JP2024013086A - Method for bonding metal plate and metal sheet, method for manufacturing bus bar module, and method for manufacturing battery module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for bonding a metal plate and a metal sheet, a method for manufacturing a bus bar module, and a method for manufacturing a battery module that secure bonding force.

SOLUTION: At least a part (connection piece 252) of a metal plate (bus bar 25), and at least a part of a metal sheet (circuit body 20) thinner than the metal plate are superposed, and the superposed portion of the metal plate (bus bar 25) and the metal sheet (circuit body 20) is irradiated with laser light from a side of the metal plate (bus bar 25), in order to bond the metal plate (bus bar 25) and the metal sheet (circuit body 20).

SELECTED DRAWING: Figure 5

COPYRIGHT: (C)2024,JPO&INPIT

Description

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

BACKGROUND ART Bus bar modules have conventionally been used, for example, to be assembled into battery assemblies as drive power sources mounted on electric vehicles, hybrid vehicles, and the like. A battery assembly is configured by stacking a plurality of battery cells.

For example, a busbar module includes a plurality of stacked busbars that connect the positive and negative electrodes between adjacent battery cells, and a voltage that is connected to each of the plurality of busbars to monitor the voltage of each battery cell. It is equipped with a detection line.

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

Aluminum is easily oxidized and the oxide film repels solder, so tin (Sn) plating is required to solder to aluminum busbars, which increases component costs. Furthermore, since this soldering process is performed in a reflow oven, the number of steps increases.

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, a copper connection plate is pressed against an aluminum busbar and laser light is irradiated to melt the aluminum material, which has a low melting point.

Japanese Patent Application Publication No. 2014-220128 JP 2021-034302 Publication

However, in Patent Document 2, since the laser beam is irradiated from the copper material side, the aluminum material is easily melted and an alloy layer is easily formed at the joint, so there is a concern that the joining strength may decrease.

The present invention has been made in view of the above circumstances, and its objects are to provide a method for joining metal plates and metal sheets, a method for manufacturing a busbar module, and a method for manufacturing a busbar module, which can ensure the bonding force between the metal plates and the metal sheets. An object of the present invention is to provide a method for manufacturing a battery module.

In order to achieve the above-mentioned object, the metal plate joining method according to the present invention has the following features.
overlapping at least a portion of the metal plate and at least a portion of a metal sheet thinner than the metal plate,
irradiating a portion where the metal plate and the metal sheet are overlapped with a laser beam from the metal plate side to join the metal plate and the metal sheet;
Joining method.

Moreover, in order to achieve the above-mentioned object, the method for manufacturing a busbar module according to the present invention has the following features.
A method of manufacturing a bus bar module including an aluminum bus bar as the metal plate and a flexible wiring board as the metal sheet using the above bonding method,
overlapping at least a portion of the bus bar and at least a portion of the flexible wiring board;
irradiating a portion where the bus bar and the flexible wiring board are overlapped with the laser light from the bus bar side to join the bus bar and the flexible wiring board;
Method.

Furthermore, in order to achieve the above-mentioned object, the method for manufacturing a battery module according to the present invention has the following features.
A method of manufacturing a battery module including a battery assembly and a busbar module, the method comprising:
manufacturing the bus bar module by the above method;
assembling the bus bar module to the battery assembly;
Method.

According to the present invention, it is possible to provide a method for bonding metal plates and metal sheets, a method for manufacturing a bus bar module, and a method for manufacturing a battery module that can ensure the bonding force between the metal plates and the metal sheets. .

The present invention has been briefly described above. Furthermore, the details of the present invention will be further clarified by reading the mode for carrying out the invention (hereinafter referred to as "embodiment") described below with reference to the accompanying drawings. .

1 is a perspective view of a bus bar module including a bus bar and a circuit body that are joined by a joining method according to an embodiment of the present invention. FIG. 2 is a perspective view of a battery assembly to which the bus bar module of FIG. 1 is assembled. It is a side view which expands and shows the joint part of a bus bar and a circuit body. 4 is a partially enlarged view of FIG. 3. FIG. FIG. 6 is a partially enlarged end view for explaining the anchor effect caused by laser irradiation on the bus bar and the circuit body. FIG. 3 is a diagram for explaining a laser irradiation state, with the upper side showing a state where laser light is continuously irradiated, and the lower side showing a state where laser light is intermittently irradiated. FIG. 6 is a diagram showing the order of movement of irradiation points in the welding target region. It is a figure which shows the state where the periphery of the welding target area is pushed in with the pushing jig. FIG. 3 is a diagram for explaining welding locations by laser irradiation.

Hereinafter, a bus bar module 10 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 10 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 form a battery module.

(Structure of battery assembly 1)
First, the battery assembly 1 to which the bus bar module 10 of this embodiment is attached will be described. As shown in FIG. 2, the battery assembly 1 is constructed by connecting a plurality of unit cells 2 in series. Each of the plurality of unit cells 2 has a positive electrode 4 and a negative electrode 5 protruding from the upper part of a battery body 3 formed in the shape of a rectangular parallelepiped. The positive electrode 4 and the negative electrode 5 are arranged apart from each other on the electrode surface 6 of the battery main body 3, and each is provided so as to protrude substantially vertically upward from the electrode surface 6 in a cylindrical shape.

The battery assembly 1 is arranged such that the cells 2 are stacked in a predetermined direction (stacking direction) so that the positive electrodes 4 and negative electrodes 5 of adjacent cells 2 alternate. In this battery assembly 1, for example, among the cells 2 corresponding to both ends of the cells 2 connected in series, the positive electrode 4 of one cell 2 is the total positive electrode, and the negative electrode 5 of the other cell 2 is the total positive electrode. It becomes a total negative electrode.

(Overall structure of busbar module 10)
Next, the bus bar module of this embodiment will be explained. As shown in FIG. 1, the bus bar module 10 is composed of a flexible printed circuit (FPC). The bus bar module 10 houses and holds a circuit body 20 to which a bus bar 25 (see FIG. 3) connected to the positive electrode 4 and the negative electrode 5 of the unit cell 2 is attached, and the circuit body 20 is attached to the battery assembly 1. It has a holder 30 for attachment. The circuit body 20 is an example of a metal sheet.

As shown in FIG. 1, the circuit body 20 has a belt-shaped main line 21 arranged along the stacking direction on each unit cell 2 and provided with a plurality of 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).

A strip-shaped branch line portion extending in a direction intersecting the longitudinal direction and the thickness direction of the main line 21 (outside in the width direction of the main line 21) is provided on a side portion along the longitudinal direction of the main line 21. The main line 21 and the branch line section are made of FPC. Therefore, the main line 21 and the branch line portion can be flexibly deformed, especially in a direction perpendicular to each plane. A bus bar 25 is joined to the tip of the branch line portion, as will be described later. Since the circuit body 20 is connected to the electrode of each unit cell 2 via the branch line portion and the bus bar 25, the voltage detection line 211 is connected to the electrode.

As shown in FIG. 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 this order from above. The coverlays 201 and 204 and the base film 203 are resin layers, and are made of polyimide, for example. The conductive layer 202 is made of copper (Cu) foil and copper plating, for example, and forms a circuit. The thickness of the conductive layer 202 is, for example, 30 μm to 50 μm. The coverlays 201, 204 and the base each have a thickness of 25 μm, for example. In the circuit body 20, a conductive layer 202 disposed on a base film 203 is protected with coverlays 201 and 204. The coverlay 201 is provided with appropriate openings to ensure electrical connection of the circuit. Note that, in reality, the circuit body 20 is provided with an adhesive layer (not shown) that tightly fixes these layers to each other.

As shown in FIG. 3, the bus bar 25 is an example of a metal plate, and is made of aluminum, for example. The bus bar 25 includes a bus bar main body 251 having an overall rectangular shape, and a connecting piece 252 protruding from the bus bar main body 251 toward the main line 21 side. The bus bar main body 251 is provided with two electrode holes through which the positive electrodes 4 or negative electrodes 5 of adjacent cell cells 2 are respectively passed. The connection piece 252 is a part that 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.

The bus bars provided at both longitudinal ends of the main line 21 are connected to all positive electrodes or all negative electrodes, and are provided with one electrode hole through which all positive electrodes or all negative electrodes are passed. A power cable (not shown) that draws power from the battery assembly 1 is connected to this bus bar.

(Structure of holder 30)
The holder 30 shown in FIG. 1 is made of resin, for example, and accommodates a main line accommodating part that accommodates and holds the main line 21 of the circuit body 20, and bus bars 25 provided on both widthwise outer sides of the main line accommodating part. It has a bus bar accommodating part. The holder 30 holds the circuit body 20 to which the bus bar 25 is bonded by laser beam irradiation using a method described later.

(Method of joining bus bar 25 and circuit body 20)
Next, a method for joining the bus bar 25 and the circuit body 20 will be explained. First, as shown in FIG. 3, the bus bar 25 and the circuit body 20 are stacked so that the upper surface of the end of the circuit body 20 contacts the lower surface of the connection piece 252 of the bus bar 25. Then, the portion where the connection piece 252 of the bus bar 25 and the end of the circuit body 20 are overlapped is irradiated with laser light from the bus bar 25 side, specifically from the top surface 253 side of the bus bar 25, as shown by the symbol LB, The bus bar 25 and the circuit body 20 are joined.

Here, if the laser light irradiation is performed continuously as shown in the upper side of FIG. 6, there is a concern that the bus bar 25 and the circuit body 20 may be damaged by the laser light irradiation. Therefore, by irradiating the laser beam intermittently, that is, in a pulsed manner, as shown in the lower part of FIG. 6, while moving the irradiation location, the melting of the aluminum material of the bus bar 25 can be suppressed, and the bonding area can be reduced. can be secured.

Further, by irradiating the laser beam in a pulsed manner, a through hole 25a passing through the connection piece 252 of the bus bar 25 is formed at each point as shown in FIG. A through hole 20a passing through the body 20 is formed. The through hole 25a extends from the upper surface 253 to the lower surface 254 of the connection 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 beam passes through the through hole 20a of the circuit body 20, wraps around 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 part A between the connection piece 252 of the bus bar 25 and the circuit body 20 has the anchor part 25b, thereby creating an anchor effect that increases the joint force between the bus bar 25 and the circuit body 20, and making them stronger. Can be joined.

The bus bar 25 is made of aluminum, and its melting point is lower than the melting point of copper that constitutes the conductive layer 202 of the circuit body 20. Therefore, it is conceivable to irradiate laser light from the side of the circuit body 20 containing a copper material with a high melting point to melt the bus bar 25, that is, the aluminum material with a low melting point. However, in this case, it is necessary to irradiate a high-output laser beam to melt the copper material, which has a high light reflectance.As a result of increasing the output of the laser beam, the aluminum material melts more easily, and There is a risk that an alloy layer will easily form and the bonding strength will decrease.

Therefore, in this embodiment, by irradiating laser light from the thick bus bar 25 (metal plate) side, it is possible to bond to the thin circuit body 20 (metal sheet). Furthermore, by irradiating the laser beam intermittently, in other words, in a pulsed manner for each dot, it is possible to suppress the generation of intermetallic compounds and to achieve strong bonding due to the anchor effect.

(Laser light irradiation location and irradiation order)
In this embodiment, when joining the bus bar 25 and the circuit body 20, by moving the laser beam irradiation point in a predetermined order, the bus bar 25 and the circuit body 20, which are the joining workpieces, are not affected by heat as much as possible. The amount of melted aluminum material can be controlled to obtain stable bonding strength.

As shown in FIG. 9, the joining target region R1 where the bus bar 25 and the circuit body 20 are overlapped is set as a processing range, and each spot S is sequentially irradiated with laser light in the order shown in FIG. When irradiating the laser beam, the connecting piece 252 of the bus bar 25 is pushed into the circuit body 20 using a pushing jig 41 shown in FIG. The pushing jig 41 is arranged so that the welding target region R1 is located in the opening 411 provided at the center, and the edge of the region one size larger than the welding target region R1 is pushed in by the pushing jig 41. This becomes the push-in position R2 (see FIG. 9). The welding target region R1 has a square shape with one side of 1.5 mm, for example. As an example, the pushing position R2 has a square shape with one side of 2.5 mm surrounding the welding target region R1 by 0.5 mm outside.

While the periphery of the welding target region R1 (pushing position R2) is pushed in with the pushing jig 41, the laser beam is applied to the welding target region R1 in the numerical order (1, 2, 3, ..., 64) shown in FIG. , each spot S is irradiated. In FIG. 7, the lower side of the welding target region R1 is the irradiation origin side of the laser beam. The laser light is first applied to a spot S1 at the lower left corner of the welding target region R1, and then applied to a diagonally opposite spot S2 at the upper right corner. Thereafter, the laser beam is applied to a spot S3 at the upper left corner of the welding target region R1, and is applied to a diagonally opposite spot S4 at the lower right corner. A spot S2 that is irradiated next to the spot S1 is arranged at a position symmetrical to the spot S1 with respect to the center of gravity O of the welding target region R1. A spot S3 that is irradiated next to the spot S2 is arranged at a position that is line symmetrical with the spot S2 with respect to a virtual straight line L1 passing through the center of gravity O. A spot S4, which is irradiated next to the spot S3, is arranged at a position symmetrical to the spot S3 with respect to the center of gravity O of the welding target region R1. In this way, the spots (S1 to S28) on the outermost edge of the welding target region R1 are sequentially irradiated counterclockwise so that they are discontinuously arranged.

Next, each spot (S29 to S48) inside the outermost periphery of the welding target region R1 is sequentially irradiated in the same manner, and each spot (S61 to S64) on the innermost periphery is sequentially irradiated, so that the entire welding target region R1 is irradiated. The joining is completed. In other words, each spot S in the welding target region R1 is irradiated with laser light so that the spots S are discontinuously arranged from the outer periphery toward the inside, as shown by arrows 101, 102, 103, and 104 in FIG. be done.

For example, the laser beam irradiation in the welding target region R1 is performed in a processing range (range of the welding target region R1) of 1.5 mm x 1.5 mm, processing points (number of spots): 64 points, spot diameter of 45 μm, and adjacent spots. This is carried out under the conditions that the S interval is 0.1 mm and the keyhole diameter is 75 μm to 100 μm. Further, the pushing position R2 is offset by 0.5 mm on each side with respect to the outer periphery of the welding target region R1. Note that the laser beam irradiation conditions are appropriately set depending on the shape and size of the region R1 to be welded, the material of the workpiece to be welded, and the like.

According to the joining method of the present embodiment, by bringing the pressing position R2, which is the range pressed by the pressing jig 41, as close as possible to the outer periphery of the joining target region R1, the gap between the connecting piece 252 and the circuit body 20 can be eliminated. Therefore, stable connection between the bus bar 25 and the circuit body 20 is possible.

(Battery assembly manufacturing method)
A bus bar module 10 is manufactured by joining a plurality of bus bars 25 and a circuit body 20. As described above, the circuit body 20 (conductive layer 202) and each bus bar 25 are stacked by overlapping the connecting piece 252 of the bus bar 25 and a part of the circuit body 20 that is thinner than the connecting piece 252, and then forming a layer on the overlapping part. Laser light is intermittently irradiated from the bus bar 25 side to bond them. The bus bar module 10 manufactured in this way is assembled on the upper surface of the battery assembly 1.

As explained above, according to the bonding method of this embodiment, laser light is intermittently irradiated from the thick bus bar 25 side to the bonding target region R1 where the connection piece 252 and a part of the circuit body 20 are overlapped. do. By irradiating the laser beam in this way, the bus bar 25 and the circuit body 20 can be bonded 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. can. In addition, by suppressing thermal effects, it is possible to suppress the melting of one metal into the other metal, and to suppress the formation of intermetallic compounds (alloy layers), thereby securing the bonding area and ensuring the intended bonding force. can. Furthermore, the anchor effect enables a strong connection between the bus bar 25 and the circuit body 20.

When joining the aluminum bus bar 25 and the circuit body 20 (FPC) by soldering, tin (Sn) plating is required to place the solder on the aluminum, which increases component costs, or requires soldering in a reflow oven. There are concerns that the number of steps will increase due to this. However, according to the joining method of this embodiment, since the bus bar 25 and the circuit body 20 can be joined by laser welding, plating is eliminated and the manufacturing cost of the bus bar module 10 including the bus bar 25 and the circuit body 20 is reduced. can be reduced.

Further, according to the bonding method of the above embodiment, by irradiating the laser beam so that the irradiation points are discontinuous, it is possible to suppress thermal effects such as burning of the FPC, and to reduce the amount of melting of the aluminum material constituting the bus bar 25. Since this can be controlled, the generation of intermetallic compounds (alloy layers) can be suppressed. Therefore, stable bonding force can be obtained. In addition, by bringing the range held down by the pushing jig 41 (pushing position R2) as close as possible to the welding target area R1, there is no gap between the workpieces (between the bus bar 25 and the circuit body 20), and stable connection is possible. becomes.

<Other forms>
Note that the present invention is not limited to the above embodiments, 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. In addition, the material, shape, size, number, arrangement location, etc. of each component in the above-described embodiments are arbitrary as long as the present invention can be achieved, and are not limited.

In the above embodiment, a part of the bus bar 25 and a part of the circuit body 20 are overlapped, and a laser beam is intermittently irradiated from the bus bar 25 side to the overlapped part, so that the bus bar 25 and the circuit body 20 are overlapped. Although an example of bonding is shown, the member bonded to the bus bar 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 may be bonded to a thick bus bar. Furthermore, the joining method of the present invention can be used for joining busbars and thin metal sheets other than busbar modules assembled into battery assemblies.

Here, the characteristics of the method for joining metal plates and metal sheets, the method for manufacturing a busbar module, and the method for manufacturing a battery module according to the embodiments of the present invention described above are briefly summarized in [1] to [7] below, respectively. Listed below.

[1] Overlapping at least a portion (connection piece 252) of a metal plate (bus bar 25) and at least a portion of a metal sheet (circuit body 20) thinner than the metal plate,
irradiating a portion where the metal plate and the metal sheet are overlapped with a laser beam from the metal plate side to join the metal plate and the metal sheet;
Joining method.

According to the bonding method having the configuration [1] above, by irradiating the laser beam from the thick metal plate side, the metal plate and the metal sheet can be bonded while suppressing the thermal influence of the laser beam on the metal sheet. Furthermore, since the generation of intermetallic compounds (alloy layers) can be suppressed by suppressing thermal effects, a decrease in bonding force can be suppressed and bonding force between the metal plates and the metal sheets can be ensured.

[2] Intermittently irradiating the laser beam while moving the irradiation location (spot S);
The joining method described in [1] above.

According to the bonding method having the configuration [2] above, since the laser light is not continuously irradiated but is irradiated intermittently, melting of the metal plate material can be suppressed and a bonding area can be secured.

[3] The melting point of the metal plate (bus bar 25) is lower than the melting point of the metal sheet (circuit body 20).
The joining method according to [1] or [2] above.

According to the bonding method having the configuration [3] above, the output of the laser beam can be set to a level that melts the metal plate having a low melting point, so that the thermal influence on the metal sheet can be further suppressed.

[4] The metal plate (busbar 25) is an aluminum busbar,
The metal sheet (circuit body 20) is a flexible wiring board configured to include copper foil (conductive layer 202),
The joining method according to any one of [1] to [3] above.

According to the bonding method having the configuration [4] above, bonding force between the aluminum bus bar and the flexible wiring board including copper foil can be ensured.

[5] forming an anchor portion (25b) on a surface of the metal sheet opposite to the surface on which the metal plates are stacked, by irradiating the laser beam;
The joining method according to any one of [1] to [4] above.

According to the joining method having the configuration [5] above, since the anchor portion is formed, the metal sheet and the metal plate can be firmly joined.

[6] A bus bar module comprising an aluminum bus bar as the metal plate and a flexible wiring board as the metal sheet, using the bonding method according to any one of [1] to [5] above. A method of manufacturing,
overlapping at least a portion of the bus bar (25) and at least a portion of the flexible wiring board (circuit body 20);
irradiating a portion where the bus bar and the flexible wiring board are overlapped with the laser light from the bus bar side to join the bus bar and the flexible wiring board;
Method.

According to the busbar module manufacturing method having the configuration [6] above, by irradiating laser light from the thick busbar side, the busbar and the flexible wiring board are bonded while suppressing the thermal influence of the laser light on the flexible wiring board. can. Moreover, since the generation of intermetallic compounds (alloy layers) can be suppressed by suppressing thermal effects, a decrease in bonding force can be suppressed and bonding force between the bus bar and the flexible wiring board can be ensured. Therefore, the connection reliability between the bus bar and the flexible wiring board in the bus bar module can be improved.

[7] A method for manufacturing a battery module including a battery assembly (1) and a busbar module (10), comprising:
Manufacturing the busbar module by the method described in [6] above,
assembling the bus bar module to the battery assembly;
Method.

According to the battery module manufacturing method having the configuration of [7] above, by irradiating laser light from the thick bus bar side, the bus bar and the flexible wiring board are bonded while suppressing the thermal influence of the laser light on the flexible wiring board. can. Moreover, since the generation of intermetallic compounds (alloy layers) can be suppressed by suppressing thermal effects, a decrease in bonding force can be suppressed and bonding force between the bus bar and the flexible wiring board can be ensured. Therefore, the connection reliability between the bus bar and the flexible wiring board in the battery module can be improved.

1 Battery assembly 2 Cell 10 Busbar module 20 Circuit body 21 Main line 25 Busbar 30 Holder

Claims (7)

overlapping at least a portion of the metal plate and at least a portion of a metal sheet thinner than the metal plate,
irradiating a portion where the metal plate and the metal sheet are overlapped with a laser beam from the metal plate side to join the metal plate and the metal sheet;
Joining method. irradiating the laser beam intermittently while moving the irradiation location;
The joining method according to claim 1. the melting point of the metal plate is lower than the melting point of the metal sheet,
The joining method according to claim 1. The metal plate is an aluminum bus bar,
The metal sheet is a flexible wiring board configured to include copper foil.
The joining method according to claim 1. forming an anchor portion on a surface of the metal sheet opposite to the surface on which the metal plates are stacked, by irradiating the laser beam;
The joining method according to claim 1. A method of manufacturing a bus bar module comprising an aluminum bus bar as the metal plate and a flexible wiring board as the metal sheet using the bonding method according to claim 1,
overlapping at least a portion of the bus bar and at least a portion of the flexible wiring board;
irradiating a portion where the bus bar and the flexible wiring board are overlapped with the laser light from the bus bar side to join the bus bar and the flexible wiring board;
Method. A method of manufacturing a battery module including a battery assembly and a busbar module, the method comprising:
manufacturing the busbar module by the method according to claim 5;
assembling the bus bar module to the battery assembly;
Method.

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