Method for replacing a defective flexible conductor element

Abstract

The invention relates to a method for replacing a defective flexible conductor element (2) which has a soldered welding pad (3), wherein the welding pad (3) is welded to a component (4) to be electrically contacted, wherein the soldered connection between the welding pad (3) and the flexible conductor element (2) is released, wherein the welded welding pad (3) remains on the component (4), after which a new flexible conductor element (20) with a soldered welding pad (30) is inserted, wherein the new welding pad (30) is electrically connected to the original welding pad (3), and wherein the electrically conductive connection between the original welding pad (3) and the new welding pad (30) is made in a surface area which differs from the surface area in which the original welding pad (3) was soldered to the original flexible conductor element (2), wherein the electrically conductive connection between the welding pads (3,30) is realized by welding, wherein the surface section is a surface section of the original welding pad (3), and wherein the electrically conductive connection between the original welding pad (3) and the new welding pad (30) is located on the opposite side of the originally soldered surface section of the original welding pad (3).

Description

[0001] The invention relates to a method for replacing a defective flexible conductor element, which has at least one soldered welding pad, according to the type defined in more detail in the preamble of claim 1.

[0002] The use of so-called flexible conductor elements, also known as flex films or flexible printed circuits (FPCs), is known from the prior art. There are various methods for electrically contacting such flexible conductor elements. For example, DE 10 2010 039 189 A1 describes a very complex arrangement for contacting flex films, in which electrical contact is achieved via heat input. DE 11 2020 003 216 T5, on the other hand, deals with strain relief for a flex film.

[0003] German patent DE 103 04 634 A1 describes a method for repairing flexible circuits. In this process, defective areas are separated before a repair element is soldered between additional solder points of the flexible circuit.

[0004] Furthermore, DE 10 2021 209 324 A1 describes a battery module with a plurality of battery cells arranged in parallel to each other. A flexible printed circuit board is provided within the module, which is arranged on two different longitudinal sides of the battery module.

[0005] A common use for such flexible conductor elements is, for example, their use within larger batteries or battery modules to tap the voltages of the individual battery cells, which are measured for battery management.

[0006] The flexible conductor elements typically have a very thin overall thickness of less than 0.5 mm, especially in the range of 0.2 to 0.3 mm. They consist of a base film and printed conductive traces made of copper or aluminum, which are typically less than 50 µm thick. These are covered by a top film. In practice, particularly during handling and battery production, the flexible conductive traces, which are very susceptible to cracking due to their thin material, are occasionally damaged. This represents a significant disadvantage.

[0007] Especially for the aforementioned application in battery modules, it is typically the case that the flexible conductor tracks have soldered welding pads, which are then welded to the corresponding component, for example, to the cell connectors when individual voltages are tapped. If the flexible conductor element is damaged during assembly or operation, then in the worst case the entire battery or battery module is defective and must be scrapped.

[0008] There is therefore an urgent need for a repair solution to reduce the amount of scrap and the associated disadvantages in terms of costs and environmental impact. Accordingly, the object of the present invention is to provide such a method and a suitable electrical contacting element for this purpose.

[0009] According to the invention, this problem is solved by a method with the features in claim 1, and in particular in the characterizing part of claim 1. Advantageous embodiments and further developments are described in the dependent claims.

[0010] The repair method according to the invention aims to replace a defective flexible conductor element that has been damaged, for example, during the production or handling of a component equipped with it, such as a battery module for the at least partial electric drive of a motor vehicle. The method according to the invention requires a flexible conductor element with soldered welding pads, wherein the welding pads are welded to the components to be contacted. To replace the flexible conductor element, the soldered connection between the welding pad and the flexible conductor element is then broken according to the invention.

[0011] The welded pad remains securely welded and connected to the component. A new flexible conductor element with a soldered-on weld pad is then inserted. The soldered weld pad on the new flexible conductor element can then be easily and efficiently connected to the original weld pad already welded to the component.

[0012] This makes repairs correspondingly simple and efficient, since, for example, under the appropriate environment in a workshop or production facility, the very sensitive flexible conductor element itself does not need to be re-contacted. Instead, only the original welding pad remaining on the component needs to be connected to the welding pad of the new flexible conductor element. The welding pads themselves are very robust compared to the flexible conductor element, so they can be easily connected by welding. According to a particularly advantageous further development, it is also possible to reconnect the new welding pad to the original welding pad using laser welding.

[0013] In the method according to the invention, the electrically conductive connection between the original welding pad and the new welding pad is made in a surface area of ​​the original welding pad that differs from the surface area in which the original welding pad was soldered to the original flexible conductor element. Thus, the original welding pad is not contacted with the new welding pad in the surface area where it was previously soldered to the flexible conductor element. Because the contact is made in a new surface area, cleaning the old surface area to ensure a good electrical connection is unnecessary, which makes the method according to the invention particularly simple and efficient.

[0014] According to the invention, the area to be joined is located on the opposite side of the originally soldered area of ​​the original solder pad. The connection between the original solder pad and the new solder pad is thus made on the opposite side of the previously severed connection between the original solder pad and the defective flexible conductor element. This allows the aforementioned advantages, such as the elimination of cleaning, to be achieved in a very space-saving manner, since no additional surface area is required on one side of the original solder pad, and it can therefore remain very compact in its overall dimensions.

[0015] According to a highly advantageous further development, the soldered connection between the original solder pad and the original, now defective, flexible conductor element can be broken very easily and efficiently by holding the solder pad in its welded position and tearing the flexible conductor element away from the solder pad. Tearing off the damaged flexible conductor element can preferably be done manually. This is very quick and efficient. Furthermore, unlike desoldering, which is also conceivable in principle, it does not subject the component contacted via the solder pad to (renewed) heat.

[0016] A particularly advantageous embodiment of the method according to the invention can provide that a stepped welding pad is used as the original welding pad. Such a stepped welding pad makes it possible to create a construction space extending over a certain extent in one vertical direction, so that the soldered connection to the original flexible conductor element can be made on the underside of the upper level, while the top side of the upper level can then be used for the connection with the new welding pad of the replacement for the new flexible conductor element.

[0017] Accordingly, in a particularly advantageous embodiment of the inventive method, the soldered surface section of the original welding pad can be arranged on a side of the original welding pad facing away from a visible surface, with the electrically conductive connection to the new welding pad being made on the visible surface. Ideally, the welding pad soldered to the original flexible conductor element can be positioned such that, in subsequent use, the soldering is carried out from the visible side underneath the welding pad. Since the soldering takes place outside the actual assembly, for example, the battery module, this is easily achievable. The soldered welding pad then projects beyond the soldered area, ideally with a downward step, so that it can be welded to the component to be contacted, preferably with its lower plane.If the flexible conductor element becomes damaged, it can be easily torn out, even if this leaves behind a surface underneath contaminated with remnants of the conductor element and / or solder. However, the visible surface is still unused and therefore always clean, allowing the new welding pad to be attached, for example, by laser welding. Because this is the visible surface, easy and efficient access to the area used for the connection is also ensured.

[0018] As already mentioned, the method can preferably be used for battery modules, so that, according to a very advantageous further development of the idea, the components to be contacted are tap points for a voltage on individual battery cells of a battery module.

[0019] The new welding pad can be flat, especially if a stepped welding pad is used as the original welding pad, in order to keep the repaired structure compact in height.

[0020] Advantageous embodiments and further developments of the repair method, as well as a suitable electrical contacting element, can also be seen in the exemplary embodiment, which is described in more detail below with reference to the figures.

[0021] This shows: Fig. 1 A three-dimensional view of an electrical contacting element connected to a cell connector of a battery module for tapping a cell voltage; Fig. 2 the structure according to Fig. 1 after the removal of a flexible conductor element of the electrical contacting element; and Fig. 3 the structure according to Fig. 1 and Fig. 2 after successful repair.

[0022] In the presentation of the Fig. Figure 1 shows an electrical contact element 1, which comprises a flexible conductor element 2 (not shown in its entirety) and a welding pad 3. This welding pad 3 is connected to a cell connector 4 of a single battery cell (not shown in its entirety) via an indicated weld 5, in order to tap into the cell voltage. The weld 5 is shown here purely as an example of a double laser weld; of course, other types of welds, such as ultrasonic welding or the like, are also conceivable, which would result in a different appearance or geometry of the weld 5.

[0023] The special feature of the electrical contacting element 1 lies in the fact that the soldered connection, which is known in principle, between the flexible conductor element 2 and the welding pad 3 is realized here on the lower side of the welding pad 3 as shown in the figures. For this purpose, the pad is angled or stepped. It has an upper level 3a and a lower level 3b. These are connected by a section 3c, which, for example, runs vertically. Section 3c could also run diagonally or have a wave-like shape, for example, to provide additional mechanical flexibility to the welding pad. This stepped design of the welding pad 3 allows sufficient installation space to be created below the upper level 3a. The soldered connection to the flexible conductor element 2 is then located in this space.Due to the very small thickness of the flexible conductor element, the step can be much smaller in practice than shown in the figures.

[0024] If a defect occurs, for example a crack in the flexible conductor element 2, it can simply be torn off the welding pad 3, preferably by holding the welding pad 3 in addition to its weld 5, in order to avoid any adverse effect on the weld 5. Essentially, the component that remains in Fig. The assembly shown in Figure 2 remains, in which the welding pad 3 is left without the flexible conductor element 2. Solder and remnants of the flexible conductor element 2 may still be present below the upper level of the welding pad 3; however, this is irrelevant for the repair method described below and offers the crucial advantage that cleaning the area where the solder joint has been detached is unnecessary.

[0025] As the presentation of Fig. As can be seen in Figure 3, a new flexible conductor element, designated here as 20, with a soldered-on welding pad 30 (hereinafter also referred to as the new welding pad 30), can be used to replace the existing flexible conductor element 2. Unlike the construction of the welding pad 3, the construction of the new welding pad is flat. The new flexible conductor element 20 is soldered onto this new welding pad 30 from above. This is a common and therefore readily available construction. This assembly can now be placed with the free underside of the new welding pad 30 onto the upper level 3a of the original welding pad 3. This is shown in the illustration of the Fig.3. Both the underside of the new welding pad 30 and the top surface of the original welding pad 3 in its upper level 3a are in pristine condition and can therefore be positioned flush against each other without the need for extensive cleaning or similar procedures. Subsequently, an electrically conductive connection can be established between the original welding pad 3 and the new welding pad 30, preferably by laser welding, in order to repair the defective electrical contact element 1.

Claims

[1] Method for replacing a defective flexible conductor element (2) having a soldered welding pad (3), wherein the welding pad (3) is welded to an electrically contactable component (4), wherein the soldered connection between the welding pad (3) and the flexible conductor element (2) is removed, the welded welding pad (3) remaining on the component (4), after which a new flexible conductor element (20) with a soldered welding pad (30) is inserted, wherein the new welding pad (30) is electrically connected to the original welding pad (3), and wherein the electrically conductive connection between the original welding pad (3) and the new welding pad (30) is made in a surface area which differs from the surface area in which the original welding pad (3) was soldered to the original flexible conductor element (2), characterized by, that the electrically conductive connection between the welding pads (3, 30) is realized by welding, wherein the surface section is a surface section of the original welding pad (3), and wherein the electrically conductive connection between the original welding pad (3) and the new welding pad (30) is on the opposite side of the originally soldered surface section of the original welding pad (3). [2] Method according to claim 1, characterized by , that the electrically conductive connection between the welding pads (3, 30) is realized by laser welding. [3] Method according to claim 1 or 2, characterized by , that the originally soldered surface section of the original welding pad (3) is arranged on a side of the original welding pad (3) facing away from a visible surface, wherein the electrically conductive connection with the new welding pad (30) is made in a surface section on the visible surface. [4] Method according to any one of claims 1 to 3, characterized by , that a step-shaped welding pad (3) is used as the original welding pad (3). [5] Method according to any one of claims 1 to 4, characterized by , that the components to be contacted (4) represent points of application for a voltage on individual battery cells of a battery module. [6] Method according to any one of claims 1 to 5, characterized by , that the solder joint is released by holding the original welding pad (3) and tearing off the flexible conductor element (2). [7] Method according to any one of claims 1 to 6, characterized by , that a flat welding pad (30) is used as the new welding pad (30).

Images