Biostimulator with flexible circuit assembly

Abstract

A biostimulator, such as a leadless cardiac pacemaker, having a flexible circuit assembly is described. The flexible circuit assembly is housed within the electronics chamber between the battery of the biostimulator, the housing, and the end cap assembly. The flexible circuit assembly includes a flexible substrate that is folded into a stacked configuration in which electronic components and electrical connectors of the flexible circuit assembly are surrounded by the flexible substrate. The aperture is located in the folded region of the flexible substrate to allow the feed-through pin of the end cap assembly to pass through the folded structure to electrically contact the electrical connector. The electronic component may be a processor that controls delivery of pacing pulses through the feed-through pin to the pacing tip. Other embodiments are also described and claimed.

Description

[0001] This application is a divisional application of a patent application for invention, with the application number 201980076232.6, the application date of November 19, 2019, and the invention title of "Bio - stimulator with Flexible Circuit Assembly".

[0002] Cross - reference to Related Applications

[0003] This application claims the benefit of priority of U.S. Provisional Patent Application No. 62 / 770,088, filed on November 20, 2018, and U.S. Non - Provisional Patent Application No. 16 / 687,477, filed on November 18, 2019, which are hereby incorporated by reference in their entirety to provide continuity of disclosure. Technical Field

[0004] The present disclosure relates to bio - stimulators. More specifically, the present disclosure relates to leadless bio - stimulators having flexible circuit assemblies. Background Art

[0005] When the heart's own natural pacemaker and / or conduction system fails to provide synchronous atrial and ventricular contractions at a rate and interval sufficient to keep the patient healthy, cardiac pacing by an artificial pacemaker provides electrical stimulation to the heart. Such pacing to avoid bradycardia alleviates symptoms for tens of thousands of patients and even provides life support. Cardiac pacing can also provide electrical overdrive stimulation to suppress or convert tachyarrhythmias, again alleviating symptoms and preventing or terminating arrhythmias that can lead to sudden cardiac death.

[0006] Cardiac pacing by currently available or conventional pacemakers is typically performed by implanting a pulse generator subcutaneously or submuscularly within or near the patient's thoracic region. The parameters of the pulse generator are typically queried and modified by an external programming device via a loose - coupling transformer implemented by one inductor in the body and another inductor outside the body, or via electromagnetic radiation implemented by one antenna in the body and another antenna outside the body. The generator is typically connected to the proximal end of one or more implantable leads, the distal end of which contains one or more electrodes for positioning at locations adjacent to the inner or outer wall of the heart chamber. The lead has one or more insulated electrical conductors for connecting the pulse generator to the electrodes in the heart. Such electrode leads typically have a length of 50 to 70 centimeters.

[0007] The pulse generator can have electronic circuitry to control cardiac pacing through the leads. For example, the electronic circuitry can include a printed circuit board. The electronic circuitry can include integrated circuits to control the transfer of pacing pulses from the interior of a tightly sealed battery container to the external lead connections. Summary of the Invention

[0008] Conventional pacemakers have several drawbacks, including the complex connection between the lead and the pulse generator, and the risk of infection and morbidity due to the separate lead and pulse generator components. Many of the problems associated with conventional pacemakers can be addressed by developing self - contained and self - sustaining biostimulators or so - called leadless biostimulators. A leadless biostimulator can be attached to tissue in a dynamic environment, such as within the chambers of a beating heart. However, the attachment of a leadless biostimulator within the target anatomy increases the importance of miniaturization of the device profile. Thus, it is desirable to increase the packaging efficiency of the device, including reducing the overall volume of the electronic circuitry. In addition, the co - location of the battery and the electronic circuitry and the reduction in the overall volume of the electronic circuitry increase the risk of short - circuiting of the battery or the circuit caused by conductive residues during the manufacturing process for fabricating the leadless biostimulator. Therefore, isolating the battery conductor and the electronic circuitry from each other and from the surrounding conductive structures can improve device reliability.

[0009] A biostimulator is provided that has a flexible circuit assembly and optionally other components configured and arranged to reduce the likelihood of short - circuiting. In one embodiment, the flexible circuit assembly includes a flexible substrate having a mounting surface for carrying electrical and electronic components. The flexible substrate can be folded along a folding region such that a first mounting region and a second mounting region of the mounting surface face each other. In a folded or stacked configuration, feed - through connectors and electronic components that are both on the mounting surface can be encapsulated by the folded flexible substrate. Thus, the feed - through connectors and the electronic components can be protected and separated from surrounding conductive components, such as a housing or a battery.

[0010] The flexible circuit assembly can have an aperture in the folding region. The aperture can be centered on the mounting surface. For example, the aperture can be at the center of the folding region. The aperture axis of the aperture can extend aligned (e.g., or through or above) with the feed - through connector. Thus, a feed - through pin of an end - cap assembly can be inserted through the aperture to connect to the feed - through connector. The feed - through pin can conduct electrical pulses from the flexible circuit assembly to the target tissue.

[0011] In one embodiment, a battery connector is also on the mounting surface. For example, the feed - through connector and the battery connector can be on the first mounting region of the mounting surface, while electronic components (such as a processor) can be on the second mounting region of the mounting surface. The feed - through connector and the battery connector can be socket connectors, and the respective socket axes of the socket connectors extend parallel to each other. In one embodiment, the socket axis of the feed - through portion is laterally between the socket axes of the battery connector. Thus, when engaged with the respective connectors, the electrical pins of the feed - through portion and the battery can support the flexible circuit assembly evenly at multiple points.

[0012] The foldable flexible circuit assembly can be folded such that the flexible substrate contacts an adjacent housing and / or battery. Accordingly, the flexible substrate can separate and insulate the electrical connectors and electronic components from the surrounding structures. Alternatively, the flexible circuit assembly can be insulated from the housing and / or battery by one or more external components. In one embodiment, an end insulator is located between the battery and the flexible circuit assembly. The end insulator can be a thin-walled planar dielectric film that separates the flexible circuit assembly from the battery. The end insulator can have slits to allow battery pins to pass through the end insulator to connect to the battery connector. In one embodiment, the bio - stimulator includes a wall insulator located between the housing and the flexible circuit assembly. The wall insulator can be a thin-walled tubular dielectric sleeve that extends around the flexible circuit assembly to insulate the flexible circuit assembly from the housing.

[0013] A method of assembling a bio - stimulator having a flexible circuit assembly is described. The method can have operations performed in sequence depending on whether the electrical connector on the flexible substrate is a socket connector or a metal pad. In one embodiment, the method includes securing a housing to an end - cap assembly and a battery using a circumferential weld. The weld can hermetically seal an electronics chamber that contains the flexible circuit assembly. Accordingly, the bio - stimulator can include a desiccant within the electronics chamber to remove residual moisture that could negatively impact the performance of the electrical connectors or electronic components within the electronics chamber.

[0014] The foregoing summary does not include an exhaustive list of all aspects of the present invention. It is contemplated that the present invention includes all systems and methods that can be practiced from all suitable combinations of the various aspects outlined above and those directions disclosed in the detailed description below and particularly pointed out in the claims filed in conjunction with this application. Such combinations have specific advantages not specifically recited in the foregoing summary. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The novel features of the invention are set forth in the appended claims. The features and advantages of the invention will be better understood by reference to the following detailed description, which sets forth illustrative embodiments that utilize the principles of the invention, in the drawings:

[0016] Figure 1A-1B are a perspective view and an exploded view of a bio - stimulator according to one embodiment, respectively.

[0017] Figure 2A-2B is a perspective view of a wall insulator according to one embodiment.

[0018] Figure 3 is a perspective view of the inner side of a flexible circuit assembly in a flattened configuration according to one embodiment.

[0019] Figure 4Is a plan view of the inner side of a flexible circuit assembly according to one embodiment.

[0020] Figure 5 Is a perspective view of the outer side of a flexible circuit assembly in a flattened configuration according to one embodiment.

[0021] Figure 6 Is a plan view of the outer side of a flexible circuit assembly according to one embodiment.

[0022] Figure 7 Is a perspective view of a flexible circuit assembly in a stacked configuration according to one embodiment.

[0023] Figure 8 Is a perspective view of an end insulator of a biostimulator according to one embodiment.

[0024] Figure 9 Is a perspective view of a battery pin extending through the end insulator of a biostimulator according to one embodiment.

[0025] Figure 10 Is a cross-sectional view of an electronic device chamber of a biostimulator having a flexible circuit assembly according to one embodiment.

[0026] Figure 11 Is a cross-sectional view of an electronic device chamber of a biostimulator having a flexible circuit assembly according to one embodiment.

[0027] Figure 12 Is a cross-sectional view of a biostimulator having a flexible circuit assembly according to one embodiment.

[0028] Figure 13 Is a cross-sectional view of an end cap assembly connected to a flexible circuit assembly according to one embodiment.

[0029] Figure 14 Is a cross-sectional view of an end cap assembly and a battery connected to a flexible circuit assembly according to one embodiment.

[0030] Figure 15 Is a cross-sectional view of an electronic device chamber of a biostimulator accommodating a wall insulator and a flexible circuit assembly according to one embodiment.

[0031] Figure 16 Is a perspective view of an electronic device chamber of a biostimulator accommodating a wall insulator overmolded on a flexible circuit assembly according to one embodiment.

[0032] Figure 17 Is a perspective view of a desiccant in an electronic device chamber of a biostimulator according to one embodiment.

[0033] Figure 18 Is a perspective view of a desiccant holder according to one embodiment.

[0034] Figure 19 Perspective view of a desiccant in an electronic device chamber of a biostimulator according to one embodiment.

[0035] Figure 20 Perspective view of a desiccant holder according to one embodiment.

[0036] Figure 21 Perspective view of a lid insulator according to one embodiment.

[0037] Figure 22 Perspective view of an insulating cover according to one embodiment. Detailed Description

[0038] The embodiments describe a biostimulator, such as a leadless cardiac pacemaker, having a flexible circuit assembly that includes: a flexible substrate that carries electronic components and electrical connectors; and apertures in the flexible substrate to allow feedthrough pins to pass through the flexible substrate to the electrical connectors. The electronic components can include a processor to control the transmission of pacing pulses from a battery to target tissue. The flexible circuit assembly can be folded into a stacked configuration in which the flexible substrate insulates the electronic components from surrounding structures (e.g., the housing of the biostimulator). Additional components, such as wall insulators or end insulators, can further insulate the flexible circuit assembly from surrounding structures. As described below, the biostimulator can be used to pace cardiac tissue. Alternatively, the biostimulator can be used in other applications, such as deep brain stimulation. Thus, referring to the biostimulator as a cardiac pacemaker is not limiting.

[0039] In the various embodiments, the description is made with reference to the accompanying drawings. However, certain embodiments can be practiced without one or more of these specific details, or in combination with other known methods and configurations. In the following description, numerous specific details are set forth, such as specific configurations, dimensions, and processes, to provide a thorough understanding of the embodiments. In other instances, well-known processes and manufacturing techniques have not been described in particular detail so as not to unnecessarily obscure the description. Throughout the specification, references to "one embodiment", "an embodiment", etc. mean that the particular feature, structure, configuration, or characteristic described is included in at least one embodiment. Thus, the phrases "one embodiment", "an embodiment", etc. that appear throughout the specification are not necessarily referring to the same embodiment. Additionally, in one or more embodiments, the specific features, structures, configurations, or characteristics can be combined in any suitable manner.

[0040] Throughout the specification, the use of relative terms may denote relative position or orientation. For example, "distal" may indicate a first direction along the longitudinal axis of the biostimulator. Similarly, "proximal" may indicate a second direction opposite the first direction. These terms are provided to establish a relative frame of reference, but are not intended to limit the use or orientation of the biostimulator to the specific configurations described in the various embodiments below.

[0041] In one aspect, a biostimulator is provided. The biostimulator includes a pacing tip for delivering pacing pulses to a target tissue. The pacing pulses may be controlled and / or transmitted by a flexible circuit assembly housed within an electronics chamber of the biostimulator, the flexible circuit assembly having electronic components and electrical connectors. More particularly, the flexible circuit assembly includes electronic components and electrical connectors on a mounting surface of a flexible substrate that is folded in half within the electronics chamber. A first mounting area carrying the electronic components and a second mounting area carrying the electrical connectors may face each other such that the electronic components and electrical connectors are sandwiched between and enclosed by the mounting areas. The electronic components and electrical connectors may be insulated from surrounding structures (such as the housing of the biostimulator) by one or more of the flexible substrate, a wall insulator, or an end insulator. For example, the wall insulator may separate the flexible circuit assembly from the housing, and the end insulator may separate the flexible circuit assembly from the battery to reduce the likelihood of an electrical short circuit between the conductive portions of the flexible circuit assembly and the housing or the battery.

[0042] Referring Figure 1A , a perspective view of a biostimulator according to one embodiment is shown. The biostimulator 100 may be a leadless biostimulator, such as a leadless cardiac pacemaker. The biostimulator 100 may include a distal electrode 104 and a proximal electrode 106 disposed thereon. The electrodes may be integral with or connected to the housing 102, such as connected to the housing 102 at a distance of less than a few centimeters from the housing 102. The housing 102 may house an energy source 107 to provide power to the pacing electrodes. The energy source 107 may be a battery, such as a lithium carbon monofluoride (CFx) battery, or a hybrid battery, such as a combined CFx and silver vanadium oxide (SVO / CFx) hybrid chemical battery. Similarly, the energy source 107 may be a supercapacitor. In one embodiment, the energy source 107 may be an energy harvesting device, such as a piezoelectric device that converts mechanical stress into current or voltage. The energy source 107 may also be an ultrasonic transmitter that uses ultrasonic technology to transfer energy from an ultrasonic subcutaneous pulse generator to a receiving electrode implanted on the endocardial wall.

[0043] The biostimulator 100 may have a longitudinal axis 108. The longitudinal axis 108 may be an axis of symmetry along which a plurality of biostimulator components are arranged. For example, the end cap assembly 110 may be mounted at the distal end of the housing 102 along the longitudinal axis 108. The end cap assembly 110 may include an electrical feedthrough assembly that includes an electrical feedthrough (not shown) and a distal electrode 104, such as a pacing tip. The end cap assembly 110 may include a helical mount 112 mounted on the electrical feedthrough assembly about the longitudinal axis 108. In one embodiment, the fixing element 114 is mounted on the helical mount 112 along the longitudinal axis 108. The assembled components of the biostimulator 100 may provide a distal region that is attached to the target tissue, for example, via the engagement of the fixing element 114 with the target tissue. The distal region may deliver a pacing pulse to the target tissue, for example, via the distal electrode 104 held against the target tissue.

[0044] Referring Figure 1B , an exploded view of a biostimulator having a flexible circuit assembly is shown in accordance with one embodiment. The housing 102 may house an electronics chamber 116. More specifically, the housing 102 may have a housing wall that laterally surrounds the electronics chamber 116, such as a cylindrical wall. In one embodiment, the housing wall has an inner surface 118 that extends around the housing 102 along the longitudinal axis 108. The housing wall may include a conductive, biocompatible, inert, and anodically safe material, such as titanium, 316L stainless steel, or other similar materials, to laterally enclose the electronics chamber 116. The electronics chamber 116 may be axially enclosed at the proximal end by a battery. More specifically, the distal surface or distal face of the battery may define the proximal end of the electronics chamber 116. The electronic components 116 may be axially enclosed at the distal end by the end cap assembly 110. More specifically, the proximal surface of the end cap assembly 110 may define the distal end of the electronics chamber 116. The housing 102 may be attached (e.g., welded) to the end cap assembly 110 and the battery 107. Thus, the electronics chamber 116 may be housed between the battery, the inner surface of the housing 102, and the end cap assembly 110.

[0045] In one embodiment, the flexible circuit assembly 120 is housed within the electronic device chamber 116. The flexible circuit assembly 120 may include a flexible substrate with one or more electronic components mounted thereon. For example, the flexible circuit assembly 120 may include one or more passive electronic components (such as capacitors) and one or more active electronic components (such as processors). The electronic components may be interconnected via electrical traces, vias, or other electrical connectors. In one embodiment, the electronic assembly includes one or more electrical connectors, such as socket connectors and pin connectors or metallized contact pads, to connect to the battery and the electrical feedthrough assembly. For example, the electrical connector may be a socket connector or a metal pad to receive and / or connect to electrode pins or terminal pins, as described below.

[0046] The electrical connectors of the flexible circuit assembly 120 may accidentally short circuit to other conductive components of the bio - stimulator 100, such as the housing 102 or the battery 107. To reduce the likelihood of such events occurring, the bio - stimulator 100 may include components to electrically insulate and / or protect the components of the flexible circuit assembly from short - circuiting. For example, the bio - stimulator 100 may include an end insulator 122. The end insulator 122 may include a planar structure to form a wall between the flexible circuit assembly 120 and the energy source 107. As described below, the end insulator 122 may separate the battery (more particularly, the enclosure of the battery) from the flexible circuit assembly 120. The bio - stimulator 100 may also include a wall insulator 124. As described below, the wall insulator 124 may separate the flexible circuit assembly 120 from the inner surface 118 of the housing 102. It can be understood that the flexible substrate of the flexible circuit assembly 120 may provide sufficient insulation and isolation from the housing 102 and the battery. Thus, the end insulator 122 and the wall insulator 124 are optional. Nevertheless, the insulating components are described as part of the following embodiments.

[0047] Referring to Figure 2A , a perspective view of a wall insulator according to one embodiment is shown. During the manufacture and use of the bio - stimulator 100, the flexible circuit assembly 120 may be separated from the housing 102 to reduce the likelihood of a short circuit occurring between the electronic components on the flexible circuit assembly 120 and the housing 102. The wall insulator 124 may be a tubular assembly. For example, the wall insulator 124 may be in the form of a cylindrical tube. The cylindrical tube may include a wall outer surface 202 and a wall inner surface 204 extending between a distal wall end 206 and a proximal wall end 208, both of which may be cylindrical. The tubular structure of the wall insulator 124 allows the insulator to be mounted on the flexible circuit assembly 120 to circumferentially enclose the flexible circuit assembly 120. More specifically, the wall insulator 124 may extend around the flexible circuit assembly 120 within the electronic device chamber 116 of the bio - stimulator 100. Thus, the wall insulator 124 may separate the flexible circuit assembly 120 from the inner wall 118 of the housing 102.

[0048] In one embodiment, the cross-sectional profile of the wall insulator 124 taken in a plane extending perpendicular to the longitudinal axis 108 is circular. More specifically, the profiles of the outer wall surface 202 and the inner wall surface 204 may be circular. Alternatively, the cross-sectional profile of the wall insulator 124 may be polygonal, elliptical, or other shapes.

[0049] In one embodiment, the wall insulator 124 is formed of a thin dielectric film. For example, the wall insulator 124 may be a thin cylindrical insulating sleeve formed of any material having good dielectric properties (electrical insulation). As described below, the wall insulator 124 may be assembled between the housing 102 and the flexible circuit assembly 120 within the electronic device chamber 116, and thus it may be advantageous for the wall insulator 124 to be formed of a material capable of forming thin walls with tight tolerances. The wall insulator 124 may also benefit from having good hoop strength. Thus, the wall insulator 124 may be formed of polytetrafluoroethylene or polyimide because these materials have the desired properties.

[0050] Referring to Figure 2B , a perspective view of a wall insulator according to one embodiment is shown. The wall insulator 124 may be an expandable sleeve. In one embodiment, the wall insulator 24 has a bellows-like structure. For example, the tubular structure may have a plurality of longitudinal folds 210 extending between the distal wall end 206 and the proximal wall end 208 in the longitudinal direction 318. The folds 210 or corrugations impart a non-circular profile to the outer wall surface 202 and the inner wall surface 204. The tubular surface of the wall insulator 124 may define a thin wall that undulates in the circumferential direction around the longitudinal axis 108.

[0051] The longitudinal folds 210 of the wall insulator 124 allow the insulator to expand and contract radially. For example, an inward radial force applied to the outer wall surface 202 may cause the angle between the undulating surfaces to decrease, thereby reducing the diameter of the wall insulator 124. Conversely, an outward radial force applied to the inner wall surface 204 may cause the angle between the undulating surfaces to increase, thereby increasing the diameter of the wall insulator 124. The expandable / collapsible tubular structure may allow the wall insulator 124 to conform to adjacent components. For example, the wall insulator 124 may be disposed within the housing 102 and may collapse such that the outer wall surface 202 contacts and fits within the inner surface 118 of the housing 102. Similarly, the wall insulator 124 may be disposed on the flexible circuit assembly 120 and may expand such that the inner wall surface 204 contacts the exterior of the flexible circuit assembly 120. The wall insulator 124 can thus adapt to adjacent structures to provide a tight fit, thereby using a minimum amount of space between the housing 102 and the flexible circuit assembly 120.

[0052] As described above, the wall insulator 124 can be formed of any electrically insulating material. In one embodiment, the wall insulator 124 is formed of a heat-shrinkable material. For example, the wall insulator 124 can be a heat-shrinkable tube formed of a polyolefin or fluoropolymer material. In this case, heat can be applied to the wall insulator 124 to cause it to shrink onto the flexible circuit assembly 120 and conform to the flexible circuit assembly 120. When in the shrunk state, the heat-shrinkable tube can encase the electronic components of the flexible circuit assembly 120 and isolate the electronic components from the surrounding structure (such as the housing 102).

[0053] Reference Figure 3 , a perspective view of the inner side of a flexible circuit assembly in a flattened configuration according to one embodiment is shown. The flexible circuit assembly 120 for the bio-stimulator 100 can have a flattened configuration 302. In one embodiment, the flexible circuit assembly 120 includes a flexible substrate 304. For example, the flexible substrate 304 can include a flexible polymer film, such as a film containing: polyester, polyethylene naphthalate, polyetherimide, fluoropolymer, and combinations thereof. In one embodiment, the flexible substrate 304 is a polyimide substrate that can be elastically bent or folded.

[0054] The flexible substrate 304 can include a plurality of mounting surfaces facing in opposite directions, such as a top surface ( Figure 3 ), and a bottom surface ( Figure 5 ). Figure 3 The top surface shown in can also be referred to as the inner side of the flexible circuit assembly 120 because when the flexible circuit assembly 120 is folded from the flattened configuration 302 into a stacked configuration, this top surface faces the internal gap of the folded structure, as described below. In one embodiment, the mounting surface includes a mounting surface 306 that bears one or more electrical connectors 308 and one or more electronic components 310. The mounting surface 306 can be a flat surface in the flattened configuration 302 and can have a plurality of regions designated according to it.

[0055] In one embodiment, the mounting surface 306 of the flexible substrate 304 includes a first mounting area 312 and a second mounting area 314. One or more electrical connectors 308 and / or electronic components 310 can be mounted on the first mounting area 312. Similarly, one or more electrical connectors 308 and / or electronic components 310 can be mounted on the second mounting area 314. In one embodiment, only one mounting area bears the electrical connectors 308.

[0056] The mounting surface 306 can include a folding region 316 between a first mounting region 312 and a second mounting region 314. For example, each mounting region can have a region boundary defined by a longitudinal boundary separated in the longitudinal direction 318 and a lateral boundary separated in the lateral direction 320. The folding region 316 can be a part of the flexible substrate 304 that extends across the mounting surface 306 in the lateral direction 320 from a first lateral edge 322 of the flexible substrate 304 to a second lateral edge 324 of the flexible substrate 304. The flexible substrate 304 is configured to be folded along the folding region 316 into a stacked configuration ( Figure 7 ) such that the first mounting region 312 of the inner surface faces the second mounting region 314 of the inner surface in a transverse direction 325 that is orthogonal to the longitudinal direction 318 and the lateral direction 320.

[0057] In one embodiment, one or more electrical traces 350 extend across the folding region 316. More specifically, the electrical traces 350 can extend across the folding region 316 from the first mounting region 312 to the second mounting region 314. The electrical traces 350 can be disposed on the flexible substrate 304 or embedded within the flexible substrate 350. The electrical traces 350 can electrically connect a first component (e.g., a socket connector) mounted on the first mounting region 312 to a second component (e.g., a processor) mounted on the second mounting region 314. Thus, the electrical traces 350 can perform an electrical communication function.

[0058] The electrical traces 350 can also perform a mechanical function. In one embodiment, the electrical traces 350 serve as stress relief to evenly distribute stress across the folding region 316. The electrical traces 350 can have a thickness and / or width to prevent kinking in the folding region 316. Additionally, the electrical traces 350 can be formed of a kink-resistant and ductile material. For example, the electrical traces 350 can be copper alloy traces having a predetermined size and trace density per inch that are embedded within the flexible substrate 304 within the folding region 316 such that when the flexible circuit assembly is folded into a stacked configuration ( Figure 7 ) the folding region 316 extends along an arcuate path (e.g., a smooth curve) rather than kinking or bending abruptly.

[0059] In one embodiment, the flexible substrate 304 includes an aperture 326 extending through the flexible substrate 304. More specifically, the aperture 326 can be a hole or slit extending from the inner side of the flexible substrate 304 to the outer side on the opposite side of the flexible substrate 304. The aperture 326 can be in the folding region 316 and can have an aperture axis 352. The aperture axis 352 can be defined relative to the edge of the aperture 326. For example, the aperture plane can include the edge extending around the aperture 326, and the aperture axis 352 can extend perpendicular to the aperture plane. Thus, when the flexible circuit assembly 120 is in the flattened configuration 302, the aperture axis 352 can be parallel to the lateral direction 325. Conversely, when the flexible circuit assembly 120 is in the stacked state, the aperture axis 352 can be parallel to the longitudinal direction 108. In the stacked configuration, the axis 352 can be parallel to the longitudinal axis 108, as described below.

[0060] In one embodiment, the aperture 326 can be centered on the mounting surface 306. For example, the folding region 316 can be equidistantly spaced between the first longitudinal edge 330 and the second longitudinal edge 332 of the flexible substrate 304. Thus, the aperture 326 in the folding region 316 can be longitudinally centered between the first longitudinal edge 330 and the second longitudinal edge 332. Similarly, the aperture 326 in the folding region 316 can be laterally centered between the first lateral edge 322 and the second lateral edge 324. Thereby, the aperture 326 can be located at the center of the mounting surface 306.

[0061] Referring Figure 4 , a plan view of the inner side of a flexible circuit assembly according to one embodiment is shown. The electrical connector 308 on the mounting surface 306 can include a feedthrough connector 402 mounted on the first mounting region 312. The feedthrough connector 402 can be one of several types of electrical connectors 308. For example, the feedthrough connector 402 can be a socket connector ( Figure 3-7 and 10-12) or a metal pad ( Figure 13-15 ). The feedthrough connector 402 can be configured to receive an electrical pin of another component of the biological stimulator 100. For example, the feedthrough connector 402 can receive and / or attach to a feedthrough pin of the end cap assembly 110, which transmits the pacing pulse from the flexible circuit assembly 120 to the pacing tip of the biological stimulator 100.

[0062] In one embodiment, the feedthrough connector 402 is a socket connector and has a socket axis 404 passing through the lumen of the socket connector. The socket axis 404 can extend in the longitudinal direction 318. In one embodiment, the socket axis 404 is laterally aligned with the center 406 of the mounting surface 306. Thus, the socket axis 404 can be laterally aligned with the aperture 326.

[0063] As described above, the aperture 326 may be centered on the mounting surface 306. The center 406 may be aligned with the receptacle axis 404, which is equally spaced between the first lateral edge 322 and the second lateral edge 324. Similarly, the center 406 may be aligned with the centerline 408 of the mounting surface 306, which extends orthogonally to the receptacle axis 404. The centerline 408 may be equally spaced between the first longitudinal edge 330 and the second longitudinal edge 332 of the flexible substrate 304.

[0064] The flexible circuit assembly 120 may include a plurality of electrical connectors 308 on the mounting surface 306. For example, one or more battery connectors 410 may be on the mounting surface 306. The battery connector 410 may be one of several types of electrical connectors 308. For example, the battery connector 410 may be a receptacle connector ( Figure 3-7 and 10-12) or a metal pad ( Figure 13-15 ). The battery connector 410 may be configured to receive and / or attach to the electrical pins of another component of the biological stimulator 100. For example, the battery connector 410 may receive the battery pins of the energy source 107 to transfer power from the battery to the flexible circuit assembly 120. The battery pins may be the positive terminal post and the negative terminal post of the battery. Thus, power may be input into the flexible circuit assembly 120 via the battery connector 410, and power may be output from the flexible circuit assembly 120 via the feedthrough connector 402.

[0065] Each battery connector 410 may be a receptacle connector having a corresponding receptacle axis 404. The corresponding receptacle axes 404 of the battery connectors 410 may extend parallel to the receptacle axis 404 of the feedthrough connector 402. In one embodiment, the receptacle axis 404 of the flexible circuit assembly 120 extends along the longitudinal direction 318 of the biological stimulator 100. For example, when the flexible circuit assembly 120 is housed within the electronic device chamber 116 of the housing 102, the receptacle axis may be parallel to the longitudinal axis 108. Note that in such a configuration, the receptacle axis 404 may also be parallel to the aperture axis 352. Thus, as further described below, when the flexible circuit assembly 120 is folded about the fold region 316 to mount the flexible circuit assembly 120 within the electronic device chamber 116, the reference geometry of the receptacle axis 404 extends longitudinally through the fold region 316 of the mounting surface 306. More specifically, the receptacle axis 404 may extend parallel to the mounting surface 306 on the first and second mounting regions, and extend orthogonally to the mounting surface 306 at the location where its axis intersects the fold region 316.

[0066] The electrical connector 308 of the flexible circuit assembly 120 can be positioned to stably support the flexible circuit assembly 120 on the electrical pins received by the socket connector. In one embodiment, external pins (such as feedthrough pins and battery pins) can be evenly loaded by the electrical connector 308 on the mounting surface 306. For example, the socket axis 404 of the feedthrough connector 402 can be located between the socket axes 404 of the battery connector 410. More specifically, the socket axis 404 of the feedthrough connector 402 can be laterally located between the socket axes 404 of the battery connector 410 with respect to the lateral direction 320. In one embodiment, the socket axes 404 of the feedthrough connector 402 are equally spaced between the socket axes 404 of the battery connector 410. Thus, the mechanical connection formed between the electrical connector 308 of the flexible circuit assembly 120 and the external biostimulator component can be symmetrically located on the first mounting area 312.

[0067] Still referring to Figure 4 , in addition to having several electrical connectors 308, the flexible substrate 304 can also carry one or more electronic components 310 on the mounting surface 306. In one embodiment, the one or more electronic components 310 are in the second mounting area 314 of the mounting surface 306. For example, the electronic components 310 on the second mounting area 314 can include active electronic components 420, such as semiconductor devices. The electronic components 310 on the second mounting area 314 can include one or more processors 422. More specifically, the electronic components 310 can include an integrated circuit (such as an application-specific integrated circuit) having a microprocessor and / or storage block designed to operate in the biostimulator 100 to provide cardiac pacing. In one embodiment, the one or more processors 422 are configured to execute instructions stored in a non-transitory computer-readable medium to cause the biostimulator 100 to perform various operations, including but not limited to generating pacing pulses and transmitting them to the target tissue.

[0068] In addition to the active components 420, the flexible circuit assembly 120 can also include one or more passive electronic components 424 mounted on the mounting surface 306. For example, the passive electronic components 424 can include one or more capacitors. By way of example, the capacitors can be polymer or ceramic capacitors.

[0069] In one embodiment, an epoxy underfill may be used to mitigate shear stress applied to an electronic component 310 and / or an electrical connector 308 mounted on a mounting surface 306. More specifically, the epoxy underfill may be disposed between the mounting surface 306 and the electrical / electronic component 310 during manufacturing. The epoxy underfill may be an epoxy adhesive layer that flows between the electrical / electronic component 310 and the mounting surface 306 after the electrical / electronic component 310 is mounted on the mounting surface 306. For example, surface mount technology (e.g., reflow solder balls) may be used to electrically connect and / or physically connect the component to electrical contacts on the mounting surface 306, and a gap may be left between the component and the surface after the component is attached. The epoxy adhesive may flow into the gap to further stabilize and secure the component on the mounting surface 306. In one embodiment, the thickness of the underfill layer may be from 0.008 inches to 0.1 inches, such as 0.010 inches.

[0070] Referring Figure 5 , a perspective view of an outer side of a flexible circuit assembly in a flattened configuration according to one embodiment is shown. In the flattened configuration 302, the second surface of the flexible substrate 304 may have a corresponding mounting surface 306 that is divided into regions as described above. For example, the mounting surface 306 may have a first mounting region 312 and a second mounting region 314. The second surface may be referred to as the outer side of the flexible circuit assembly 120 because when the flexible substrate 304 is folded from the flattened configuration 302 into a stacked configuration, the second surface may face outwardly toward the housing 102, as described below.

[0071] Referencing Figure 6, which shows a plan view of the outer side of a flexible circuit assembly according to an embodiment. The mounting areas on the bottom surface can carry one or more electronic components 310, which can be active components 420 or passive components 424. For example, the electronic components 310 can include diodes, transistors, capacitors, etc. In one embodiment, the mounting areas on the outer side carry one or more sensors 602. The sensors 602 can detect temperature, acceleration, etc. For example, a microelectromechanical system (MEMS) sensor can be mounted on the flexible substrate 304. For example, the MEMS sensor can be a giant magnetoresistive (GMR) sensor. Similarly, an electronic oscillator circuit 604 can be mounted on the flexible substrate 304. It should be understood that the above electronic components 310 are provided as examples, and other electronic components 310 can be mounted on the flexible substrate 304. More particularly, surface mount technology can be used to produce a flexible circuit assembly 120 in which components are directly mounted or arranged on the flexible substrate 304. Electrical connections between the various components can be made using traces, electrical vias, pins, contacts, etc. For example, as described above, the electrical trace 350 can extend from a component on the first mounting area 312 to a component on the second mounting area 314 over the folding area 316. The electrical trace 350 can be exposed or buried, for example, by lamination. Thus, a double-sided flexible circuit assembly 120 with a centrally arranged aperture 326 can be provided for use in the biological stimulator 100.

[0072] Referring to Figure 7 , which shows a perspective view of a flexible circuit assembly in a stacked configuration according to an embodiment. The flexible circuit assembly 120 can be folded along the folding area 316 into a stacked configuration 702. In the stacked configuration 702, the socket axis 404 of the feedthrough connector 402 can extend in the longitudinal direction 318 through the aperture 326 ( Figure 11 ). Similarly, the aperture axis 352 can extend between the first mounting area 312 and the second mounting area 314 in the stacked configuration 702. For example, the socket axis 404 can extend through the aperture 326 parallel to the longitudinal axis 108, and the aperture axis 352 can extend through the aperture 326 aligned with the feedthrough connector 402. More particularly, the aperture axis 352 can extend through the pin port of a socket connector that receives external pins. Similarly, the socket axis 404 of the battery connector 410 can extend in the longitudinal direction 318 opposite to the socket axis 404 of the feedthrough connector 402 to emerge from a protection gap 704 defined between the first longitudinal edge 330 and the second longitudinal edge 332. The aperture axis 352 can extend between the mounting areas to emerge from the protection gap 704 laterally between the socket axes of the battery connector 410.

[0073] The protection gap 704 can be a space enclosed by a flexible substrate between the first mounting area 312 and the second mounting area 314. In the stacked configuration 702, the first mounting area 312 faces the second mounting area 314 across the protection gap 704. Thus, in the stacked configuration 702, the electrical connectors 308 and / or electronic components 310 mounted on the inner side of the flexible circuit assembly 120 are received within the protection gap 704. For example, the feedthrough connector 402 and the electronic component 310 can be stacked on top of each other and thus be in the stacked configuration 702. The flexible substrate 304 can wind around the electronic component 310 and the electrical connector 308. Thus, these components are enclosed within the protection gap 704, and thus the likelihood of conductive debris forming a short circuit between the electronic component 310 and the electrical connector 308 is reduced. By closing the ends of the protection gap 704, i.e., the positions where the protection gap 704 is open to the surrounding environment in the longitudinal direction 318 or the lateral direction 320, this likelihood can be further reduced.

[0074] Reference Figure 8 , a perspective view of an end insulator of a bio - stimulator according to one embodiment is shown. The end insulator 122 can be disposed between the opening of the protection gap 704 and the surrounding environment. In one embodiment, the end insulator 122 is flat, for example, having a flat distal face 806 and a flat proximal face (not visible in the figure). More particularly, the end insulator 122 can be a thin, flat, disk - shaped insulator. The end insulator 122 can include a dielectric film formed of a dielectric material such as polyimide. The end insulator 122 can include an outer edge 802 that defines the profile of the end insulator 122. For example, the profile of the end insulator 122 can be circular, as Figure 8 shown. Alternatively, the end insulator 122 can have a polygonal, elliptical or other profile shape.

[0075] In one embodiment, the end insulator 122 includes one or more slits 804 that extend through the thin wall of the insulator. For example, the end insulator 122 can include a plurality of slits 804, each slit having its own size and profile. As shown, the plurality of slits 804 can include a pair of slits 804, each slit 804 having a circular profile. The slits can be elliptical, polygonal, etc. However, the dimensions of the profile (e.g., the diameter of a circle) can be different. For example, the first slit 804 of the end insulator 122 can have a larger diameter than the second slit 804 of the end insulator 122. Alternatively, the slits 804 can have the same size and shape. For example, the slits 804 of the end insulator 122 can be elliptical and have the same length and width.

[0076] Referring to Figure 9, shows a perspective view of battery pins extending through an end insulator of a biostimulator. The end insulator 122 can be configured to cover the end face of the energy source 107 while allowing the terminal posts of the battery to pass through the end insulator 122 to make electrical contact with the electrical connectors 308 of the flexible circuit assembly 120. In one embodiment, the battery includes one or more battery pins 902, which can be the positive terminal post and the negative terminal post of the battery. The battery pins 902 can extend from the distal face 904 of the battery in the longitudinal direction 318 (e.g., parallel to the longitudinal axis 108). More specifically, the battery pins 902 can have corresponding pin axes 902, and when the flexible circuit assembly 120 is in the stacked configuration 702, the pin axes 902 can extend parallel to the orifice axis 352. During the assembly of the biostimulator 100, the battery pins 902 can be inserted into the corresponding slots 804 of the end insulator 122. Thus, the end insulator 122 can be placed on the distal face 904 of the battery to isolate the distal face 904 and the active terminal pins from conductive debris located on the opposite side of the end insulator 122 (e.g., toward the distal tip of the battery pins 902).

[0077] In one embodiment, the battery pins 902 include a positive pin 906 and a negative pin 908. The outer diameter dimensions and lengths of each battery pin 902 can vary to allow the pins to be correctly placed individually in their respective battery connectors 410 on the flexible circuit assembly 120. These differently sized battery pins 902 can prevent misinsertion into the battery connectors 410, which could lead to potential and catastrophic failures within the flexible circuit assembly 120. For example, the positive pin 906 can have a larger diameter than the negative pin 908, and thus, the battery connector 410 that receives the negative pin 908 can have a socket with a socket port that is too small to accommodate the positive pin 906. Thus, the pin sizes ensure that the battery will be correctly oriented relative to the flexible circuit assembly 120 when the components are assembled.

[0078] In addition to controlling the pin orientation, the size of the pins can preferentially direct forces to one of the battery pins 902. For example, the positive pin 906 can mate with the glass-to-metal feedthrough of the battery. Thus, it may be advantageous to direct deflection forces to the negative pin 908 that mates with the battery metal plug. More specifically, the glass-to-metal feedthrough may be more fragile than the battery metal plug. Thus, it may be advantageous to apply stress to the negative pin 908, which transfers the force to the battery metal plug rather than to the positive pin 906 that transfers the force to the glass-to-metal feedthrough. For example, off-axis assembly forces, such as those generated during manual assembly, can be directed or concentrated on the negative pin 908 to protect the positive pin 906 and the glass-to-metal feedthrough seal. This preferred direction of off-axis assembly forces can occur for a variety of reasons. First, the negative pin 908 can be longer than the positive pin 906. Thus, the negative pin 908 can be contacted by the assembler or an external component before contacting the positive pin 906. Second, the negative pin 908 can be narrower and / or longer than the positive pin 906 and thus will deflect more readily under the action of off-axis assembly forces. Thus, deflection and stress can be directed to the negative pin 908 to reduce the likelihood of damaging the glass-to-metal seal.

[0079] Referring Figure 10 , a cross-sectional view of an electronic device chamber of a biostimulator having a flexible circuit assembly is shown in accordance with one embodiment. Each battery pin 902 of the battery can be connected to and / or mounted on or within a corresponding battery connector 410. For example, in the case of a socket connector, each battery pin 902 can extend through a corresponding slit 804 in the end insulator 122 and can extend through the slit 804 into the socket of the corresponding battery connector 410. Similarly, in the case of a metal pad, each battery pin 902 can extend through a corresponding slit 804 in the end insulator 122 and can be attached to the metal pad of the flexible circuit assembly 120. Thus, in the assembled state, when the battery pins 902 are connected to the corresponding battery connectors 410, the end insulator 122 can be located between the distal side 904 of the battery and the flexible circuit assembly 120. Thus, the flexible circuit assembly 120 can include a plurality of battery connectors 410 mounted on or attached to the respective battery pins 902 of the battery, and the conductive components of the flexible circuit assembly 120 can be isolated from the distal side 904 of the battery by the end insulator 122.

[0080] Still referring Figure 10, the housing 102 can be mounted on the wall insulator 124 and on the battery to accommodate the flexible circuit assembly 120 within the electronic device chamber 116. More specifically, the inner surface 118 of the housing 102 can extend around the flexible circuit assembly 120 to laterally surround the flexible circuit assembly 120. In one embodiment, the end cap assembly 110 can be mounted on the housing 102 to enclose the electronic device chamber 116 within the biostimulator 100.

[0081] The end cap assembly 110 can include several sub-components. For example, the end cap assembly 110 can include a flange 1004 that has a mounting wall to accommodate the screw mount 112. In one embodiment, the flange 1004 is formed of titanium. The flange 1004 can be mounted on the housing 102 and connected to the housing 102 by an airtight seal (e.g., by a weld). For example, the airtight weld can be formed circumferentially around the seam between the proximal end of the flange 1004 and the distal end of the housing 102. In one embodiment, the screw mount 112 is mounted on the flange 1004 by a threaded connection. The flange 1004 can have an external thread that mates with the internal thread of the screw mount 112. Thus, the screw mount 112 can be screwed onto the mounting wall of the flange 1004. Alternatively, the screw mount 112 can be press-fitted onto the mounting wall, the screw mount 112 can be thermally bonded or adhesively bonded to the mounting wall, or the screw mount 112 and the electrical feedthrough assembly can be joined in another way such as by swaging. Thus, the electronic device chamber 116 can be enclosed between the battery, the inner surface 118 of the housing 102, and the end cap assembly 110.

[0082] In one embodiment, the end cap assembly 110 includes a fixation element 114, such as a screw. The screw can extend distally from the screw mount 112 about the longitudinal axis 108. For example, the screw can revolve about the longitudinal axis 108. The screw can include a helix that extends about the longitudinal axis 108 in a rotational direction, which is formed by coiling or by cutting from a pipe wall. For example, the screw can revolve about the longitudinal axis 108 in a right-handed direction.

[0083] The screw can be adapted to attach the biostimulator 100 to tissue, such as heart tissue. For example, in the case of a right-handed screw direction, the biostimulator 100 can be advanced into contact with the target tissue, and then, the biostimulator 100 can be rotated in the right-handed direction to screw the screw into the tissue.

[0084] Refer to Figure 11, showing a cross-sectional view of a biostimulator having a flexible circuit according to an embodiment. The end cap assembly 110 may include a feedthrough 1102 to transmit a pacing pulse from the flexible circuit assembly 120 into a target tissue. For example, the feedthrough 1102 may have a feedthrough pin 1104. The feedthrough pin 1104 may extend in a proximal direction through the flange 1004 into the electronic device chamber 116 to engage the feedthrough connector 402. More specifically, the feedthrough pin 1104 may pass through an aperture 326 in the folded region 316 of the flexible substrate 304 and be inserted into the feedthrough connector 402. Thus, the feedthrough pin 1104 may be mechanically and electrically connected to the feedthrough connector 402 between a first mounting area 312 and a second mounting area 314 of the mounting surface 306.

[0085] The feedthrough 1102 may further include an electrode tip 1106, which may be electrically continuous with the feedthrough pin 1104. Thus, when the fixation element 114 engages the target tissue, the electrode tip 1106 may be held against the tissue, and thus, a pacing pulse may be transmitted from the feedthrough connector 402 into the feedthrough pin 1104 and through the electrode tip 1106 to the target tissue.

[0086] Since the flexible circuit assembly 120 may provide power to the feedthrough 1102 via the feedthrough connector 402, the flexible circuit assembly 120 may receive power from a battery through a battery connector 410. More specifically, the battery pins 902 may extend through a slit 804 of the end insulator 122 into the electronic device chamber 116. The battery pins 902 may have respective pin axes 910, and each pin axis 910 may be parallel to the aperture axis 352. The battery pins 902 may be mechanically and electrically connected to the battery connector 410. Thus, the electrical connector 308 of the flexible circuit assembly 120 may form a firm and stable connection with the battery pins 902 and the feedthrough pins 1104 to allow power transmission and reduce the likelihood of the electrical connector 308 shorting to another component of the biostimulator 100.

[0087] Refer to Figure 12, showing a cross-sectional view of a bio-stimulator having a flexible circuit assembly according to an embodiment. In addition to the protective function of the folded flexible circuit assembly 120, the stacked configuration 702 allows the electronic device chamber 116 to be effectively occupied by circuit components. For example, the stacked electrical connectors 308 and electronic components 310 allow for more circuits per unit length in the longitudinal direction 318 within the electronic device chamber 116. In one embodiment, the stacked flexible circuit assembly 120 may be circumferentially enclosed by a wall insulator 124, which may electrically isolate the assembly from the inner surface 118 of the housing 102. As shown, the end insulator 122 may have an outer edge 802 with a circular profile, and the inner surface 118 of the housing 102 and / or the inner surface 204 of the housing 102 may have the same circular profile. The circular profile is provided by way of example only, and the inner surface 118 and / or the outer edge 802 may have alternative profiles, such as a polygonal or elliptical profile. The profiles of the inner surface 118 (or the inner surface 204) and the outer edge 802 may be dimensioned similarly, for example, may have the same diameter within a tolerance range of + / - 10%, to allow the wall insulator 124 and the end insulator 122 to completely surround the flexible circuit assembly 120 and its components while still fitting within the housing 102.

[0088] The bio-stimulator 100 may include components for further insulating and protecting the flexible circuit assembly. In one embodiment, the bio-stimulator 100 includes a foam strip 1202 between the electrical connector 308 and the electronic component 310 (which is mounted within the protective gap 704). For example, the foam strip 1202 may be a strip having a peripheral dimension that is the same as the peripheral dimension of the first mounting area 312 and / or the second mounting area 314. The foam strip 1202 may be a single-sided or double-sided strip, and when the flexible circuit assembly 120 is in the flattened configuration 302, the foam strip 1202 may be mounted on the first mounting area 312 or the second mounting area 314. When the flexible circuit assembly 120 is folded into the stacked configuration 702, the first side of the strip may face the first mounting area 312, while the second side may face the second mounting area 314. The foam strip 1202 may adhere to the electronic component 310 and / or the electrical connector 308 on the inner side of the folded substrate to hold the flexible circuit assembly 120 in the folded state until the socket connector is mounted on the plug connector of the bio-stimulator 100. Additionally, the foam strip 1202 may be made of an insulating foam material, and thus may reduce the likelihood of electrical contact between the electronic components on the first mounting area 312 and the electronic components on the second mounting area 314.

[0089] In one embodiment, the flexible substrate 304 of the flexible circuit assembly 120 insulates and stabilizes the electronic components 310 and the electrical connector 308 relative to the housing 102. As described above, the flexible substrate 304 can be a thin dielectric film, e.g., a flexible polyimide strip. The flexible substrate 304 can have a peripheral edge 1204 that extends around the mounting surface 306 of the flexible circuit assembly 120, e.g., along the lateral and longitudinal edges of the mounting area and the folding area 316. More specifically, the peripheral edge 1204 can include the lateral and longitudinal edges of the mounting area and the folding area 316. At least a portion of the peripheral edge 1204 can contact the wall insulator 124 along the inside of the housing 102. For example, when the flexible circuit assembly 120 is in the stacked configuration 702 and enclosed within the electronic device chamber 116, the mounting areas can move away from each other, e.g., if the foam tape 1202 loses adhesion to one side of the substrate, and as the substrate halves move outwardly, the peripheral edge 1204 can contact the inner surface of the wall insulator 124. The wall insulator can restrain the outward movement of the flexible substrate 304, and a portion of the peripheral edge 1204 (e.g., the first lateral edge 322 or the second lateral edge 324) can contact the wall insulator 124 on the side of the insulator wall opposite the housing 102. The portion of the flexible circuit assembly 120 that contacts the wall insulator 124, e.g., the first lateral edge 322 or the second lateral edge 324 of the flexible substrate 304, can be formed of an insulating material. More particularly, the peripheral edge 1204 of the flexible substrate 304 can be free of conductive traces or conductive components thereon such that the contact between the flexible circuit assembly 120 and the inner surface of the wall insulator 124 is not an electrical contact.

[0090] Physical non - electrical contact between the wall insulator 124 and the flexible circuit assembly 120 can stabilize the flexible circuit assembly 120 within the electronic device chamber 116. When the peripheral edge 1204 of the flexible substrate 304 bears against the inner surface 204 of the electronic device chamber 116, the wall insulator 124 and the housing 102 surrounding the wall insulator 124 essentially act as an external frame for the flexible circuit assembly 120. Impacts, vibrations, or other forces acting on the flexible circuit assembly 120 can be counteracted by the wall insulator 124 and the housing 102. Thus, the physical contact between the wall insulator 124 and the flexible circuit assembly 120 can limit the deflection and loading of the flexible circuit assembly 120. More specifically, the stress applied by the electrical connector 308 to the connector pins (such as feed - through pins 1104 and / or battery pins 902) is restricted by the external support provided by the wall insulator 124 and the housing 102. Additionally, compared to the case of using a separate external frame to support the flexible circuit assembly 120 within the electronic device chamber 116, the external frame provided by the wall insulator 124 and the housing 102 requires fewer components and is more space - efficient. Thus, a length of the peripheral edge 1204 of the flexible circuit assembly 120 supported by the wall insulator 124 and the housing 102 along the insulating (non - conductive) portion of the flexible substrate 304 provides a robust and compact bio - stimulator 100.

[0091] The embodiments of the wall insulator and the end insulator described above are provided by way of example and not limitation. For example, in one embodiment, the wall insulator 124 can be replaced by an insulating coating applied to the inner surface 118 of the housing 102. The insulating coating can be a conformal coating such as parylene, for example, and can insulate the material of the metal housing 102 from the flexible circuit assembly 120. Thus, the wall insulator 124 can be a separate component or can be integrally formed with the housing 102.

[0092] Referring to Figure 21, a perspective view of a cover insulator according to an embodiment is shown. The wall insulator 124 and the end insulator 122 may be integrally formed. For example, the wall insulator 124 may be the tubular sidewall of the cover insulator 2100, and the end insulator 122 may be the flat end of the cover insulator. The cover insulator 2100 may have a shape obtained by combining the wall insulator 124 and the end insulator 122. More specifically, the cover insulator 2100 may be formed by joining the outer edge 802 of the end insulator 122 to the distal sidewall end 206 or the proximal sidewall end 208 of the wall insulator 124. The edges may be joined, for example, by a thermal welding or an adhesive welding process. Alternatively, the cover insulator 2100 may be formed by a molding or a thermoforming process in which the end insulator 122 and the wall insulator 124 portions are manufactured integrally. Similarly, a slit 804 may be formed as a hole in the end of the insulating cover during or after the molding or thermoforming process to allow an electrical pin to pass through.

[0093] It should be understood that the cover insulator 2100 may be disposed on the flexible circuit assembly 120 to constrain the flexible circuit assembly 120 and isolate it from adjacent conductive components. In addition, several covers may be used to isolate the flexible circuit assembly 120 at both ends. For example, a first cover insulator may be used to isolate the proximal portion of the flexible circuit assembly 120, and a second cover insulator may be used to isolate the distal portion of the flexible circuit assembly 120. The cover insulators may have walls sized to overlap each other, for example, by sliding one cover wall into and over another cover wall in a sliding fit. The cover insulators may also have holes sized to receive battery pins (in the case of the proximal cover insulator) or feedthrough pins (in the case of the distal cover insulator). Thus, the cover insulators may be assembled together to completely encapsulate the flexible circuit assembly 120 within an insulating cavity surrounded by the cover insulator walls and ends.

[0094] Based on the above assembly structure, it will be understood that the various components of the electrical feedthrough assembly may be assembled together during assembly (e.g., in the method of manufacturing the bio stimulator 100). The method may include a series of operations. These operations are described below in one order, which may be applicable to the flexible circuit assembly 120 having a socket connector for connection to an external electrical pin. In an alternative embodiment, for example, when the flexible circuit assembly 120 has metal pads for connection to external electrical pins, these operations may be performed in an alternative order.

[0095] In one operation, the flexible circuit assembly 120 can be folded into a stacked configuration 702 along the fold region 316. In the stacked configuration 702, the first mounting region 312 faces the second mounting region 314 in the lateral direction 325. Optionally, a foam strip can be disposed between the mounting region faces before folding the flexible circuit assembly 120, and thus, the flexible circuit assembly 120 can be temporarily held in the stacked configuration 702 during the assembly process.

[0096] In one operation, the battery pins 902 can be inserted through corresponding slots 804 in the end insulator 122. Thus, the battery pins 902 can extend distally to a pin tip that is separated from the distal face 904 of the battery by the end insulator 122.

[0097] In one operation, the battery pins 902 of the battery can be inserted into corresponding battery connectors 410 on the folded mounting surface 306. When the folded flexible circuit assembly 120 is loaded onto the battery pins 902, the longitudinal edges of the flexible substrate 304 can be in the same longitudinal position and can be separated from the distal face 904 of the battery by the end insulator 122. Thus, the protection gap 704 inside the folded flexible circuit assembly 120 can accommodate the battery pins 902 and can be separated from the battery by the end insulator 122.

[0098] In one operation, the wall insulator 124 can be disposed on and around the folded flexible circuit assembly 120. The housing 102 can be loaded onto the wall insulator 124 and mounted on the battery such that the inner surface 118 of the housing 102 extends around the insulator 124 and the flexible circuit assembly 120. The peripheral edge 1204 of the flexible circuit assembly 120 can physically contact the inner surface of the wall insulator 124 and can radially outwardly squeeze the wall insulator 124 to contact the inner surface 118 of the housing 102. Thus, the housing 102 can provide external support for the flexible circuit assembly 120.

[0099] In one operation, the feedthrough pins 1104 are inserted through apertures 326 in the fold region 316 of the flexible circuit assembly 120. The feedthrough pins 1104 can engage feedthrough connectors 402 on the mounting surface 306, such as being insertable into socket connectors, such that the feedthrough pins 1104 extend from a tip inside the protection gap to a base outside the protection gap. The fold region 316 of the flexible substrate 304 can separate the protection gap from the distal region of the electronic device chamber 116. The battery can be hermetically sealed to the proximal end of the housing 102 by a first circumferential weld, and the end cap assembly 110 can be hermetically sealed to the distal end of the housing 102 by a second circumferential weld. Then, the assembled biostimulator 100 can be delivered and implanted into a target site to deliver pacing pulses to the target site.

[0100] Figure 13-16 Shows the components of the biostimulator 100, and more particularly, shows the components of the biostimulator 100 having a flexible circuit assembly 120 that includes metal pads 1302 for connection to feedthrough pins 1104 and battery pins 902. It will be understood that the assembly operations described below can be performed in any order. For example, although in the following description the housing 102 can be loaded onto the flexible circuit assembly 120 after the feedthrough pins 1104 are attached to the metal pads 1302, it should be understood that in the above-described embodiments, the housing 102 can be loaded onto the flexible circuit assembly 120 before the feedthrough pins 1104 are attached to the socket connector.

[0101] Referring Figure 13 , a cross-sectional view of an end cap assembly connected to a flexible circuit assembly according to one embodiment is shown. In one embodiment, the feedthrough connector 402 and the battery connector 410 are metal pads 1302. For example, the pads can be formed on the flexible substrate 304 using semiconductor manufacturing processes. The flexible circuit assembly 120 can be folded along the folding region 316 into a stacked configuration 702.

[0102] In one embodiment, when the flexible circuit assembly 120 is in the stacked configuration 702, the aperture axis 352 can extend between a first mounting area 312 and a second mounting area 314, for example, above the metal pads 1302. For example, the aperture axis 352 can be parallel to the longitudinal axis 108 and aligned with the feedthrough connector 402. More specifically, when the flexible circuit assembly 120 is in the stacked member 702, the aperture axis 352 can be laterally aligned between the feedthrough connector 402 and the electronic component 310. In the lateral alignment, a lateral plane containing the aperture axis 352 and extending in the transverse direction 325 can intersect the feedthrough connector 402. Thus, the feedthrough pin 1104 can extend through the aperture 326 and extend over the feedthrough connector 402 to be arranged in contact with the metal pad 1302.

[0103] In one embodiment, the feedthrough pin 1104 is spot welded to the metal pad 1302 of the feedthrough connector 402. Alternatively, the pin can be soldered to the pad. The feedthrough pin 1104 can be shorter when the electrical connector 308 is a metal pad 1302 compared to when the electrical connector 308 is a socket connector because spot welding that requires minimal space can connect the feedthrough pin 1104 to the feedthrough connector 402. The feedthrough pin 1104 can be connected to the feedthrough connector 402 before the battery pin 902 is connected to the battery connector 410. For example, the feedthrough pin 1104 can be fusion welded or brazed to the metal pad 1302.

[0104] Referring Figure 14, showing a cross-sectional view of an end cap assembly and a battery connected to a flexible circuit assembly. The battery pins 902 may be disposed on corresponding metal pads 1302 of the flexible circuit assembly 120. For example, the battery pins 902 may be inserted through corresponding slots 804 in the end insulator 122 and disposed on or within the battery connector 410. The battery pins 902 may be connected to the corresponding battery connectors 410 by corresponding spot welds. Alternatively, the pins may be soldered to the pads. When the battery pins 902 are attached to the corresponding battery connectors 410 by thermal welding or by inserting the pins into spring connectors as described above, the end insulator 122 may be held between the flexible circuit assembly 120 and the distal face 904 of the battery.

[0105] The use of metal pads 1302 or similar electrical connections that use fusion or brazing structures to transfer power between the flexible circuit assembly 120 and an external component (e.g., an energy source 107 (battery)) has several advantages. As described above, the metal pads 1302 use less space than socket connectors, and thus the overall size of the biostimulator 100 can be reduced. Second, welded attachments can be produced at a lower cost than other connectors such as socket connectors. Third, welded attachments can be easily verified, which can improve manufacturability and contribute to the long-term reliability of the biostimulator 100.

[0106] In one embodiment, after connecting the feedthrough pins 1104 to the feedthrough connectors 402 and connecting the battery pins 902 to the battery connectors 410, a double-sided foam tape 1202 may be disposed between the mounting surfaces 306. Then, the flexible circuit assembly 120 may be folded to press the mounting surfaces 306 against the foam tape 1202. Thus, the foam tape 1202 may hold the flexible circuit assembly 120 in a folded or stacked configuration.

[0107] Referring to Figure 15 , showing a cross-sectional view of an electronic device chamber of a biostimulator according to one embodiment, the electronic device chamber accommodating a wall insulator and a flexible circuit assembly. In one operation, the wall insulator 124 may be mounted on the stacked flexible circuit assemblies 120. For example, the wall insulator 124 may slide over the flange 1004 until the proximal wall end 208 contacts the end insulator 122 and / or the distal face 904 of the battery. When the wall insulator 124 is disposed on the flange 1004, the distal wall end 206 may be adjacent to the proximal edge of the flange 1004, and thus the wall insulator 124 may extend around the flexible circuit assembly 120. More particularly, the flexible circuit assembly 120 may include a flexible circuit assembly 120 having electrical connectors 308 that are connected to the feedthroughs 1102 and the battery.

[0108] After the wall insulator 124 is slid over the flexible circuit assembly 120, the housing 102 can be added to the wall insulator 124. More specifically, the housing 102 can be assembled over the folded flexible circuit assembly 120 to isolate and house the electrical components. The housing 102 can slide over the flange 1004 until the proximal end of the housing 102 abuts the battery. Conversely, the distal end of the housing 102 is adjacent to the flange 1004. Thus, when the housing 102 is mounted on the battery, the inner surface 118 can extend around the end insulator 122, the wall insulator 124, and the flexible circuit assembly 120.

[0109] The bio-stimulator 100 assembly can be secured by attaching the end cap assembly 110 (e.g., the flange 1004) to the housing 102 and by attaching the housing 102 to the battery. In one embodiment, a first circumferential weld 1502 is formed along the seam between the flange 1004 and the distal end of the housing 102. Similarly, a second circumferential weld 1504 can be formed along the seam between the housing 102 and the battery. The circumferential welds secure and seal the components. More particularly, the welds can be airtight welds that isolate the components within the electronic device chamber 116 from the surrounding environment.

[0110] In one embodiment, when the housing 102 and the wall insulator 124 are secured around the flexible circuit assembly 120, these components are tightly fitted together. For example, when the foam tape 1202 loses its grip, the peripheral edge 1204 can deflect outward and press against the inner surface of the wall insulator 124. In the case of the corrugated wall insulator 124, the wall insulator 124 can expand outward and press against the inner surface 118 of the housing 102. Thus, the wall insulator 124 can be sandwiched between the inner surface 118 of the housing 102 and the peripheral edge 1204 of the flexible circuit assembly 120.

[0111] In one embodiment, one or more end insulators 122 or wall insulators 124 include an adhesive film (not shown). The adhesive film may include a pressure-sensitive adhesive or other adhesive that covers one or more surfaces of the end insulator 122 or the wall insulator 124. For example, the inner surface of the wall insulator 124 and the upper surface of the end insulator 122 may include an adhesive. Thus, the surface facing the flexible circuit assembly 120 may have an adhesive, and thus, the adhesive film may attach the insulators 122, 124 to the flexible circuit assembly 120. In the above embodiment, using an adhesive to bond the components within the housing 102 to each other can achieve several advantages. First, the adhesive can improve placement by reducing the likelihood of components moving within the housing 102. Second, insulation of the electrical components can be ensured by the adhesive. For example, by reducing the likelihood of displacement of the electronic components, gaps between the insulators 122, 124 can be prevented from forming, thereby reducing the likelihood that the electronic components of the flexible circuit assembly 120 may be exposed to the inner surface of the conductive housing 102.

[0112] Reference Figure 16 , a perspective view of an electronic device chamber of a biostimulator according to one embodiment is shown, the electronic device chamber housing a wall insulator overmolded on a flexible circuit assembly. The wall insulator 124 may be overmolded onto the flexible circuit assembly 120. The overmolding operation may occur, for example, after the feedthrough pins 1104 and the battery pins 902 are connected to the corresponding electrical connectors 308 on the flexible circuit assembly 120. The overmolding 1602 may be placed on and around the components of the folded flexible circuit assembly 120. The overmolding 1602 may be, for example, a polymeric material and may isolate and electrically insulate the components from the housing 102. More specifically, when the housing 102 is loaded onto the overmolded wall insulator 124, the overmolding 1602 material may separate the electrical connectors 308 of the flexible circuit assembly 120 from the inner surface 118 (not shown) of the housing 102. Thus, the overmolded wall insulator 124 substantially functions the same as the tubular insulating sleeve described above. As described above, the overmolding 1602 can be hermetically sealed within the electronic device chamber 116 by forming a circumferential weld around the housing 102 at the flange 1004 and the battery.

[0113] Refer to Figure 17, showing a cross-sectional view of a desiccant in an electronic device chamber of a bio-stimulator according to one embodiment. The electronic device chamber 116 can be hermetically sealed within the bio-stimulator 100. For example, the end cap assembly 110 can be coupled to the distal end (not shown) of the housing 102 by an airtight weld around the periphery of the distal end. Similarly, the battery can be coupled to the proximal end (not shown) of the housing 102 by an airtight weld around the periphery of the proximal end. Thus, any moisture trapped within the electronic device chamber 116 during the manufacturing process can remain therein unless steps are taken to remove the moisture.

[0114] In one embodiment, the bio-stimulator 100 includes a desiccant 1702 within the electronic device chamber 116. The desiccant 1702 can be a drying agent that absorbs residual moisture within the electronic device chamber 116. The desiccant 1702 can include a drying agent within a permeable matrix such as a polymer. An example of a suitable drying agent material includes zeolite, however, other drying agents can also be used in the desiccant 1702.

[0115] The desiccant 1702 can be loaded into and held by an absorbent holder 1704. The absorbent holder 1704 can be mounted on a component within the electronic device chamber 116, such as on the proximal face or surface of the end cap assembly 110. The absorbent holder 1704 can occupy space within the electronic device chamber 116 without interfering with components of the flexible circuit assembly 120.

[0116] Referring to Figure 18 , a perspective view of a desiccant holder according to one embodiment is shown. The getter holder 1704 can include a cavity 1802. For example, the cavity 1802 can be a recess machined or otherwise formed in the surface of the getter holder 1704 to allow sufficient desiccant 1702 to be loaded into the cavity 1802 to remove moisture from the electronic device chamber 1702. In one embodiment, the cavity 1802 has a volume of 1.5 - 2.5 mm 3 , such as 1.9 mm 3 , to accommodate a corresponding volume of absorbent material. The desiccant 1702 can be loaded (e.g., injected) into the cavity 1802. In one embodiment, the cavity 1802 has an opening facing proximally within the electronic device chamber 116. For example, the getter holder 1704 can be fastened to the end cap assembly 110 such that the opening of the cavity 1802 faces the battery. Alternatively, the getter holder 1704 can be mounted in the proximal region of the electronic device chamber 116 and the opening of the cavity 1802 can face the end cap assembly 110.

[0117] In one embodiment, the getter retainer 1704 is made of a low-moisture material. For example, the getter retainer 1704 can be machined from a glass-reinforced epoxy laminate. Alternatively, the getter retainer 1704 can be molded from a thermosetting polymer, a ceramic material, or other low-moisture materials.

[0118] Referring to Figure 19 , a perspective view of a moisture getter in an electronic device chamber of a biostimulator according to one embodiment is shown. The getter retainer 1704 can be integral with another component of the biostimulator 100 rather than a separate component. For example, the getter retainer 1704 can be fastened to or formed integrally with the end insulator 122. In one embodiment, the getter retainer 1704 is bonded to the distal side of the end insulator 122, and the opening of the cavity 1802 that houses the moisture getter 1702 can face the end cap assembly 110 in the distal direction.

[0119] Referring to Figure 20 , a perspective view of a moisture getter retainer according to one embodiment is shown. The getter retainer 1704 can be integrally formed with the end insulator 122. For example, the end insulator 122 can have a flat proximal side and a non-flat distal side. Instead of having a flat distal side, the getter retainer 1704 can be a groove extending from the distal side 904. The integrally formed end insulator 122 can separate the battery from the flexible circuit assembly 120 and can hold the moisture getter 1702. As described above, the integrally formed end insulator 122 can include a slit 804 for receiving the battery pins 902. In one embodiment, the getter retainer portion of the end insulator 122 and the flat portion of the end insulator 122 having the slit 804 can be formed from a glass-reinforced epoxy laminate or from another material having low moisture and having electrical insulation properties. Thus, the end insulator 122 can facilitate the removal of moisture from the electronic device chamber 116 and can reduce the likelihood of an electrical short circuit between the components of the flexible circuit assembly and other biostimulator components.

[0120] Within the scope of this specification, alternative insulation structures for isolating the flexible circuit assembly 120 from the housing 102 are contemplated. Referring to Figure 22, shows a perspective view of an insulating cover according to an embodiment. The insulating cover 2200 may be an insulator having one or more foldable segments 2202, such as a polyimide sheet or another insulating material. The foldable segments 2202 may be rectangular or other shaped segments joined along respective fold lines (dashed lines). In one embodiment, the foldable segments 2202 are folded relative to each other to wrap around the flexible circuit assembly 120 and isolate the electronic components from the surrounding structure. For example, when the flexible circuit assembly 120 is in a folded configuration, the first fold segment 2202a may be disposed on the back side of the first mounting area 312 during assembly. Then, one or more additional fold segments, such as the top fold segment 2202b and / or the bottom fold segment 2202c, may be folded along the respective fold lines so that the flaps wrap around the top and bottom ends of the folded circuit assembly and are disposed on the back side of the second mounting area 314. Optionally, then one or more side fold segments 2202d may be folded along the respective fold lines so that the flaps wrap around the sides of the folded circuit assembly. Thus, the flaps of the insulating cover 2200 may be folded around the electronic components to encapsulate the flexible circuit assembly 120 and isolate the electronic components from the housing 102. A slit 804 may be formed in the insulating cover 2200 to accommodate feedthrough pins or battery pins. The slit 804 may be located in the insulating material sheet along the fold line that separates the first fold segment 2202a from the adjacent fold segment.

[0121] Several embodiments described above are summarized in the following paragraphs. In one embodiment, a flexible circuit assembly for a bio - stimulator includes a flexible substrate. The flexible substrate includes a mounting surface having a fold region between a first mounting area and a second mounting area. The flexible substrate is configured to be folded along the fold region into a stacked configuration such that the first mounting area faces the second mounting area. The flexible substrate includes an aperture in the fold region, the aperture having an aperture axis.

[0122] The flexible circuit assembly may include a feedthrough connector on the mounting surface. When the flexible substrate is in the stacked configuration, the aperture axis may extend between the first mounting area and the second mounting area in alignment with the feedthrough connector. The flexible circuit assembly may include electronic components on the mounting surface.

[0123] The feedthrough connector may be on the first mounting area, and the electronic components may be on the second mounting area.

[0124] The aperture may be centered on the mounting surface.

[0125] The flexible circuit assembly may include a plurality of battery connectors on the mounting surface.

[0126] The feedthrough connector and the plurality of battery connectors can be socket connectors having respective socket axes that extend parallel to each other. The socket axis of the feedthrough connector can be laterally positioned between the socket axes of the battery connectors. The feedthrough connector and the plurality of battery connectors can be metal pads.

[0127] In one embodiment, the biostimulator includes a housing having an inner surface that surrounds an electronic device chamber. The biostimulator includes a flexible circuit assembly within the electronic device chamber. The flexible circuit assembly includes a flexible substrate that includes a mounting surface having a fold region between a first mounting region and a second mounting region. The flexible substrate is folded along the fold region such that the first mounting region faces the second mounting region. The flexible substrate includes an aperture in the fold region. The aperture has an aperture axis. The flexible circuit assembly includes a feedthrough connector on the mounting surface. The aperture axis extends aligned with the feedthrough connector. The flexible circuit assembly includes electronic components on the mounting surface.

[0128] The feedthrough connector can be on the first mounting region and the electronic components can be on the second mounting region such that the feedthrough connector and the electronic components are in a stacked configuration.

[0129] The aperture can be centered on the mounting surface.

[0130] The biostimulator can include a foam strip between the feedthrough connector and the electronic components.

[0131] The biostimulator can include a battery having a plurality of battery pins that extend longitudinally from a distal side. The flexible circuit assembly includes a plurality of battery connectors that are connected to respective battery pins of the battery. The battery pins have respective pin axes that extend parallel to the aperture axis of the aperture. The biostimulator can include an end insulator between the distal side of the battery and the flexible circuit assembly. The end insulator can be planar and can include a plurality of slots. The plurality of battery pins can extend through the plurality of slots into the electronic device chamber. The end insulator can have an outer edge. The outer edge and the inner surface of the housing can have the same profile.

[0132] The biostimulator can include a wall insulator that extends around the flexible circuit assembly within the electronic device chamber.

[0133] The biostimulator can include a moisture absorber within the electronic device chamber.

[0134] In one embodiment, a method includes folding a flexible circuit assembly along a fold region into a stacked configuration. The flexible circuit assembly includes a mounting surface having a fold region between a first mounting area and a second mounting area. When the flexible circuit assembly is in the stacked configuration, the first mounting area faces the second mounting area in a lateral direction. The method includes connecting feedthrough pins between the first mounting area and the second mounting area to feedthrough connectors on the mounting surface. The feedthrough pins extend through apertures in the fold region. The method includes connecting a plurality of cell pins of a battery to corresponding cell connectors on the mounting surface.

[0135] The method may include inserting the plurality of cell pins through respective slots in an end insulator. The end insulator may be located between the battery and the flexible circuit assembly when the plurality of cell pins are attached to the corresponding cell connectors. The method may include mounting a wall insulator on the stacked flexible circuit assembly such that the wall insulator extends around the flexible circuit assembly. The method may include mounting a housing on the battery such that an inner surface of the housing extends around the end insulator, the wall insulator, and the flexible circuit assembly. The wall insulator may be sandwiched between the inner surface of the housing and a peripheral edge of the flexible circuit assembly. The method may include attaching the housing to an end cap assembly and the battery to accommodate an electronic device chamber between the battery, the inner surface of the housing, and end cap pins. The flexible circuit assembly may be within the electronic device chamber. The end cap assembly may include a feedthrough portion having feedthrough pins, an electrode head, and a fixing element.

[0136] In the foregoing specification, the invention has been described with reference to specific exemplary embodiments of the invention. Obviously, various modifications can be made thereto without departing from the broader spirit and scope of the invention as set forth in the appended claims. Accordingly, the specification and drawings are to be regarded as illustrative rather than restrictive.

Claims

1. A flexible circuit assembly for a bio - stimulator, comprising: A flexible substrate, including a mounting surface having a fold region between a first mounting region and a second mounting region, wherein the flexible substrate is configured to be folded along the fold region into a stacked configuration such that the first mounting region faces the second mounting region, and wherein the flexible substrate includes an aperture centered in the fold region; and An electronic component, on the mounting surface.

2. The flexible circuit assembly according to claim 1, wherein, The aperture is longitudinally centered on the mounting surface between a first longitudinal edge and a second longitudinal edge of the flexible substrate.

3. The flexible circuit assembly according to claim 2, wherein, The aperture is equidistantly spaced between the first longitudinal edge and the second longitudinal edge.

4. The flexible circuit assembly according to claim 1, wherein, The aperture is laterally centered on the mounting surface between a first lateral edge and a second lateral edge of the flexible substrate.

5. The flexible circuit assembly according to claim 4, wherein, The aperture is equidistant from the first lateral edge and the second lateral edge.

6. The flexible circuit assembly according to claim 1, wherein, The electronic component is a processor configured to control the generation of pacing pulses and further includes a feedthrough connector located on the mounting surface such that when the flexible substrate is in the stacked configuration, the feedthrough connector receives and transmits the pacing pulses through the aperture to a target tissue.

7. The flexible circuit assembly according to claim 6, wherein, When the flexible substrate is in the stacked configuration, the feedthrough connector is aligned with the aperture.

8. The flexible circuit assembly according to claim 7, further comprising a plurality of battery connectors located on the mounting surface.

9. The flexible circuit assembly according to claim 8, wherein, The feedthrough connector is located between battery connectors.

10. A bio - stimulator, comprising: A housing, having an inner surface surrounding an electronic device chamber; And A flexible circuit assembly, located within the electronic device chamber, wherein the flexible circuit assembly includes: A flexible substrate, the flexible substrate including a mounting surface having a fold region between a first mounting region and a second mounting region, wherein the flexible substrate is configured to be folded along the fold region into a stacked configuration such that the first mounting region faces the second mounting region, and wherein the flexible substrate includes an aperture centered in the fold region, and An electronic component, on the mounting surface.

11. The flexible circuit assembly according to claim 10, wherein, The aperture is longitudinally centered on the mounting surface between a first longitudinal edge and a second longitudinal edge of the flexible substrate.

12. The flexible circuit assembly according to claim 11, wherein, The aperture is equidistantly spaced between the first longitudinal edge and the second longitudinal edge.

13. The flexible circuit assembly according to claim 10, wherein, The aperture is laterally centered on the mounting surface between a first lateral edge and a second lateral edge of the flexible substrate.

14. The flexible circuit assembly according to claim 13, wherein, The aperture is equidistant from the first lateral edge and the second lateral edge.

15. The flexible circuit assembly according to claim 10, wherein, The electronic component is a processor configured to control the generation of pacing pulses and further includes a feedthrough connector located on the mounting surface such that when the flexible substrate is in the stacked configuration, the feedthrough connector receives and transmits the pacing pulses through the aperture to a target tissue.

16. The flexible circuit assembly according to claim 15, wherein, When the flexible substrate is in the stacked configuration, the feedthrough connector is aligned with the aperture.

17. The flexible circuit assembly according to claim 16, further comprising a plurality of battery connectors located on the mounting surface.

18. A method, comprising: Fold the flexible circuit assembly along the fold region into a stacked configuration, wherein the flexible circuit assembly includes a mounting surface having a fold region between a first mounting region and a second mounting region, wherein the flexible substrate is configured to be folded along the fold region into a stacked configuration such that the first mounting region faces the second mounting region, and the flexible substrate includes an aperture centered in the center of the fold region; and Mount a processor on the mounting surface, wherein the processor is configured to control the delivery of pacing pulses to be transmitted through the aperture to a target tissue.

19. The method according to claim 18, further comprising connecting a feedthrough pin of the end cap assembly to a feedthrough connector on the mounting surface between the first mounting area and the second mounting area, wherein the feedthrough pin extends through an aperture of the folding area.

20. The method according to claim 19, further comprising connecting a plurality of cell pins of the battery to corresponding cell connectors on the mounting surface.

21. A biostimulator, comprising: A housing, having an electronic device chamber; A flexible circuit assembly, located within the electronic device chamber, the flexible circuit assembly including a plurality of battery connectors; A battery, having a plurality of battery pins extending from a distal face; And An end insulator, between the distal face of the battery and the flexible circuit assembly, wherein the end insulator includes a plurality of slits through which a plurality of battery pins extend into the electronic device chamber to connect to a plurality of battery connectors.

22. The biostimulator according to claim 21, wherein, The end insulator is flat.

23. The biostimulator according to claim 21, wherein, One or more of the slits have an oval profile.

24. The biostimulator according to claim 21, wherein, The size of the first slit among the plurality of slits is larger than the size of the second slit.

25. The biostimulator according to claim 21, wherein, The inner surface of the housing extends around the end insulator and the flexible circuit assembly.

26. The biostimulator according to claim 25, wherein, The end insulator has an outer edge, and the outer edge and the inner surface of the housing have the same profile.

27. The biostimulator according to claim 26, wherein, The outer diameter of the outer edge is within 10% of the inner diameter of the inner surface.

28. The biostimulator according to claim 21, wherein, The end insulator includes a dielectric film.

29. The biostimulator according to claim 21, wherein, The end insulator includes a desiccant holder and further includes a desiccant located in the cavity of the desiccant holder.

30. The biostimulator according to claim 21, wherein, The end insulator is a folded section of an insulating cover that has a foldable section, and wherein the foldable section wraps around the flexible circuit assembly.

31. The biostimulator according to claim 21, wherein, The flexible substrate includes a mounting surface that has a fold region between a first mounting region and a second mounting region, wherein the flexible substrate is configured to fold along the fold region into a stacked configuration such that the first mounting region faces the second mounting region, and the flexible substrate includes an aperture centered in the fold region.

32. The biostimulator according to claim 31, further comprising a processor and a feedthrough connector located on the mounting surface, wherein the processor is configured to control the generation of pacing pulses, and the feedthrough connector is configured to receive and transmit the pacing pulses through the aperture to the target tissue.

33. The biostimulator according to claim 21, further comprising an end cap assembly mounted on the housing such that the flexible circuit assembly is enclosed between the end cap assembly, the housing, and the battery.

34. A method, comprising: Insert a plurality of battery pins of the battery through the plurality of slits of the end insulator; And Connect a plurality of battery connectors of the flexible circuit assembly to the plurality of battery pins, wherein the end insulator is located between the distal face of the battery and the flexible circuit assembly.

35. The method according to claim 34, wherein The end insulator is flat.

36. The method according to claim 34, wherein One or more of the slits have an oval profile.

37. The method according to claim 34, further comprising mounting the housing on the battery such that the flexible circuit assembly is located within the electronic device chamber of the housing.

38. The method according to claim 37, wherein The inner surface of the housing extends around the end insulator and the flexible circuit assembly.

39. The method according to claim 37, further comprising mounting the end cap assembly on the housing such that the flexible circuit assembly is enclosed between the end cap assembly, the housing, and the battery.

40. The method according to claim 34, further comprising folding the flexible circuit assembly along a folding region into a stacked configuration, wherein the flexible circuit assembly includes a mounting surface having a folding region between a first mounting region and a second mounting region, and wherein When the flexible circuit assembly is in the stacked configuration, the first mounting region faces the second mounting region in the lateral direction.

41. A biostimulator, comprising: A housing, having an inner surface surrounding the electronic device chamber; A flexible circuit assembly, located within the electronic device chamber; And A wall insulator, extending around the flexible circuit assembly within the electronic device chamber.

42. The biostimulator according to claim 41, wherein The wall insulator separates the flexible circuit assembly from the housing.

43. The biostimulator according to claim 41, wherein The wall insulator has a tubular structure.

44. The biostimulator according to claim 43, wherein The cross-sectional profile of the tubular structure is circular.

45. The biostimulator according to claim 43, wherein The cross-sectional profile of the tubular structure is corrugated such that the wall insulator can expand radially.

46. The biostimulator according to claim 41, wherein The inner wall surface of the wall insulator contacts the exterior of the flexible circuit assembly.

47. The biostimulator according to claim 41, wherein The wall insulator includes a coating applied to the inner surface of the housing.

48. The biostimulator according to claim 41, wherein The wall insulator is overmolded on the flexible circuit assembly.

49. The biostimulator according to claim 41, wherein, The wall insulator includes a dielectric material.

50. The biostimulator according to claim 41, wherein, The wall insulator is a folded portion of an insulating cover that has a foldable section, and wherein the foldable section wraps around the flexible circuit assembly.

51. The biostimulator according to claim 41, wherein, The flexible circuit assembly includes a mounting surface that has a fold region between a first mounting region and a second mounting region, wherein the flexible circuit assembly is configured to fold along the fold region into a stacked configuration such that the first mounting region faces the second mounting region, and the flexible circuit assembly includes an aperture centered in the fold region.

52. The biostimulator according to claim 51, further comprising a processor and a feedthrough connector located on the mounting surface, wherein the processor is configured to control the generation of pacing pulses, and the feedthrough connector is configured to receive and transmit the pacing pulses through the aperture to the target tissue.

53. The biostimulator according to claim 41, further comprising an end cap assembly and a battery, wherein the housing is mounted on the battery, and the end cap assembly is mounted on the housing such that the flexible circuit assembly and the wall insulator are enclosed between the end cap assembly, the housing, and the battery.

54. A method, comprising: Connect a plurality of battery connectors of the flexible circuit assembly to the plurality of battery pins of the battery; And Insert the wall insulator onto the flexible circuit assembly such that the wall insulator extends around the flexible circuit assembly.

55. The method according to claim 54, further comprising mounting the housing on the battery such that the inner surface of the housing extends around the electronic device chamber, and the flexible circuit assembly and the wall insulator are located within the electronic device chamber.

56. The method according to claim 55, further comprising mounting the end cap assembly on the housing such that the flexible circuit assembly and the wall insulator are enclosed between the end cap assembly, the housing, and the battery.

57. The method according to claim 55, wherein, The wall insulator is sandwiched between the inner surface of the housing and the peripheral edge of the flexible circuit assembly.

58. The method according to claim 55, wherein, Inserting a wall insulator onto a flexible circuit assembly includes coating the inner surface of a housing with the wall insulator.

59. The method according to claim 54, wherein, Inserting a wall insulator onto a flexible circuit assembly includes overmolding the wall insulator onto the flexible circuit assembly.

60. The method according to claim 54, further comprising folding the flexible circuit assembly into a stacked configuration along the folding region, wherein the flexible circuit assembly includes a mounting surface having a folding region between a first mounting region and a second mounting region, and when the flexible circuit assembly is in the stacked configuration, the first mounting region faces the second mounting region in the lateral direction.

61. A biostimulator, comprising: A housing having an electronic device chamber and an inner surface surrounding the electronic device chamber; A flexible circuit assembly located within the electronic device chamber; And A wall insulator extending around the flexible circuit assembly within the electronic device chamber, wherein the wall insulator includes a cylindrical sleeve that fits within the electronic device chamber to space and electrically insulate the flexible circuit assembly from the housing.

62. The biostimulator according to claim 61, wherein, The wall insulator is sandwiched between the peripheral edge of the flexible circuit assembly and the housing.

63. The biostimulator according to claim 61, wherein, The wall insulator has a tubular structure.

64. The biostimulator according to claim 63, wherein, The cross-sectional profile of the tubular structure is circular.

65. The biostimulator according to claim 61, wherein, The inner wall surface of the wall insulator contacts the outer surface of the flexible circuit assembly.

66. The biostimulator according to claim 61, wherein, The inner wall surface of the wall insulator includes an adhesive coating.

67. The biostimulator according to claim 61, wherein, The wall insulator includes a dielectric material.

68. The biostimulator according to claim 61, wherein, The flexible circuit assembly includes a mounting surface having a fold region between a first mounting region and a second mounting region, wherein the flexible circuit assembly is configured to fold along the fold region into a stacked configuration such that the first mounting region faces the second mounting region, and the flexible circuit assembly includes an aperture in the fold region.

69. The biostimulator according to claim 68, further comprising a processor and a feedthrough connector located on the mounting surface, wherein the processor is configured to control the generation of pacing pulses, and the feedthrough connector is configured to receive and transmit the pacing pulses through the aperture to the target tissue.

70. The biostimulator according to claim 61, further comprising an end cap assembly and a battery, wherein the housing is mounted on the battery, and the end cap assembly is mounted on the housing such that the flexible circuit assembly and the wall insulator are enclosed between the end cap assembly, the housing, and the battery.

71. A method, comprising: Connecting a plurality of battery connectors of the flexible circuit assembly to a plurality of battery pins of a battery, wherein the flexible circuit assembly is fitted within the electronic device chamber of the housing; And Inserting a wall insulator onto the flexible circuit assembly such that the wall insulator extends around the flexible circuit assembly, wherein the wall insulator includes a cylindrical sleeve that fits within the electronic device chamber to space and electrically insulate the flexible circuit assembly from the housing.

72. The method according to claim 71, further comprising mounting the housing on the battery such that the inner surface of the housing extends around the electronic device chamber, and the flexible circuit assembly and the wall insulator are located within the electronic device chamber.

73. The method according to claim 72, further comprising mounting the end cap assembly on the housing such that the flexible circuit assembly and the wall insulator are enclosed between the end cap assembly, the housing, and the battery.

74. The method according to claim 72, wherein, The wall insulator is sandwiched between the inner surface of the housing and the peripheral edge of the flexible circuit assembly.

75. The method according to claim 71, further comprising folding the flexible circuit assembly into a stacked configuration along the folding region, wherein the flexible circuit assembly includes a mounting surface having a folding region between a first mounting region and a second mounting region, and when the flexible circuit assembly is in the stacked configuration, the first mounting region faces the second mounting region in the lateral direction.

76. The method according to claim 71, wherein, The inner wall surface of the wall insulator contacts the outer surface of the flexible circuit assembly.

77. The method according to claim 76, wherein, The inner wall surface of the wall insulator includes an adhesive coating.

78. A leadless cardiac pacemaker, comprising: A housing having an electronic device chamber and an inner surface surrounding the electronic device chamber; An end cap assembly mounted on the housing, wherein the end cap assembly includes a pacing electrode; A flexible circuit assembly located within the electronic device chamber, wherein the flexible circuit assembly includes one or more electronic components electrically connected to the pacing electrode; And A wall insulator extending around the flexible circuit assembly within the electronic device chamber, wherein the wall insulator includes a cylindrical sleeve that fits within the electronic device chamber to space and electrically insulate the flexible circuit assembly from the housing.

79. The leadless cardiac pacemaker according to claim 78, wherein, The wall insulator is sandwiched between the peripheral edge of the flexible circuit assembly and the housing.

80. The leadless cardiac pacemaker according to claim 78, wherein, The wall insulator has a tubular structure.

81. A biological stimulator, comprising: A housing having an inner surface surrounding an electronic device chamber; A flexible circuit assembly located within the electronic device chamber; And A wall insulator overmolded around the flexible circuit assembly within the electronic device chamber.

82. The biological stimulator according to claim 81, wherein, The wall insulator spaces the flexible circuit assembly from the housing.

83. A biological stimulator, comprising: A housing having an inner surface surrounding an electronic device chamber; A flexible circuit assembly located within the electronic device chamber; And A cover insulator including a wall insulator integrally formed with an end insulator, wherein the cover insulator spaces the flexible circuit assembly from the housing.

84. The biological stimulator according to claim 83, wherein, The wall insulator includes a tubular sidewall having a proximal end, and the end insulator includes a plane connected to the proximal end.

85. A biological stimulator, comprising: A housing having an electronic device chamber sealed within a biostimulator; A flexible circuit assembly, located inside the electronic device chamber; and a moisture absorbent, located inside the electronic device chamber.

86. The biological stimulator according to claim 85, wherein, The moisture absorbent includes a desiccant located in a permeable matrix.

87. The biological stimulator according to claim 86, wherein, The moisture absorbent includes zeolite, and the permeable matrix includes a polymer.

88. The biological stimulator according to claim 85, further comprising a desiccant holder having a cavity containing a desiccant.

89. The biological stimulator according to claim 88, further comprising an end cap assembly, wherein the opening of the cavity faces the end cap assembly.

90. The biostimulator according to claim 85, wherein, The moisture absorbent holder is made of a low moisture absorption material.

91. A biostimulator, comprising: A housing, having an electronic device chamber; a flexible circuit assembly, located inside the electronic device chamber; and an insulating cover, having a plurality of folded portions wrapped around the flexible circuit assembly.

92. The biostimulator according to claim 91, wherein, The plurality of folded portions are connected along their respective fold lines.

93. The biostimulator according to claim 91, wherein, One or more of the folded portions include slits for receiving one or more of the feedthrough pins or battery pins.

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