Method for joining metal plates, method for manufacturing a busbar module, and method for manufacturing a battery module

Abstract

To provide a joining method for metal plate, a manufacturing method for bus bar module and a manufacturing method for battery module that can secure joining force between metal plates.SOLUTION: A joining method for metal plate includes: overlapping at least a part of a first metal plate with at least a part of a second metal plate; and irradiating a joining object region R1 where the first metal plate and the second metal plate overlap with each other with laser light so that irradiation places are arranged discontinuously from an outer peripheral part of the joining object region toward an inner part.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a method for joining metal plates, a method for manufacturing a bus bar module, and a method for manufacturing a battery module.

Background Art

[0002] Conventionally, a bus bar module is used, for example, to be assembled into a battery assembly as a driving power source mounted on an electric vehicle or a hybrid vehicle. The battery assembly is configured by stacking a plurality of battery cells.

[0003] As an example, the bus bar module includes a plurality of bus bars that are stacked and connect the positive electrode and the negative electrode between adjacent battery cells, and voltage detection lines that are connected to each of the plurality of bus bars to monitor the voltage of each battery cell.

[0004] Also known is a battery module in which voltage detection lines connected to each of a plurality of bus bars are arranged on a flexible printed circuit board (FPC) (see, for example, Patent Document 1). In this battery module, the bus bar and the FPC are connected by, for example, a soldering method.

[0005] Since aluminum is easily oxidized and the oxide film repels solder, in order to solder an aluminum bus bar, a tin (Sn) plating treatment is required, which increases the component cost. In addition, since this soldering process is performed in a reflow furnace, the number of processes increases.

[0006] Therefore, it has been proposed to connect the bus bar and the metal plate included in the FPC by laser irradiation. For example, Patent Document 2 discloses a method of connecting an aluminum bus bar and a copper connection plate by laser irradiation. In the method of Patent Document 2, laser light is irradiated in a state where the copper connection plate is pressed against the aluminum bus bar to melt and infiltrate the aluminum material with a low melting point.

Prior Art Documents

Patent Documents

[0007] [Patent Document 1] Japanese Patent Publication No. 2014-220128 [Patent Document 2] Japanese Patent Publication No. 2021-034302 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, in the above-mentioned Patent Document 2, since the laser light is irradiated from the copper material side, the aluminum material becomes more likely to dissolve, and an alloy layer is more likely to form at the joint, raising concerns about a decrease in bonding strength.

[0009] The present invention has been made in view of the above circumstances, and its object is to provide a method for joining metal plates, a method for manufacturing a busbar module, and a method for manufacturing a battery module that can ensure sufficient bonding force between metal plates. [Means for solving the problem]

[0010] To achieve the aforementioned objectives, the metal plate joining method according to the present invention is characterized by the following: At least a portion of the first metal plate and at least a portion of the second metal plate are overlapped. In the joining region of the portion where the first metal plate and the second metal plate are overlapped, laser light is irradiated such that the irradiation points are arranged discontinuously from the outer periphery of the joining region toward the interior. Method of joining metal plates And, With the area to be joined pressed in with a pressing jig, the laser light is irradiated. Joining method .

[0011] Furthermore, in order to achieve the aforementioned objectives, the method for manufacturing a busbar module according to the present invention is characterized by the following: A method for manufacturing a busbar module using the above joining method, The busbar module comprises an aluminum busbar as the first metal plate and a flexible wiring board that is thinner than the busbar as the second metal plate. The area to be joined is the portion where at least a part of the busbar and at least a part of the flexible wiring board overlap. In the area to be joined, the laser light is irradiated such that the irradiation points are arranged discontinuously from the outer periphery to the interior of the area to be joined. method.

[0012] Furthermore, in order to achieve the aforementioned objectives, the method for manufacturing a battery module according to the present invention is characterized by the following: A method for manufacturing a battery module comprising a battery assembly and a busbar module, The busbar module is manufactured by the method described above. The busbar module is assembled to the battery assembly. method. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a method for joining metal plates, a method for manufacturing a busbar module, and a method for manufacturing a battery module, all of which can ensure sufficient bonding strength between metal plates.

[0014] The present invention has been briefly described above. Furthermore, the details of the present invention will be further clarified by referring to the attached drawings and reading through the embodiments for carrying out the invention described below (hereinafter referred to as "embodiments"). [Brief explanation of the drawing]

[0015] [Figure 1] This is a perspective view of a busbar module including a busbar and a circuit body joined by a joining method according to an embodiment of the present invention. [Figure 2] Figure 1 is a perspective view of the battery assembly to which the busbar module is assembled. [Figure 3]It is a side view showing an enlarged view of the joint portion between the bus bar and the circuit body. [Figure 4] It is a partially enlarged view of FIG. 3. [Figure 5] It is a partially enlarged end face view for explaining the anchor effect by laser irradiation on the bus bar and the circuit body. [Figure 6] It is a diagram for explaining the laser irradiation state, where the upper side shows the state of continuous laser light irradiation and the lower side shows the state of intermittent laser light irradiation. [Figure 7] It is a diagram showing the order of movement of the irradiation positions in the joining target area. [Figure 8] It is a diagram showing the state where the periphery of the joining target area is pushed in with a pressing jig. [Figure 9] It is a diagram for explaining the welding portion by laser irradiation.

Mode for Carrying Out the Invention

[0016] Hereinafter, a bus bar module including a bus bar and a circuit body joined by a joining method according to an embodiment of the present invention will be described with reference to the drawings. The bus bar module

[0017] according to the present embodiment is assembled into a battery assembly as a driving power source mounted on, for example, an electric vehicle or a hybrid vehicle to constitute a battery module.

[0017] (Structure of Battery Assembly 1) First, the battery assembly 1 to which the bus bar module of the present embodiment is attached will be described. As shown in FIG. 2, the battery assembly 1 is configured by connecting a plurality of single cells 2 in series. The plurality of single cells 2 are each provided with a positive electrode 4 and a negative electrode 5 protruding from the upper part of a battery body 3 formed in a rectangular parallelepiped shape. The positive electrode 4 and the negative electrode 5 are arranged apart from each other on the electrode surface 6 of the battery body 3, and each protrudes upward substantially perpendicularly from the electrode surface 6 in a cylindrical shape.

[0018] The battery assembly 1 is arranged so that the positive electrode 4 and negative electrode 5 of adjacent cell cells 2 are alternated, and the cell cells 2 are stacked in a predetermined direction (stacking direction). In this battery assembly 1, for example, among the cell cells 2 at both ends of a series-connected cell cell 2, the positive electrode 4 of one cell cell 2 becomes the total positive electrode, and the negative electrode 5 of the other cell cell 2 becomes the total negative electrode.

[0019] (Overall structure of busbar module 10) Next, the busbar module of this embodiment will be described. As shown in Figure 1, the busbar module 10 is made of a flexible printed circuit board (FPC). The busbar module 10 has a circuit body 20 to which busbars 25 (see Figure 3) connected to the positive electrode 4 and negative electrode 5 of the single cell 2 are attached, and a holder 30 for housing and holding the circuit body 20 and for attaching it to the battery assembly 1. The circuit body 20 is an example of a metal sheet.

[0020] As shown in Figure 1, the circuit body 20 is arranged on each single cell 2 along the stacking direction and has a strip-shaped main line 21 with multiple wiring patterns. A connector 212 is attached to the end of the main line 21 via a voltage detection line 211 drawn out from the main line 21. The connector 212 can be connected to a voltage detection device (not shown).

[0021] A strip-shaped branch wire section is provided on the side of the main wire 21 along its longitudinal direction, extending in a direction intersecting the longitudinal and thickness directions of the main wire 21 (outside the width direction of the main wire 21). The main wire 21 and the branch wire section are made of FPC (flexible printed circuit). Therefore, the main wire 21 and the branch wire section can be flexibly deformed, especially in directions perpendicular to their respective surfaces. A busbar 25 is joined to the tip of the branch wire section, as will be described later. Since the circuit body 20 is connected to the electrodes of each cell 2 via the branch wire section and the busbar 25, the voltage detection line 211 is connected to the electrodes.

[0022] As shown in Figure 4, the circuit body 20 is constructed by laminating a coverlay 201, a conductive layer 202, a base film 203, and a coverlay 204 in that order from top to bottom. Coverlays 201, 204, and the base film 203 are resin layers, and are composed of polyimide as an example. The conductive layer 202 is composed of copper (Cu) foil and copper plating as an example and constitutes the circuit. The thickness of the conductive layer 202 is, for example, 30 μm to 50 μm. The thickness of coverlays 201, 204, and the base is, for example, 25 μm each. In the circuit body 20, the conductive layer 202, which is placed on the base film 203, is protected by coverlays 201 and 204. The coverlay 201 is provided with openings as appropriate to ensure the electrical connection of the circuit. In practice, an adhesive layer (not shown) is provided on the circuit body 20 to tightly fix these layers together.

[0023] As shown in Figure 3, the busbar 25 is an example of a metal plate, for example, made of aluminum. The busbar 25 has an overall rectangular busbar body 251 and a connecting piece 252 that protrudes from the busbar body 251 toward the main line 21. The busbar body 251 is provided with two electrode holes through which the positive electrode 4 or negative electrode 5 of an adjacent cell 2 is passed, respectively. The connecting piece 252 is the point where it is electrically connected to the conductive layer 202 of the circuit body 20. The thickness of the connecting piece 252 is, for example, 0.25 mm to 1.0 mm.

[0024] The busbars provided at both longitudinal ends of the main line 21 are connected to either the total positive electrode or the total negative electrode, and each busbar has a single electrode hole through which the total positive electrode or total negative electrode passes. Power cables (not shown) that draw power from the battery assembly 1 are connected to these busbars.

[0025] (Structure of holder 30) The holder 30 shown in Figure 1 is molded from, for example, resin, and has a main line housing section that houses and holds the main lines 21 of the circuit body 20, and busbar housing sections provided on both outer sides in the width direction of the main line housing section for housing the busbars 25. The holder 30 holds the circuit body 20 to which the busbars 25 have been joined by laser irradiation in a method described later.

[0026] (Method of connecting busbar 25 and circuit board 20) Next, the method for joining the busbar 25 and the circuit body 20 will be described. First, as shown in Figure 3, the busbar 25 and the circuit body 20 are placed on top of each other so that the upper surface of the end of the circuit body 20 is in contact with the lower surface of the connecting piece 252 of the busbar 25. Then, a laser beam is shone onto the overlapping portion of the connecting piece 252 of the busbar 25 and the end of the circuit body 20 from the busbar 25 side, more specifically from the upper surface 253 side of the busbar 25, as indicated by the symbol LB, to join the busbar 25 and the circuit body 20.

[0027] If the laser beam is irradiated continuously as shown in the upper part of Figure 6, there is a concern that the laser beam may damage the busbar 25 and the circuit body 20. Therefore, by irradiating the laser beam intermittently, i.e., in a pulsed manner, while moving the irradiation point, as shown in the lower part of Figure 6, the penetration of the aluminum material of the busbar 25 can be suppressed, and the bonding area can be secured.

[0028] Furthermore, by irradiating with laser light in a pulsed manner, a through-hole 25a is formed at each pulse point, as shown in Figure 5, penetrating the connecting piece 252 of the busbar 25, and a through-hole 20a is formed continuously with the through-hole 25a, penetrating the circuit body 20. The through-hole 25a extends from the upper surface 253 to the lower surface 254 of the connecting piece 252, and the through-hole 20a extends from the upper surface 206 to the lower surface 207 of the circuit body 20. The aluminum melted by the laser light passes through the through-hole 20a of the circuit body 20, wraps around to the lower surface 207 of the circuit body 20, and hardens, forming an anchor portion 25b around the through-hole 20a. In other words, the joint A between the connecting piece 252 of the busbar 25 and the circuit body 20 has an anchor portion 25b, which creates an anchoring effect that increases the bonding force between the busbar 25 and the circuit body 20, allowing them to be firmly joined together.

[0029] The busbar 25 is made of aluminum, and its melting point is lower than that of the copper that makes up the conductive layer 202 of the circuit body 20. Therefore, it is conceivable to irradiate the busbar 25, i.e., the aluminum material with a low melting point, with laser light from the circuit body 20 side, which contains the copper material with a high melting point. However, in this case, it is necessary to irradiate with a high-power laser beam in order to melt the copper material, which has a high light reflectivity. As a result of increasing the output of the laser beam, the aluminum material may melt more easily, making it easier for an alloy layer to form at the joint, which may reduce the bonding strength.

[0030] Therefore, in this embodiment, by irradiating the thicker busbar 25 (metal plate) with laser light, bonding to the thinner circuit body 20 (metal sheet) becomes possible. Furthermore, by irradiating the laser light intermittently, in other words, in a pulsed manner, the formation of intermetallic compounds is suppressed, and a strong bond is possible due to the anchoring effect.

[0031] (Laser beam irradiation area and irradiation sequence) In this embodiment, when joining the busbar 25 and the circuit body 20, the irradiation points of the laser beam are moved in a predetermined order, thereby minimizing the thermal impact on the joining workpieces, the busbar 25 and the circuit body 20, and enabling control over the amount of aluminum material melted, thereby obtaining a stable bonding force.

[0032] As shown in Figure 9, the joining target area R1, where the busbar 25 and the circuit body 20 are superimposed, is used as the processing area, and laser light is sequentially irradiated onto each spot S in the order shown in Figure 7. When irradiating with laser light, the connecting piece 252 of the busbar 25 is pressed into the circuit body 20 using the pressing jig 41 shown in Figure 8. The pressing jig 41 is positioned so that the joining target area R1 is located within the opening 411 provided in the center, and the edge of an area slightly larger than the joining target area R1 becomes the pressing position R2 (see Figure 9) where the pressing jig 41 presses. The joining target area R1 is, for example, a square with sides of 1.5 mm. The pressing position R2 is, for example, a square with sides of 2.5 mm that surrounds an area 0.5 mm outside the joining target area R1.

[0033] With the area to be joined R1 pressed in by the pressing jig 41, laser light is shone onto each spot S in the order of the numbers shown in Figure 7 (1, 2, 3, ..., 64). In Figure 7, the lower edge of the area to be joined R1 is the origin of the laser light. The laser light is first shone onto spot S1 at the lower left corner of the area to be joined R1, and then onto spot S2 at the diagonally opposite upper right corner. After that, the laser light is shone onto spot S3 at the upper left corner of the area to be joined R1, and then onto spot S4 at the diagonally opposite lower right corner. Spot S2, which is shone after spot S1, is positioned point-symmetric to spot S1 with respect to the centroid O of the area to be joined R1. Spot S3, which is shone after spot S2, is positioned line-symmetric to spot S2 with respect to a virtual line L1 passing through the centroid O. The spot S4, which is irradiated after spot S3, is positioned point-symmetric to spot S3 with respect to the centroid O of the joining region R1. In this way, the spots (S1 to S28) on the outermost edge of the joining region R1 are arranged discontinuously, and are irradiated sequentially in a counterclockwise direction.

[0034] Next, each spot (S29 to S48) on the innermost edge of the joining region R1 is sequentially irradiated in the same manner, and then each spot (S61 to S64) on the innermost edge is sequentially irradiated, completing the joining of the entire joining region R1. In other words, each spot S within the joining region R1 is irradiated with laser light in such a discontinuous manner from the outer edge towards the interior, as indicated by arrows 101, 102, 103, and 104 in Figure 9.

[0035] Laser irradiation of the joining area R1 is performed, for example, under the following conditions: processing area (area of ​​joining area R1) 1.5 mm × 1.5 mm, processing points (number of spots) 64 points, spot diameter 45 μm, spacing between adjacent spots S 0.1 mm, and keyhole diameter 75 μm to 100 μm. The indentation position R2 is offset by 0.5 mm on each side from the outer circumference of the joining area R1. The laser irradiation conditions are set appropriately according to the shape and size of the joining area R1, the material of the workpiece to be joined, etc.

[0036] According to the joining method of this embodiment, by bringing the pressing position R2, which is the area pressed by the pressing jig 41, as close as possible to the outer circumference of the joining target area R1, the gap between the connecting piece 252 and the circuit body 20 can be eliminated, thereby enabling a stable connection between the busbar 25 and the circuit body 20.

[0037] (Battery assembly manufacturing method) A busbar module 10 is manufactured by joining multiple busbars 25 and a circuit body 20. The circuit body 20 (conductive layer 202) and each busbar 25 are joined by overlapping the connecting piece 252 of the busbar 25 with a part of the circuit body 20 that is thinner than the connecting piece 252, as described above, and intermittently irradiating the overlapped portion with laser light from the busbar 25 side to join them. The busbar module 10 manufactured in this way is then assembled onto the upper surface of the battery assembly 1.

[0038] As described above, according to the joining method of this embodiment, a laser beam is intermittently irradiated from the thicker busbar 25 side onto the joining target area R1, where the connecting piece 252 and a part of the circuit body 20 overlap. By irradiating with laser light in this way, the busbar 25 and the circuit body 20 can be joined while suppressing thermal effects such as burning of the circuit body 20 that may occur if the laser beam were irradiated from the circuit body 20 side. Furthermore, by suppressing thermal effects, the melting of one metal into the other metal is suppressed, and the formation of intermetallic compounds (alloy layers) can be suppressed, thereby securing the joining area and ensuring the intended joining strength. In addition, a strong bond between the busbar 25 and the circuit body 20 is possible due to the anchoring effect.

[0039] When joining an aluminum busbar 25 and a circuit board 20 (FPC) by soldering, there are concerns that tin (Sn) plating will be required to allow solder to adhere to the aluminum, increasing component costs, and that the process will be increased due to the use of a reflow oven for soldering. However, with the joining method of this embodiment, the busbar 25 and the circuit board 20 can be joined by laser welding, thus eliminating the need for plating and reducing the manufacturing cost of the busbar module 10 equipped with the busbar 25 and the circuit board 20.

[0040] Furthermore, according to the joining method of the above embodiment, by irradiating the laser beam in a discontinuous manner, thermal effects such as FPC burning can be suppressed, and the amount of melted aluminum material constituting the busbar 25 can be controlled, thereby suppressing the formation of intermetallic compounds (alloy layers). Thus, a stable joining force can be obtained. In addition, by bringing the area pressed by the pressing jig 41 (pressing position R2) as close as possible to the joining target area R1, the gap between the workpieces (between the busbar 25 and the circuit body 20) is eliminated, enabling a stable connection.

[0041] <Other forms> It should be noted that the present invention is not limited to the embodiments described above, and various modifications can be adopted within the scope of the present invention. For example, the present invention is not limited to the embodiments described above, and can be modified, improved, etc. as appropriate. Furthermore, the material, shape, dimensions, number, placement, etc. of each component in the embodiments described above are arbitrary and not limited as long as they can achieve the present invention.

[0042] In the above embodiment, an example was shown in which a part of the busbar 25 and a part of the circuit body 20 are overlapped, and laser light is intermittently irradiated from the busbar 25 side onto the overlapping portion to join the busbar 25 and the circuit body 20. However, the member to be joined to the busbar is not limited to the circuit body 20 including the FPC. For example, a thin metal sheet such as copper foil or a printed circuit body may be joined to a thick busbar. Furthermore, the joining method of the present invention can also be used to join busbars to thin metal sheets other than busbar modules assembled into battery assemblies.

[0043] Herein, the features of the metal plate joining method, busbar module manufacturing method, and battery module manufacturing method according to the embodiments of the present invention described above are briefly summarized below in [1] to [7].

[0044] [1] At least a portion of the first metal plate (bus bar 25) and at least a portion of the second metal plate (circuit body 20) are overlapped. In the joining target region (R1) where the first metal plate and the second metal plate are overlapped, laser light is irradiated such that the irradiation points (spots S) are arranged discontinuously from the outer periphery of the joining target region toward the interior (arrows 101, 102, 103, 104). A method for joining metal plates.

[0045] According to the metal plate joining method of the configuration described in [1] above, by irradiating the metal plate with laser light in a discontinuous manner, the thermal effect on the metal plate can be suppressed and the amount of melting of the metal plate can be controlled, thereby suppressing the formation of intermetallic compounds (alloy layers). Therefore, a stable bonding force can be obtained and the bonding force between the metal plates can be ensured.

[0046] [2] With the area to be joined (R1) pressed in (pressed position R2) by the pressing jig (41), the laser light is irradiated. The joining method described in [1] above.

[0047] According to the metal plate joining method of the configuration described in [2] above, by pressing down on the area to be joined with a pressing jig, gaps between the metal plates are eliminated, enabling a stable connection.

[0048] [3] The second irradiation site, which is irradiated after the first irradiation site, is positioned point-symmetric with respect to the centroid (O) of the area to be joined. The joining method described in [1] or [2] above.

[0049] According to the metal plate joining method of the configuration described in [3] above, the second irradiation site is positioned at a distance from the first irradiation site, so the thermal impact on the metal plate can be reduced and the amount of melting can be suppressed.

[0050] [4] The second irradiation site, which is irradiated after the first irradiation site, is positioned symmetrically with respect to the first irradiation site with respect to a straight line (virtual straight line L1) passing through the centroid (O) of the region to be joined. The joining method described in [1] or [2] above.

[0051] According to the metal plate joining method of the configuration described in [4] above, the second irradiation site is positioned at a distance from the first irradiation site, so the thermal impact on the metal plate can be reduced and the amount of melting can be suppressed.

[0052] [5] An anchor portion (25b) is formed at the irradiation site. The joining method described in any of the above [1] to [4].

[0053] According to the metal plate joining method of the configuration described in [5] above, an anchor portion is formed at the irradiated area, so the metal plates can be firmly joined.

[0054] [6] A method for manufacturing a busbar module (10) using the joining method described in any of [1] to [5] above, The busbar module (10) comprises an aluminum busbar (25) as the first metal plate, and a flexible wiring board (circuit body 20) that is thinner than the busbar as the second metal plate. The joining region (R1) is a portion where at least a part of the busbar (25) (connecting piece 252) and at least a part of the flexible wiring board (circuit body 20) overlap. In the area to be joined, the laser light is irradiated such that the irradiation points are arranged discontinuously from the outer periphery of the area to be joined toward the interior (arrows 101, 102, 103, 104). method.

[0055] According to the busbar module manufacturing method of the configuration described in [6] above, by irradiating the metal plate with laser light in a discontinuous manner, the thermal effect on the metal plate can be suppressed and the amount of melting of the metal plate can be controlled, thereby suppressing the formation of intermetallic compounds (alloy layers). Therefore, a stable bonding force can be obtained. Consequently, the reliability of the connection between the busbar and the flexible wiring board in the busbar module can be improved.

[0056] [7] A method for manufacturing a battery module comprising a battery assembly (1) and a busbar module (10), The busbar module (10) is manufactured by the method described above. The busbar module (10) is assembled to the battery assembly (1). method.

[0057] According to the battery module manufacturing method of the configuration described in [7] above, by irradiating the metal plate with laser light in a discontinuous manner, the thermal effect on the metal plate can be suppressed and the amount of melting of the metal plate can be controlled, thereby suppressing the formation of intermetallic compounds (alloy layers). As a result, a stable bonding force can be obtained. Therefore, a battery module with improved connection reliability between the busbar and the flexible wiring board can be provided. [Explanation of Symbols]

[0058] 1 battery assembly 2 single batteries 10 Busbar Modules 20 Circuit body 21 Main Line 25 Busba 30 holders

Claims

1. At least a portion of the first metal plate and at least a portion of the second metal plate are placed on top of each other. In the joining region of the portion where the first metal plate and the second metal plate are overlapped, laser light is irradiated such that the irradiation points are arranged discontinuously from the outer periphery of the joining region toward the interior. A method for joining metal plates, With the area to be joined pressed in with a pressing jig, the laser light is irradiated. Joining method.

2. The second irradiation location, which is irradiated after the first irradiation location, is positioned point-symmetric to the first irradiation location with respect to the centroid of the area to be joined. The joining method according to claim 1.

3. The second irradiation point, which is irradiated after the first irradiation point, is positioned symmetrically to the first irradiation point with respect to a straight line passing through the centroid of the region to be joined. The joining method according to claim 1.

4. An anchor portion is formed at the irradiation site. The joining method according to claim 1.

5. A method for manufacturing a busbar module using the joining method described in claim 1, The busbar module comprises an aluminum busbar as the first metal plate and a flexible wiring board that is thinner than the busbar as the second metal plate. The area to be joined is the portion where at least a part of the busbar and at least a part of the flexible wiring board overlap. In the area to be joined, the laser light is irradiated such that the irradiation points are arranged discontinuously from the outer periphery to the interior of the area to be joined. method.

6. A method for manufacturing a battery module comprising a battery assembly and a busbar module, The busbar module is manufactured by the method described in claim 5, The busbar module is assembled to the battery assembly. method.

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