Contact assembly with soldered flexible circuit board

Abstract

The invention relates to a contact assembly. The contact arrangement has at least one electrically conductive substrate, in particular a circuit carrier. The contact arrangement also has an in particular flexible circuit board, the flexible circuit board having at least one, in particular reversibly flexible, electrically insulating film and at least one or only one electrically conductive layer. The conductive layer of the flexible circuit board is connected with the substrate in a conductive mode. The contact assembly has an electrically conductive connecting element which is arranged on an electrically conductive layer of the flexible circuit board such that the connecting element and the substrate enclose the flexible circuit board between the connecting element and the substrate. The connecting element is soldered to the electrically conductive layer of the flexible circuit board and to the substrate in such a way that a soldered connection extends from the connecting element, in particular in such a way as to extend transversely to the plane of the flexible circuit board, through the electrically conductive layer of the flexible circuit board until into the substrate.

Description

Technical Field

[0001] The invention relates to a contact assembly. The contact assembly has at least one electrically conductive substrate, in particular a circuit carrier. The contact assembly also has a circuit board, in particular a flexible circuit board, wherein the flexible circuit board has at least one electrically insulating film, in particular a reversibly bendable film, and at least one or only one electrically conductive layer. The electrically conductive layer of the flexible circuit board is electrically conductively connected to the substrate, in particular in a manner that it lies flat on the substrate. Background Art

[0002] Patent document DE 10 2019 128 634 B3 discloses a connected self-supporting conductor connection between two connection locations, wherein in a connecting step a material connection of the self-supporting conductor to the connection surface is produced at each connection location and the conductor forms a connection ring between the two connection locations. Summary of the invention

[0003] According to the invention, the contact assembly has an electrically conductive connecting element, which is arranged on the conductive layer of the flexible printed circuit board, so that the connecting element and the substrate surround the flexible printed circuit board between the connecting element and the substrate. The connecting element is soldered to the conductive layer of the flexible printed circuit board and to the substrate, so that the soldered connection extends from the connecting element, in particular in a manner extending transversely to the plane of the flexible printed circuit board, through the conductive layer of the flexible printed circuit board until it enters the substrate. Advantageously, a low-resistance and in particular solder-free electrical connection can be formed between the flexible printed circuit board and the substrate, in particular a circuit carrier, such as a DCB substrate (DCB=Direct-Copper-Bonded) or an AMB substrate (AMB=Active-Metal-Brazed).

[0004] It has been recognized that the connecting element can reinforce the conductive layer of the flexible printed circuit board so that the conductive layer of the flexible printed circuit board is advantageously not burned off during laser welding.

[0005] The flexible printed circuit board is preferably configured to bend transversely to its plane without breaking. Preferably, the flexible printed circuit board has a polyimide layer, a polyamide layer, a PET layer (PET=Poly-Ethylen-Terephtalat, polyethylene terephthalate), a PVB layer (Poly-Vinyl-Butyral, polyvinyl butyral), a PVF layer (PVF=Poly-Vinyl-Fluorid, polyvinyl fluoride) or an EVA layer (EVA=Ethylen-Vinyl-Acetat, ethylene vinyl acetate) as an electrical insulating layer or an electrical insulating film. The conductive layer of the flexible printed circuit board is preferably a copper layer or a metal layer made of a copper alloy.

[0006] Preferably, the connecting element is designed to at least partially absorb the heat generated during soldering. Advantageously, the connecting element can form both a heat reservoir for excess process heat during soldering and a material supply source that can advantageously reinforce the conductive layer in the region of the soldered connection during soldering of the flexible circuit board to the substrate.

[0007] In a preferred embodiment of the contact arrangement, the soldered connection is a laser soldered connection. Advantageously, the circuit carrier, in particular a ceramic circuit carrier, can be soldered to the flexible circuit board only from one side.

[0008] In another embodiment, the substrate is formed by a stamped grid, in particular a metal sheet or a lead frame. In this embodiment, the welded connection is, for example, a resistance spot welded connection. Advantageously, additional welding material can be formed during resistance welding by means of the connecting element to form an electrical contact bridge between the flexible circuit board and the substrate.

[0009] In a preferred embodiment, the connecting element has a surface extension which extends radially outwards in particular in the plane of the flexible printed circuit beyond the spatial extension of the solder connection, wherein the connecting element covers the flexible printed circuit outside the solder connection. Advantageously, a mechanical reinforcement structure and a form-fitting retaining feature, in particular a collar, can be formed around the solder connection, wherein the collar can mechanically retain and stabilize the flexible printed circuit in the region of the solder connection.

[0010] In a preferred embodiment of the contact assembly, the solder connection is formed by a solder groove extending in a plane, in particular longitudinally, in the plane of the substrate. The solder groove extends in the connecting element, the flexible printed circuit board and the substrate. Preferably, the solder groove is configured to completely penetrate the connecting element, the flexible printed circuit board, in particular completely penetrate at least one conductive layer of the flexible printed circuit board. Advantageously, an electrically conductive material connection can be formed between the joining parts.

[0011] In a preferred embodiment, the solder connection is formed only partially along the extended thickness of the substrate, in particular the conductive layer of the substrate, in particular the redistribution layer. Advantageously, the conductive layer of the substrate, in particular the ceramic substrate, is thus not mechanically deformed by heat input.

[0012] In a preferred embodiment of the contact assembly, the substrate has at least one electrically insulating ceramic layer and at least one conductive layer. The substrate is, for example, a DCB substrate (DCB = Direct-Copper-Bonded), an AMB substrate (AMB = Active-Metal-Brazed), an IMS substrate (IMS = Insulated-Metal-Substrate), an LTCC substrate (LTCC = Low-Temperature-Cofired-Ceramic) or a HTCC substrate (HTCC = High-Temperature-Cofired-Ceramic).

[0013] Advantageously, the flexible printed circuit board can thus be connected to, in particular, a ceramic substrate without solder. Advantageously, the flexible printed circuit board is also protected from accidental tearing by the connecting element, insofar as the connecting element forms a collar protruding laterally beyond the solder connection, which collar is configured to hold and / or press the flexible printed circuit board onto the substrate.

[0014] In a preferred embodiment, the extension thickness of the connecting element is greater than the extension thickness of the conductive layer of the flexible printed circuit board. Advantageously, an additional material portion and a mechanical collar for fixing the flexible printed circuit board on the substrate can thus be formed during soldering.

[0015] In a preferred embodiment, the welded connection, in particular the weld groove, has an extension width which is the same as the extension thickness of the connection element. For example, the extension width of the weld groove is between 100 and 300 microns, preferably between 180 and 220 microns, or 200 microns. An exemplary thickness of the connection element is between 150 and 250 microns, preferably between 180 and 220 microns. Thus, a stable and well-conducting welded connection can be advantageously formed.

[0016] In a preferred embodiment of the contact assembly, the connecting element is a longitudinal section of a connecting tape, more preferably made of copper or a copper alloy. Advantageously, the connecting element can be applied to the flexible circuit board in a cost-effective manner by means of the connecting device. More advantageously, the connecting element can be unwound from a supply of connecting tape, in particular a connecting tape roll, and the longitudinal section can be soldered to the circuit carrier and cut off.

[0017] In a preferred embodiment, the connecting element is a metal plate. Advantageously, the connecting element can thus be placed in the region of the electrical connection point on the circuit carrier, in particular the flexible printed circuit board, by vacuum assembly, in particular by an automatic assembly machine. The metal plate is, for example, designed to be self-adhesive and has adhesive at least on the side facing the flexible printed circuit board or only on partial surface areas that are not to be soldered.

[0018] For example, the connecting element, in particular a metal plate, for example a copper plate, can be placed on the circuit carrier by an automatic assembly machine, which is configured to hold the metal plate by vacuum force, place the metal plate on the circuit carrier and press it onto the circuit carrier, in particular a flexible printed circuit board, and during the pressing process, a laser beam is directed in the region of the pressing element onto the metal plate and the metal plate is welded together with the flexible printed circuit board and the substrate. Advantageously, welding can thus be integrated into the automatic assembly process when assembling the circuit carrier.

[0019] Advantageously, a materially connected three-layer composite can thus be produced from the above-described joining element.

[0020] The invention also relates to a contact system having at least one contact assembly according to the type described above. The contact assembly has at least one further substrate, wherein the substrate and the further substrate are electrically conductively connected to each other via a flexible printed circuit board. Preferably, the electrical connection of the flexible printed circuit board to the substrate is produced by a connecting element arranged on the flexible printed circuit board and a materially connected solder connection extending through the connecting element and the flexible printed circuit board until it enters the substrate. Advantageously, different substrates, in particular circuit carriers, can thus be electrically connected to each other in a cost-effective manner via the flexible printed circuit board.

[0021] In a preferred embodiment, the flexible printed circuit board has a plug for electrically connecting the substrate. The plug can be connected to the flexible printed circuit board in addition to the already mentioned further substrate or instead of the further substrate. Advantageously, the electrical connection of the substrate, in particular the ceramic circuit carrier, to the plug connector can thus be produced in a cost-effective, process-reliable and permanently durable manner.

[0022] In a preferred embodiment, the flexible printed circuit board can be designed as an additionally arranged redistribution layer on the circuit carrier, on which electronic components, such as sensors, can be arranged. Advantageously, the flexible printed circuit board can be soldered to the circuit carrier without solder, so that the layer assembly comprising the circuit carrier and the flexible printed circuit board can be inserted into a soldering furnace for reflow soldering of electronic components onto the layer assembly without the layer assembly produced without solder being melted again.

[0023] The invention also relates to a method for materially connecting a flexible printed circuit board and a substrate, wherein a surface area of ​​the flexible printed circuit board is connected to the substrate in an electrically conductive and materially connected manner.

[0024] Preferably, a planar connecting element is placed on a surface area of ​​the flexible printed circuit board, and the resulting three-layer assembly comprising substrate, flexible printed circuit board and planar connecting element is welded by a laser beam into a three-layer composite, wherein the joining parts are preferably materially connected to each other in a superimposed manner.

[0025] Preferably, the three-layer composite is welded by a laser beam from one side of the connecting element. Advantageously, a durable, low-resistance electrical connection can thus be produced between the flexible printed circuit board and the substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The invention is explained below with reference to the drawings and further exemplary embodiments. Further advantageous variants result from the combination of the features described in the dependent claims and the drawings.

[0027] Figure 1 A welding device and a method for welding a flexible printed circuit board and a circuit carrier are shown, wherein a connecting element formed by a longitudinal section of a connecting tape is arranged on the flexible printed circuit board, and the connecting element is welded together with the flexible printed circuit board and the circuit carrier by a laser beam, and after welding, the longitudinal section of the connecting tape is cut off from the remaining connecting tape;

[0028] Figure 2 Shows the use of Figure 1 An embodiment of an electric contact arrangement structure produced by the welding device and method shown;

[0029] Figure 3 Shows Figure 1 A variant of the method is shown in which a metal plate is placed on a flexible printed circuit board and is soldered to the flexible printed circuit board and the circuit carrier to form a three-layer connection structure. DETAILED DESCRIPTION

[0030] Figure 1 An exemplary embodiment of a method 1 for producing a connection assembly by means of a soldering device 9 is schematically shown. The connection assembly comprises a circuit carrier 2, a flexible printed circuit board 3 and an electrically conductive connection element 6. In this exemplary embodiment, the connection element 6 is formed by a longitudinal strip section of a connection strip 7.

[0031] In the method, a welding device 9 with a hold-down holder 10 and a laser 12 designed to generate a laser beam 11 are placed on a three-layer assembly comprising a circuit carrier 2, a flexible printed circuit board 3 and a connecting element 6 formed by a longitudinal section of a connecting strip. The hold-down holder 10 is designed to press onto the connecting element 6 transversely to the planar extension 40 of the circuit carrier 2 and the connecting element is pressed against the flexible printed circuit board 3 and thus also against the base formed by the circuit carrier 2. The hold-down holder 10 is shown in a holding position 10' supported on the connecting element 6.

[0032] The flexible printed circuit board 3 has an electrically insulating film 5 and an electrically conductive layer 4, in particular a copper layer, extending in the plane of the flexible film. The laser beam 11 connects the connecting strip longitudinal section 6, the electrically conductive layer 4 and the electrically conductive redistribution layer 17 of the circuit carrier 2 to each other in a form-fitting manner, in particular solders them.

[0033] For this purpose, the region of the connecting element 6 formed by the connecting strip longitudinal section and swept by the laser beam 11 can be vaporized and / or melted by the laser beam 11, wherein metal regions arranged adjacently within the scope of the vaporization zone can melt into the vaporization zone and thus can form a molten metal furnace generated in the region of the laser beam 11. The region of liquefied metal extends through the connecting element 6, in particular the connecting strip section, and further through the conductive layer 4 and further to the conductive layer 17, in particular the redistribution layer of the circuit carrier 2. Thus, the melt zone formed in the depth of the layers formed by the connecting strip section 6, the conductive layer 4 and the circuit carrier 2 lying on top of each other can produce a form-fitting solder connection between the conductive layer of the flexible printed circuit 3 and the circuit carrier 2, in particular the conductive layer 17, after solidification.

[0034] The solder connection 8 formed along the extension width 15 in the planar extension 40 of the circuit carrier 2 therefore has a smaller extension width than the extension width 14 of the connecting element 6 which, in this exemplary embodiment, is separated from the connecting strip 7 by the cutter 13 moved by the cutting device 45 after the production of the solder connection 8. In this example, the cutting device 45 is a component of the soldering device and is arranged and designed to move the cutter 13 back and forth and to separate the connecting strip longitudinal sections of the connecting strip 7 extending along the extension width 14 from the connecting strip 7 and thus to produce individual connecting elements 6.

[0035] In this way, a ring 19 constructed around the soldering connection 8 can be formed, which covers the flexible circuit board 3, in particular the conductive layer 4 around the soldering connection 8, and in this embodiment also covers the area of ​​the electrically insulating layer 5, in particular in the manner of a nail head or rivet head, and can thus be tensioned between the circuit carrier 2 and the connecting element 6.

[0036] In this embodiment, the extension width 14 of the connecting element 6 is designed to be greater than the extension width 16 of the conductive layer 4 formed in the flexible circuit board 3. With the extension width 14 of the connecting element 6, the surface area on the flexible circuit board 3 corresponding to the extension width 14 is also covered by the connecting element 6, and the surface area extends radially outward beyond the solder connection 8. In this way, a kind of collar is formed, which can press and fix the flexible circuit board soldered to the circuit carrier on the circuit carrier.

[0037] The flexible printed circuit board 3 has a polyimide film, a polyamide film, a polyester film layer, in particular a polyethylene terephthalate layer or an elastomer layer as the electrically insulating material 5 .

[0038] The flexible printed circuit board is designed to be flexible so that it can be bent back and forth transversely to the plane extension of the flexible printed circuit board without breaking.

[0039] Figure 2 Schematically shows the Figure 1 The connection assembly 20 produced by the method 1 shown in the figure includes a substrate 2, which in this embodiment is a ceramic circuit carrier and includes Figure 1 The circuit carrier 2 also includes an electrically insulating ceramic layer 18 and an electrically conductive redistribution layer 17, in particular a copper layer. In addition to the redistribution layer 17, the circuit carrier 2 also includes an electrically conductive backing layer 46, which together with the electrically conductive redistribution layer 17 surrounds the electrically insulating layer 18 between the backing layer and the redistribution layer. The connection assembly 20 also includes a flexible printed circuit board 3 and a connection element 6.

[0040] In the connection assembly 20, the three layers of the three-layer composite formed by the circuit carrier 2, the flexible printed circuit board 3 and the connection element 6 are placed one on top of the other, wherein the materially connected solder connection 8 connects the three connection parts (i.e. the connection element 6, the flexible printed circuit board 3, in particular the conductive layer 4 of the flexible printed circuit board 3 and the circuit carrier 2, in particular the conductive layer 17 of the circuit carrier 2) to one another in a materially connected manner and penetrates the three connection parts at least partially or completely transversely to the plane extension 40 of the circuit carrier 2. In this embodiment, the solder connection 8 extends through the circuit carrier 2 to a depth that is smaller than the extension thickness 41 of the circuit carrier 2 and to a depth that is smaller than the extension thickness 42 of the conductive layer 17, in particular the redistribution layer.

[0041] The extended thickness 44 of the connecting element 6 is designed to be greater than the extended thickness 43 of the conductive layer 4 of the flexible circuit board 3 or the flexible circuit board itself. The extended thickness of the conductive layer 4 can be equal to the extended thickness of the electrical insulation layer 5. Thus, the flexible circuit board 3 can have an isotropic thickness.

[0042] As an alternative to a ceramic circuit carrier 2 , the connecting component 20 can, in another embodiment, have a stamped metal sheet (also called a stamped grid or lead frame) as a substrate.

[0043] Figure 3 An exemplary embodiment of a connecting method 21 for materially and electrically conductively connecting a circuit carrier 31 to a flexible printed circuit board 30 is schematically shown.

[0044] exist Figure 3 In the joining method shown, the laser welding device 22 has a laser 23 for generating a laser beam 24 and a hold-down member formed by a tube 25, wherein the laser 23 is arranged and constructed to emit the laser beam 24 through a cylindrical cavity 26 surrounded by the tube 25 and along the longitudinal extension of the cavity 26.

[0045] The tube 25 has an end face 37 which is configured to be placed on a connecting element 29 which in this embodiment is formed by a metal plate, a stamped grid or a lead frame or a metal sheet so as to transport the connecting element to a welding position on the circuit carrier 31 and to evacuate the cavity 26 adjacent to the connecting element 29 by means of a vacuum pump 28 so that the connecting element 29 can be sucked against the end face 37 of the tube 25.

[0046] The suction channel 27 connects the cavity 26 to the vacuum pump 28. The laser welding device 22 can be a component of the production device and can be moved upward or downward at least transversely to the planar extension 40 of the circuit carrier 31, as indicated by the arrow 38. In this way, the laser welding device 22 can, after suctioning the connecting element 29 formed by the metal sheet, place the connecting element 29 in the direction 39 of the circuit carrier 31 on the flexible printed circuit board 30 lying on the circuit carrier 31 and press it there by the laser welding device 22.

[0047] The laser welding device 22 may be designed to press the tube 25 , in particular the end face 37 of the tube 25 , against the connecting element 29 , so that the flexible printed circuit board 30 is firmly clamped between the connecting element 29 and the circuit carrier 31 in the region of the end face 37 .

[0048] A solder connection 36 can then be produced by the laser beam 24 , which fuses the connecting element 29 , the flexible printed circuit board 30 and the electrically conductive layer 33 of the circuit carrier 31 to one another and can thus connect them to one another in a materially bonded manner.

[0049] After the welded connection 36 has cooled and solidified, the manufacturing device 22 can switch off the vacuum pump 28 , so that the connecting element 29 is released after the tube 25 has been lifted from the connecting element 29 .

[0050] In this exemplary embodiment, the circuit carrier 31 comprises an electrically insulating layer 32 , in particular a ceramic layer, which is enclosed, in particular in the manner of a sandwich, between an electrically conductive layer 33 and a further electrically conductive backing layer 34 .

[0051] In this embodiment, the flexible printed circuit 30 has, for example, a plug 35, so that the electrical or electronic circuit arrangement structure formed on the circuit carrier 31 can be electrically connected to other external electronic components through the plug 35. Instead of the plug, the flexible printed circuit 30 can be plug-connected, welded, or soldered to another circuit carrier.

Claims

1. A contact assembly (20) comprising at least one electrically conductive substrate (2, 31) and in particular a flexible printed circuit board (3, 30), wherein: The flexible printed circuit board (3, 30) comprises at least one, in particular reversibly bendable, electrically insulating film (5) and at least one or only one conductive layer (4), wherein the conductive layer of the flexible printed circuit board (3, 30) is conductively connected to the substrate (2, 31), in particular in a manner of lying flat on the substrate, It is characterized in that The contact assembly comprises an electrically conductive connecting element (6, 29), which is arranged on the electrically conductive layer of the flexible printed circuit (3, 30), so that the connecting element and the substrate (2, 31) surround the flexible printed circuit (3, 30) between the connecting element and the substrate, wherein the connecting element (6, 29) is soldered to the electrically conductive layer of the flexible printed circuit (3, 30) and to the substrate (2, 31) in such a way that a soldered connection (8, 36) extends from the connecting element (6, 29), in particular in a manner extending transversely to the plane of the flexible printed circuit (3, 30), through the electrically conductive layer (4) of the flexible printed circuit (3, 30) until entering the substrate (2, 31).

2. The contact assembly (20) according to claim 1, It is characterized in that The welded connection (8, 36) is a laser welded connection.

3. The contact assembly (20) according to claim 1 or 2, It is characterized in that The connecting element (6, 29) extends from the solder connection (8, 36) in a radially outward manner covering the flexible printed circuit board (3, 30).

4. The contact assembly (20) according to any one of the preceding claims, It is characterized in that The solder connection (8, 36) is formed by a solder groove extending in a plane along the substrate plane (40), in particular extending longitudinally, the solder groove extending in the connecting element (6, 29), the flexible printed circuit board (3, 30) and the substrate (2, 31), wherein the solder groove is configured to completely penetrate the connecting element (6, 29) and the flexible printed circuit board (3, 30), in particular at least completely penetrate the conductive layer (4).

5. The contact assembly (20) according to any one of the preceding claims, It is characterized in that The solder connection (8, 36) is formed only partially along an extended thickness (41) of the base plate (2, 31).

6. The contact assembly (20) according to any one of the preceding claims, It is characterized in that The substrate has at least one electrically insulating ceramic layer and at least one conductive layer.

7. The contact assembly (20) according to any one of the preceding claims, It is characterized in that The extended thickness (44) of the connecting element (6) is greater than the extended thickness (43) of the conductive layer (17) of the flexible circuit board (3, 30).

8. The contact assembly (20) according to any one of the preceding claims, It is characterized in that The welding groove has an extension width (15) which is the same as the extension thickness (44) of the connecting element (6).

9. The contact assembly (20) according to any one of the preceding claims, It is characterized in that The connecting element (6) is formed by connecting strip longitudinal sections (7, 14).

10. The contact assembly (20) according to any one of the preceding claims, It is characterized in that The connecting element (29) is a metal plate.

11. A contact system having at least one contact assembly (20) according to any one of the preceding claims, in, The contact assembly comprises at least one other substrate, and the substrate (2, 31) and the other substrate are conductively connected to each other via the flexible printed circuit (3, 30). It is characterized in that The electrical connection point between the flexible printed circuit board (3, 30) and the substrate (2, 31) is produced by a connecting element (6, 29) arranged on the flexible printed circuit board (3, 30) and a materially connected solder connection (8, 36) penetrating the connecting element (6, 29) and the flexible printed circuit board (3, 30) and extending into the substrate (2, 31).

12. A contact system having at least one contact assembly according to any one of the preceding claims, It is characterized in that The flexible printed circuit board (3, 30) has a plug (35) for electrically connecting to the substrate (2, 31).

13. A method for materially connecting a flexible printed circuit board (3, 30) and a substrate (2, 31), wherein a surface area of ​​the flexible printed circuit board (3, 30) is connected to the substrate (2, 31) in an electrically conductive and materially connected manner, It is characterized in that A planar connecting element (6, 29) is placed on a surface area (14) of the flexible printed circuit board (3, 30), and the resulting three-layer assembly is welded by means of a laser beam (11, 24) to form a three-layer composite.

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