traces 225, conductive traces 275, subset 290 of conductive traces, and bonding pad 295. In other words, each electrode may be electrically connected to a different bonding pad (a one-to-one relationship). In an alternative embodiment, a multiplexer chip may be used such that one or more electrodes from one or more electrodes 240 are electrically connected to a single bonding pad 295 via the wiring layer 245, optional contacts, conductive traces 225, conductive traces 275, and subset 290 of conductive traces. In other words, each electrode may be electrically connected to the same or different bonding pads (a many-to-one relationship).

[0077] One or more conductive traces 275 and a subset of conductive traces 290 can be deposited onto the surface of the support structure 260 by using thin-film deposition techniques known to those skilled in the art, such as by sputter deposition, chemical vapor deposition, metal-organic chemical vapor deposition, electroplating, electroless plating, etc. In some embodiments, the thickness of one or more conductive traces 275 and the subset of conductive traces 290 depends on the specific impedance required for the conductor in order to ensure excellent signal integrity (e.g., electrical signal integrity for stimulation or recording). For example, if a conductor with a relatively high impedance is desired, a conductive material with a small thickness should be deposited onto the support structure 260. However, if a signal plane with a relatively low impedance is desired, a conductive material with a larger thickness should be deposited onto the support structure 260. In certain embodiments, each of the one or more conductive traces 275 and the subset of conductive traces 290 has a thickness (t). In some embodiments, the thickness (t) ranges from 0.5 μm to 25 μm or from 5 μm to 10 μm, such as about 5 μm or about 8 μm. In some embodiments, each of the one or more conductive traces 275 and the subset of conductive traces 290 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 and the subset of conductive traces 290 has a width (w) of from 2.0 μm to 500 μm (e.g., about 30 μm or about 50 μm).

[0078] As Figure 3 shown, in accordance with aspects of the present disclosure, a branch connector 300 (e.g., such as the branch connector 255 discussed with respect to Figure 2 ) can be formed on the support structure 305 in a predetermined shape at the proximal end 310 of the cable 315. Specifically, as described in more detail herein, the branch connector 300 can be formed in a predetermined shape from a pre-fabricated dielectric material wafer or panel or alternatively from a substrate. For example, the branch connector 300 can be laser cut from a pre-fabricated wafer or panel into a bifurcated or multi-branched shape. Two branches are shown (branched out) in some of the figures, but it should be understood that more than two branches (multi-branched) can be used. The bifurcated or multi-branched shape can include features designed to maximize the number of contacts or bonding pads that can be fabricated for the connector while minimizing the footprint of the connector.

[0079] In some embodiments, as Figure 4AAs shown, the branch connector 400 can be formed on the support structure 405 at the proximal end 410 of the cable 415. The branch connector 400 can include: (i) a body 420 including the support structure 405 and a plurality of conductive traces 425; and (ii) a plurality of plugs 430 extending from the body 420. Each of the plurality of plugs 430 can include the support structure 405 and a subset of conductive traces 435 from the plurality of conductive traces 425. Each trace from the subset of conductive traces 435 can terminate at a bonding pad 440 exposed on the surface 445 of the support structure 405. As Figure 4A shown, one or more of the plugs 430 (or the ends of the support structure) are planar. In some embodiments, each plug 430 (or the end of the support structure) is planar. As used herein, "planar" means related to or in the form of a plane. In some embodiments, two or more of the plugs 430 (or the ends of the support structure) are coplanar with each other. In some embodiments, one or more of the plugs 430 (or the ends of the support structure) are coplanar with the body. As used herein, "coplanar" means in the same plane.

[0080] As Figure 4B (in the cross-section along X-X of the plug 430 Figure 4A ) shown, the support structure 405 of each plug 430 includes a first layer of dielectric material 450 and a second layer of dielectric material 455, and the subset of conductive traces 435 is buried between the first layer of dielectric material 450 and the second layer of dielectric material 455. In some embodiments, the first layer of dielectric material 450 includes at least one contact via 460 for each bonding pad 440. The contact via 460 can include a conductive material for electrically connecting each bonding pad 440 to at least one trace in the subset of conductive traces 435 such that each trace from the subset of conductive traces 435 terminates at the bonding pad 440. The contact via 460 can be directly or indirectly connected to at least one trace in the subset of conductive traces 435 through a wiring layer (not shown). In some embodiments, the conductive material lines at least a portion of the wall of the via hole. In additional embodiments, the conductive material fills the via hole. In some embodiments, the first layer of dielectric material 450 is a high-temperature liquid crystal polymer and the second layer of dielectric material 455 is a low-temperature liquid crystal polymer. As used herein, "high-temperature liquid crystal polymer" refers to a liquid crystal polymer having a high melting temperature above 300 °C. As used herein, "low-temperature liquid crystal polymer" refers to a liquid crystal polymer having a low melting temperature below 300 °C. In additional embodiments, as Figure 5A 、 Figure 5B 、 Figure 5C 、 Figure 5F and Figure 5GAs shown, the branch connector 500 can be formed on the support structure 505 at the proximal end 510 of the cable 515. The branch connector 500 can include: (i) a body 520 including the support structure 505 and a plurality of conductive traces 525; and (ii) a plurality of plugs 530 extending from the body 520. Each of the plurality of plugs 530 can include the support structure 505 and a subset 535 of the conductive traces from the plurality of conductive traces 525. Each trace from the subset 535 of conductive traces can terminate at a bonding pad 540 exposed on the surface 545 of the support structure 505. As Figure 5F shown, one or more of the plugs 530 (or the ends of the support structure) are cylindrical tubes 565. Although the plugs are described herein with respect to the cylindrical tube shape, it should be understood that other shapes of the plugs have been contemplated, such as spherical, cubic, toroidal, ellipsoidal, etc. In some embodiments, each plug 530 (or the end of the support structure) is a cylindrical tube 565. As used herein, "cylindrical" means having straight parallel sides and a circular or oval cross-section; being of cylindrical shape or form.

[0081] As Figure 5G (in the cross-section along Figure 5B Y-Y of the plug 530) shown, the support structure 505 of each plug 530 includes a first dielectric material 550 and a second dielectric material 555, and the subset 535 of conductive traces is buried between the first dielectric material 550 and the second dielectric material 555. In some embodiments, the first dielectric material 550 includes at least one via contact 560 for each bonding pad 540. The via contact 560 can include a conductive material for electrically connecting each bonding pad 540 to at least one trace in the subset 535 of conductive traces such that each trace from the subset 535 of conductive traces terminates at the bonding pad 540. The via contact 560 can be directly or indirectly connected to at least one trace in the subset 535 of conductive traces through a wiring layer (not shown). In some embodiments, the conductive material is lined on at least a portion of the wall of the via hole. In additional embodiments, the via hole is filled with the conductive material. In some embodiments, the first dielectric material 550 is a high-temperature liquid crystal polymer and the second dielectric material 555 is a low-temperature liquid crystal polymer.

[0082] As Figure 5FAs shown, the cylindrical tube 565 includes one or more layers of dielectric material 550 / 555. The first layer of dielectric material 550 may define the outer diameter (d) of the cylindrical tube 565, and the second layer of dielectric material 555 may define the inner diameter (d') of the tube. The cylindrical tube 565 may further include a core 570 that at least partially fills the interior of the cylindrical tube 565 defined by the inner diameter (d') of the cylindrical tube 565. The core 570 may be composed of one or more layers of material such that the core 570 has a Shore hardness greater than 70D. In some embodiments, one or more layers of material of the core 570 are polyimide, liquid crystal polymer, parylene, polyetheretherketone, polyurethane, metal, or a combination thereof. In certain embodiments, one or more layers of material of the core 570 are thermoset or thermoplastic polyurethane. One or more layers of dielectric material 550 / 555 may at least partially wrap around the core 570. In certain embodiments, one or more layers of dielectric material 550 / 555 are formed as a split cylindrical tube that wraps around the core 570, and the split cylindrical tube includes a gap 575 for the split having a predetermined width (z). The predetermined width may be between 0.1 mm and 10 mm, such as about 2 mm.

[0083] As Figure 5A , Figure 5B , Figure 5C and Figure 5FAs shown, in some embodiments, one or more of the bonding pads 540 are split annular rings that are positioned about the axis 580 of the cylindrical tube 565 and exposed on the surface 585 of the cylindrical tube 565. Each split annular ring may be spaced from each other on the surface 585 of the cylindrical tube 565 by a region 590 of the first dielectric material 550. The width (p) of the region 590 of the first dielectric material 550 that separates each split annular ring may be between 1.0 mm and 10 mm, such as about 3 mm. In some embodiments, each split annular ring is connected to a single trace from a subset of the conductive traces 535. In additional embodiments, each split annular ring is connected to two or more traces from the subset of conductive traces 535. For example, the left side of the split annular ring may be connected to a first trace and the right side of the annular ring may be connected to a second trace. Alternatively, a multiplexer chip may be used to drive the signals, and thus the split annular ring may be connected to multiple traces from the conductive traces 535. In various embodiments, eight bonding pads 540 or split annular rings are positioned about the axis 580 of each cylindrical tube 565 and exposed on the surface 585 of each cylindrical tube 565; however, it should be understood that more or fewer than eight bonding pads 540 or split annular rings may be located on the cylindrical tube 565. For example, each cylindrical tube 565 may have the same or different numbers of bonding pads 540 or split annular rings (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, etc.) to enhance the design flexibility of the branch connector 500.

[0084] As Figures 5A - 5F shown, in various embodiments, the branch connector 500 may be part of a monolithic thin film lead assembly 592 that includes a cable 515 and an electrode assembly 594 (e.g., the cable 205 and electrode assembly 230 discussed with respect to Figure 2 ). In some embodiments, the support structure of the cable 515 and the support structure of the branch connector 500 are the same structure (i.e., the support structure is continuous from the proximal end 510 to the distal end), which thus creates a monolithic cable. The branch connector 500 may include a stylus lumen 595 that is integral with or a connected extension of the lumen of the cable 515. The stylus lumen 595 provides compatibility with existing surgical techniques in which the lead assembly 592 is implanted by sliding a rigid stylus through the center of the cable 515.

[0085] Although the branch connector has been described in terms of a certain length and some details with respect to specific design and / or performance requirements, this is not intended to limit the branch connector to any such specific design and / or performance requirements. Instead, it should be understood that the branch connectors described herein are exemplary embodiments, and the branch connectors will be construed in the broadest sense to include variations of the specific design and / or performance requirements described herein as well as other variations known to those skilled in the art. In particular, the shape and location of components and layers in the branch connector can be adjusted or modified to meet specific design and / or performance requirements. Additionally, it will be understood that other structures have been omitted from the description of the branch connector for clarity. The omitted structures can include insulating layers, interconnecting components, passive devices, and the like.

[0086] IV. Method for Manufacturing a Branch Connector

[0087] Figures 6A - 6M Shown are structures and corresponding processing steps for manufacturing a flexible printed circuit board 600 (e.g., as described with respect to Figure 2 , Figure 3 , Figure 4A , Figure 4B and Figures 5A - 5G ). Those skilled in the art will appreciate that the flexible printed circuit board 600 can be manufactured in many different ways using many different tools. However, in general, the methods and tools for forming the structures of the various embodiments can be adopted from integrated circuit (IC) technology. For example, the structures of the various embodiments (e.g., support structures, conductive traces, electrodes, sensors, wiring layers, bond / contact pads, etc.) can be built with or without a substrate and implemented as a patterned film of material via a lithographic process. Specifically, the fabrication of the various structures described herein generally can use three basic building blocks: (i) depositing a film of material on a substrate and / or a previous (multiple) film, (ii) applying a patterned mask over the (multiple) film via lithographic imaging, and (iii) selectively etching the (multiple) film to the mask.

[0088] As used herein, the term "deposition" can include any known or later developed technique suitable for the material to be deposited, including but not limited to, for example: chemical vapor deposition (CVD), low pressure CVD (LPCVD), plasma enhanced CVD (PECVD), sub-atmospheric pressure CVD (SACVD), and high density plasma CVD (HDPCVD), rapid thermal CVD (RTCVD), ultra-high vacuum CVD (UHVCVD), limited reaction processing CVD (LPRCVD), metalorganic CVD (MOCVD), sputter deposition, ion beam deposition, electron beam deposition, laser-assisted deposition, thermal oxidation, thermal nitridation, spin coating methods, physical vapor deposition (PVD), atomic layer deposition (ALD), chemical oxidation, molecular beam epitaxy (MBE), plating (e.g., electroplating) or evaporation.

[0089] Figure 6A A cross-section of a starting structure (support structure) is shown, which includes a first polymer layer 605 superimposed on an optional substrate 610 (e.g., a backing). In some embodiments, the starting structure can be provided, obtained, or fabricated as a single sheet or panel having a diameter, length, and / or width of less than 15 cm. In additional embodiments, the starting structure can be provided, obtained, or fabricated for a reel-to-reel process where the substrate is long and large to reduce costs. For example, a panel that is at least 20×23 cm rectangular can be used. Substrate 610 can be composed of any type of metal or non-metal material. For example, substrate 610 can be formed from but not limited to the following materials: silicon, germanium, silicon-germanium, silicon carbide, and those materials substantially composed of one or more group III-V compound semiconductors, the group III-V compound semiconductors having a composition defined by the chemical formula AlX1GaX2InX3AsY1PY2NY3SbY4, where X1, X2, X3, Y1, Y2, Y3, and Y4 represent relative proportions each greater than or equal to zero, and X1+X2+X3+Y1+Y2+Y3+Y4 = 1 (1 being the total relative molar amount). Substrate 610 can additionally or alternatively be composed of a group II-VI compound semiconductor having a composition ZnA1CdA2SeB1TeB2, where A1, A2, B1, and B2 are relative proportions each greater than or equal to zero, and A1+A2+B1+B2 = 1 (1 being the total molar amount). As shown and described, the processes for providing, obtaining, or fabricating substrate 610 are well known in the art and thus no further description is provided here.

[0090] The first polymer layer 605 can be composed of a dielectric material (i.e., an insulator). The dielectric material can be selected from the group of flexible non-conductive materials consisting of organic or inorganic polymers, polyimide-epoxy resins, epoxy-fiberglass, etc. In certain embodiments, the dielectric material is a thermoplastic or thermosetting polymer. For example, the polymer can be polyimide, LCP, parylene, PEEK, or a combination thereof. The formation of the first polymer layer 605 can include depositing and curing the dielectric material directly on the substrate 610 without an adhesion promoter. For example, a solution composed of an imidizable polyamic acid compound dissolved in an evaporable organic solvent without an adhesion promoter can be deposited (e.g., spin-coated) onto the substrate 610. Then the solution can be heated at a temperature preferably below 250 °C to imidize the polyamic acid compound, thereby forming the desired polyimide and evaporating the solvent. Then the first polymer layer 605 can be thinned to a desired thickness by planarization, grinding, wet etching, dry etching, oxidation followed by oxide etching, or any combination thereof. This process can be repeated to achieve the desired thickness of the first polymer layer 605. In some embodiments, the first polymer layer 605 can have a thickness ranging from 10 μm to 150 μm. In some embodiments, the first polymer layer 605 can have a thickness ranging from 25 μm to 100 μm. In some embodiments, the first polymer layer 605 can have a thickness ranging from 35 μm to 75 μm. Figure 6B A top view showing the starting structure is presented, which shows that the first polymer layer 605 can include a main body portion 615 and a plurality of end portions 620 extending from the main body portion 605. In some embodiments, the main body portion 615 and the plurality of end portions 620 are coplanar.

[0091] Figure 6C A conductive trace 625 formed as a first pattern on the main body portion 615 of the first polymer layer 605 is shown. In some embodiments, forming the conductive trace 625 includes depositing a seed layer (e.g., a platinum (Pt) seed layer, a platinum / iridium (Pt / Ir) seed layer, etc.) on top of the first polymer layer 605. The seed layer can be configured to enable the formation of a conductive trace on the first polymer layer 605 (e.g., by platinum (Pt) electroplating, platinum / iridium (Pt / Ir) electroplating, etc.). Optionally, an adhesion layer can be deposited on top of the first polymer layer 605 before forming the seed layer to enable sufficient application of the seed layer. The deposition of one or both of the adhesion layer and the seed layer can include sputter deposition.

[0092] After depositing the seed layer, a resist pattern can be formed over the first polymer layer 605. The resist pattern can include openings aligned over at least a portion of the first polymer layer 605 for forming multiple conductive traces 625 (e.g., a conductive layer having a cross-sectional thickness from 0.5 μm to 100 μm or from 25 μm to 50 μm) on the first polymer layer 605. For example, the resist can be patterned with the openings to form: (i) a first conductive trace 625 over a first region of the first polymer layer 605, (ii) a second conductive trace 625 over a second region of the first polymer layer 605, (iii) a third conductive trace 625 over a third region of the first polymer layer 605, and (iv) a fourth conductive trace 625 over a fourth region of the first polymer layer 605. In various embodiments, the openings in the resist can have a first pattern that maintains a first predetermined distance between each of the conductive traces 625. The first pattern can include features designed to minimize the footprint of the flexible printed circuit board 600. Although only four conductive traces are described with respect to the processes discussed above, it should be understood that any number of individual conductive traces can be deposited onto the first polymer. For example, each of the four conductive traces described above can actually include four individual conductive traces to provide a total of sixteen conductive traces that are respectively connected to the contact pads described herein (see, e.g., step 6J).

[0093] In various embodiments, the conductive traces 625 can be deposited by electroplating (e.g., by Cu electroplating, Au electroplating, Sn electroplating, Ag electroplating, Au / Cr electroplating, etc.) and can be located over at least a portion (e.g., the first region, the second region, the third region, and the fourth region) of the first polymer layer 605. The electroplating can be performed at a current density of from about 4.0 mA / cm2 to about 4.5 mA / cm2. In some embodiments, the exposed area or portion of the first polymer layer 605 can enclose from about 2 cm 2 to about 8 cm 2 . The current can be from about 14 mA to about 18 mA and the duration can be from about 110 minutes to about 135 minutes to form a conductive trace 625 having a thickness of from about 8 μm to about 10 μm. In additional embodiments, the exposed area or portion of the first polymer layer 605 can enclose from about 1 cm 2 to about 12 cm 2 . The current can be from about 18 mA to about 28 mA and the duration can be from about 35 minutes to about 50 minutes to form a conductive trace 625 having a thickness of from about 2 μm to about 5 μm.

[0094] After depositing the conductive traces 625, the intermediate structure can be subjected to a lift-off resist to remove the resist pattern and expose portions of the seed layer (portions where no wire is formed), and optionally expose the adhesive layer. Then, the exposed portions of the seed layer and optionally the adhesive layer can be subjected to etching (e.g., wet etching, dry etching, etc.) to remove those portions, thereby isolating the conductive traces 625 over at least a portion of the first polymer layer 605. Figure 6D A top view showing the conductive traces 625 formed as a first pattern on the main body portion 615 of the first polymer layer 605.

[0095] Figure 6E A subset of conductive traces 630 formed as a second pattern on each of the plurality of ends 620 is shown. In some embodiments, the subset of conductive traces 630 is formed in a manner similar to that described for the conductive traces 625 and will not be repeated here. In certain embodiments, the subset of conductive traces 630 can be formed synergistically or simultaneously with the conductive traces 625. In additional embodiments, the subset of conductive traces 630 can be formed after the conductive traces 625. In various embodiments, the openings in the resist can have a second pattern that maintains a second predetermined distance between each of the traces in the subset of conductive traces 630. The second pattern electrically connects each of the traces in the subset of conductive traces 630 to each of the plurality of traces 625, respectively. In some embodiments, the first pattern and the second pattern are the same. In additional embodiments, the first pattern and the second pattern are different. Similarly, the first predetermined distance and the second predetermined distance can be the same or different. The second pattern can include features designed to minimize the footprint of the flexible printed circuit board 600 and maximize the possible number of contacts for each branch. Figure 6F A top view showing a subset of conductive traces 630 formed as a second pattern on each of the plurality of ends 620.

[0096] Figure 6G A second polymer layer 635 formed over the first polymer layer 605, the plurality of conductive traces 625, and each subset of conductive traces 630 is shown. The second polymer layer 635 can be composed of a dielectric material (i.e., an insulator). The dielectric material can be selected from the group of flexible non-conductive materials consisting of organic or inorganic polymers, polyimide-epoxy resins, epoxy-fiberglass, etc. In certain embodiments, the dielectric material is a thermoplastic or thermosetting polymer. For example, the polymer can be polyimide, LCP, silicone, parylene, PEEK, or a combination thereof. The second polymer layer 635 can be composed of the same or different material as the material of the first polymer layer 605. For example, the first layer of dielectric material can be a high-temperature liquid crystal polymer and the second layer of dielectric material can be a low-temperature liquid crystal polymer.

[0097] The formation of the second polymer layer 635 can include depositing and curing a polymer material directly on the first polymer layer 605, the plurality of conductive traces 625, and each subset of conductive traces 630. For example, a solution composed of an imidizable polyamic acid compound dissolved in an evaporable organic solvent can be applied to the first polymer layer 605, the plurality of conductive traces 625, and each subset of conductive traces 630. The solution can then be heated at a temperature preferably below 250 °C to imidize the polyamic acid compound, thereby forming the desired polyimide and evaporating the solvent. The second polymer layer 635 can then be thinned to a desired thickness by planarization, grinding, wet etching, dry etching, oxidation followed by re-oxide etching, or any combination thereof. This process can be repeated to achieve the desired thickness of the second polymer layer 635.

[0098] In some embodiments, the second polymer layer 635 can have a thickness ranging from 1.0 μm to 50.0 μm. In some embodiments, the second polymer layer 635 can have a thickness ranging from 4.0 μm to 15.0 μm. In some embodiments, the second polymer layer 635 can have a thickness ranging from 5.0 μm to 7.0 μm. Figure 6H A top view showing the second polymer layer 635 formed on the first polymer layer 605, the plurality of conductive traces 625, and each subset of conductive traces 630.

[0099] In various embodiments, the flexible printed circuit board 600 can further include one or more contact vias 640 and one or more bonding pads 645 that support electrical connection to the electronic module of the nerve stimulator. Figure 6I Shown formed in Figure 6G At least one contact via 640 is formed on the second polymer layer 635, which is electrically connected to at least one trace of the plurality of conductive traces 625 and at least one trace of the subset of conductive traces 630. In some embodiments, forming the flexible printed circuit board 600 further includes forming at least one contact via 640 in the second polymer layer 635 at each of the plurality of ends 620 such that at least one contact via 640 is in electrical contact with at least one trace of the plurality of conductive traces 625 and at least one trace of the subset of conductive traces 630. The contact via 640 can be formed of a conductive material, for example, using conventional photolithography, etching, and cleaning processes known to those skilled in the art. The contact via 640 can be directly or indirectly connected to at least one trace of the subset of conductive traces 630 through a wiring layer (e.g., a wiring layer formed in cooperation with the deposition of the subset of conductive traces 630 in step 6C). In some embodiments, a conductive material is lined on at least a portion of the wall of the via hole. In additional embodiments, the via hole is filled with a conductive material.

[0100] Figure 6JIt is shown that at least one bonding pad 645 is formed on the second polymer layer 635 at each of the plurality of ends 620 such that each bonding pad 645 is in electrical contact with at least one contact via 640.

[0101] In some embodiments, forming the bonding pads 645 includes patterning a wiring layer on the second polymer layer 635. The wiring layer can be formed in a manner similar to that described with respect to the conductive traces 625 and the subset of conductive traces 630, and thus will not be repeated here. Figure 6K A top view showing the bonding pads 645 formed on each of the plurality of ends 620 is shown.

[0102] Figure 6L An optional third polymer layer 655 is shown which is formed over the second polymer layer 635 in the region 660 between the body portion 615 and the plurality of ends 620 to strengthen the connection between each end 620 and the body portion 615. The third polymer layer 655 can be composed of a dielectric material (i.e., an insulator). The dielectric material can be selected from the group of flexible non-conductive materials consisting of organic or inorganic polymers, polyimide-epoxy resins, epoxy-fiberglass, etc. In certain embodiments, the dielectric material is a thermoplastic or thermosetting polymer. For example, the polymer can be polyimide, LCP, silicone, parylene, PEEK, or a combination thereof. The third polymer layer 655 can be composed of the same or different material as the material of the first polymer layer 605 and / or the second polymer layer 635.

[0103] Figure 6M A final integrated structure of the flexible printed circuit board 600 including the body portion 615 and the plurality of ends 620 is shown. For example, the flexible printed circuit board 600 can be cut from the first polymer layer 605 and the second polymer layer 635 and includes the body portion 615 and the plurality of ends 620 extending from the body portion 605. In some embodiments, the cutting is done using a laser and known techniques. Optionally, the flexible printed circuit board 600 can be separated from the substrate 610.

[0104] Figures 7A - 7H A structure and corresponding processing steps for manufacturing a thin film branch connector 700 (e.g., a branch connector manufactured by injecting and curing a thermosetting polymer) according to various aspects of the present invention are shown. Figure 7A A starting structure 705 for a branch connector is shown which includes a body portion 710 and a plurality of ends 715 extending from the body portion 710. The starting structure 705 can be formed according to the process described herein with reference to Figures 6A - 6M For example, the starting structure 705 can be laser cut from the first and second polymer layers manufactured with electroplated traces and bonding pads in a branched design.

[0105] Figure 7B Each end 715 is shown, which is at least partially wound around the mandrel 720 respectively, such that each end 715 is in the shape of a cylindrical tube to form an intermediate structure 725. In various embodiments, the mandrel 720 is selected and the winding is controlled such that the cylindrical tube includes one or more features including a radius, a slit or gap, or non-overlapping ends. The radius is determined by the outer diameter of the mandrel 720 and can be from 300 μm to 900 μm, from 500 μm to 800 μm, or from 600 μm to 700 μm, for example, about 650 μm. In some embodiments, each end 715 is partially wound around the mandrel 720 respectively such that the plurality of cylindrical ends are a plurality of split cylindrical ends, and each split cylindrical end of the plurality of split cylindrical ends includes a gap for a slit having a predetermined width. In some embodiments, the mandrel 720 includes a coating such as polytetrafluoroethylene (PTFE) for easier removal of the end 715 from the mandrel 720.

[0106] Figure 7C The ends 715 of the intermediate structure 725 are shown to be inserted into heat shrink tubes 730 respectively to form an intermediate structure 735. In various embodiments, the heat shrink tubes 730 are composed of one or more polymer resins (e.g., fluoropolymers such as peelable heat shrink tubes, fluorinated ethylene propylene (FEP), etc.). Figure 7D The intermediate structure 735 is shown to be heated to cause the heat shrink tubes 730 to thermally contract, thereby defining the outer diameter of the cylindrical tube of the intermediate structure 735. The heating process can include baking the structure in an oven, using a heat gun, applying hot air, similar methods, or any combination thereof. In various embodiments, the intermediate structure 735 is heated at 170 °C to 210 °C (e.g., about 190 °C) for 15 to 40 minutes (e.g., 25 minutes). Thereafter, the intermediate structure 735 is cooled (e.g., at ambient temperature), and the mandrel 720 is withdrawn to obtain the intermediate structure 740, as Figure 7E shown. In various embodiments, the heating process causes each end 715 to be in the shape of a cylindrical tube having an inner cavity 745.

[0107] Figure 7FIt is shown that the polymer 750 is injected into each end 715 of the intermediate structure 740. In various embodiments, the polymer consists of a medical-grade polymer material (e.g., a polymer such as epoxy resin, polyurethane, copolymers thereof, or mixtures thereof). In some embodiments, the polymer is a thermosetting polymer. In certain embodiments, the polymer consists of a medical-grade polymer material having a Shore hardness greater than 70D measured on the Shore 00 scale when cured. (The Shore hardness is defined as the resistance of a material to indentation). The polymer 750 can be injected into each end 715 one or more times to completely fill the length of the cylindrical tube or a portion of the length of the cylindrical tube to obtain the intermediate structure 755.

[0108] Figure 7G It is shown that the intermediate structure 755 is heated to thermally cure (e.g., thermoset) the polymer 750. The heating process can include heating the structure in an oven, using a heat gun, applying hot air, similar methods, or any combination thereof. In various embodiments, the intermediate structure 755 is heated at 80 °C to 115 °C (e.g., about 100 °C) for 5 to 20 minutes, e.g., 10 minutes. Thereafter, the intermediate structure 755 is cooled (e.g., at ambient temperature), and the heat shrink tube 730 is peeled off to obtain Figure 7H the final structure of the thin film branch connector 700 shown. The final structure includes each end 715 having first and second polymer layers that at least partially wrap around a core made of the polymer 750. In some embodiments, the injection process and the heating process cause at least a portion of each end 715 to be respectively embedded in the polymer 750. In some embodiments, the injection process and the heating process embed a portion of each end 715 respectively in the polymer 750, forming a combined solid tube without a lumen.

[0109] Figures 8A - 8E It is shown the structure and corresponding processing steps for manufacturing an alternative thin film branch connector 800 (e.g., a branch connector manufactured by reflowing a pre-defined thermoplastic polymer core) according to various aspects of the present invention. Figure 8A It is shown a starting structure 805 for a branch connector, which includes a body portion 810 and a plurality of ends 815 extending from the body portion 810. The starting structure 805 can be formed according to the process described herein with reference to Figures 6A - 6M the description. For example, the starting structure 805 can be laser cut from first and second polymer layers manufactured with electroplated traces and bonding pads in a branched design.

[0110] Figure 8BEach end 815 is shown, which is at least partially wound around a polymer tube 820 such that each end 815 has a cylindrical tube shape to form an intermediate structure 825. In various embodiments, the polymer tube 820 is selected and the winding is controlled such that the cylindrical tube includes one or more features including a radius, a slit or gap, or non-overlapping ends. The radius is determined by the outer diameter of the polymer tube 820 and can be from 50 μm to 700 μm, from 100 μm to 600 μm, or from 100 μm to 450 μm, such as about 350 μm. In some embodiments, each end 815 is partially wound around the polymer tube 820 such that the plurality of cylindrical ends are a plurality of split cylindrical ends, and each of the plurality of split cylindrical ends includes a gap for the slit having a predetermined width. In some embodiments, the polymer tube 820 includes a thermoplastic polymer. In certain embodiments, the thermoplastic polymer is polyurethane.

[0111] Figure 8C The ends 815 of the intermediate structure 825 are shown inserted into a heat shrink tube 830 to form an intermediate structure 835. In various embodiments, the heat shrink tube 830 is composed of one or more polymer resins (e.g., fluoropolymers such as peelable heat shrink tube, fluorinated ethylene propylene (FEP), etc.). Figure 8D The intermediate structure 835 is shown being heated to cause the heat shrink tube 830 to thermally shrink, thereby defining the outer diameter of the cylindrical tube of the intermediate structure 835, while melting and reflowing the polymer tube 820 to embed each end 815 respectively within the polymer tube 820. The heating process can include baking the structure in an oven, using a heat gun, applying hot air, similar methods, or any combination thereof. In various embodiments, the intermediate structure 835 is heated at 170 °C to 210 °C (e.g., about 190 °C) for 15 to 40 minutes, such as 25 minutes. Thereafter, the intermediate structure 835 is cooled (e.g., at ambient temperature), and the heat shrink tube 830 is peeled off to obtain Figure 8E the final structure of the thin film branch connector 800 as shown. The final structure includes each end 815 having first and second polymer layers that at least partially wind around a core made of the polymer tube 820. In some embodiments, the heating process causes at least a portion of each end 815 to be respectively embedded within the polymer tube 820. In some embodiments, the heating process embeds a portion of each end 815 respectively within the polymer tube 820 to form a combined solid tube without a lumen.

[0112] Although the manufacturing processes of the branch connectors have been described in a certain length and with a certain level of detail regarding specific steps, it is not intended that these processes be limited to any such particular set of steps. Rather, it should be understood that the manufacturing processes described herein are exemplary embodiments, and the manufacturing processes will be construed in the broadest sense to include variations of the steps that meet the specific design and / or performance requirements described herein, as well as other variations known to those skilled in the art. For example, the various intermediate and final structures described can be adjusted or modified through processing to improve the wettability of the thin film lead assembly or seal the ends of the sealed lumen, so as to meet specific design and / or performance requirements. In addition, it will be understood that other steps have been omitted from the description of the manufacturing processes for simplicity and clarity. The omitted steps may include obtaining or manufacturing polymer tubes, obtaining or manufacturing heat shrink tubes, waiting for a predetermined amount of time for curing or thermal curing, and the like.

[0113] Although the present invention has been described in detail, modifications within the spirit and scope of the present invention will be readily apparent to those skilled in the art. It should be understood that aspects of the present invention and parts of various embodiments, as well as the various features recited in the foregoing and / or appended claims, may be combined or interchanged, in whole or in part. In the foregoing description of the various embodiments, those embodiments that refer to another embodiment may be appropriately combined with other embodiments, as will be understood by those skilled in the art. In addition, those skilled in the art will understand that the foregoing description is merely exemplary and is not intended to limit the present invention.

Claims

1. A proximal branch connector, comprising: a body including a base of a support structure and a plurality of conductive traces formed on the base, wherein the base of the support structure is composed of a multi-layer dielectric material; and a plurality of plugs extending and branching from the body, each of the plurality of plugs including: an end of the support structure composed of the multi-layer dielectric material; and a subset of conductive traces from the plurality of conductive traces, wherein each trace from the subset of conductive traces terminates at a bonding pad exposed on a surface of the end of the support structure, wherein each of the ends of the support structure is a cylindrical tube, wherein the multi-layer dielectric material includes a first layer dielectric material and a second layer dielectric material, and the subset of conductive traces is buried between the first layer dielectric material and the second layer dielectric material, and wherein the cylindrical tube includes: (i) the first layer dielectric material and the second layer dielectric material, wherein the first layer dielectric material defines an outer diameter of the cylindrical tube, and the second layer dielectric material defines an inner diameter of the cylindrical tube; and (ii) a core at least partially filling an interior of the cylindrical tube defined by the inner diameter of the cylindrical tube.

2. The proximal branch connector according to claim 1, wherein the dielectric material is polyimide, liquid crystal polymer, parylene, polyether ether ketone, or a combination thereof.

3. The proximal branch connector according to claim 1 or 2, wherein a coefficient of thermal expansion of the plurality of conductive traces is approximately equal to a coefficient of thermal expansion of the support structure.

4. The proximal branch connector according to claim 1 or 2, wherein the base of the support structure and each of the ends of the support structure are integral.

5. The proximal branch connector according to claim 1, wherein each bonding pad is a split annular ring positioned around an axis of the cylindrical tube and exposed on a surface of the cylindrical tube.

6. The proximal branch connector according to claim 5, wherein each split annular ring is spaced apart from each other on the surface of the cylindrical tube by a region of the first layer dielectric material.

7. The proximal branch connector according to claim 6, wherein a width of the region of the first layer dielectric material separating each split annular ring is between 1.0 mm and 10 mm.

8. The proximal branch connector according to claim 1, wherein the first layer dielectric material and the second layer dielectric material at least partially wind around the core.

9. The proximal branch connector according to claim 8, wherein the first layer dielectric material and the second layer dielectric material are formed as a split cylindrical tube winding around the core, and the split cylindrical tube includes a gap for a split with a predetermined width.

10. The proximal branch connector according to claim 9, wherein the predetermined width is between 0.1 mm and 10 mm.

11. The proximal branch connector according to claim 8, wherein the first layer of dielectric material includes at least one via for each bonding pad, and the at least one via includes a conductive material for electrically connecting each bonding pad to at least one trace of the subset of conductive traces such that each trace from the subset of conductive traces terminates at a bonding pad.

12. The proximal branch connector according to claim 8, wherein the first layer of dielectric material is a high-temperature liquid crystal polymer and the second layer of dielectric material is a low-temperature liquid crystal polymer.

13. The proximal branch connector according to claim 8, wherein the core is composed of one or more layers of material such that the core has a Shore hardness greater than 70D.

14. The proximal branch connector according to claim 13, wherein the one or more layers of material of the core are polyimide, liquid crystal polymer, parylene, polyether ether ketone, polyurethane, metal, or a combination thereof.

15. The proximal branch connector according to claim 13, wherein the one or more layers of material of the core are thermosetting or thermoplastic polyurethane.

16. An integral thin-film lead assembly, comprising: A cable including a proximal end, a distal end, a support structure extending from the proximal end to the distal end, and a plurality of conductive traces formed on a portion of the support structure, wherein the support structure is composed of a multi-layer dielectric material; An electrode assembly formed on the support structure at the distal end of the cable, wherein the electrode assembly includes one or more electrodes electrically connected to one or more of the plurality of conductive traces; And A branch connector formed on the support structure at the proximal end of the cable, wherein the branch connector includes: (i) a body including the support structure and the plurality of conductive traces, and (ii) a plurality of plugs extending and branching from the body, each of the plurality of plugs including the support structure and a subset of conductive traces from the plurality of conductive traces, wherein each trace from the subset of conductive traces terminates at a bonding pad exposed on a surface of the support structure.

17. The integral thin-film lead assembly according to claim 16, wherein the dielectric material is polyimide, liquid crystal polymer, parylene, polyether ether ketone, or a combination thereof.

18. The integral thin-film lead assembly according to claim 16 or 17, wherein the support structure of each plug is planar.

19. The integral thin-film lead assembly according to claim 16 or 17, wherein the support structure of each plug is a cylindrical tube.

20. The integral thin-film lead assembly according to claim 19, wherein the support structure of each plug includes a first layer of dielectric material and a second layer of dielectric material, and the subset of conductive traces is buried between the first layer of dielectric material and the second layer of dielectric material.

21. The integral thin-film lead assembly according to claim 20, wherein each bonding pad is a split annular ring positioned around an axis of the cylindrical tube and exposed on a surface of the cylindrical tube.

22. The monolithic thin film lead assembly according to claim 21, wherein each split annular ring is spaced apart from each other on the surface of the cylindrical tube by a region of the first dielectric material.

23. The integral thin film lead assembly according to claim 20, wherein the cylindrical tube comprises: (i) The first dielectric material and the second dielectric material, wherein the first dielectric material defines the outer diameter of the cylindrical tube, and the second dielectric material defines the inner diameter of the cylindrical tube; and (ii) a core that at least partially fills the interior of the cylindrical tube defined by the inner diameter of the cylindrical tube.

24. The monolithic thin film lead assembly according to claim 23, wherein the first dielectric material and the second dielectric material at least partially wind around the core.

25. The monolithic thin film lead assembly according to claim 24, wherein the first dielectric material and the second dielectric material are formed as a split cylindrical tube that winds around the core, and the split cylindrical tube includes a gap for the split having a predetermined width.

26. The monolithic thin film lead assembly according to claim 25, wherein the first dielectric material includes at least one via for each bonding pad, and the at least one via includes a conductive material for electrically connecting each bonding pad to at least one trace in the subset of conductive traces such that each trace from the subset of conductive traces terminates at a bonding pad.

27. The monolithic thin film lead assembly according to claim 24, wherein the first dielectric material is a high temperature liquid crystal polymer, and the second dielectric material is a low temperature liquid crystal polymer.

28. The monolithic thin film lead assembly according to claim 24, wherein the core is composed of one or more layers of material such that the core has a Shore hardness greater than 70D.

29. A thin film lead assembly, comprising: a cable including a proximal end, a distal end, a first support structure extending from the proximal end to the distal end, and a plurality of conductive traces formed on a portion of the first support structure; an electrode assembly formed on the first support structure at the distal end of the cable, wherein the electrode assembly includes one or more electrodes electrically connected to one or more of the plurality of conductive traces; and a branch connector at the proximal end of the cable and including: (i) a body including a second support structure and a plurality of conductive connection traces, and (ii) a plurality of plugs extending and branching from the body, each of the plurality of plugs including the second support structure and a subset of the conductive connection traces from the plurality of conductive connection traces, wherein each trace from the subset of conductive connection traces terminates at a bonding pad exposed on the surface of the second support structure, and wherein the plurality of conductive connection traces of the branch connector are in electrical contact with the plurality of conductive traces of the cable, respectively.

30. The thin film lead assembly according to claim 29, wherein the second support structure is composed of a multi-layer dielectric material, and the dielectric material is polyimide, liquid crystal polymer, parylene, polyether ether ketone, or a combination thereof.

31. The thin film lead assembly according to claim 29 or 30, wherein the second support structure of each plug is planar.

32. The thin film lead assembly according to claim 30, wherein the second support structure of each plug is a cylindrical tube.

33. The thin film lead assembly according to claim 32, wherein the second support structure of each of the plugs includes a first layer of dielectric material and a second layer of dielectric material, and the subset of conductive connection traces is buried between the first layer of dielectric material and the second layer of dielectric material.

34. The thin film lead assembly according to claim 33, wherein each bonding pad is a split annular ring positioned around the axis of the cylindrical tube and exposed on the surface of the cylindrical tube.

35. The thin film lead assembly according to claim 34, wherein each split annular ring is spaced apart from each other on the surface of the cylindrical tube by a region of the first layer of dielectric material.

36. The thin film lead assembly according to claim 33, 34 or 35, wherein the cylindrical tube comprises: (i) The first layer of dielectric material and the second layer of dielectric material, wherein the first layer of dielectric material defines the outer diameter of the cylindrical tube, and the second layer of dielectric material defines the inner diameter of the cylindrical tube; and (ii) a core, at least partially filling the interior of the cylindrical tube defined by the inner diameter of the cylindrical tube.

37. The thin film lead assembly according to claim 36, wherein the first layer of dielectric material and the second layer of dielectric material at least partially wind around the core.

38. The thin film lead assembly according to claim 37, wherein the first layer of dielectric material and the second layer of dielectric material are formed as a split cylindrical tube winding around the core, and the split cylindrical tube includes a gap for the split with a predetermined width.

39. The thin film lead assembly according to claim 38, wherein the first layer of dielectric material includes at least one via for each bonding pad, and the at least one via includes a conductive material for electrically connecting each bonding pad to at least one of the traces in the subset of conductive connection traces, such that each trace from the subset of conductive connection traces terminates at a bonding pad.

40. The thin film lead assembly according to claim 37, wherein the first layer of dielectric material is a high-temperature liquid crystal polymer, and the second layer of dielectric material is a low-temperature liquid crystal polymer.

41. The thin film lead assembly according to claim 37, wherein the core is composed of one or more layers of materials such that the core has a Shore hardness greater than 70D.

42. A neuromodulation system, comprising: a nerve stimulator, including an electronic module; a cable, including a support structure and a plurality of conductive traces formed on a part of the support structure, wherein the support structure is composed of a multi-layer dielectric material; An electrode assembly formed on the support structure, wherein the electrode assembly includes one or more electrodes electrically connected to one or more of the plurality of conductive traces; and A branch connector formed on the support structure at the proximal end of the cable, wherein the branch connector includes: (i) a body including the support structure and the plurality of conductive traces, and (ii) a plurality of plugs extending and branching from the body, each of the plurality of plugs including the support structure and a subset of the conductive traces from the plurality of conductive traces, wherein the branch connector electrically connects each subset of conductive traces from the plurality of conductive traces to the electronic module.

43. The neuromodulation system according to claim 42, wherein each trace from the subset of conductive traces terminates at a bond pad exposed on the surface of the support structure.

44. The neuromodulation system according to claim 43, wherein the dielectric material is polyimide, liquid crystal polymer, parylene, polyether ether ketone, or a combination thereof.

45. The neuromodulation system according to claim 43 or 44, wherein the support structure of each plug is planar.

46. The neuromodulation system according to claim 43 or 44, wherein the support structure of each plug is a cylindrical tube.

47. The neuromodulation system according to claim 46, wherein the support structure of each plug includes a first layer of dielectric material and a second layer of dielectric material, and the subset of conductive traces is buried between the first layer of dielectric material and the second layer of dielectric material.

48. The neuromodulation system according to claim 47, wherein each bond pad is a split annular ring positioned around the axis of the cylindrical tube and exposed on the surface of the cylindrical tube.

49. The neuromodulation system according to claim 48, wherein each split annular ring is spaced apart from each other on the surface of the cylindrical tube by a region of the first layer of dielectric material.

50. The neuromodulation system according to claim 47, wherein the cylindrical tube comprises: (i) The first layer of dielectric material and the second layer of dielectric material, wherein the first layer of dielectric material defines the outer diameter of the cylindrical tube, and the second layer of dielectric material defines the inner diameter of the cylindrical tube; and (ii) a core at least partially filling the interior of the cylindrical tube defined by the inner diameter of the cylindrical tube.

51. The neuromodulation system according to claim 50, wherein the first layer of dielectric material and the second layer of dielectric material at least partially wind around the core.

52. The neuromodulation system according to claim 51, wherein the first layer of dielectric material and the second layer of dielectric material are formed as a split cylindrical tube winding around the core, and the split cylindrical tube includes a gap for the split having a predetermined width.

53. The neuromodulation system according to claim 52, wherein the first dielectric material layer includes at least one via for each bonding pad, and the at least one via includes a conductive material for electrically connecting each bonding pad to at least one trace in the subset of conductive traces such that each trace from the subset of conductive traces terminates at a bonding pad.

54. The neuromodulation system according to claim 51, wherein the first dielectric material layer is a high-temperature liquid crystal polymer and the second dielectric material layer is a low-temperature liquid crystal polymer.

55. The neuromodulation system according to claim 51, wherein the core is composed of one or more layers of material such that the core has a Shore hardness greater than 70D.

56. A method of manufacturing a proximal branch connector, comprising: obtaining a flexible printed circuit board structure including: (i) a body including a support structure and a plurality of conductive traces, and (ii) a plurality of ends extending and branching from the body, each of the plurality of ends including the support structure and a subset of conductive traces from the plurality of conductive traces, wherein each trace from the subset of conductive traces terminates at a bonding pad exposed on a surface of the support structure, and wherein the support structure includes a first polymer layer and a second polymer layer, and the subset of conductive traces is buried between the first polymer layer and the second polymer layer; respectively winding at least a portion of each of the plurality of ends around a mandrel such that each of the plurality of ends assumes a cylindrical tube shape; placing a heat shrink tube over each of the plurality of ends and the mandrel to form a first intermediate structure; heating the first intermediate structure to cause each heat shrink tube to shrink and form a second intermediate structure; removing the mandrel from the second intermediate structure such that each of the plurality of ends has an internal cavity; injecting a polymer into the internal cavity of the second intermediate structure to form a third intermediate structure; heating the third intermediate structure to form the proximal branch connector having a plurality of cylindrical ends; and removing the heat shrink tube from the proximal branch connector having the plurality of cylindrical ends, wherein each of the plurality of cylindrical ends includes the first polymer layer and the second polymer layer at least partially winding a core made of the polymer.

57. The method according to claim 56, wherein the first polymer layer is polyimide, liquid crystal polymer, parylene, polyether ether ketone, or a combination thereof.

58. The method according to claim 56 or 57, wherein the second polymer layer is polyimide, liquid crystal polymer, parylene, polyether ether ketone, or a combination thereof.

59. The method according to claim 56 or 57, wherein each end is respectively partially wound around the mandrel such that the plurality of cylindrical ends are a plurality of split cylindrical ends, and each of the plurality of split cylindrical ends includes a gap for the split having a predetermined width.

60. The method according to claim 56 or 57, further comprising forming a third polymer layer on the second polymer layer in a region between the body and the plurality of ends.

61. The method according to claim 60, wherein the third polymer layer is silicone.

62. A method of manufacturing a proximal branch connector, comprising: obtaining a flexible printed circuit board structure comprising: (i) a body including a support structure and a plurality of conductive traces, and (ii) a plurality of ends extending and branching from the body, each of the plurality of ends including the support structure and a subset of conductive traces from the plurality of conductive traces, wherein each trace from the subset of conductive traces terminates at a bonding pad exposed on a surface of the support structure, and wherein the support structure includes a first polymer layer and a second polymer layer, and the subset of conductive traces is buried between the first polymer layer and the second polymer layer; wrapping each of the plurality of ends at least partially around a polymer tube such that each of the plurality of ends is in a cylindrical tube shape; placing a heat shrink tube over each of the plurality of ends and the polymer tube to form a first intermediate structure; heating the first intermediate structure having the heat shrink tube to form the proximal branch connector having a plurality of cylindrical ends; and removing the heat shrink tube from the proximal branch connector having the plurality of cylindrical ends, wherein the heating embeds each of the plurality of ends separately into the polymer tube, and wherein each of the plurality of cylindrical ends includes the first polymer layer and the second polymer layer at least partially wrapping a core made of the polymer tube.

63. The method according to claim 62, wherein the first polymer layer is polyimide, liquid crystal polymer, parylene, polyether ether ketone, or a combination thereof.

64. The method according to claim 62 or 63, wherein the second polymer layer is polyimide, liquid crystal polymer, parylene, polyether ether ketone, or a combination thereof.

65. The method according to claim 62 or 63, wherein each end is separately partially wrapped around the polymer tube such that the plurality of cylindrical ends are a plurality of split cylindrical ends, and each of the plurality of split cylindrical ends includes a gap for the split having a predetermined width.

66. The method according to claim 62 or 63, further comprising forming a third polymer layer on the second polymer layer in a region between the body and the plurality of ends.

67. The method according to claim 66, wherein the third polymer layer is silicone.

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