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 in an electronics compartment between a battery, a housing, and an end cap assembly of the biostimulator. The flexible circuit assembly includes a flexible substrate that is folded into a stacked configuration in which electronic components and an electrical connector of the flexible circuit assembly are surrounded by the flexible substrate. An orifice is located in the folded region of the flexible substrate to allow a feedthrough pin of the end cap assembly to pass through the folded structure to make electrical contact with the electrical connector. The electronic component may be a processor that controls the delivery of pacing pulses through the feedthrough pins to the pacing tip. Other embodiments are also described and claimed.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority to 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 incorporated herein by reference in their entireties to provide continuity of disclosure. Technical Field

[0003] The present disclosure relates to biostimulators. More particularly, the present disclosure relates to leadless biostimulators having flexible circuit assemblies. Background Art

[0004] Cardiac pacing by an artificial pacemaker provides electrical stimulation to the heart when the heart's own natural pacemaker and / or conduction system fails to provide synchronized atrial and ventricular contractions at a rate and interval sufficient to keep the patient healthy. This bradycardia-avoiding pacing has provided symptom relief and even life support for tens of thousands of patients. Cardiac pacing can also provide electrical overdrive stimulation to suppress or convert tachyarrhythmias, again relieving symptoms and preventing or terminating arrhythmias that could lead to sudden cardiac death.

[0005] Cardiac pacing by currently available or conventional pacemakers is typically performed by implanting a pulse generator subcutaneously or submuscularly in or near the patient's chest region. The parameters of the pulse generator are typically queried and modified by an external programming device, a loosely coupled converter implemented via an inductor inside the body and another inductor outside the body, or electromagnetic radiation implemented via an antenna inside the body and another antenna outside the body. The generator is typically connected to the proximal end of one or more implanted leads, the distal end of which contains one or more electrodes for positioning 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 electrodes in the heart. Such electrode leads typically have a length of 50 to 70 centimeters.

[0006] The pulse generator may have an electronic circuit to control cardiac pacing through the lead wires. For example, the electronic circuit may include a printed circuit board. The electronic circuit may include an integrated circuit to control the transmission of pacing pulses from the interior of the tightly sealed battery container to the external lead wire connection. Summary of the invention

[0007] Conventional pacemakers have several disadvantages, including complex connections between the leads and the pulse generator, and the risk of infection and morbidity due to 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. Leadless biostimulators can be attached to tissue in dynamic environments, such as within the chambers of a beating heart. However, the attachment of leadless biostimulators within the target anatomical structure increases the importance of miniaturization of the device profile. Therefore, 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 batteries and electronic circuitry and the reduction in the overall volume of the electronic circuitry increase the risk of shorting the battery or circuitry caused by conductive residues from the manufacturing process used to manufacture the leadless biostimulator. Therefore, isolating the battery conductors and the electronic circuitry from each other and from the surrounding conductive structures can improve device reliability.

[0008] A biostimulator is provided having a flexible circuit assembly, and optionally other components configured and arranged to reduce the possibility of short circuits. 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 area so that a first mounting area and a second mounting area of ​​the mounting surface face each other. In a folded or stacked configuration, a feed-through connector and electronic components, both of which are on the mounting surface, can be encapsulated by the folded flexible substrate. Thus, the feed-through connector and the electronic components can be protected and separated from surrounding conductive components (such as a housing or a battery).

[0009] The flexible circuit assembly can have an orifice in the folded region. The orifice can be centered on the mounting surface. For example, the orifice can be at the center of the folded region. The orifice axis of the orifice can extend in alignment with (e.g., through or above) the feed-through connector. Thus, a feed-through pin of the end cap assembly can be inserted through the orifice to connect to the feed-through connector. The feed-through pin can conduct electrical pulses from the flexible circuit assembly to the target tissue.

[0010] In one embodiment, the battery connector is also on the mounting surface. For example, the feed-through connector and the battery connector can be on a first mounting area of ​​the mounting surface, and the electronic component (e.g., a processor) can be on a second mounting area 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 is laterally between the socket axes of the battery connector. Therefore, when engaged with the corresponding connector, the electrical pins of the feed-through and the battery can evenly support the flexible circuit assembly at multiple points.

[0011] The folded flexible circuit assembly can be folded so that the flexible substrate contacts the adjacent housing and / or battery. Thus, the flexible substrate can separate the electrical connector and electronic components from the surrounding structure and insulate them. 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 a slit to allow the battery pin to pass through the end insulator to connect to the battery connector. In one embodiment, the biostimulator 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.

[0012] A method of assembling a biostimulator 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 the housing to the end cap assembly and the battery using a circumferential weld. The weld can hermetically seal an electronics compartment containing the flexible circuit assembly. Accordingly, the biostimulator can include a moisture absorbent within the electronics compartment to remove residual moisture that may negatively affect the performance of the electrical connector or electronic components within the electronics compartment.

[0013] The above summary does not include an exhaustive list of all aspects of the 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 summarized above and all suitable combinations of those directions disclosed in the detailed description below and particularly pointed out in the claims filed with the present application. Such combinations have specific advantages not specifically recited in the above summary. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The novel features of the present invention are set forth in the appended claims. The features and advantages of the present invention may be better understood by referring to the following detailed description and the accompanying drawings, which set forth illustrative embodiments utilizing the principles of the present invention, in which:

[0015] Figure 1A-1B 1 and 2 are a perspective view and an exploded view, respectively, of a biostimulator according to one embodiment.

[0016] Figure 2A-2B is a perspective view of a wall insulator according to one embodiment.

[0017] Figure 3 is a perspective view of the inside of a flexible circuit assembly in a flattened configuration according to one embodiment.

[0018] Figure 4is a plan view of the inside of a flexible circuit assembly according to one embodiment.

[0019] Figure 5 is a perspective view of the outside of a flexible circuit assembly in a flattened configuration according to one embodiment.

[0020] Figure 6 is a plan view of the outside of a flexible circuit assembly according to one embodiment.

[0021] Figure 7 is a perspective view of a flexible circuit assembly in a stacked configuration according to one embodiment.

[0022] Figure 8 is a perspective view of an end insulator of a biostimulator according to one embodiment.

[0023] Fig. 9 is a perspective view of battery pins extending through an end insulator of a biostimulator according to one embodiment.

[0024] Fig.10 is a cross-sectional view of an electronics compartment of a biostimulator having a flexible circuit assembly according to one embodiment.

[0025] Fig.11 is a cross-sectional view of an electronics compartment of a biostimulator having a flexible circuit assembly according to one embodiment.

[0026] Fig.12 is a cross-sectional view of a biostimulator having a flexible circuit assembly according to one embodiment.

[0027] Fig.13 is a cross-sectional view of an end cap assembly connected to a flexible circuit assembly according to one embodiment.

[0028] Fig.14 is a cross-sectional view of an end cap assembly and a battery connected to a flexible circuit assembly according to one embodiment.

[0029] Fig.15 is a cross-sectional view of an electronics compartment of a biostimulator housing a wall insulator and a flexible circuit assembly according to one embodiment.

[0030] Fig.16 is a perspective view of an electronics compartment of a biostimulator housing a wall insulator overmolded onto a flexible circuit assembly according to one embodiment.

[0031] Fig.17 is a perspective view of a moisture absorber in an electronics compartment of a biostimulator according to one embodiment.

[0032] Fig.18 is a perspective view of a desiccant holder according to one embodiment.

[0033] Fig.19 is a perspective view of a moisture absorber in an electronics compartment of a biostimulator according to one embodiment.

[0034] Fig. 20 is a perspective view of a desiccant holder according to one embodiment.

[0035] Fig.21 is a perspective view of a cover insulator according to one embodiment.

[0036] Fig. 22 is a perspective view of an insulation cover according to one embodiment. DETAILED DESCRIPTION

[0037] Embodiments describe a biostimulator, such as a leadless cardiac pacemaker, having a flexible circuit assembly comprising: a flexible substrate that carries electronic components and an electrical connector; and an aperture in the flexible substrate to allow a feedthrough pin to pass through the flexible substrate to the electrical connector. The electronic components may include a processor to control the transmission of pacing pulses from a battery to a 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., a 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. Therefore, referring to the biostimulator as a pacemaker is not restrictive.

[0038] In various embodiments, description is made with reference to the accompanying drawings. However, certain embodiments may be practiced without one or more of these specific details, or may be practiced in combination with other known methods and configurations. In the following description, many specific details, such as specific configurations, dimensions, and processes, are described to provide a thorough understanding of the embodiments. In other cases, known processes and manufacturing techniques are not particularly described in detail to avoid making the description unclear unnecessarily. Throughout the specification, references to "one embodiment", "one embodiment", etc. refer to specific features, structures, configurations, or characteristics described being included in at least one embodiment. Therefore, phrases "one embodiment", "one embodiment", etc. that appear throughout the specification do not necessarily refer to the same embodiment. In addition, in one or more embodiments, specific features, structures, configurations, or characteristics may be combined in any suitable manner.

[0039] Throughout the specification, the use of relative terms may indicate relative positions or directions. 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 following embodiments.

[0040] In one aspect, a biostimulator is provided. The biostimulator includes a pacing tip for delivering pacing pulses to a target tissue. The pacing pulses can be controlled and / or transmitted by a flexible circuit assembly housed in an electronics compartment of the biostimulator, the flexible circuit assembly having an electronic assembly and an electrical connector. More particularly, the flexible circuit assembly includes electronic components and an electrical connector on a mounting surface of a flexible substrate, the flexible substrate being folded in half in the electronics compartment. A first mounting area carrying the electronic components and a second mounting area carrying the electrical connector can face each other, such that the electronic components and the electrical connector are sandwiched between and enclosed by the mounting areas. The electronic components and the electrical connector can be insulated from surrounding structures (e.g., a housing of the biostimulator) by one or more of the flexible substrate, a wall insulator, or an end insulator. For example, the wall insulator can separate the flexible circuit assembly from the housing, and the end insulator can separate the flexible circuit assembly from the battery to reduce the possibility of an electrical short circuit between a conductive portion of the flexible circuit assembly and the housing or the battery.

[0041] Reference Figure 1A , showing a perspective view of a biostimulator according to one embodiment. The biostimulator 100 can be a leadless biostimulator, such as a leadless cardiac pacemaker. The biostimulator 100 can include a distal electrode 104 and a proximal electrode 106 disposed thereon. The electrodes can be integral with the housing 102 or connected to 102, such as connected to the housing 102 at a distance less than a few centimeters from the housing 102. The housing 102 can house an energy source 107 to provide power to the pacing electrodes. The energy source 107 can 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 can be a supercapacitor. In one embodiment, the energy source 107 can be an energy harvesting device, such as a piezoelectric device that converts mechanical stress into current or voltage. The energy source 107 can also be an ultrasound transmitter that uses ultrasound technology to transfer energy from an ultrasonic subcutaneous pulse generator to a receiving electrode implanted on the endocardial wall.

[0042] The biostimulator 100 can have a longitudinal axis 108. The longitudinal axis 108 can be an axis of symmetry along which a plurality of biostimulator components are arranged. For example, an end cap assembly 110 can be mounted at a distal end of the housing 102 along the longitudinal axis 108. The end cap assembly 110 can include an electrical feedthrough assembly including an electrical feedthrough portion (not shown) and a distal electrode 104, such as a pacing tip. The end cap assembly 110 can include a helical mounting bracket 112 mounted on the electrical feedthrough assembly about the longitudinal axis 108. In one embodiment, a fixation element 114 is mounted on the helical mounting bracket 112 along the longitudinal axis 108. The assembled components of the biostimulator 100 can provide a distal region that is attached to a target tissue, such as via engagement of the fixation element 114 with the target tissue. The distal region can deliver pacing pulses to the target tissue, such as via the distal electrode 104 held against the target tissue.

[0043] Reference Figure 1B , shows an exploded view of a biostimulator with a flexible circuit assembly according to one embodiment. The housing 102 can house an electronics chamber 116. More specifically, the housing 102 can have a housing wall, such as a cylindrical wall, that laterally surrounds the electronics chamber 116. In one embodiment, the housing wall has an inner surface 118 that extends around the housing 102 on the longitudinal axis 108. The housing wall can include a conductive, biocompatible, inert, and anodically safe material, such as titanium, 316L stainless steel, or other similar material, to laterally enclose the electronics chamber 116. The electronics chamber 116 can be axially enclosed by the battery at the proximal end. More specifically, the distal surface or distal side of the battery can define the proximal end of the electronics chamber 116. The electronic components 116 can be axially enclosed by the end cap assembly 110 at the distal end. More specifically, the proximal surface of the end cap assembly 110 can define the distal end of the electronics chamber 116. The housing 102 can be attached (e.g., welded) to the end cap assembly 110 and the battery 107. Thus, electronics compartment 116 may be contained between the battery, the interior surface of housing 102 , and end cap assembly 110 .

[0044] 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 on which one or more electronic components are mounted. For example, the flexible circuit assembly 120 may include one or more passive electronic components (e.g., capacitors) and one or more active electronic components (e.g., 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 a socket connector and a pin connector or a metalized contact pad to connect to a battery and an electrical feedthrough assembly. For example, the electrical connector may be a socket connector or a metal pad to receive and / or connect to an electrode pin or a terminal pin, as described below.

[0045] The electrical connector of the flexible circuit assembly 120 may accidentally short to other conductive components of the biostimulator 100, such as the housing 102 or the battery 107. To reduce the likelihood of such an event, the biostimulator 100 may include some components to electrically insulate and / or protect the components of the flexible circuit assembly from being shorted. For example, the biostimulator 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 battery's casing) from the flexible circuit assembly 120. The biostimulator 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 will be appreciated that the flexible substrate of the flexible circuit assembly 120 may provide sufficient insulation and isolation from the housing 102 and the battery, and therefore, the end insulator 122 and the wall insulator 124 are optional. Nevertheless, the insulating component is still described as a part of the following embodiments.

[0046] Reference Figure 2A , showing a perspective view of a wall insulator according to one embodiment. During manufacture and use of the biostimulator 100, the flexible circuit assembly 120 can be spaced apart from the housing 102 to reduce the possibility of a short circuit between the electronic components on the flexible circuit assembly 120 and the housing 102. The wall insulator 124 can be a tubular component. For example, the wall insulator 124 can have the form of a cylindrical tube. The cylindrical tube can 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 can 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 can extend around the flexible circuit assembly 120 within the electronics compartment 116 of the biostimulator 100. Thus, the wall insulator 124 can space the flexible circuit assembly 120 from the inner wall 118 of the housing 102.

[0047] In one embodiment, the cross-sectional profile of the wall insulator 124 taken along a plane extending perpendicular to the longitudinal axis 108 is circular. More specifically, the profiles of the wall outer surface 202 and the wall inner surface 204 can be circular. Alternatively, the cross-sectional profile of the wall insulator 124 can be polygonal, elliptical, or other shapes.

[0048] In one embodiment, the wall insulator 124 is formed of a thin dielectric film. For example, the wall insulator 124 can be a thin cylindrical insulating sleeve formed of any material having good dielectric properties (electrical insulation). As described below, the wall insulator 124 can be assembled between the housing 102 and the flexible circuit assembly 120 within the electronic equipment chamber 116, so it may be advantageous to form the wall insulator 124 from a material that can form a thin wall with a tight tolerance. The wall insulator 124 may also benefit from having good hoop strength. Therefore, the wall insulator 124 may be formed of polytetrafluoroethylene or polyimide because these materials have desirable properties.

[0049] Reference Figure 2B , shows a perspective view of a wall insulator according to one embodiment. The wall insulator 124 can be an expandable sleeve. In one embodiment, the wall insulator 24 has a corrugated tubular structure. For example, the tubular structure can 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 wall outer surface 202 and the wall inner surface 204. The tubular surface of the wall insulator 124 can define a thin wall that undulates in a circumferential direction about the longitudinal axis 108.

[0050] The longitudinal folds 210 of the wall insulator 124 allow the insulator to expand and contract in the radial direction. For example, an inward radial force applied to the wall outer 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 wall inner 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 be collapsed so that the wall outer 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 be expanded so that the wall inner surface 204 contacts the exterior of the flexible circuit assembly 120. The wall insulator 124 may thus conform to adjacent structures to provide a tight fit, thereby using minimal space between the housing 102 and the flexible circuit assembly 120.

[0051] 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 shrink tubing formed of a polyolefin or fluoropolymer material. In this case, heat can be applied to the wall insulator 124 to shrink it onto the flexible circuit assembly 120 and conform to the flexible circuit assembly 120. When in a contracted state, the heat shrinkable tubing can wrap around the electronic components of the flexible circuit assembly 120 and isolate the electronic components from surrounding structures (e.g., the housing 102).

[0052] refer to Figure 3 , shows a perspective view of the inside of a flexible circuit assembly in a flattened configuration according to one embodiment. The flexible circuit assembly 120 for the biostimulator 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 including 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.

[0053] The flexible substrate 304 may include multiple mounting surfaces facing opposite directions, such as a top surface ( Figure 3 ) and bottom surface ( Figure 5 ). Figure 3 The top surface shown in the figure may also be referred to as the inside of the flexible circuit assembly 120 because when the flexible circuit assembly 120 is folded from the flat configuration 302 to the stacked configuration, the top surface faces the inner gap of the folded structure, as described below. In one embodiment, the mounting surface includes a mounting surface 306 that carries one or more electrical connectors 308 and one or more electronic components 310. The mounting surface 306 can be a flat surface in the flat configuration 302 and can have multiple areas designated therefrom.

[0054] 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 may be mounted on the first mounting area 312. Similarly, one or more electrical connectors 308 and / or electronic components 310 may be mounted on the second mounting area 314. In one embodiment, only one mounting area carries the electrical connector 308.

[0055] The mounting surface 306 may include a folding region 316 between the first mounting region 312 and the second mounting region 314. For example, each mounting region may have a region boundary defined by a longitudinal boundary separated in a longitudinal direction 318 and a lateral boundary separated in a lateral direction 320. The folding region 316 may be a portion of the flexible substrate 304 that extends across the mounting surface 306 from a first lateral edge 322 of the flexible substrate 304 to a second lateral edge 324 of the flexible substrate 304 in the lateral direction 320. The flexible substrate 304 is configured to be folded into a stacked configuration ( Figure 7 ), so that the first mounting area 312 of the inner surface faces the second mounting area 314 of the inner surface in a transverse direction 325 orthogonal to the longitudinal direction 318 and the lateral direction 320.

[0056] In one embodiment, one or more electrical traces 350 extend over the folding region 316. More specifically, the electrical traces 350 may extend from the first mounting region 312 to the second mounting region 314 across the folding region 316. The electrical traces 350 may be arranged on the flexible substrate 304, or embedded within the flexible substrate 350. The electrical traces 350 may 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 may perform an electrical communication function.

[0057] The electrical traces 350 may also perform a mechanical function. In one embodiment, the electrical traces 350 act as stress relief to evenly distribute stress across the folding region 316. The electrical traces 350 may have a thickness and / or width to prevent kinking in the folding region 316. In addition, the electrical traces 350 may be formed of a ductile material that resists kinking. For example, the electrical traces 350 may be copper alloy traces having a predetermined size and trace density per inch that are embedded in the flexible substrate 304 within the folding region 316 so that when the flexible circuit assembly is folded into a stacked configuration ( Figure 7 ), the fold region 316 extends along an arcuate path (e.g., a smooth curve) rather than an abrupt kink or bend.

[0058] 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 inside of the flexible substrate 304 to the outside on the opposite side of the flexible substrate 304. The aperture 326 can be in the folded area 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 an edge extending around the aperture 326, and the aperture axis 352 can extend perpendicular to the aperture plane. Therefore, when the flexible circuit assembly 120 is in the flattened configuration 302, the aperture axis 352 can be parallel to the lateral direction 325, and 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.

[0059] In one embodiment, the aperture 326 can be centered on the mounting surface 306. For example, the fold region 316 can be equally spaced between the first longitudinal edge 330 and the second longitudinal edge 332 of the flexible substrate 304. Thus, the aperture 326 in the fold region 316 can be centered longitudinally between the first longitudinal edge 330 and the second longitudinal edge 332. Similarly, the aperture 326 in the fold region 316 can be centered laterally between the first lateral edge 322 and the second lateral edge 324. Thus, the aperture 326 can be located at the center of the mounting surface 306.

[0060] Reference Figure 4 , which shows a plan view of the inside of a flexible circuit assembly according to one embodiment. The electrical connector 308 on the mounting surface 306 may include a feed-through connector 402 mounted on the first mounting area 312. The feed-through connector 402 may be one of several types of electrical connectors 308. For example, the feed-through connector 402 may be a socket connector ( Figure 3-7 and 10-12) or metal pads ( Figure 13-15 ). The feed-through connector 402 can be configured to receive an electrical pin of another component of the biostimulator 100. For example, the feed-through connector 402 can receive and / or attach to a feed-through pin of the end cap assembly 110 that transmits pacing pulses from the flexible circuit assembly 120 to a pacing tip of the biostimulator 100.

[0061] In one embodiment, the feed-through connector 402 is a socket connector and has a socket axis 404 that passes through an inner cavity 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. Therefore, the socket axis 404 can be laterally aligned with the aperture 326.

[0062] As described above, the aperture 326 can be centered on the mounting surface 306. The center 406 can 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 can be aligned with a centerline 408 of the mounting surface 306, which extends orthogonal to the receptacle axis 404. The centerline 408 can be equally spaced between the first longitudinal edge 330 and the second longitudinal edge 332 of the flexible substrate 304.

[0063] 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 socket connector ( Figure 3-7 and 10-12) or metal pads ( Figure 13-15 ). The battery connector 410 can be configured to receive and / or attach to electrical pins of another component of the biostimulator 100. For example, the battery connector 410 can receive battery pins of the energy source 107 to transfer power from the battery to the flexible circuit assembly 120. The battery pins can be the positive terminal posts and the negative terminal posts of the battery. Thus, power can be input to the flexible circuit assembly 120 via the battery connector 410, and power can be output from the flexible circuit assembly 120 via the feed-through connector 402.

[0064] Each battery connector 410 may be a receptacle connector having a respective receptacle axis 404. The respective receptacle axis 404 of the battery connector 410 may extend parallel to the receptacle axis 404 of the feed-through connector 402. In one embodiment, the receptacle axis 404 of the flexible circuit assembly 120 extends along the longitudinal direction 318 of the biostimulator 100. For example, when the flexible circuit assembly 120 is housed within the electronics compartment 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 electronics compartment 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 at the first and second mounting regions and extend orthogonal to the mounting surface 306 where its central axis intersects the fold region 316 .

[0065] 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, the external pins (e.g., feed-through pins and battery pins) can be evenly loaded on the mounting surface 306 by the electrical connector 308. For example, the socket axis 404 of the feed-through connector 402 can be located between the socket axes 404 of the battery connector 410. More specifically, the socket axis 404 of the feed-through connector 402 can be located laterally relative to the lateral direction 320 between the socket axes 404 of the battery connector 410. In one embodiment, the socket axes 404 of the feed-through connector 402 are equally spaced between the socket axes 404 of the battery connector 410. Therefore, 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.

[0066] Still reference Figure 4 In addition to having several electrical connectors 308, the flexible substrate 304 may also carry one or more electronic components 310 on the mounting surface 306. In one embodiment, the one or more electronic components 310 are on the second mounting area 314 of the mounting surface 306. For example, the electronic components 310 on the second mounting area 314 may include active electronic components 420, such as semiconductor devices. The electronic components 310 on the second mounting area 314 may include one or more processors 422. More specifically, the electronic components 310 may include an integrated circuit (such as an application specific integrated circuit) having a microprocessor and / or a memory 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 target tissue.

[0067] In addition to the active components 420, the flexible circuit assembly 120 may also include one or more passive electronic components 424 mounted on the mounting surface 306. For example, the passive electronic components 424 may include one or more capacitors. For example, the capacitors may be polymer or ceramic capacitors.

[0068] In one embodiment, the shear stress applied to the electronic components 310 and / or the electrical connectors 308 mounted on the mounting surface 306 can be relieved by epoxy underfill. More specifically, the epoxy underfill can be arranged between the mounting surface 306 and the electrical / electronic components 310 during manufacturing. The epoxy underfill can be an epoxy adhesive layer that flows between the electrical / electronic components 310 and the mounting surface 306 after the electrical / electronic components 310 are mounted on the mounting surface 306. For example, surface mounting technology (e.g., reflow solder balls) can be used to electrically and / or physically connect components to electrical contacts on the mounting surface 306, and a gap can be left between the components and the surface after the components are attached. The epoxy adhesive can flow into the gap to further stabilize and fix the components on the mounting surface 306. In one embodiment, the thickness of the underfill layer can be 0.008 inches to 0.1 inches, for example 0.010 inches.

[0069] Reference Figure 5 , shows a perspective view of the outside of the flexible circuit assembly in a flattened configuration according to one embodiment. In the flattened configuration 302, the second surface of the flexible substrate 304 can have a corresponding mounting surface 306 divided into regions as described above. For example, the mounting surface 306 can have a first mounting area 312 and a second mounting area 314. The second surface can be referred to as the outside of the flexible circuit assembly 120 because when the flexible substrate 304 is folded from the flattened configuration 302 to the stacked configuration, the second surface can face outwardly to the housing 102, as described below.

[0070] refer to Figure 6, shows a plan view of the outside of a flexible circuit assembly according to one embodiment. The mounting area of ​​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 area of ​​the outside carries one or more sensors 602. The sensor 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 magnetoresistance (GMR) sensor. Similarly, an electronic oscillator circuit 604 can be mounted on the flexible substrate 304. It should be understood that the above-mentioned electronic components 310 are provided as examples, and other electronic components 310 can be mounted on the flexible substrate 304. More specifically, the flexible circuit assembly 120 in which the components are directly mounted or arranged on the flexible substrate 304 can be produced using surface mounting technology. 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 on the fold region 316. The electrical trace 350 can be exposed or buried, such as laminated. Thus, a double-sided flexible circuit assembly 120 with a centrally arranged aperture 326 can be provided for use in a biostimulator 100.

[0071] Reference Figure 7 , shows a perspective view of a flexible circuit assembly in a stacked configuration according to one embodiment. The flexible circuit assembly 120 can be folded along the folding region 316 into a stacked configuration 702. In the stacked configuration 702, the receptacle axis 404 of the feed-through connector 402 can extend through the aperture 326 ( Fig.11 ). Similarly, the aperture axis 352 may extend between the first mounting area 312 and the second mounting area 314 in the stacked configuration 702. For example, the socket axis 404 may extend through the aperture 326 parallel to the longitudinal axis 108, and the aperture axis 352 may extend through the aperture 326 aligned with the feed-through connector 402. More particularly, the aperture axis 352 may extend through a pin port of the socket connector that receives an external pin. Similarly, the socket axis 404 of the battery connector 410 may extend in the longitudinal direction 318 opposite to the socket axis 404 of the feed-through connector 402 to emerge from the protective gap 704 defined between the first longitudinal edge 330 and the second longitudinal edge 332. The aperture axis 352 may extend between the mounting areas to emerge from the protective gap 704 laterally between the socket axis of the battery connector 410.

[0072] The protection gap 704 may be a space enclosed by the 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. Therefore, in the stacked configuration 702, the electrical connector 308 and / or the electronic component 310 mounted on the inner side of the flexible circuit assembly 120 are accommodated within the protection gap 704. For example, the feed-through connector 402 and the electronic component 310 may be stacked on each other, thus being in the stacked configuration 702. The flexible substrate 304 may wrap around the electronic component 310 and the electrical connector 308. Therefore, these components are enclosed within the protection gap 704, and therefore, the possibility of conductive debris forming a short circuit between the electronic component 310 and the electrical connector 308 is reduced. This possibility may be further reduced by closing the ends of the protection gap 704, i.e., closing the position where the protection gap 704 is open to the surrounding environment in the longitudinal direction 318 or the lateral direction 320.

[0073] refer to Figure 8 , shows a perspective view of an end insulator of a biostimulator according to one embodiment. The end insulator 122 can be arranged between the opening of the protective 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 specifically, the end insulator 122 can be a thin, flat, disc-shaped insulator. The end insulator 122 may include a dielectric film formed of a dielectric material such as polyimide. The end insulator 122 may include an outer edge 802 that defines the outline of the end insulator 122. For example, the outline of the end insulator 122 can be circular, such as Figure 8 Alternatively, the end insulator 122 may have a polygonal, oval or other contoured shape.

[0074] In one embodiment, the end insulator 122 includes one or more slits 804 extending through the thin wall of the insulator. For example, the end insulator 122 may include a plurality of slits 804, each having a respective size and profile. As shown, the plurality of slits 804 may include a pair of slits 804, each having a circular profile. The slits may be elliptical, polygonal, etc. However, the size of the profile (e.g., the diameter of the circle) may be different. For example, a first slit 804 of the end insulator 122 may have a larger diameter than a second slit 804 of the end insulator 122. Alternatively, the slits 804 may have the same size and shape. For example, the slits 804 of the end insulator 122 may be elliptical and have the same length and width.

[0075] Reference Fig. 9, shows a perspective view of a battery pin extending through an end insulator of a biostimulator according to one embodiment. The end insulator 122 can be configured to cover an end face of the energy source 107 while allowing a terminal post of the battery to pass through the end insulator 122 to make electrical contact with the electrical connector 308 of the flexible circuit assembly 120. In one embodiment, the battery includes one or more battery pins 902, which can be a positive terminal post and a negative terminal post of the battery. The battery pins 902 can extend from a distal surface 904 of the battery in a longitudinal direction 318 (e.g., parallel to the longitudinal axis 108). More specifically, the battery pins 902 can have respective 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 assembly of the biostimulator 100, the battery pins 902 can be inserted into respective slits 804 of the end insulator 122. Thus, the end insulator 122 may be placed on the distal surface 904 of the battery to isolate the distal surface 904 and the active terminal pins from conductive debris located on the opposite side of the end insulator 122 (eg, toward the distal tips of the battery pins 902 ).

[0076] In one embodiment, the battery pins 902 include a positive pin 906 and a negative pin 908. The outer diameter size and length of each battery pin 902 can vary to allow the pins to be individually and correctly placed in their respective battery connectors 410 on the flexible circuit assembly 120. These differently sized battery pins 902 can prevent incorrect insertion into the battery connector 410, which can lead to potential and catastrophic failure within the flexible circuit assembly 120. For example, the positive pin 906 can have a larger diameter than the negative pin 908, and therefore, the battery connector 410 that receives the negative pin 908 can have a socket whose socket port is too small to accommodate the positive pin 906. Thus, the pin size ensures that the battery will be properly oriented relative to the flexible circuit assembly 120 when the components are assembled.

[0077] In addition to controlling the orientation of the pins, the size of the pins can also preferentially direct the force to one of the battery pins 902. For example, the positive pin 906 can be docked with the glass-metal feedthrough of the battery, and therefore, it may be advantageous to direct the deflection force to the negative pin 908 that docks with the battery metal plug. More specifically, the glass-metal feedthrough can be more fragile than the battery metal plug, and therefore, it may be advantageous to apply stress to the negative pin 908, which transmits the force to the battery metal plug, rather than to the positive pin 906, which transmits the force to the glass-metal feedthrough. For example, off-axis assembly forces generated, for example, during manual assembly, can be directed or concentrated on the negative pin 908 to protect the positive pin 906 and the glass-metal feedthrough seal. This preferred direction of the off-axis assembly force may occur for a variety of reasons. First, the negative pin 908 can be longer than the positive pin 906, and therefore, 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, therefore, can be more easily deflected by off-axis assembly forces. Thus, deflection and stress can be directed toward the negative pin 908 to reduce the possibility of damaging the glass-to-metal seal.

[0078] Reference Fig.10 , shows a cross-sectional view of an electronics compartment of a biostimulator with a flexible circuit assembly according to one embodiment. Each battery pin 902 of the battery can be connected to and / or mounted on or inside 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 a metal pad of the flexible circuit assembly 120. In this way, in an assembled state, when the battery pin 902 is connected to the corresponding battery connector 410, the end insulator 122 can be located between the distal side 904 of the battery and the flexible circuit assembly 120. Therefore, the flexible circuit assembly 120 can include a plurality of battery connectors 410 mounted 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.

[0079] Still reference Fig.10, the housing 102 can be mounted on the wall insulator 124 and on the battery to house the flexible circuit assembly 120 within the electronics chamber 116. More specifically, the inner surface 118 of the housing 102 can extend around the flexible circuit assembly 120 to laterally enclose the flexible circuit assembly 120. In one embodiment, the end cap assembly 110 can be mounted on the housing 102 to house the electronics chamber 116 within the biostimulator 100.

[0080] The end cap assembly 110 may include several subassemblies. For example, the end cap assembly 110 may include a flange 1004 having a mounting wall to accommodate the screw mount 112. In one embodiment, the flange 1004 is formed of titanium. The flange 1004 may be mounted on the housing 102 and connected to the housing 102 by a gas-tight seal (e.g., by a weld). For example, the gas-tight weld may 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 may have an external thread that matches the internal thread of the screw mount 112. Therefore, the screw mount 112 may be screwed to the mounting wall of the flange 1004. Alternatively, the screw mount 112 may be press-fitted to the mounting wall, the screw mount 112 may be bonded to the mounting wall by heat bonding or adhesive, or the screw mount 112 and the electrical feedthrough assembly may be bonded in another manner, such as by swaging. Thus, electronics compartment 116 may be contained between the battery, interior surface 118 of housing 102 , and end cap assembly 110 .

[0081] In one embodiment, the end cap assembly 110 includes a fixing element 114, such as a spiral. The spiral can extend distally from the spiral mounting frame 112 around the longitudinal axis 108. For example, the spiral can rotate around the longitudinal axis 108. The spiral can include a spiral line extending in a rotational direction around the longitudinal axis 108, the spiral line being formed by coiling or by cutting from the pipe wall. For example, the spiral can rotate around the longitudinal axis 108 in a right-hand direction.

[0082] The helix can be adapted to attach the biostimulator 100 to tissue, such as cardiac tissue. For example, in the case of a right-handed helical 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 helix into the tissue.

[0083] Reference Fig.11, shows a cross-sectional view of a biostimulator with a flexible circuit according to one embodiment. The end cap assembly 110 may include a feedthrough 1102 to transmit pacing pulses from the flexible circuit assembly 120 to the 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 electronics compartment 116 to engage the feedthrough connector 402. More specifically, the feedthrough pin 1104 may be inserted into the feedthrough connector 402 through the aperture 326 in the folded area 316 of the flexible substrate 304. Thus, the feedthrough pin 1104 may be mechanically and electrically connected to the feedthrough connector 402 between the first mounting area 312 and the second mounting area 314 of the mounting surface 306.

[0084] Feedthrough 1102 may also include electrode tip 1106, which may be electrically continuous with feedthrough pin 1104. Thus, when fixation element 114 is engaged with target tissue, electrode tip 1106 may be held against the tissue, and thus, pacing pulses may be delivered from feedthrough connector 402 into feedthrough pin 1104 and through electrode tip 1106 into the target tissue.

[0085] Since the flexible circuit assembly 120 can provide power to the feedthrough 1102 via the feedthrough connector 402, the flexible circuit assembly 120 can receive power from the battery through the battery connector 410. More specifically, the battery pins 902 can extend through the slots 804 of the end insulator 122 into the electronics chamber 116. The battery pins 902 can have corresponding pin axes 910, and each pin axis 910 can be parallel to the aperture axis 352. The battery pins 902 can be mechanically and electrically connected to the battery connector 410. Therefore, the electrical connector 308 of the flexible circuit assembly 120 can form a secure and stable connection with the battery pins 902 and the feedthrough pins 1104 to allow power transfer and reduce the possibility of the electrical connector 308 shorting to another component of the biostimulator 100.

[0086] Reference Fig.12, shows a cross-sectional view of a biostimulator with a flexible circuit assembly according to one embodiment. In addition to the protective function of the folded flexible circuit assembly 120, the stacked configuration 702 allows the electronic equipment compartment 116 to be efficiently 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 equipment compartment 116. In one embodiment, the stacked flexible circuit assembly 120 can be circumferentially enclosed by a wall insulator 124 that can electrically isolate the assembly from the inner surface 118 of the housing 102. As shown, the end insulator 122 can have an outer edge 802 that has a circular profile, and the inner surface 118 of the housing 102 and / or the inner surface 204 of the housing 102 can 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 can have alternative profiles, such as a polygonal or elliptical profile. The profiles of the inner surface 118 (or inner surface 204 ) and the outer edge 802 may be similarly dimensioned, 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 fully surround the flexible circuit assembly 120 and its components while still fitting within the housing 102 .

[0087] The biostimulator 100 may include components for further insulating and protecting the flexible circuit assembly. In one embodiment, the biostimulator 100 includes a foam tape 1202 between the electrical connector 308 and the electronic component 310 (which is mounted within the protective gap 704). For example, the foam tape 1202 may be a strip having a perimeter dimension that is the same as the perimeter dimension of the first mounting area 312 and / or the second mounting area 314. The foam tape 1202 may be a single-sided or double-sided tape, and the foam tape 1202 may be mounted on the first mounting area 312 or the second mounting area 314 when the flexible circuit assembly 120 is in the flattened configuration 302. When the flexible circuit assembly 120 is folded into the stacked configuration 702, the first side of the tape may face the first mounting area 312, and the second side may face the second mounting area 314. The foam tape 1202 may be adhered 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 receptacle connector is mounted on the plug connector of the biostimulator 100. Additionally, foam strip 1202 may be made of an insulating foam material, thereby reducing the likelihood of electrical contact between electronic components on first mounting area 312 and electronic components on second mounting area 314 .

[0088] 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, such as 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, such as along the lateral edges and longitudinal edges of the mounting area and folding area 316. More specifically, the peripheral edge 1204 can include the lateral edges and longitudinal edges of the mounting area and folding area 316. At least a portion of the peripheral edge 1204 can be in contact with the wall insulator 124 along the inner side of the housing 102. For example, when the flexible circuit assembly 120 is in the stacked configuration 702 and enclosed within the electronics compartment 116, the mounting areas may move away from each other, such as if the foam strip 1202 loses adhesion to one side of the substrate, and as the substrate halves move outward, the peripheral edge 1204 may contact the inner surface of the wall insulator 124. The wall insulator may constrain 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) may 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, such as the first lateral edge 322 or the second lateral edge 324 of the flexible substrate 304, may be formed of an insulating material. More specifically, the peripheral edge 1204 of the flexible substrate 304 may not have conductive traces or conductive features 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.

[0089] The 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 is pressed 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 outer frame for the flexible circuit assembly 120. Shock, vibration, or other forces acting on the flexible circuit assembly 120 can be offset by the wall insulator 124 and the housing 102. Therefore, 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 (e.g., the feed-through pins 1104 and / or the battery pins 902) is limited by the outer support provided by the wall insulator 124 and the housing 102. Furthermore, the external frame provided by the wall insulator 124 and the housing 102 requires fewer parts and is more space efficient than using a separate external frame to support the flexible circuit assembly 120 within the electronics compartment 116. 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 insulated (non-conductive) portion of the flexible substrate 304 provides a robust and compact biostimulator 100.

[0090] 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 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.

[0091] Reference Fig.21, showing a perspective view of a cover insulator according to one embodiment. The wall insulator 124 and the end insulator 122 can be formed integrally. For example, the wall insulator 124 can be a tubular sidewall of the cover insulator 2100, and the end insulator 122 can be a flat end of the cover insulator. The cover insulator 2100 can have a shape obtained by combining the wall insulator 124 with the end insulator 122. More specifically, the cover insulator 2100 can be formed by joining the outer edge 802 of the end insulator 122 to the distal wall end 206 or the proximal wall end 208 of the wall insulator 124. The edges can be joined, for example, by a thermal welding or adhesive welding process. Alternatively, the cover insulator 2100 can be formed by a molding or thermoforming process, in which the end insulator 122 and the wall insulator 124 are partially manufactured as a whole. Similarly, the slit 804 can be formed as a hole in the end of the insulating cover during or after the molding or thermoforming process to allow the electrical pin to pass through.

[0092] It should be understood that the cover insulator 2100 can be arranged on the flexible circuit assembly 120 to constrain the flexible circuit assembly 120 and isolate it from adjacent conductive components. In addition, several covers can be used to isolate the flexible circuit assembly 120 at both ends. For example, a first cover insulator can be used to isolate the proximal portion of the flexible circuit assembly 120, and a second cover insulator can be used to isolate the distal portion of the flexible circuit assembly 120. The cover insulators can have walls sized to overlap each other, for example, by sliding one cover wall into another cover wall and on another cover wall to fit in a sliding manner. The cover insulator can also have holes sized to accommodate battery pins (in the case of a proximal cover insulator) or feed-through pins (in the case of a distal cover insulator). Therefore, the cover insulators can be assembled with each other to completely encapsulate the flexible circuit assembly 120 in an insulating cavity surrounded by the cover insulator walls and ends.

[0093] Based on the assembly structure described above, it will be understood that the various components of the electrical feedthrough assembly can be assembled together during assembly (e.g., in a method of manufacturing the biostimulator 100). The method can include a series of operations. These operations are described below in a sequence that is applicable to a flexible circuit assembly 120 having a socket connector for connecting to an external electrical pin. In an alternative embodiment, such as when the flexible circuit assembly 120 has metal pads to connect to external electrical pins, these operations can be performed in an alternative sequence.

[0094] In one operation, the flexible circuit assembly 120 can be folded along the fold region 316 into the stacked configuration 702. 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, so that the flexible circuit assembly 120 can be temporarily held in the stacked configuration 702 during the assembly process.

[0095] In one operation, the battery pins 902 can be inserted through the corresponding slots 804 in the end insulator 122. Thus, the battery pins 902 can extend distally to pin tips separated from the distal side 904 of the battery by the end insulator 122.

[0096] In one operation, the battery pins 902 of the battery can be inserted into the 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 side 904 of the battery by the end insulator 122. Therefore, the protective 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.

[0097] In one operation, the wall insulator 124 can be arranged on and around the folded flexible circuit assembly 120. The housing 102 can be loaded on the wall insulator 124 and mounted on the battery so 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 press the wall insulator 124 radially outward to contact the inner surface 118 of the housing 102. Thus, the housing 102 can provide external support for the flexible circuit assembly 120.

[0098] In one operation, the feedthrough pin 1104 is inserted through the aperture 326 in the folded region 316 of the flexible circuit assembly 120. The feedthrough pin 1104 can engage the feedthrough connector 402 on the mounting surface 306, such as can be inserted into a receptacle connector, so that the feedthrough pin 1104 extends from a tip within the protective gap to a base outside the protective gap. The folded region 316 of the flexible substrate 304 can separate the protective gap from a distal region of the electronics compartment 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. The assembled biostimulator 100 can then be delivered and implanted at a target site to deliver pacing pulses to the target site.

[0099] Figure 13-16 The assembly of the biostimulator 100 is shown, and more specifically, the assembly of the biostimulator 100 having the flexible circuit assembly 120 is shown, the flexible circuit assembly 120 including the metal pads 1302 for connecting to the feedthrough pins 1104 and the 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 on 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 embodiment, the housing 102 can be loaded on the flexible circuit assembly 120 before the feedthrough pins 1104 are attached to the receptacle connector.

[0100] Reference Fig.13 , shows a cross-sectional view of an end cap assembly connected to a flexible circuit assembly according to one embodiment. In one embodiment, the feed-through connector 402 and the battery connector 410 are metal pads 1302. For example, the pads can be formed on the flexible substrate 304 using a semiconductor manufacturing process. The flexible circuit assembly 120 can be folded into a stacked configuration 702 along the folding region 316.

[0101] In one embodiment, when the flexible circuit assembly 120 is in the stacked configuration 702, the aperture axis 352 can extend between the first mounting area 312 and the second mounting area 314, such as extending above the metal pad 1302. For example, the aperture axis 352 can extend parallel to the longitudinal axis 108 and be aligned with the feed-through connector 402. More specifically, when the flexible circuit assembly 120 is in the stacked configuration 702, the aperture axis 352 can be between and laterally aligned with the feed-through connector 402 and the electronic component 310. When aligned laterally, a transverse plane containing the aperture axis 352 and extending in the transverse direction 325 can intersect the feed-through connector 402. Thus, the feed-through pin 1104 can extend through the aperture 326 and extend over the feed-through connector 402 to be arranged in contact with the metal pad 1302.

[0102] In one embodiment, the feed-through pin 1104 is spot welded to the metal pad 1302 of the feed-through connector 402. Alternatively, the pin can be soldered to the pad. When the electrical connector 308 is a metal pad 1302, the feed-through pin 1104 can be shorter than when the electrical connector 308 is a socket connector, because the spot welding that requires the minimum space can connect the feed-through pin 1104 to the feed-through connector 402. Before connecting the battery pin 902 to the battery connector 410, the feed-through pin 1104 can be connected to the feed-through connector 402. For example, the feed-through pin 1104 can be welded or brazed to the metal pad 1302.

[0103] Reference Fig.14, shows a cross-sectional view of an end cap assembly and a battery connected to a flexible circuit assembly according to one embodiment. The battery pins 902 can be arranged on corresponding metal pads 1302 of the flexible circuit assembly 120. For example, the battery pins 902 can be inserted through corresponding slits 804 in the end insulator 122 and arranged on or in the battery connector 410. The battery pins 902 can be connected to the corresponding battery connector 410 by corresponding spot welding. Alternatively, the pins can be welded to the pads. When the battery pins 902 are attached to the corresponding battery connector 410 by heat welding or by inserting the pins into the spring connector as described above, the end insulator 122 can be held between the flexible circuit assembly 120 and the distal side 904 of the battery.

[0104] The use of metal pads 1302 or similar electrical connections that use a welded or soldered structure to transfer power between the flexible circuit assembly 120 and an external component, such as the energy source 107 (battery), has several advantages. As described above, the metal pads 1302 use less space than a socket connector, and therefore the overall size of the biostimulator 100 can be reduced. Second, the solder attachment can be produced at a lower cost than other connectors such as a socket connector. Third, the solder attachment can be easily verified, which can improve manufacturability and contribute to the long-term reliability of the biostimulator 100.

[0105] In one embodiment, after the feedthrough pins 1104 are connected to the feedthrough connector 402 and the battery pins 902 are connected to the battery connector 410, the double-sided foam tape 1202 may be disposed between the mounting surfaces 306. The flexible circuit assembly 120 may then 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 the folded or stacked configuration.

[0106] Reference Fig.15 , shows a cross-sectional view of an electronics compartment of a biostimulator housing a wall insulator and a flexible circuit assembly according to one embodiment. In one operation, the wall insulator 124 can be installed on the stacked flexible circuit assembly 120. For example, the wall insulator 124 can be slid over the flange 1004 until the proximal wall end 208 contacts the distal side 904 of the end insulator 122 and / or the battery. When the wall insulator 124 is arranged on the flange 1004, the distal wall end 206 can be adjacent to the proximal edge of the flange 1004, and thus, the wall insulator 124 can extend around the flexible circuit assembly 120. More specifically, the flexible circuit assembly 120 can include a flexible circuit assembly 120 having an electrical connector 308 that is connected to a feed-through 1102 and a battery.

[0107] After sliding the wall insulator 124 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 on the folded flexible circuit assembly 120 to isolate and contain the electrical components. The housing 102 can be slid 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 installed on the battery, the inner surface 118 can extend around the end insulator 122, the wall insulator 124, and the flexible circuit assembly 120.

[0108] The biostimulator 100 assembly can be secured by attaching the end cap assembly 110 (e.g., 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 a seam between the flange 1004 and the distal end of the housing 102. Similarly, a second circumferential weld 1504 can be formed along a seam between the housing 102 and the battery. The circumferential weld secures and seals the components. More particularly, the weld can be a hermetic weld that isolates the components within the electronics compartment 116 from the surrounding environment.

[0109] In one embodiment, when the housing 102 and the wall insulator 124 are secured around the flexible circuit assembly 120, the components fit tightly together. For example, when the foam strip 1202 loses its grip, the peripheral edge 1204 can deflect outward and press outward against the inner surface of the wall insulator 124. In the case of a 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.

[0110] In one embodiment, one or more of the end insulators 122 or the wall insulators 124 include an adhesive film (not shown). The adhesive film may include a pressure-sensitive adhesive or other adhesive covering one or more surfaces of the end insulators 122 or the wall insulators 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 embodiments, the use of an adhesive to bond the components within the housing 102 to each other may achieve multiple advantages. First, the adhesive may improve placement by reducing the likelihood of movement of the components within the housing 102. Second, insulation of the electrical components may be ensured by the adhesive. For example, by reducing the likelihood of displacement of the electronic components, a gap may be prevented from forming between the insulators 122, 124, 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.

[0111] refer to Fig.16 , shows a perspective view of an electronics compartment of a biostimulator according to one embodiment, the electronics compartment housing a wall insulator overmolded on a flexible circuit assembly. The wall insulator 124 can be overmolded onto the flexible circuit assembly 120. The overmolding operation can 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 overmold 1602 can be placed on and around the components of the folded flexible circuit assembly 120. The overmold 1602 can be, for example, a polymer material and can isolate and electrically insulate the components from the housing 102. More specifically, when the housing 102 is loaded on the overmold wall insulator 124, the overmold 1602 material can separate the electrical connector 308 of the flexible circuit assembly 120 from the inner surface 118 (not shown) of the housing 102. Therefore, the overmold wall insulator 124 essentially performs the same function as the tubular insulating sleeve described above. As described above, overmold 1602 may be hermetically sealed within electronics compartment 116 by forming a circumferential weld around housing 102 at flange 1004 and the battery.

[0112] Reference Fig.17, shows a cross-sectional view of a moisture absorber in the electronics compartment of a biostimulator according to one embodiment. The electronics compartment 116 can be hermetically sealed within the biostimulator 100. For example, the end cap assembly 110 can be bonded to the distal end of the housing 102 (not shown) by a hermetic weld around the perimeter of the distal end. Similarly, the battery can be bonded to the proximal end of the housing 102 (not shown) by a hermetic weld around the perimeter of the proximal end. Therefore, unless steps are taken to eliminate moisture, any moisture trapped within the electronics compartment 116 during the manufacturing process can remain therein.

[0113] In one embodiment, the biostimulator 100 includes a moisture absorber 1702 within the electronics compartment 116. The moisture absorber 1702 may be a desiccant that absorbs residual moisture within the electronics compartment 116. The moisture absorber 1702 may include a desiccant within a permeable matrix, such as a polymer. One example of a suitable desiccant material includes zeolite, however, other desiccants may also be used in the moisture absorber 1702.

[0114] The moisture absorbent 1702 may be loaded into and held by an absorbent holder 1704. The absorbent holder 1704 may be mounted on a component within the electronics compartment 116, such as on a proximal side or surface of the end cap assembly 110. The absorbent holder 1704 may occupy space within the electronics compartment 116 without interfering with components of the flexible circuit assembly 120.

[0115] Reference Fig.18 , shows a perspective view of a moisture absorbent holder according to one embodiment. The getter holder 1704 may include a cavity 1802. For example, the cavity 1802 may be a recess machined or otherwise formed on the surface of the getter holder 1704 to allow enough moisture absorbent 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 diameter of 1.5-2.5 mm. 3 Volume, for example 1.9mm 3 , to accommodate a corresponding volume of hygroscopic material. The hygroscopic agent 1702 can be loaded (e.g., injected) into the cavity 1802. In one embodiment, the cavity 1802 has an opening facing the proximal side within the electronic device chamber 116. For example, the dehumidifier holder 1704 can be fastened to the end cap assembly 110 so that the opening of the cavity 1802 faces the battery. Alternatively, the dehumidifier holder 1704 can be installed in the proximal area of ​​the electronic device chamber 116, and the opening of the cavity 1802 can face the end cap assembly 110.

[0116] In one embodiment, the getter holder 1704 is made of a low moisture material. For example, the getter holder 1704 can be processed from a glass reinforced epoxy laminate. Alternatively, the getter holder 1704 can be molded from a thermosetting polymer, a ceramic material, or other low moisture material.

[0117] Reference Fig.19 , shows a perspective view of a moisture absorbent in an electronics compartment of a biostimulator according to one embodiment. The getter holder 1704 can be integral with another component of the biostimulator 100, rather than a separate component. For example, the getter holder 1704 can be fastened to or integral with the end insulator 122. In one embodiment, the getter holder 1704 is coupled to a distal surface of the end insulator 122, and the opening of the cavity 1802 containing the moisture absorbent 1702 can face the end cap assembly 110 in a distal direction.

[0118] Reference Fig. 20 , showing a perspective view of a moisture absorbent holder according to one embodiment. The getter holder 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 holder 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 retain the moisture absorbent 1702. As described above, the integrally formed end insulator 122 can include a slit 804 for accommodating the battery pin 902. In one embodiment, the getter holder portion of the end insulator 122 and the flat portion of the end insulator 122 having the slit 804 can be formed of a glass reinforced epoxy laminate, or another material having low moisture and having electrical insulating properties. Therefore, the end insulator 122 can promote the removal of moisture from the electronics chamber 116 and can reduce the possibility of electrical shorting between components of the flexible circuit assembly and other biostimulator components.

[0119] Alternative insulating structures for isolating the flexible circuit assembly 120 from the housing 102 are contemplated within the scope of the present description. Fig. 22, shows a perspective view of an insulating cover according to one embodiment. The insulating cover 2200 can be an insulator, such as a polyimide sheet or another insulating material, having one or more foldable segments 2202. The foldable segments 2202 can be rectangular or other shaped segments that are joined along various 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 folded segment 2202a can be arranged to the back of the first mounting area 312 during assembly. Then, one or more additional folded segments, such as the top folded segment 2202b and / or the bottom folded segment 2202c, can be folded along the corresponding fold lines to wrap the flaps around the top and bottom ends of the folded circuit assembly and arranged on the back of the second mounting area 314. Optionally, one or more side folded segments 2202d can then be folded along the corresponding fold lines to wrap the flaps around the sides of the folded circuit assembly. Thus, the flaps of the insulating cover 2200 can be folded around the electronic components to encapsulate the flexible circuit assembly 120 and isolate the electronic components from the housing 102. Slits 804 can be formed in the insulating cover 2200 to accommodate feed-through pins or battery pins. The slits 804 can be located in the sheet of insulating material along a fold line that distinguishes a first folded segment 2202a from an adjacent folded segment.

[0120] Several embodiments described above are summarized in the following paragraphs. In one embodiment, a flexible circuit assembly for a biostimulator includes a flexible substrate. The flexible substrate includes a mounting surface having a folding region between a first mounting area and a second mounting area. The flexible substrate is configured to be folded into a stacked configuration along the folding region so that the first mounting area faces the second mounting area. The flexible substrate includes an aperture in the folding region, the aperture having an aperture axis.

[0121] The flexible circuit assembly may include a feed-through 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 feed-through connector. The flexible circuit assembly may include an electronic component on the mounting surface.

[0122] The feed-through connector may be on the first mounting area and the electronic component may be on the second mounting area.

[0123] The aperture may be centered on the mounting surface.

[0124] The flexible circuit assembly may include a plurality of battery connectors on the mounting surface.

[0125] The feed-through connector and the plurality of battery connectors may be socket connectors having respective socket axes extending parallel to each other. The socket axes of the feed-through connector may be laterally located between the socket axes of the battery connectors. The feed-through connector and the plurality of battery connectors may be metal pads.

[0126] In one embodiment, a biostimulator includes a housing having an inner surface extending around an electronics chamber. The biostimulator includes a flexible circuit assembly within the electronics chamber. The flexible circuit assembly includes a flexible substrate including a mounting surface having a folding region between a first mounting area and a second mounting area. The flexible substrate is folded along the folding region so that the first mounting area faces the second mounting area. The flexible substrate includes an orifice in the folding region. The orifice has an orifice axis. The flexible circuit assembly includes a feed-through connector on the mounting surface. The orifice axis extends in alignment with the feed-through connector. The flexible circuit assembly includes an electronic component on the mounting surface.

[0127] The feed-through connector may be on the first mounting area and the electronic component may be on the second mounting area such that the feed-through connector and the electronic component are in a stacked configuration.

[0128] The aperture may be centered on the mounting surface.

[0129] The biostimulator may include a foam strip between the feed-through connector and the electronic components.

[0130] The biostimulator may include a battery having a plurality of battery pins extending from a distal side in a longitudinal direction. The flexible circuit assembly includes a plurality of battery connectors connected to corresponding battery pins of the battery. The battery pins have respective pin axes extending parallel to the orifice axis of the orifice. The biostimulator may include an end insulator between the distal side of the battery and the flexible circuit assembly. The end insulator may be planar and may include a plurality of slits. The plurality of battery pins may extend into the electronic device compartment through the plurality of slits. The end insulator may have an outer edge. The outer edge and the inner surface of the housing may have the same profile.

[0131] The biostimulator may include a wall insulator extending around the flexible circuit assembly within the electronics compartment.

[0132] The biostimulator may include a moisture absorber within the electronics compartment.

[0133] In one embodiment, a method includes folding a flexible circuit assembly into a stacked configuration along a folding region. The flexible circuit assembly includes a mounting surface having a folding region between a first mounting region and a second mounting region. When the flexible circuit assembly is in the stacked configuration, the first mounting region faces the second mounting region in a lateral direction. The method includes connecting a feedthrough pin between the first mounting region and the second mounting region to a feedthrough connector on the mounting surface. The feedthrough pin extends through an aperture in the folding region. The method includes connecting a plurality of battery pins of a battery to corresponding battery connectors on the mounting surface.

[0134] The method may include inserting a plurality of battery pins through corresponding slits in the end insulator. When the plurality of battery pins are attached to the corresponding battery connector, the end insulator may be located between the battery and the flexible circuit assembly. The method may include mounting a wall insulator on the stacked flexible circuit assembly so that the wall insulator extends around the flexible circuit assembly. The method may include mounting a housing on the battery so that the 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 the peripheral edge of the flexible circuit assembly. The method may include attaching the housing to the end cap assembly and the battery to accommodate an electronic device chamber between the battery, the inner surface of the housing and the end cap pins. The flexible circuit assembly may be within the electronic device chamber. The end cap assembly may include a feed-through portion having a feed-through pin, an electrode head and a fixing element.

[0135] In the foregoing description, the present invention has been described with reference to specific exemplary embodiments of the present invention. It will be apparent that various modifications may be made thereto without departing from the broader spirit and scope of the present invention as set forth in the appended claims. Therefore, the present description and the accompanying drawings should be considered illustrative rather than restrictive.

Claims

1. A flexible circuit assembly for a biostimulator, comprising: a flexible substrate comprising a mounting surface having a folding region between a first mounting area and a second mounting area, wherein the flexible substrate is configured to be folded along the folding region into a stacked configuration such that the first mounting area faces the second mounting area, and wherein the flexible substrate comprises an aperture in the folding region, the aperture having an aperture axis; a feed-through connector on the mounting surface, wherein the aperture axis extends in alignment with the feed-through connector between the first mounting area and the second mounting area when the flexible substrate is in the stacked configuration; and a processor on the mounting surface, wherein the processor is configured to execute instructions stored in a non-transitory computer-readable medium to cause the biostimulator to generate and transmit pacing pulses to the target tissue, and wherein the feedthrough connector is configured to receive a feedthrough pin extending through the aperture in the fold region to transmit the pacing pulses from the flexible circuit assembly to the target tissue.

2. The flexible circuit assembly according to claim 1, wherein: The feed-through connector is on the first mounting area and the processor is on the second mounting area.

3. The flexible circuit assembly according to claim 1, wherein: The aperture is centered on the mounting surface.

4. The flexible circuit assembly of claim 1 further comprising a plurality of battery connectors on the mounting surface.

5. The flexible circuit assembly of claim 4, wherein: The feed-through connector and the plurality of battery connectors are receptacle connectors whose respective receptacle axes extend parallel to each other.

6. The flexible circuit assembly of claim 5, wherein: The socket axis of the feed-through connector is laterally located between the socket axes of the battery connectors.

7. The flexible circuit assembly according to claim 5, wherein: The feed-through connector and the plurality of battery connectors are metal pads.

8. A biostimulator, comprising: a housing having an inner surface extending around the electronics compartment; and A flexible circuit assembly, the flexible circuit assembly being within the electronic equipment chamber, wherein the flexible circuit assembly comprises: A flexible substrate comprising a mounting surface having a folding area between a first mounting area and a second mounting area, wherein the flexible substrate is folded along the folding area so that the first mounting area faces the second mounting area, and wherein the flexible substrate comprises an aperture in the folding region, the aperture having an aperture axis, a feed-through connector on the mounting surface, wherein the aperture axis extends in alignment with the feed-through connector, and a processor on the mounting surface, wherein the processor is configured to execute instructions stored in a non-transitory computer-readable medium to cause the biostimulator to generate and transmit pacing pulses to the target tissue, and wherein the feedthrough connector is configured to receive a feedthrough pin extending through the aperture in the fold region to transmit the pacing pulses from the flexible circuit assembly to the target tissue.

9. The biostimulator according to claim 8, wherein: The feed-through connector is on the first mounting area and the processor is on the second mounting area such that the feed-through connector and the processor are in a stacked configuration.

10. The biostimulator according to claim 8, wherein: The aperture is centered on the mounting surface.

11. The biostimulator of claim 8, further comprising a foam strip between the feed-through connector and the processor.

12. The biostimulator of claim 8, further comprising a battery having a plurality of battery pins extending from the distal surface in a longitudinal direction, wherein: The flexible circuit assembly includes a plurality of battery connectors connected to respective battery pins of the battery, and wherein respective pin axes of the battery pins extend parallel to an aperture axis of the aperture.

13. The biostimulator of claim 12, further comprising an end insulator between the distal surface of the battery and the flexible circuit assembly, wherein the end insulator is planar and includes a plurality of slits, and wherein, The plurality of battery pins extend through the plurality of slots into the electronics compartment.

14. The biostimulator according to claim 13, wherein: The end insulator has an outer edge, and wherein the outer edge and the inner surface of the housing have the same profile.

15. The biostimulator of claim 8, further comprising a wall insulator extending around the flexible circuit assembly within the electronics compartment.

16. The biostimulator of claim 8, further comprising a moisture absorbent within the electronics compartment.

17. A method of manufacturing a biostimulator, comprising: folding a flexible circuit assembly along a folding region into a stacked configuration, wherein the flexible circuit assembly includes a mounting surface having the folding region between a first mounting region and a second mounting region, and wherein the first mounting region faces the second mounting region in a lateral direction when the flexible circuit assembly is in the stacked configuration; connecting a feedthrough pin 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 in the fold region; connecting a plurality of battery pins of a battery to respective battery connectors on the mounting surface; and A processor is mounted on the mounting surface, wherein the processor is configured to execute instructions stored in a non-transitory computer-readable medium to cause the biostimulator to generate and transmit pacing pulses to the target tissue, and wherein the feedthrough connector is configured to receive a feedthrough pin extending through the aperture in the fold region to transmit the pacing pulses from the flexible circuit assembly to the target tissue.

18. The method of claim 17, further comprising inserting the plurality of battery pins through corresponding slots in the end insulator, wherein: The end insulator is located between the battery and the flexible circuit assembly when the plurality of battery pins are attached to corresponding battery connectors.

19. The method of claim 18, further comprising mounting a wall insulator on the stacked flexible circuit assemblies such that the wall insulator extends around the flexible circuit assemblies.

20. The method of claim 19, further comprising mounting a housing on the battery such that an inner surface of the housing extends around the end insulators, the wall insulators, and the flexible circuit assembly.

21. The method according to claim 20, wherein: The wall insulator is sandwiched between the inner surface of the housing and a peripheral edge of the flexible circuit assembly.

22. The method of claim 20 further comprising attaching the housing to an end cap assembly and the battery to accommodate an electronics chamber between the battery, the inner surface of the housing, and the end cap assembly, wherein the flexible circuit assembly is within the electronics chamber, wherein the end cap assembly comprises a feed-through portion having feed-through pins, an electrode head, and a fixing element.

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