Printed circuit board connection

Abstract

The invention relates to a printed circuit board connection (1) comprising two flexible printed circuit boards (2, 3), the conductor tracks (21, 31) of which are connected by an anisotropically conductive adhesive layer (10). It is proposed to provide a clamping device (5) which is configured to clamp the conductor tracks (2, 3) in a region of overlap (100) and thereby increase the stability of the electrical connection.

Description

[0001] 202406156

[0002] 1

[0003] Description

[0004] PCB connection

[0005] The present invention relates to a printed circuit board connection having the features of claim 1 and to the use of such a printed circuit board connection having the features of claim 11.

[0006] In particular, the present invention relates to circuit board connections of at least two flexible circuit boards that are electrically connected to each other for signal or power transmission. In other words, the present invention relates in particular to the field of electrical connection technology for flat and flexible conductive structures.

[0007] Flexible printed circuit boards (PCBs), or conductive films, e.g., based on polyimide films, are used in many applications in electronics and sensor technology. For example, in electronic devices, flexible PCBs are frequently used to provide space-saving wiring for moving parts. Furthermore, electronic components that implement sensory and / or actuator functions can be manufactured using flexible PCBs.

[0008] In all these applications, it is common for several flexible printed circuit boards to need to be electrically connected or contacted together.

[0009] An electrical connection can be made, for example, using a plug-socket connection. Connecting a plug or socket to the flexible printed circuit board (PCB) can be reversible (e.g., via zero-force sockets, also known as zero insertion force) or irreversible (e.g., via crimp connections). A disadvantage of this connection technology is that attaching the plugs or sockets to the PCB is complex and the plugs or sockets require additional installation space. Furthermore, the plugs or sockets must always be compatible with the specific PCB geometry. 202406156

[0010] 2

[0011] One approach to completely eliminating the need for plugs or sockets involves connecting two flexible printed circuit boards (PCBs) with their respective contact areas facing each other via an anisotropically conductive layer. An anisotropically conductive layer is a layer that is electrically conductive in one spatial direction, for example, orthogonal to the PCB plane, and electrically insulating in the other two spatial directions, for example, parallel to the PCB plane. This connection technique enables the simple contacting of flat conductive structures regardless of the film type and thickness and is compatible with a wide variety of conductor geometries.

[0012] Examples of such printed circuit board connections are described in EP 0232 127 A2 and EP 1 928218 A1. The joining of the two flexible printed circuit boards is carried out under pressure and high temperature using heating presses, as shown, for example, in US 2022 / 0215989 A1.

[0013] For some applications where flexible printed circuit boards are subjected to mechanical stress, this connection technology does not offer sufficient stability to guarantee a reliable electrical connection over the long term. Even a reinforcing layer encasing the connection section, made of glass fiber reinforced plastic or polyimide as described in EP 1 928 218 A1, is often insufficient on its own to provide a permanently robust contact.

[0014] The object of the present invention is therefore to provide a printed circuit board connection of the type mentioned above, in which a more stable electrical connection is ensured. In particular, a printed circuit board connection is to be provided that maintains an optimal electrical connection even under mechanical stress.

[0015] This problem is solved by a printed circuit board connection with the features of claim 1. Preferred features are the subject of the dependent claims. Further advantages and features are described in the general description 202406156.

[0016] 3 and the exemplary embodiments. Furthermore, the use of such a printed circuit board connection according to claim 11 is also part of the invention.

[0017] The printed circuit board connection according to the invention contains

[0018] - a first flexible printed circuit board with a first substrate layer and a first conductor track arranged on a first surface of the first substrate layer,

[0019] - a second flexible printed circuit board with a second substrate layer and a second conductor track arranged on a first surface of the second substrate layer, as well as

[0020] - an anisotropically conductive adhesive layer that connects a contact section of the first conductor track to a contact section of the second conductor track both electrically and mechanically.

[0021] The printed circuit board connection according to the invention is characterized by a clamping device which is designed to apply a pressing force to the first flexible printed circuit board and the second flexible printed circuit board, such that the contact section of the first conductor track and the contact section of the second conductor track are each pressed onto the adhesive layer.

[0022] The invention is based on the idea of ​​increasing the stability of the electrical connection by providing a force-fit connection. For this purpose, the flexible printed circuit boards are pressed together or clamped by means of a clamping device. In this way, the printed circuit board connection can better withstand mechanical stresses, in particular tensile forces acting along a plane of the printed circuit board.

[0023] Anisotropically conductive adhesive layers can be, for example, an anisotropically conductive adhesive film or a layer of an anisotropically conductive adhesive (ACA), which is applied in a liquid phase and then cures to a solid. 202406156

[0024] 4

[0025] Various materials are suitable for the substrate layers or films, provided they are non-conductive or dielectric and sufficiently flexible. Preferably, the substrate layer material(s) contains at least one polymer, in particular a thermoplastic such as PET, PP, PC, and / or a thermoplastic elastomer such as TPV or TPU. The substrate layer thickness is preferably 100 nm to 1 mm, more preferably 10 pm to 250 pm, and most preferably 50 pm to 150 pm.

[0026] For the conductive traces, various inorganic materials (such as metals) and organic materials (such as conductive polymers, carbon, graphite, graphene, etc.), as well as combinations thereof, are suitable, provided they are conductive. If a conductive trace is printed, i.e., manufactured using additive manufacturing processes, materials are used that can be processed using printing methods (e.g., as ink or paste). Preferably, the height of the conductive traces, measured orthogonally to the printed circuit board plane, is between 1 nm and 50 pm. This allows for a particularly compact design of the flexible printed circuit boards. A height of 500 nm to 15 pm is especially preferred, enabling reliable production using established printing processes.

[0027] The contact section of the first conductor track is, in particular, an uncovered or exposed surface of the first conductor track facing away from the first substrate layer. The contact section of the second conductor track is, in particular, an uncovered or exposed surface of the second conductor track facing away from the second substrate layer. Preferably, the first conductor track and / or the second conductor track have a constant layer thickness.

[0028] The printed circuit boards preferably have a layer thickness of 25 pm to 500 pm, measured orthogonally to the board plane, and particularly preferably of 50 pm to 250 pm. 202406156

[0029] 5

[0030] In a preferred embodiment of the printed circuit board connection according to the invention, the clamping device comprises a first rigid clamping plate and a second rigid clamping plate, wherein in an overlap area where the first flexible printed circuit board and the second flexible printed circuit board overlap to establish an electrical contact, the first flexible printed circuit board, the second flexible printed circuit board, and the adhesive layer between the clamping plates are clamped. The clamping plates are plate-shaped and rigid (particularly in relation to the flexible printed circuit boards) in order to advantageously apply a clamping surface load to both sides of the printed circuit boards. Preferably, the clamping plates contain a polymeric material. Preferably, the clamping plates have a higher flexural stiffness than the printed circuit boards, in particular a flexural stiffness at least three times higher than that of the printed circuit boards.Preferably, the first clamping plate and / or the second clamping plate has a width that corresponds to 80% to 120% of the width of the overlap area, and / or the first clamping plate and / or the second clamping plate has a length that corresponds to 80% to 120% of the length of the overlap area. In this way, a clamping surface load can be applied over a large part of the overlap area.

[0031] In a further preferred embodiment of the printed circuit board connection according to the invention, the clamping plates are fixed to one another, preferably releasably, by means of one or more clamping means, such that in the fixed state of the clamping plates, the distance between the facing front surfaces of the clamping plates is less than the combined thickness of the printed circuit boards and the adhesive layer in the overlap area. In this way, a kind of press fit is achieved between the clamping device on the one hand and the printed circuit boards arranged between the clamping plates, including the adhesive layer, on the other.

[0032] In a further preferred embodiment of the printed circuit board connection according to the invention, the clamping device has a clamping means separate from the clamping plates, which is designed to be applied to a respective adhesive layer 202406156

[0033] 6. Apply a force to the opposite back side of the clamping plates so that the contact section of the first conductor track and the contact section of the second conductor track are each pressed onto the adhesive layer. In this way, the clamping plates can be easily arranged in the overlap area, e.g., attached to the back sides of the printed circuit boards, and the clamping element can be provided in a further step. Preferably, the clamping element is ring-shaped and arranged such that it grips the clamping plates under radial preload and presses them onto the printed circuit boards arranged between them.

[0034] In a further preferred embodiment of the printed circuit board connection according to the invention, the clamping element is a heat-shrink tube that is pushed onto the printed circuit boards in the overlap area and shrunk to create a radial preload. This makes it possible to establish a force-fit connection that stabilizes the electrical connection in a particularly simple and reliable manner. The heat-shrink tube can also provide protection for the electrical connection against the elements. The heat-shrink tube usually contains a thermoplastic that contracts when heat is applied, for example, by a hot air blower, so that the heat-shrink tube adapts to the shape of the clamping plates and the intermediate layers and, in its cooled state, applies a preload to these components.

[0035] In a further preferred embodiment of the printed circuit board connection according to the invention, the clamping means is a ring made of an elastomeric material, which is pushed onto the printed circuit boards in the overlap area under radial preload.

[0036] In a further preferred embodiment of the printed circuit board connection according to the invention, the clamping means has two clamping arms connected by a bridge, each of which is designed to apply a force to a respective back side of the clamping plates facing away from the adhesive layer, so that the contacting section of the first conductor track and the contacting section 202406156

[0037] 7 of the second conductor track are pressed onto the adhesive layer. Preferably, the clamping arms are fixed to one another, particularly by means of a clamping device, preferably detachably fixed to one another, such that in the fixed state the distance between the facing front surfaces of the clamping arms is less than the cumulative layer height of the printed circuit boards, the adhesive layer, and the clamping plates in the overlap area. In this way, a kind of press fit is achieved between the clamping device on the one hand and the clamping plates and the printed circuit boards arranged between them, including the adhesive layer, on the other.

[0038] The printed circuit board connection according to the invention is ideally suited for the electrical connection of two electronic components or for the voltage or power supply of an electrical component.

[0039] It is expressly pointed out that the embodiments of the invention described above can each be combined individually or in any technically meaningful combination with each other with the subject matter of the independent claims.

[0040] Variations and embodiments of the invention, as well as further advantages and details of the invention, can be found in the following description and the drawings. The schematic figures show:

[0041] Fig. 1 shows a first embodiment of a device according to the invention.

[0042] PCB interconnection in a top view;

[0043] Fig. 2 shows the printed circuit board connection from Fig. 1 in sectional view according to

[0044] Section line II;

[0045] Fig. 3 shows the printed circuit board connection from Fig. 1 in sectional view according to

[0046] Intersection line II-II; 202406156

[0047] 8

[0048] Fig. 4 shows part of a second embodiment of a device according to the invention.

[0049] Printed circuit board connection in a view analogous to Fig. 3; and

[0050] Fig. 5 shows part of a third embodiment of a device according to the invention.

[0051] Printed circuit board connection in a view analogous to Fig. 3.

[0052] Parts that have the same or similar effects are provided with identical reference numerals, if applicable.

[0053] Individual technical features of the embodiments described below can also be combined with previously described embodiments as well as the features of the independent claims and any further claims to create objects according to the invention.

[0054] Figures 1 to 3 show a first embodiment of a printed circuit board connection 1 according to the invention comprising a first flexible printed circuit board 2 and a second flexible printed circuit board 3, which overlap in an overlap area 100 and are connected to each other via an adhesive layer 10 to produce an electrical contact.

[0055] Fig. 1 shows the printed circuit board connection 1 in a top view of a printed circuit board plane E defined by the two parallel printed circuit boards 2, 3. In this case, the printed circuit boards 2, 3 have the same width measured in a lateral direction B. In principle, the printed circuit boards 2, 3 can also have different widths. The overlap area 100 has a width a and a length b measured in a longitudinal direction L.

[0056] Fig. 2 shows the printed circuit board connection 1 in a sectional view along line I-I from Fig. 1, i.e., a section along the longitudinal direction L. Fig. 3 shows the printed circuit board connection 1 in a sectional view along line 11-11 from Fig. 1, i.e., a section along the lateral direction B. 202406156

[0057] 9

[0058] The first flexible printed circuit board 2 has a first substrate layer 20 and a first conductor 21 arranged on a first surface 200 of the first substrate layer 20. The second flexible printed circuit board 3 has a second substrate layer 30 and a second conductor 31 arranged on a first surface 300 of the second substrate layer 30. Both conductors 21 and 31 are electrically conductive. Optionally, the first conductor 21 and the second conductor 31 are covered with a respective cover layer 22, 32 made of a dielectric material.

[0059] The printed circuit board connection 1 further comprises an anisotropically conductive adhesive layer 10, which connects a contact section 211 of the first conductor 21 to a contact section 311 of the second conductor 31. The anisotropically conductive adhesive layer 10 is a layer that is electrically conductive in the spatial direction orthogonal to the printed circuit board plane E and in one vertical direction H, and electrically insulating in the other two spatial directions (lateral direction B and longitudinal direction L). The contact section 211 of the first conductor 21 is a surface of the first conductor 21 that is not covered by the cover layer 22 and faces away from the first substrate layer 20. The contact section 311 of the second conductor 31 is a surface of the second conductor 31 that is not covered by the cover layer 32 and faces away from the second substrate layer 30.The first conductor track 21 and / or the second conductor track 31 each have a layer thickness that is constant and measured in a height direction H or orthogonally to the printed circuit board plane E.

[0060] The printed circuit board connection 1 has a clamping device 5 configured to apply a pressing force K to the first flexible printed circuit board 2 and the second flexible printed circuit board 3, such that the contact section 211 of the first conductor 21 and the contact section 311 of the second conductor 31 are each pressed onto the adhesive layer 10. This creates a frictional connection that promotes both the mechanical adhesion and the electrical contact of the printed circuit board connection 1. Thus, the printed circuit board connection 1 is more resistant to mechanical stresses, in particular to tensile forces acting parallel to the printed circuit board plane E. 202406156

[0061] 10

[0062] The clamping device 5 comprises a first rigid clamping plate 50a and a second rigid clamping plate 50b, between which the first flexible printed circuit board 2, the second flexible printed circuit board 3, and the adhesive layer 10 are clamped in the overlap area 100. In this way, a clamping surface load is applied to both sides of the printed circuit boards 2 and 3. As can be seen from Figures 1 to 3, the first clamping plate 50a and the second clamping plate 50b have a width and a length that correspond essentially to the width a and length b, respectively, of the overlap area 100, so that the clamping plates 50a and 50b can provide an optimal surface load.

[0063] The clamping device 5 has a clamping means 55 which is designed to apply a force to a respective back side 501a, 501b of the clamping plates 50a, 50b facing away from the adhesive layer 10, so that the contacting section 211 of the first conductor track 21 and the contacting section 311 of the second conductor track 31 are each pressed onto the adhesive layer 10.

[0064] In the first embodiment according to Figures 1 to 3, the clamping element 55 is a heat-shrink tube 56, which is pushed onto the printed circuit boards 2, 3 in the overlap area 100 and shrunk to form a radial preload. The heat-shrink tube 56 has a predetermined shrink ratio (e.g., 2:1) and a predetermined shrink temperature, so that it contracts when heat is applied. In doing so, the heat-shrink tube 56 conforms to the shape of the clamping plates 50a, 50b and the intermediate layers 10, 20, 21, 30, 31, so that the heat-shrink tube 56 applies a radial preload to these components when cooled.

[0065] Fig. 4 shows part of a second embodiment of a printed circuit board connection 1 according to the invention in a view analogous to Fig. 3. In this embodiment, a clamping means 55 can be omitted, because the clamping plates 50a, 50b are connected to each other via a bridge 50c and are detachably fixed to each other by means of a clamping means 57, e.g. a clamping screw. 202406156

[0066] 11

[0067] In the fixed state shown here, the distance d1 between the facing front surfaces 500a, 500b of the clamping plates 50a, 50b is smaller than the cumulative layer height h1 (see Fig. 3) of the printed circuit boards 2, 3 and the adhesive layer 10 in the overlap area 100. The clamping device 5 can thus be slid laterally over the printed circuit boards 2, 3 and the adhesive layer 10 in the overlap area 100 and then fixed by means of the clamping element 57, so that the layer assembly 10, 20, 21, 30, 31 is clamped between the clamping plates 50a, 50b. The clamping element 57 can alternatively also have a snap-fit ​​connection. Instead of the web 50c, another clamping element 57 could alternatively be provided.

[0068] Fig. 5 shows part of a third embodiment of a printed circuit board connection 1 according to the invention in a view analogous to Fig. 3. In this embodiment, the clamping means 55 is not a heat shrink tube 56, but the clamping means 55 has two clamping arms 55a, 55b connected by a bridge 55c, each designed to apply a force to a respective back side 501a, 501b of the clamping plates 50a, 50b facing away from the adhesive layer 10, so that the contact section 211 of the first conductor 21 and the contact section 311 of the second conductor 31 are each pressed onto the adhesive layer 10. The clamping arms 55a, 55b are detachably fixed to one another by means of a clamping device 58, e.g. a clamping screw, such that a distance d2 between the facing front surfaces 550a, 550b of the clamping arms 55a, 55b is less than a cumulative layer height h2 (see Fig.3) of the printed circuit boards 2, 3, the adhesive layer 10, and the clamping plates 50a, 50b in the overlap area 100. The clamping device 5 can thus be slid laterally over the clamping plates 50a, 50b, the printed circuit boards 2, 3, and the adhesive layer 10 in the overlap area 100 and then fixed by means of the clamping element 58, so that the layer assembly 10, 20, 21, 30, 31, including the clamping plates 50a, 50b, is clamped between the clamping arms 55a, 55b. The clamping element 57 can alternatively also have a snap-fit ​​connection. Instead of the bridge 50c, another clamping element 57 could alternatively be provided. The clamping element 58 can alternatively also have a snap-fit ​​connection. 202406156.

[0069] 12

[0070] Instead of the bridge 55c, an alternative clamping device 58 could also be provided.

[0071] It should also be noted that "showing" does not exclude any other elements or steps and "a" or "an" does not exclude a multitude.

[0072] The scope of protection of the present invention is defined by the patent claims and is not limited by the features explained in the description or shown in the figures.

Claims

202406156 13 Patent claims 1. Circuit board connection (1) having - a first flexible printed circuit board (2) with a first substrate layer (20) and a first conductor track (21) arranged on a first surface (200) of the first substrate layer (20) , - a second flexible printed circuit board (3) with a second substrate layer (30) and a second conductor track (31) arranged on a first surface (300) of the second substrate layer (30) , - an anisotropically conductive adhesive layer (10) connecting a contact section (211) of the first conductor (21) with a contact section (311) of the second conductor (31), characterized by a clamping device (5) configured to apply a pressing force (K) to the first flexible printed circuit board (2) and the second flexible printed circuit board (3) such that the contact section (211) of the first conductor (21) and the contact section (311) of the second conductor (31) are each pressed onto the adhesive layer (10).

2. Printed circuit board connection (1) according to claim 1, wherein the clamping device (5) comprises a first rigid clamping plate (50a) and a second rigid clamping plate (50b), wherein in an overlap area (100) in which the first flexible printed circuit board (2) and the second flexible printed circuit board (3) overlap, the first flexible printed circuit board (2), the second flexible printed circuit board (3) and the adhesive layer (10) between the Clamping plates (50a, 50b) are clamped in place.

3. Printed circuit board connection (1) according to claim 2, wherein the first clamping plate (50a) and / or the second clamping plate (50b) has a width corresponding to 80% to 120% of a width (a) of the overlap area (100), and / or wherein the first clamping plate (50a) and / or the second clamping plate (50b) 202406156 14 has a length that corresponds to 80% to 120% of a length (b) of the overlap area (100).

4. Printed circuit board connection (1) according to claim 2 or 3, wherein the Clamping plates (50a, 50b) are preferably detachably fixed to each other by means of a clamping device (57) such that a distance (d1 ) between the facing front surfaces (500a, 500b) of the clamping plates (50a, 50b) is smaller than a cumulative layer height (h1 ) of the printed circuit boards (2, 3) and the adhesive layer (10) in the overlap area (100).

5. Printed circuit board connection (1 ) according to one of claims 2 to 4, wherein the clamping device (5) has a clamping means (55) which is configured to apply a force to a respective rear side (501a, 501b) of the clamping plates (50a, 50b) facing away from the adhesive layer (10), so that the contact section (211 ) of the first conductor track (21 ) and the contact section (311 ) of the second conductor track (31 ) are each pressed onto the adhesive layer (10).

6. Printed circuit board connection (1 ) according to claim 4, wherein the clamping means (55) is ring-shaped and the clamping plates (50a, 50b) are arranged circumferentially under radial preload.

7. Printed circuit board connection (1 ) according to claim 4 or 5, wherein the clamping means (55) is a heat shrink tube (56) which is pushed onto the printed circuit boards (2, 3) in the overlap area (100) and shrunk to form a radial preload.

8. Printed circuit board connection (1 ) according to claim 4 or 5, wherein the clamping means (55) is a ring made of an elastomeric material which is pushed onto the printed circuit boards (2, 3) in the overlap area (100) under radial preload. 202406156 15 9. Printed circuit board connection (1) according to claim 4 or 5, wherein the clamping means (55) has two clamping arms (55a, 55b) connected by a bridge (55c), each of which is configured to face a respective back side (501a, 501b) facing away from the adhesive layer (10) of the clamping plates (50a, 50b) to apply a force so that the contact section (211 ) of the first conductor track (21 ) and the contact section (311 ) of the second conductor track (31 ) are each pressed onto the adhesive layer (10).

10. Printed circuit board connection (1) according to claim 9, wherein the clamping arms (55a, 55b) are preferably detachably fixed to one another by means of a clamping means (58) such that a distance (d2) between the facing front surfaces (550a, 550b) of the clamping arms (55a, 55b) is smaller than a cumulative layer height (h2) of the printed circuit boards (2, 3), the adhesive layer (10) and the clamping plates (50a, 50b) in the overlap area (100).

11. Use of a printed circuit board connection (1 ) according to one of claims 1 to 10 for electrical connection of two electronic components or for voltage or power supply of an electrical component.

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