WO2023247213A1

WO2023247213A1 - Medical device, electronic module and method for producing same

Info

Publication number: WO2023247213A1
Application number: PCT/EP2023/065490
Authority: WO
Inventors: Gregor Schmidt; Marc Hauer
Original assignee: Dyconex Ag
Priority date: 2022-06-24
Filing date: 2023-06-09
Publication date: 2023-12-28

Abstract

A cost-effective method for producing an electronic module of high quality is described, comprising the following steps: providing an electronic circuit board (1) having a first side and an opposing second side and at least one first electrical contact element (2) located at the surface at its first side, a thermoplastic element (3, 30) comprising electrically conducting particles (3.1) or electrically conducting micro-structures (3.2) and an electronic component (4) having a first side and an opposing second side and comprising at least one second electrical contact element (4.1) located at the surface at its second side; arranging the electronic circuit board (1), the thermoplastic element (3, 30) and the electronic component (4) in such a way, that the thermoplastic element (3, 30) is being arranged in between the first electrical contact element (2) and the second electrical contact element (4.1); and thermocompression bonding of the electronic component (4) to the electronic circuit board (1) using the thermoplastic element (3, 30) such that the second side of the electronic component (4) is firmly attached to the first side of the electronic circuit board (1) via the thermoplastic element (3), wherein the thermoplastic element (3, 30) thereby, at the same time, establishes an electrically conductive connection between the at least one first electrical contact element (2) and the at least one second electrical contact element (4.1). Further, a respective electronic module is illustrated and a medical device comprising such electronic module.

Description

Medical Device, Electronic Module and Method for producing same

The present invention relates to an electronic module comprising an electronic circuit board having at least one first electrical contact element at the surface of its first side and an electronic component comprising at least one second electrical contact element at the surface of its second side which is electrically connected to the first electrical contact element of the electronic circuit board. The invention further relates to a method for producing such electronic module and a medical device comprising such electronic module.

One popular method for producing electronic modules is the chip-on-flex method using ACF technology. ACF technology utilizes an anisotropic conductive film (ACF) or an anisotropic conductive paste (ACP), together referred to as anisotropic conductive adhesive (ACA), which is deposited on a base substrate by laminating or printing for fixing an electronic component to the substrate. The ACA is an anisotropic material, for example a thermosetting resin containing conductive particles. After depositing the ACA layer on the base substrate, a device or second substrate is placed over the ACA layer. Then, the second substrate or device is pressed together to mount the secondary substrate or device to the base substrate. This mounting process is done with no heat or a minimal amount of heat that is just sufficient to cause the anisotropic material to become slightly tacky. In order to complete the ACF assembly, bonding is provided in a third step. For bonding, the amount of thermal energy required is higher due to the need to first flow the ACA and allow the elements to come together into electrical contact, and then to cure the adhesive and create a lasting reliable bond.

The above method has the disadvantage that it is time consuming and costly. Further, the ACA material has a large interface with the adjacent layers being different materials thereby reducing product quality with regard to a medical device such as an implantable medical device using an electronic module produced by such method because diffusion and dendritic growth can occur along these interfaces, and cracks can arise.

Accordingly, there is a need to provide an improved method for producing an electronic module leading to a less costly electronic module having a higher product quality and a correspondingly improved medical device.

This objective is solved by a method for producing an electronic module having the features of claim 1, by an electronic module having the features of claim 8 and by a medical device having the features of claim 13. Appropriate embodiments thereof are stated in the respective dependent claims and in the following description

According to claim 1 a method for producing an electronic module is provided, wherein the method has the following steps:

• providing an electronic circuit board comprising a thermoplastic substrate layer having at least one first electrical contact element arranged at the surface of a first side of the thermoplastic substrate layer and a conductive structure arranged on an opposing second side of the thermoplastic substrate layer, a thermoplastic element comprising electrically conductive particles or electrically conducting micro-structures and an electronic component having a first side and an opposing second side and comprising at least one second electrical contact element located at the surface at its second side;

• arranging the electronic circuit board, the thermoplastic element and the electronic component in such a way, that the thermoplastic element is being arranged in between the first electrical contact element and the second electrical contact element; and

• thermocompression bonding of the electronic component to the electronic circuit board using the thermoplastic element such that the second side of the electronic component is firmly attached to the first side of the thermoplastic substrate layer via the thermoplastic element, wherein the thermoplastic element thereby, at the same time, establishes an electrically conductive connection between the at least one first electrical contact element and the at least one second electrical contact element.

The electronic circuit board of the electronic module, also referred to as printed circuit board (PCB) mechanically supports and electrically, connects at least one electronic component using conductive tracks, pads and other features etched from one or more sheet layers of metal, e.g. copper, gold, platinum, palladium and the like, laminated onto and/or between sheet layers of a non-conductive substrate or added onto the non-conductive substrate by suitable methods such as, for example, physical vapor deposition (PVD). Printed circuit boards are used in different electrical products, for example in medical devices, e.g. in implantable medical devices. The PCB may be single-sided (one copper layer), double-sided (two copper layers on both sides of one substrate layer), or multi-layer (outer and inner layers of copper, alternating with layers of substrate). Multi-layer PCBs allow for much higher component density because circuit traces on the inner layers would otherwise take up surface space between components. The multi-layer PCB may comprise, for example, more than four copper layers.

Particularly, the PCB comprises at least one flat sheet of insulating material, i.e. thermoplastic substrate layer, and at least one layer of metal forming a conductive structure, e.g. made of copper, laminated to the substrate. The typical PCB conductive structures such as circuit or conductor traces, pads or vias may be provided by chemical etching, laser ablation and/or drilling and the like. Alternatively, the conductive structure(s) may be provided by additive techniques like PVD. Herein, the conductive structures, e.g. individual circuit or conductor traces, function as wires fixed in place and are insulated from each other by air and the board substrate material. The surface of a PCB may have a coating that protects the metal, e.g. copper, from corrosion and reduces the chances of solder shorts between traces or undesired electrical contact with stray bare wires. For its function in helping to prevent solder shorts, the coating may be called solder resist or solder mask.

The first side and an opposing second side of the thermoplastic substrate layer being the major surfaces of the substrate layer can also referred to as upper side and lower side of the substrate layer. The at least one first electrical contact element may be realized, for example, by conductive areas (pads) of the copper foil located at the first side or a conductive via. Particularly, the at least one first electrical contact element on the first (upper) side of the substrate layer is in electrically conductive communication with the conductive structure on the second (lower side) of the substrate layer by means of at least one via, i.e. a through-hole at least partially filled with a conductive material, e.g. a metal paste.

The electronic component may be an active or a passive electronic component, for example, a resistor, a capacitor, an inductance, a semiconductor electronic component (e.g. diode, transistor) or an integrated circuit such as an operational amplifier, a microprocessor, a sensor, a voltage source such as a battery or a current source. The electronic component forms an electronic circuit together with the traces (tracks) of the PCB after the electrically conductive connection is established between the first electrical contact element of the PCB and the second electrical contact element of the electronic component.

The electronic component has a first side (upper side) and an opposing second side (lower side) and comprises the at least one second electrical contact element located at the surface at its second side. The at least one electrical contact element may be a pad or a bump of electrically conducting material, for example. In one embodiment the electronic component comprises two or three electrical contact elements.

The thermoplastic element which is arranged in the second step of the method in between the first electrical contact element and the second electrical contact element is thereby arranged in between the second side of the electronic component and the first side of the PCB in the area where the respective electrical contact elements are located. The thermoplastic element comprises or essentially consists of a thermoplastic material, which is, in one embodiment, a liquid crystal polymer (LCP). The thermoplastic element has a planar shape or form, particularly designed in form of a film or foil. Furthermore, the thermoplastic element, is self-supporting and has a dimension much smaller than the length or width of the PCB. In one embodiment, the thermoplastic element has a maximum dimension of 50 mm x 50 mm x 0.5 mm. In a preferred embodiment, the thermoplastic element has a maximum dimension of 20 mm x 20 mm x 0.3 mm, preferably 5 mm x 5 mm x 0.1 mm. In one embodiment, the thermoplastic element may have a thickness of at least 0.025 mm.

After the above-described arrangement, the electronic component is firmly attached (i.e. fixed) to the PCB, or the thermoplastic substrate layer, respectively, using the thermoplastic element by thermocompression bonding, i.e. in one single step, wherein the thermoplastic element thereby, at the same time, establishes an electrically conductive connection between the first electrical contact element and the second electrical contact element. This means that an electrically conductive path is provided prior the bonding step or during the bonding step through the thermoplastic element. Examples for that are described below. In one embodiment, the thermoplastic element does not contain any open through hole.

The term "thermocompression bonding" also known as thermocompression welding, is used in the context of the present description in the meaning understood by a person skilled in the art, and in particular generally refers to a joining method in which two elements to be joined are interconnected using pressure and heat. In the present case, the thermocompression bonding joins the PCB, the thermoplastic element and the electronic component in the above-defined way. For example, thermocompression bonding may be carried out using uniaxial pressure and heat, for example provided by compression plates located above and below the elements of the electronic module. In order to provide the uniaxial pressing force to the elements of the electronic module, the compression plates are moved towards each other into a direction which is perpendicular to the lateral extension of the PCB layers. The pressure used for thermocompression bonding may be in the range of 0.1 N/mm² - 50 N/mm and/or the temperature may be in the range of 120 °C - 400 °C.

The above-defined method only causes small sized interfaces with the PCB and the electronic component due to the reduced dimension of the thermoplastic element. Accordingly, the area, where diffusion and dendritic growth may occur is reduced and thereby the formation of cracks is prevented over a large area of the PCB. Further, by the same reason, different mechanical and/or thermal properties of the materials connected by the thermoplastic element and of the thermoplastic element have a small impact on the properties of the whole electronic module. This enhances the quality of the electronic module and the quality of a medical device containing such electronic module. Additionally, the production method is very cost effective because there is only one bonding step necessary. The thermoplastic element is further advantageous because it has three functions. It provides the mechanical connection between the electronic component and the PCB, it realizes an underfiller for the electronic component at the PCB surface and it provides the electrical connection between the first electrical contact element and the second electrical contact element. If there are at least two first electrical contact elements and at least two second electrical contact elements, the electrical connection is established between the corresponding first and second electrical contact elements, respectively.

In one embodiment, as indicated above, the thermoplastic material of the thermoplastic element is an LCP. Among the plastic materials, inert thermoplastic materials have the lowest permeability to water and gases. In particular, the group of the liquid crystal polymers (LCP) stands out among the polymers having the lowest water or gas permeability. Further, the tightness of microelectronic packages can be considerably enhanced by using LCP. This also allows the critical dimensions (distances with respect to the surrounding area, material thickness) to be reduced. At the same time, this may be integrated into existing methods, thereby representing a very cost-effective implementation. In one further embodiment, the material of the thermoplastic substrate layer is an LCP. In one preferred embodiment, the material of the thermoplastic element and the material of the thermoplastic substrate layer is an LCP. Advantageously, when using an LCP for both the thermoplastic element and the thermoplastic substrate, respectively, interface effects may be considerable reduced.

Within the meaning of the present invention, the term "liquid crystal polymer" (LCP) is used in the meaning known to and commonly used by a person skilled in the art. A "liquid crystal polymer" refers in particular to an aromatic polymer, which has highly ordered or crystalline regions in the molten state or in solution. Non-limiting examples include aromatic polyamides such as aramid (Kevlar) and aromatic polyesters of hydroxybenzoic acid, such as a polycondensate of 4-hydroxybenzoic acid and 6-hydroxynaphthalene-2-carboxylic acid (Vectran). In one embodiment of the method, the material of the thermoplastic element has a lower melting point or glass transition point than the material of the thermoplastic substrate layer forming the surface of thermoplastic substrate layer at its first side. Accordingly, the thermoplastic element melts as soon as the melting point is reached at least at its surface and is thereby joined with the PCB, particularly with the thermoplastic substrate layer, and the electronic component. The temperature may be dependent on the pressure used during the thermocompression bonding. The melting point of the thermoplastic element is, for example, 160 °C, whereas the melting point of the surface of the thermoplastic substrate layer is, for example, 240 °C.

In one embodiment of the method, the micro-structures comprise micro-vias filled with electrically conductive material. The microstructures establish an electrically conductive path between the at least one first electrical contact element of the PCB and the at least one second electrical contact element of the electronic component in a very cost-effective way and without an additional manufacturing step. In one embodiment, the micro-vias have a diameter in the range of 100 nm to 20 pm. The micro-vias may exhibit a diameter in the range of 100 nm to 20 pm. Preferably, the micro-vias may have a diameter of about 2 pm and may be spaced apart from each other by at least 20 pm. In one embodiment, the electrically conductive material is selected from a metal or conductive carbon, wherein the metal is particularly selected from silver, gold, platinum, palladium, tin, zinc, or alloys thereof.

In one embodiment of the method, the thermoplastic element comprises conductive particles, wherein particularly the conductive particles are embedded in the material or matrix of the thermoplastic element. In one embodiment, the conductive particles essentially consist of or comprise metal, particularly selected from silver, copper, gold, platinum, palladium, tin, zinc or an alloy thereof. In one embodiment, the conductive particles essentially consist of or comprise conductive carbon, e.g. graphite or conductive carbon black. In one embodiment, the conductive particles are characterized by a mean particle size in the range of 5 pm to 60 pm. In one embodiment, the conductive particles have the shape of spheres or flakes. In one embodiment, the conductive particles comprises a core and a shell, wherein the core and the shell independently form one another may essentially consist of or comprise a metal, particularly selected from silver, copper, gold, platinum, palladium, tin, zinc or an alloy thereof, or conductive carbon, e.g. graphite or conductive carbon black. In one preferred embodiment, the conductive particles are characterized by a mean particles size of about 10 pm, wherein particularly the thermoplastic element has a thickness of about 25 pm, and wherein the thermoplastic element comprises at least two discrete cluster of conductive particles having a distance to one another along the lateral extension (perpendicular to the thickness) of the thermoplastic of at least 50 pm.

In one embodiment of the method, the electronic circuit board comprises a thermoplastic frame layer being arranged on the first side of the thermoplastic substrate layer and having at least one through-going recess, wherein the inner side wall of the at least one recess encircles at least one first contact element of the electronic circuit board leaving the at least one first contact element exposed prior the thermocompression bonding step. The thermoplastic frame layer may be also referred to as a spacing layer. In this embodiment, the thermoplastic element and, if applicable, the electronic component, is (are) placed within this recess during the arranging step and during thermocompression bonding. The thermoplastic layer on the first side of the substrate layer forms a frame, i.e. a spatial limitation, for the thermoplastic element and the electronic component by its inner side wall. Accordingly, the thermoplastic element's dimensions (length and width or diameter) is preferably equal to or less than the recess' dimension (length and width or diameter). In one embodiment, the material of the thermoplastic frame layer comprises or essentially consist of an LCP material, for example a different LCP material from or the same LCP material as the LCP material of the thermoplastic element. This embodiment eases the exact location of the thermoplastic element and the electronic component and/or provides a very good mechanical connection of the joined elements. The form of the recess and of the layer as well as the thickness of the layer may be adapted to the form, location and thickness of the thermoplastic element and/or the electronic component. In one embodiment, the inner wall of the at least one recess has an angular shape, e.g. rectangular or polygon, or a round or rounded shape, e.g. quarter round or oval. In one embodiment, the thermoplastic element comprises one or more partial opening. In one embodiment of the method, a first thermoplastic cover layer is thermocompression bonded to the first side of the electronic circuit board and the first side of the electronic component during thermocompression bonding of the electronic circuit board and the electronic component or after this step. The first cover layer encloses or wraps the electronic component and the first side of the thermoplastic substrate layer and thereby protects the electronic module, in particular its electronic component, from environmental impact and effects. The manufacturing of the electronic module is still simple with the first thermoplastic cover layer, in particular if the covering film is bonded during thermocompression bonding of the electronic component to the PCB. The first thermoplastic cover layer may be formed by a single individual thermoplastic film, e.g. an LCP film, or may be constituted by two or more thermoplastic films, e.g. two LCP films, wherein preferably the two thermoplastic films may be characterized by different. Furthermore, the second thermoplastic covering film may exhibit a recess sized and designed to receive the electronic component to be bonded to the thermoplastic substrate.

In one embodiment of the method, the material of the first thermoplastic cover layer consists of or comprises a liquid crystal polymer. As indicated above with regard to the layer, the LCP material may be, for example, a different LCP material from or the same LCP material as the LCP material of the spacing layer. Thereby a very good mechanical connection of the joined elements is provided.

In one embodiment of the method, the electronic circuit board further comprises a second thermoplastic cover layer being arranged on or bonded to the second side of the thermoplastic substrate layer and covering the conductive structure. In one embodiment, the material of the second thermoplastic cover layer essentially consists of or comprises a liquid crystal polymer. The LCP material may be, for example, a different LCP material from or the same LCP material as the LCP material of the thermoplastic substrate layer.

In one embodiment, the at least one first electrical contact element and/or the at least one second electrical contact element is designed as a pad, wherein the pad is preferably made of copper that is preferably made of gold or gold-coated copper. In a further embodiment, the at least one second contacting surface is designed as a pad, preferably made of gold or gold-coated copper.

According to claim 8, an electronic module is provided, comprising:

• an electronic circuit board comprising a thermoplastic substrate layer having a at least one first electrical contact element at the surface of a first side of the thermoplastic substrate and a conductive structure at the surface of an opposing second side of the thermoplastic substrate layer; and

• an electronic component with a first side and an opposing second side and comprising at least one second electrical contact element at the surface of its second side, wherein the electronic component is thermocompression bonded with its second side to the first side of the thermoplastic substrate, thereby forming a permanent connection via a thermoplastic element arranged in between the at least one first electrical contact element and the at least one second electrical contact element, wherein electrically conductive particles or electrically conducting micro-structures are located within the volume of the thermoplastic element providing an electrical conductive connection between the at least one first electrical contact element and the at least one second electrical contact element.

The electronic module defined above has the same advantages as the method explained above. Further, the elements of the electronic module and their properties as well as their embodiments are already described above in connection with the method for producing the electronic module. It is therefore referred to the above explanation and description of the method.

The electronic module may comprise at least two or more than two electronic components bonded to the PCB in the same way as indicated above, preferably within one single production step. The above method may be used for bonding two or more than two electronic components to the PCB by respective thermoplastic elements within the same method or production step. In one embodiment of the electronic module, as indicated above in detail, the material of thermoplastic element essentially consists of or comprises a liquid crystal polymer. In one embodiment of the electronic module, the material of the thermoplastic substrate essentially consists of or comprises a liquid crystal polymer. In a preferred embodiment, the material of the thermoplastic element and the material of the thermoplastic substrate layer essentially consist of or comprise a liquid crystal polymer.

In one embodiment of the electronic module, as indicated above in detail, the electronic circuit board comprises a thermoplastic frame layer (spacing layer) forming at least part of its first side having at least one through-going recess, wherein the inner side wall of the at least one recess encircles at least one first contact element of the electronic circuit board.

In one embodiment of the electronic module, as indicated above in detail, a first thermoplastic covering layer is thermocompression bonded to or arranged at the first side of thermoplastic substrate and/or to the first thermoplastic covering layer, if present, and the first side of the electronic component.

In one embodiment of the electronic module, as indicated above in detail, the material of the first thermoplastic covering layer and/or the material of the second thermoplastic covering film consists of or comprises a liquid crystal polymer. In one embodiment, the second thermoplastic covering film may be formed by a single individual thermoplastic film, e.g. an LCP film, or may be constituted by two or more thermoplastic films, e.g. two LCP films, wherein preferably the two thermoplastic films may be characterized by different. Furthermore, the second thermoplastic covering film may exhibit a recess sized and designed to receive the electronic component to be bonded to the thermoplastic substrate.

In one embodiment, the electronic module according to the invention further comprises a second thermoplastic cover layer being arranged on or bonded to the second side of the thermoplastic substrate layer and covering the conductive structure. In one embodiment, the material of the second thermoplastic cover layer essentially consists of or comprises a liquid crystal polymer. The LCP material may be, for example, a different LCP material from or the same LCP material as the LCP material of the thermoplastic substrate layer. According to claim 15, a medical device is provided, for example an implantable medical device, comprising an electronic module as described above.

Further electronic components provided at the PCB may be through hole components or surface mounted components mounted by their wire leads passing through the board and soldered to traces on the other side. Surface mount electronic components are attached by their leads to copper traces on the same side of the board. Part of the electronic components may be soldered onto the PCB to both electrically connect and mechanically fasten them to it.

PCBs may be manufactured and assembled automatically. Mass-producing circuits with PCBs is cheaper and faster than with other wiring methods, as components are mounted and wired in one operation. Large numbers of PCBs may be fabricated at the same time, and the layout only has to be done once. Accordingly, the electronic module comprising the abovedescribed PCB and at least one electronic module may be manufactured and assembled automatically, as well.

The present invention will now be described in further detail with reference to the accompanying schematic drawings, wherein

Fig. 1 shows an embodiment of the electronic module in an exploded cross-sectional view,

Fig. 2 depicts an embodiment of the thermoplastic element in a cross-sectional view,

Fig. 3 shows the embodiment of the electronic module of Fig. 1 prior the thermocompression bonding production step in a cross-sectional view,

Fig. 4 shows the embodiment of the electronic module of Fig. 1 after the thermocompression bonding production step in a cross-sectional view, Figs 5 and 6 show embodiments of the medical device according to the invention

Fig. 1 illustrates an embodiment of an electronic module according to the invention comprising an electronic circuit board (PCB) 1, a thermoplastic element 3, an electronic component 4 and a thermoplastic covering film 5.

The PCB 1 comprises an insulating thermoplastic substrate layer 1.3, preferably made of a liquid crystal polymer, wherein the thermoplastic substrate has a first side (upper side in Fig. 1) and an opposing second side (lower side in Fig. 1). The PCB 1 further comprises a conducting layer or structure 1.2, for example consisting of copper, arranged on and fixed to the second side of the thermoplastic substrate, and covered, essentially by its entirety by a thermoplastic cover or base layer 1.1, preferably made of a liquid crystal polymer. At the upper surface of the substrate layer 1.3 two pad-like first contact elements are accommodated which are electrically connected to the conducting layer 1.2 via a through hole (via) within the substrate layer 1.3. The PCB 1 additionally comprises a spacing or frame layer 1.4 forming at least part of its first side and having one through-going recess 1.5, wherein the inner side wall 1.6 of the recess encircles the two pad-like first contact elements 2 of the PCB 1. The form of the recess 1.5 is adapted to the form of the first contact elements 2 and the thickness of the spacing or frame layer 1.4 is adapted to the thickness of the patch-like element 3. The spacing layer 1.4 preferably consists of a liquid crystal polymer. The PCB 1 may comprise additional electronic components and structures, such as conductor paths, vias and pads on its first side.

The thermoplastic element 3 preferably consists of a liquid crystal polymer, and electrically conductive particles 3.1 forming electrically conductive micro-structures. Alternatively, the thermoplastic element 3 comprises a plurality of micro Vias in order to establish a conductive path between the contact elements 2 of the PCB1 and the contact elements 4 of the electronic contact, as described below. Preferably, the LCP of the thermoplastic element has a lower melting point than the material of the substrate layer 1.3. The LCP material of the thermoplastic element 3 forms the matrix of this element, whereas the electrically conductive particles 3.1, e.g. spheres or flake made of metal or conductive carbon, are embedded within this matrix. The thermoplastic element 3 is slightly smaller in its length and width than the recess 1.5 of the spacing layer 1.4 prior assembly.

Alternatively, as shown in Fig. 2, a thermoplastic element 30 may be used consisting of a matrix of LCP material and micro-vias 3.2 at least partially filled with electrically conductive material, e.g. a metal such as silver, gold, platinum, palladium, tin, zinc, or alloys thereof, or conductive carbon, wherein the filled micro-vias 3.2 form the electrically conducting micro-structures. The micro-vias may exhibit a diameter in the range of 100 nm to 20 pm. Preferably, the micro-vias have a diameter of about 2 pm and are spaced apart from each other by at least 20 pm.

The electronic component 4, for example an integrated circuit (IC), has a first side (upper side in Fig. 1) and an opposing second side (lower side in Fig. 1) and comprises two second electrical contact elements 4.1, for example pads or bumps, located at its second side. It may alternatively be formed as a sensor or a diode comprising for example pads or bumps as contact points for a flip-chip-contacting on the PCB 1.

The electronic module further comprise a thermoplastic cover layer 5 consist of a thermoplastic material, preferably a liquid crystal polymer and may be dimensioned so that it covers the first side of the electronic component 4 or the first side of the insulating thermoplastic substrate layer 1.3.

Fig. 3 and 4 illustrate the method for producing such electronic module. In a first step, the PCB 1, the thermoplastic element 3 comprising electrically conducting particles 3.1, the IC 4 and the thermoplastic covering film 5 are provided and arranged in the sequence shown in Fig. 3. In particular, the patch-like element 3 is located above the recess 1.5 of the spacing layer 1.4 and the IC 4 above the patch-like element 3. Further, above and below the above described elements compression plates 7 are arranged such that the elements are located between the compression plates.

As indicated in Fig. 3 and 4, the compression plates 7 apply a pressure force perpendicular to the lateral extension of the layers of the PCB 1 by moving towards each other (see arrows 8), for example a pressure force of 0,5 N/mm². Alternatively, only one of the compression plates 7 actively applies the above described pressure, while the other compression plate 7 is hold stationary and only provides a counter pressure. Additionally, heat is applied, for example a temperature of 300°C. The IC 4 is thereby thermocompression bonded to the electronic circuit board 1 using the thermoplastic element 3 such that the second side of the electronic component 4 is firmly mechanically attached to the first side of the electronic circuit board 1 via the thermoplastic element 3. The thermoplastic element 3 thereby, at the same time, establishes an electrically conductive connection between the first one of first electrical contact elements 2 and the first one of the second electrical contact elements 4.1 as well as the second one of the first electrical contact elements 2 and the second one of the second electrical contact elements by the electrically conducting particles 3.1.

Further, in the same production step, the thermoplastic cover layer 5 is thermocompression bonded to the first side of the PCB 1 and the first side of the IC 4. The final state of the electronic module at the end of the thermocompression bonding is shown in Fig. 4.

The implantable medical device is assembled using the electronic module manufactured as indicated above. An exemplary implantable medical device and its manufacturing is depicted in Figures 5 and 6. A PCB 1 is provided, in which the conductive structure 1.2 on the second side of the insulating substrate layer is in parts designed in form of several coils (left hand side of the implantable medical device), which are particularly configured to receive or transmit RF signal or are configured to receive energy from an external energy source in order to power or charge the medical device. The conductive structure is furthermore electrically contacted to one or more electrodes, which are exposed to the environment, particularly in order to contact a tissue, e.g. nerve, muscle or cardiac tissue. In accordance with the above described method of the invention, a plurality of electronic components 4 are place on and thermocompression bonded to electrical contacts elements on the PCB1 and covered by a thermoplastic cover layer 5 during the thermocompression bonding of the electronic components 4. Reference numbers

1 PCB

1.1 base layer

1.2 conducting layer

1.3 substrate layer

1.4 spacing layer

1.5 recess

1.6 inner side wall of recess 1.5

2 first contact element

3 thermoplastic patch-like element

3.1 electrically conductive particle

3.2 micro-via filled with electrically conductive material

4 IC (electronic component)

4.1 second contact element

5 covering film

6 electrode

7 compression plate

8 arrow

30 patch-like element

Claims

1. A method for producing an electronic module, comprising the following steps:

• providing an electronic circuit board (1) comprising a thermoplastic substrate layer (1.3) having at least one first electrical contact element (2) arranged at the surface of a first side of the thermoplastic substrate (1.3) and a conductive structure (1.2) arranged on an opposing second side of the thermoplastic substrate layer (1.3), a thermoplastic element (3, 30) comprising electrically conducting particles (3.1) or electrically conducting micro-structures (3.2), and an electronic component (4) having a first side and an opposing second side and comprising at least one second electrical contact element (4.1) located at the surface at its second side;

• arranging the electronic circuit board (1), the thermoplastic element (3, 30) and the electronic component (4) in such a way, that the thermoplastic element (3, 30) is being arranged in between the first electrical contact element (2) and the second electrical contact element (4.1); and

• thermocompression bonding of the electronic component (4) to the electronic circuit board (1) using the thermoplastic element (3, 30) such that the second side of the electronic component (4) is firmly attached to the first side of the thermoplastic substrate layer (1.3.) via the thermoplastic element (3), wherein the thermoplastic element (3, 30) thereby, at the same time, establishes an electrically conductive connection between the at least one first electrical contact element (2) and the at least one second electrical contact element (4.1).

2. The method for producing an electronic module according to claim 1, wherein the material of the thermoplastic element (3, 30) and/or the thermoplastic substrate layer (1.3) essentially consists of or comprises a liquid crystal polymer.

3. The method for producing an electronic module according to claims 1 or 2, wherein the material of the thermoplastic element (3, 30) has a lower melting point than the material of the thermoplastic substrate layer (1.3) forming the surface of the electronic circuit board (1) at its first side. The method for producing an electronic module according to any one of the previous claims, wherein the micro-structures comprise micro-vias (3.2) filled with an electrically conductive material. The method for producing an electronic module according to any one of the previous claims, wherein the electronic circuit board (1) comprises a thermoplastic frame layer (1.4) being arranged on the first side of the thermoplastic substrate layer (1.3) and having at least one through-going recess (1.5), wherein an inner side wall (1.6) of the at least one recess encircles at least one first contact element (2) of the electronic circuit board (1) leaving the at least one first contact element (2) exposed prior the thermocompression bonding step. The method for producing an electronic module according to any one of the previous claims, wherein a first thermoplastic cover layer (5) is thermocompression bonded to

- the first side of the thermoplastic substrate layer (1.3) and/or to the thermoplastic frame layer (1.4), and

- the first side of the electronic component (4) during thermocompression bonding of the electronic circuit board (1) and the electronic component (4) or after this step. The method for producing an electronic module according to any one of the previous claims, wherein the electronic circuit board (1) further comprises a second cover layer (1.1) arranged at the second side of the thermoplastic substrate layer (1.3) and covering the conductive structure (1.2). The method for producing an electronic module according to any one of the previous claims, wherein the material of the thermoplastic frame layer (1.4) and/or the material of the first thermoplastic cover layer (5) and/or the second thermoplastic cover layer (1.1) consists of or comprises a liquid crystal polymer. An electronic module comprising:

• an electronic circuit board (1) comprising a thermoplastic substrate layer (1.3) having at least one first electrical contact element (2) at the surface of a first side of the thermoplastic substrate and a conductive structure (1.2.) arranged on an opposing second side of the thermoplastic substrate; and

• an electronic component (4) with a first side and an opposing second side and comprising at least one second electrical contact element (4.1) at the surface of its second side, wherein the electronic component (4) is thermocompression bonded with its second side to the first side of the thermoplastic substrate (1.3), thereby forming a permanent connection via a thermoplastic element (3) arranged in between the at least one first electrical contact element (2) and the at least one second electrical contact element (4. 1), wherein electrically conducting particles (3.1) or electrically conducting micro-structures (3.2) are located within the volume of the thermoplastic element (3) providing an electrical conductive connection between the at least one first electrical contact element (2) and the at least one second electrical contact element (4.1). The electronic module according to claim 9, wherein the material of the thermoplastic element (3) and/or the thermoplastic substrate (1.3) essentially consists of or comprises a liquid crystal polymer. The electronic module according to any one of the claims 9 to 10, wherein the electronic circuit board (1) comprises a thermoplastic frame layer (1.4) forming at least part of its first side having at least one through-going recess (1.5), wherein the inner side wall (1.6) of the at least one recess encircles at least one first contact element (2) of the electronic circuit board (1). The electronic module according to any one of the claims 9 to 11, wherein a first thermoplastic cover layer (5) is thermocompression bonded to - the first side of thermoplastic substrate 81.3) and/ the first thermoplastic cover layer (1.4), and

- the first side of the electronic component (4). 13. The electronic module according to any one of claims 9 to 12, further comprising comprises a second cover layer (1.1) arranged at the second side of the thermoplastic substrate layer (1.3) and covering the conductive structure (1.2).

14. The electronic module according to any one of the claims 9 or 13, wherein the material of the thermoplastic frame layer (1.4), the material of the first thermoplastic cover layer (5) and/or the material of the second thermoplastic covering film (1.1) essentially consists of or comprises a liquid crystal polymer.

15. A medical device, for example an implantable medical device, comprising an electronic module according to any one of the claims 9 to 14.