Electrical connection assemblies and methods having a cyanoacrylate adhesive layer between soldered conductors

Abstract

The invention relates to an electrical connection assembly (2), in particular for power electronics (1) of an electrically driven vehicle, and to a method for producing such a connection assembly. Two conductors (4, 6) are connected to one another by means of a solder joint (18). A layer (12) which consists of or comprises a cyanoacrylate adhesive (14) is located between the two conductors (4, 6). The solder joint (18) is preferably located in a region (16). In addition, at least one layer (20) of a material (22) which prevents or impedes the hardening of the cyanoacrylate adhesive (14) can be present in the region (16). The thickness (12) of the material is preferably a maximum of twice the surface roughness (R) of the surface (28). In order to achieve a predetermined surface roughness R, the region (16) can be provided at least in sections with a roughening (24).

Description

TECHNICAL FIELD

[0001] The invention relates to an electrical connection assembly, wherein the connection assembly has at least two conductors which are welded to one another. Furthermore, the invention relates to a method for welding at least two conductors. Finally, the invention relates to a power electronics device having such an electrical connection assembly, in particular for an electrically driven vehicle. BACKGROUND

[0002] In the welding of a ribbon cable to a battery contact in an electrically driven vehicle, it is important to protect the conductors welded to one another from electrochemical corrosion. Furthermore, it is advantageous for the welding point to have a tension relief. SUMMARY

[0003] The invention therefore sets itself the object of providing such a connection of two conductors which, in addition to corrosion prevention and tension relief, also makes the method process simple and reduces costs.

[0004] According to the invention, the initially mentioned electrical connection assembly solves this problem, since at least one layer of cyanoacrylate adhesive is located in at least one region between the conductors.

[0005] According to the invention, the initially mentioned method solves this problem by coating at least one conductor with cyanoacrylate adhesive in at least one portion of the region to be welded, and by welding the at least two conductors to one another after the coating.

[0006] The electrical connection assembly can be part of a power electronics device for an electrically driven vehicle, wherein one of the conductors can be connected to a battery, and one of the conductors can be a ribbon cable.

[0007] The solution according to the invention is easy to manufacture and inexpensive. Cyanoacrylate adhesives are household adhesives, are easy to obtain, simple to handle and inexpensive to purchase. According to the invention, they simultaneously fulfil the functions of corrosion prevention and tension relief.

[0008] In the following, the features of the invention and their respective associated technical effects will be further described. The individual features are advantageous in themselves and can be combined with one another as desired.

[0009] It is therefore particularly advantageous if the thickness of the at least one layer at least partially corresponds to a maximum of twice the surface roughness of the surface in the at least one region coated with cyanoacrylate glue. The thickness preferably corresponds to the surface roughness of the at least one layer, with a deviation of plus or minus one third still being considered as corresponding to be appropriate. Ideally, the cyanoacrylate glue of the at least one layer can only fill the surface roughness without covering the end of the surface roughness. Thus, at the end of the film of roughness, the thickness of the layer can tend towards zero. Such a thin layer thickness makes it possible to still be able to solder the two conductors to each other despite the arrangement of a glue layer between the two conductors.

[0010] The surface roughness is preferably determined in accordance with ISO 25178 and / or DIN 4760. The surface roughness can be the average roughness, the secondary roughness, the average roughness depth or the maximum roughness depth in the region.

[0011] In a further advantageous configuration, the region provided with cyanoacrylate glue has at least partially a different surface roughness compared to the region not coated with cyanoacrylate glue. The surface roughness of the region coated with cyanoacrylate glue can be greater or less than the surface roughness of at least a portion of the region not coated. In order to obtain a different surface roughness, the surface can be subsequently treated, in particular in the region coated with cyanoacrylate glue, for example roughened or polished or smoothed.

[0012] In order to obtain a predetermined surface roughness by means of a uniform layer thickness within a narrow tolerance range and thus reproducible results, it is advantageous if at least one of the faces of the conductors pointing towards each other is at least partially roughened or polished or smoothed. Preferably, the roughened or polished region is at least partially provided with a cyanoacrylate glue layer.

[0013] The roughening can be carried out by, for example, sandblasting, mechanical processing, grinding, laser structuring and / or embossing. Of course, the cyanoacrylate glue can be arranged not only on one conductor, but also on the opposite faces of the two conductors soldered to each other.

[0014] In order to keep production costs low, at least one of the at least two conductors can be made of a sheet-like metal material at least in the at least one region. The conductors can alternatively or cumulatively be configured as disc-shaped or plate-shaped at least in the region.

[0015] In the electrical connection assembly, they are preferably stacked on top of each other over a large surface in the at least one region, so that there is a low contact resistance and the transmission of large currents does not generate too much heat.

[0016] According to another advantageous configuration, at least one conductor, preferably both conductors, can at least in at least one region be made of a material containing aluminum, including aluminum itself. Since aluminum has a low electrical resistance value, a large current can be conducted with small losses when this material is chosen.

[0017] Another advantageous configuration envisages a material which prevents or hinders the hardening of the cyanoacrylate glue at least in a sub-portion of the region. It is known that cyanoacrylate glue does not harden or hardens slowly if it is not exposed to moisture or is located in an acidic environment. The material which prevents or hinders the hardening of the cyanoacrylate glue is therefore, for example, a moisture-absorbing material, a moisture- and / or acid-resistant substance. The hydrophilic or hydrophobic layer can be produced, for example, by the pyrophosphoric acid method. The inhibition of the hardening can be carried out, for example, by using an acid together with a solvent (for example formic acid, acetone). The material which prevents or hinders the hardening of the cyanoacrylate glue can be present in the form of a layer. The layer can be located between the cyanoacrylate glue layer and the conductor and / or between two cyanoacrylate glue layers.

[0018] Alternatively, according to another advantageous configuration, an acid, in particular an organic acid, can be dispersed in the material of the insulating layer of the conductor. The dispersed acid can prevent the hardening of the cyanoacrylate glue. In this case, the cyanoacrylate glue can be subsequently hardened by exposing it to an activator (for example an alkaline environment).

[0019] In particular, at least one sub-region, or the material which prevents or hinders the hardening of the cyanoacrylate glue, is located in the vicinity of at least one soldering point at which the at least two conductors are soldered to one another. In particular, the soldering point can be at least partially, preferably completely, surrounded by the region and / or the sub-portion in which the material which prevents or hinders the hardening of the cyanoacrylate glue is located.

[0020] The material which prevents or hinders the hardening of the cyanoacrylate can be arranged, for example applied, at the soldering point at a later point in time before the soldering. After the soldering, the soldering point is located here. However, residues of the material which prevents or hinders the hardening of the cyanoacrylate glue can still be located in the vicinity of the soldering point, in particular directly in the vicinity.

[0021] The material which prevents or hinders the hardening of the cyanoacrylate glue can be applied before or after the cyanoacrylate glue is applied. The material can be located on the same conductor as the cyanoacrylate glue, or applied on this conductor, or on the conductor opposite the cyanoacrylate glue layer.

[0022] The two conductors are preferably in contact with one another at least at points outside the soldering point. This is in particular the case when the cyanoacrylate glue layer is too thin for the tips of the surface roughness of the two conductors to still be in electrical contact with one another. BRIEF DESCRIPTION OF DRAWINGS

[0023] In the following, the application is explained in more detail with reference to the drawings using exemplary embodiments. For the sake of simplicity, the same reference signs are used in the drawings for elements corresponding to each other in terms of function and / or design.

[0024] The combination of features depicted and described using exemplary embodiments is only by way of example. It can be changed in accordance with the above-described embodiments. For example, features whose technical effect is not important in a particular application can be omitted. Conversely, features not present in the shown combination of features of exemplary embodiments can be added if a particular application requires or benefits from the technical effect associated with the feature.

[0025] In the drawings:

[0026] Figure 1 A schematic view of a part of a power electronics device with an electrical connection assembly is shown, in particular for an electric vehicle;

[0027] Figure 2 A schematic view of an electrical connection assembly is shown;

[0028] Figure 3 A schematic view of Figure 2 detail III is shown;

[0029] Figure 4 A schematic view of Figure 2 detail IV is shown;

[0030] Figure 5 A schematic view of a sequence of methods for manufacturing an electrical connection assembly is shown. DETAILED DESCRIPTION

[0031] Figure 1 A part of a power electronics device 1 is shown, here only schematically, for example for an electric vehicle. The power electronics device has an electrical connection assembly 2. The electrical connection assembly 2 comprises at least two conductors 4, 6 which are welded to each other. In addition, the electrical connection assembly 2 can have further conductors 4a, 6a which are only indicated in Figure 1 dashed lines in . One of the conductors, in this case the conductor 4, can be part of a ribbon cable 8. The other conductor, in this case the conductor 6, can be connected to a battery 10.

[0032] At least one of the conductors 4, 6 can be made of an aluminum-containing material in order to keep the electrical resistance low. At least one of the conductors 4, 6 can be made of a sheet metal material and can in particular be configured as a disc or a plate.

[0033] The two conductors 4 and 6 are placed as planar as possible to each other. At least one layer 12 consisting of or containing cyanoacrylate adhesive 14 is located between them. The area 16 in which the cyanoacrylate adhesive 14 is located at least partially surrounds the solder joint 18, at which at least two conductors 4 and 6 are materially connected to each other.

[0034] Figure 2 The electrical connection assembly 2 is shown in larger detail in the illustration. It can be seen that at least one layer 20, comprising or consisting of a material that prevents or inhibits the curing of the cyanoacrylate adhesive 14, may be present near or adjacent to the solder joint 18. The material 22 that prevents or inhibits the curing of the cyanoacrylate adhesive may, for example, be a hygroscopic material and / or an acidic substance. The layer 20 comprising or including the material 22 may be arranged between the layer 12 of the cyanoacrylate adhesive 14 and the conductors 4, 6, or between two opposing layers 12 of the cyanoacrylate adhesive 14. The material layer 22 that prevents or inhibits the curing of the cyanoacrylate adhesive 14 may be present on one or both conductors 4, 6. The material 22 may be integrated into the electrical insulation of the conductors 4, 6, such as a ribbon cable, through which the material is released during soldering.

[0035] Layer 12 and / or layer 20 were initially present, at least partially, at the point where solder joint 18 was located after conductors 4 and 6 were soldered. Solder joint 18 may have completely replaced (previously) layer 20, meaning that the original layer 20 no longer exists. However, as Figure 2 As shown, there may still be residue of layer 20 between conductors 4 and 6 outside of solder joint 18.

[0036] In the regions 16 of the corresponding conductors 4 and 6 coated with cyanoacrylate adhesive 14, surface 4 can be at least partially roughened, i.e., have a roughness R greater than the remaining unroughened surface portion. Roughening in Figure 2 The figure is indicated by reference numeral 24. Roughening can be performed by embossing, grinding, machining, or sandblasting. Roughening 24 yields a predetermined surface roughness R, which varies only slightly across several different conductors 4, 6. In this case, the surface roughness is preferably measured according to ISO 25178 and / or DIN 4760. The surface roughness can be the average roughness, secondary roughness, average roughness depth, or maximum roughness depth of region 16 or its sub-regions. The surface roughness of a roughened region can be greater than that of a non-roughened region, at least partially surrounding it. If the base material of conductor 4 or 6 already has a very large surface roughness R, surface 4 can also have a lower surface roughness R in region 16, for example, by polishing or smoothing. The polished or smoothed region then corresponds to roughening 24.

[0037] exist Figure 2In detail, only one surface 28 of one conductor 4 is provided with the roughening 24. Of course, both opposite surfaces 26, 28 of the conductors 4, 6 can also be roughened.

[0038] Figure 3 Details III are shown in Figure 2 . In this case, only the conductor 6 is shown for the sake of example only. The description can analogously relate to the conductor 4.

[0039] The surface 28 of the conductor 6 has a surface roughness R. The layer 12 of cyanoacrylate adhesive 14 is located on the surface 28, which has a layer thickness 30. The layer thickness 30 corresponds to a maximum of twice the surface roughness R within a tolerance of ±30% and is preferably at least one time the surface roughness R.

[0040] Preferably, the layer thickness 30 at least approximately corresponds to the surface roughness R, which means that it almost only covers or releases the end of the surface roughness R. Thus, at the end of the surface roughness R, the layer thickness is almost zero in the preferred design. The layer 12 can also be applied without the roughening 24 Figure 2 . However, due to the varying surface roughness, the layer thickness can be subject to greater deviations in certain cases, and the properties of the connection assembly 2 are difficult to reproduce.

[0041] Figure 4 Details IV of the sub-portion 34 Figure 2 are shown, in which the layer 22 of material that prevents or prevents the cyanoacrylate adhesive 14 from hardening is located. The sub-portion 34 is preferably located completely within the region 16. The layer 20 that is composed of or includes the material 22 can be located directly on the conductor 6. However, as indicated by the dashed line, it can also be located on the layer 14 or the conductor 4.

[0042] To manufacture Figures 1 to 4 the electrical connection assembly 2 depicted in Figure 5 , the method steps schematically depicted in are carried out.

[0043] In a first alternative method step 40, at least one of the conductors 4, 6 is roughened to produce a predetermined surface roughness R.

[0044] In step 42, at least one of the conductors 4, 6 is coated with cyanoacrylate adhesive 14. Here, as described above, the layer thickness 30 is a maximum of twice the surface roughness R. If the conductor 4, 6 to which the cyanoacrylate adhesive 14 is applied has previously been roughened, the cyanoacrylate adhesive 14 is applied to the roughened region.

[0045] A further optional step 44 of the method involves applying a layer 20 of a material 22 which prevents or hinders hardening of the cyanoacrylate glue. Step 44 can be performed before or after step 42. The material 22 which prevents or hinders hardening of the cyanoacrylate glue can be applied directly on the conductors 4, 6 or on the layer 12. In this case, the material 22 can be applied to the conductors 4, 6 which are not coated with cyanoacrylate glue 14 as long as the layer 12 is located on the opposite conductors 4, 6. However, in this configuration, the two conductors should be placed directly on top of each other after coating to prevent or hinder hardening of the cyanoacrylate glue 14 in the sub-portion 34.

[0046] In step 46, the conductors 4, 6 are then soldered to each other at at least one soldering point 18. The soldering is preferably performed, inter alia, by means of ultra-short laser pulses. In this case, the soldering points are located in the region in which the layer 12 is located, i.e. in the region 16. In addition, the soldering points 18 are located in the position in which the layer 20 is also located, i.e. in the sub-portion 34 of the region 16.

[0047] In the finally manufactured electrical connection assembly 2, the conductors 4, 6 are electrically connected to each other by means of the soldering points 18. The layer 12 of cyanoacrylate glue 14 represents an additional mechanically loadable connection which can relieve the tension on the soldering points 18. Due to the thin layer thickness 30, the glue can be applied before soldering 18. The layer 12 preferably gas-tightly surrounds the soldering points 18 and thus protects them from electrochemical corrosion. Outside the soldering points 18, the two conductors 4, 6 can directly contact each other at the end of the surface conductor R, thereby further reducing the contact resistance between the conductors 4, 6.

[0048] Reference signs

[0049] 1 power electronics device

[0050] 2 electrical connection assembly

[0051] 4, 4a conductor

[0052] 6, 6a conductor

[0053] 8 ribbon cable

[0054] 10 battery

[0055] 12 layer composed of or comprising cyanoacrylate glue

[0056] 14 cyanoacrylate glue

[0057] 16 region with layer 12

[0058] 18 soldering point

[0059] 20 layer composed of or comprising a material which prevents or hinders hardening of the cyanoacrylate glue

[0060] 22 material that prevents or prevents hardening of the cyanoacrylate glue

[0061] 24 roughening

[0062] 26 surface of one conductor

[0063] 28 surface of the other conductor

[0064] 30 layer thickness of the layer consisting of or comprising cyanoacrylate glue

[0065] 32 double surface roughness R

[0066] 34 sub-portion with layer 20

[0067] 32 surface roughness

Claims

1. An electrical connection assembly (2) having at least two conductors (4, 6) welded together, characterized in that, At least one layer (12) of cyanoacrylate adhesive (14) or comprising cyanoacrylate adhesive is located in at least one region (16) between the two conductors (4, 6), and a material (22) for preventing the hardening of the cyanoacrylate adhesive (14) is located at least in a sub-part (34) of the region (16), the sub-part (34) being located near at least one weld point (18) where the at least two conductors (4, 6) are welded together, wherein the material (22) for preventing the hardening of the cyanoacrylate adhesive is present in the form of a layer or integrated into the electrical insulation of the conductors (4, 6).

2. The electrical connection assembly (2) as claimed in claim 1, characterized in that, The thickness (30) of the at least one layer (12) corresponds at least partially to twice the maximum value of the surface roughness (R) in the at least one region (16).

3. The electrical connection assembly (2) as claimed in claim 1, characterized in that, The thickness (30) of the at least one layer (12) corresponds at least partially to between one and two times the surface roughness (R) in the at least one region (16).

4. The electrical connection assembly (2) as described in any one of claims 1 to 3, characterized in that, At least one of the surfaces (26, 28) of the conductors (4, 6) pointing towards each other is roughened at least partially in at least one region (16).

5. The electrical connection assembly (2) as described in any one of claims 1 to 3, characterized in that, The two conductors (4, 6) are made of sheet metal material in at least one region (16).

6. The electrical connection assembly (2) as claimed in any one of claims 1 to 3, characterized in that, At least one of the conductors (4, 6) is made of an aluminum-containing material in at least one region (16).

7. The electrical connection assembly (2) as claimed in any one of claims 1 to 3, characterized in that, The welding point (18) is at least partially surrounded by the region (16) and / or the sub-part (34).

8. The electrical connection assembly (2) as claimed in any one of claims 1 to 3, characterized in that, The two conductors (4, 6) are in direct contact with each other, at least at points other than the welding point (18).

9. The electrical connection assembly (2) as claimed in any one of claims 1 to 3, characterized in that, One of the two conductors (4, 6) is part of a ribbon cable.

10. A power electronic device (1) for use in an electric vehicle, characterized in that, The electrical connection assembly (2) according to any one of claims 1 to 9, wherein one of the two conductors (4, 6) is connected to the battery (10).

11. A method for welding at least two conductors (4, 6), comprising the following steps: At least one region (16) of at least one conductor (4, 6) is coated with cyanoacrylate adhesive (14). Before or after the coating, material (22) is applied to at least one sub-part of the region (16), the material preventing the hardening of the cyanoacrylate adhesive (14), wherein, The material (22) exists in the form of a layer or is integrated into the electrical insulation of the conductors (4, 6); After the coating and after the application of the material (22), the at least two conductors (4, 6) are welded such that the cyanoacrylate adhesive (14) is located between the two conductors (4, 6).

12. The method of claim 11, further comprising the following step: The area (16) is roughened at least partially after the coating.

13. The method of claim 11 or 12, further comprising the following step: The at least two conductors (4, 6) are welded by laser pulse welding.

14. The method of claim 11 or 12, further comprising the following step: The at least two conductors (4, 6) are welded in a sub-section (34) of the region (16), the sub-section being one coated with the material (22).

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