Power supply device, method for manufacturing same, laser welding method, and laser welding method for metal plate

Abstract

The present invention improves reliability in fixing a secondary battery cell and a circuit board. A power supply device 100 includes: a secondary battery cell 1 including a positive electrode tab 3A and a negative electrode tab 3B; and a circuit board 2 having a pair of metal blocks 8 respectively connected to the positive electrode tab 3A and the negative electrode tab 3B of the secondary battery cell 1. A solder layer 12 is formed in at least a portion of a block arrangement region 10 where the metal blocks 8 and the circuit board 2 face each other. In a plan view of the power supply device 100, the solder layer 12 is formed in an island shape along at least a portion of the contours of the positive electrode tab 3A and the negative electrode tab 3B. In a plan view of the power supply device 100, a joining region 20 where the positive electrode and the negative electrode tab 3B are joined to the metal blocks 8 is formed in at least a portion of the interface where the positive electrode and the negative electrode tab 3B face the metal blocks 8. In a plan view of the power supply device 100, the solder layer 12 and the joining region 20 are arranged so as not to overlap each other.

Description

Power supply device, manufacturing method thereof, laser welding method, and laser welding method for metal plates

[0001] The present disclosure relates to a power supply device, a manufacturing method thereof, a laser welding method, and a laser welding method for metal plates.

[0002] Power supply devices using rechargeable secondary battery cells such as lithium-ion secondary batteries are used in a wide range of applications. Such secondary battery cells use metal tabs for the positive and negative electrodes. The metal tabs are electrically connected to a control circuit board. The circuit board has a metal block for fixing the metal tabs of the secondary battery cell.

[0003] However, when laser welding is used to fix the metal tabs of the positive and negative electrodes of such secondary battery cells to the metal block on the circuit board, there is a concern that the welding location may penetrate the metal block during welding.

[0004] Japanese Patent Application Laid-Open No. 2019-32985

[0005] One of the objectives of one form of the present disclosure is to provide a power supply device, a manufacturing method thereof, a laser welding method, and a laser welding method for metal plates with improved reliability in fixing a secondary battery cell and a circuit board. Another objective of another form is to provide a power supply device, a manufacturing method thereof, a laser welding method, and a laser welding method for metal plates with reduced risk of penetration by laser welding. Note that the description of these objectives and problems of the present disclosure does not prevent the existence of other objectives and problems. Also, one aspect of the present disclosure does not need to solve all of these problems. Furthermore, other problems can be extracted from the description of the specification, drawings, and claims of the present disclosure.

[0006] A power supply device according to one embodiment of the present disclosure comprises a secondary battery cell having a positive electrode tab and a negative electrode tab, and a circuit board having a pair of metal blocks connected to the positive electrode tab and the negative electrode tab of the secondary battery cell, wherein a solder layer is formed on at least a portion of the block arrangement region where the metal blocks and the circuit board face each other, in a plan view of the power supply device, the solder layer is formed in an island shape along at least a portion of the contours of the positive electrode tab and the negative electrode tab, in a plan view of the power supply device, a bonding region is formed where the positive electrode tab and the negative electrode tab and the metal block are joined together in at least a portion of the interface where the positive electrode and the negative electrode tab and the metal block face each other, and in a plan view of the power supply device, the solder layer and the bonding region are arranged so as not to overlap.

[0007] Furthermore, a method for manufacturing a power supply device according to another embodiment of the present disclosure is a method for manufacturing a power supply device comprising: a secondary battery cell having a positive electrode tab and a negative electrode tab; and a circuit board having a pair of metal blocks connected to the positive electrode tab and the negative electrode tab of the secondary battery cell, respectively, the method comprising: applying reflow solder to a part of a block placement area on the circuit board where the metal blocks are placed; placing the metal blocks on top of the reflow solder on the circuit board; passing the circuit board on which the metal blocks are placed through a reflow heating furnace to melt and harden the reflow solder to form a solder layer, and fixing the metal blocks to the circuit board via the solder layer; placing the positive electrode and negative electrode tabs on the metal blocks; and, with the positive electrode and negative electrode tabs placed on the metal blocks, setting a bonding area in a plan view of the power supply device that does not overlap with the solder layer, scanning the bonding area with a laser beam, and welding the positive electrode and negative electrode tabs to the metal blocks.

[0008] Furthermore, a laser welding method for a power supply device according to another embodiment of the present disclosure is a laser welding method for a power supply device comprising: a secondary battery cell having a positive electrode tab and a negative electrode tab; and a circuit board having a pair of metal blocks connected to the positive electrode tab and the negative electrode tab of the secondary battery cell, respectively, the method comprising: preparing the circuit board by placing the metal blocks on the circuit board, on top of reflow solder applied to a part of a block placement area on which the metal blocks are placed, passing the circuit board through a reflow heating furnace to melt and harden the reflow solder to form a solder layer, thereby fixing the metal blocks via the solder layer; placing the positive electrode and negative electrode tabs on the metal blocks; and, with the positive electrode and negative electrode tabs placed on the metal blocks, setting a joining area in a plan view of the power supply device that does not overlap with the solder layer, scanning the joining area with laser light to weld the positive electrode and negative electrode tabs to the metal blocks.

[0009] Furthermore, another embodiment of the present disclosure is a laser welding method for a metal plate, which involves laser welding a circuit board having a metal block connected to a metal tab, and includes the steps of: applying reflow solder to a part of a block placement area on the circuit board where the metal block is placed; placing the metal block on top of the reflow solder on the circuit board; passing the circuit board on which the metal block is placed through a reflow heating furnace to melt and harden the reflow solder to form a solder layer, and fixing the metal block to the circuit board via the solder layer; placing the metal tab on the metal block; and, with the metal tab placed on the metal block, setting a joining area in a plan view that does not overlap with the solder layer, scanning the joining area with laser light to weld the metal tab to the metal block.

[0010] According to one embodiment of the power supply device, its manufacturing method, laser welding method, and laser welding method for metal plates, in a plan view, by providing a joint area for fixing the metal tab and the metal block while avoiding the solder layer, it is possible to avoid situations that would impair reliability, such as damaging the fixing between the metal block and the circuit board, when fixing the metal tab and the metal block.

[0011] This is an enlarged perspective view of the main part of the power supply device according to Embodiment 1. This is an enlarged plan view of the main part of the power supply device in Figure 1. This is a schematic cross-sectional view showing the state in which reflow solder has been applied to the circuit board. This is a schematic cross-sectional view showing the state in which a metal block is fixed to the circuit board of Figure 3 by reflow. This is a schematic cross-sectional view showing the state in which the positive electrode tab and negative electrode tab of a secondary battery cell have been fixed to the metal block of Figure 4. This is a schematic plan view showing the area on the circuit board of the power supply device according to Embodiment 1 in which the metal block is placed. This is a schematic plan view showing the state in which the positive electrode tab and negative electrode tab have been laser-welded to the circuit board of Figure 6. This is a schematic plan view showing the area on the circuit board of the power supply device according to a comparative example in which the metal block is placed. This is a schematic plan view showing the state in which the positive electrode tab and negative electrode tab have been laser-welded to the circuit board of Figure 8. Figure 10A is a perspective view showing the solder layer on the back of the metal block of the power supply according to Embodiment 1, Figure 10B is a perspective view showing the solder layer on the back of the metal block of the power supply according to Embodiment 2, Figure 10C is a perspective view showing the solder layer on the back of the metal block of the power supply according to Embodiment 3, Figure 10D is a perspective view showing the solder layer on the back of the metal block of the power supply according to Embodiment 4, and Figure 10E is a perspective view showing the solder layer on the back of the metal block of the power supply according to Embodiment 5.

[0012] The form of this disclosure may be specified by the following configurations and features.

[0013] In other embodiments of the present disclosure, the power supply device is formed such that, in any of the above embodiments, the solder layer overlaps the corner of the metal block in a plan view of the power supply device. With this configuration, the corner of the metal block can be stably fixed to the circuit board with the solder layer.

[0014] Furthermore, in other embodiments of the power supply device according to this disclosure, the bonding region is formed in a cross-shaped pattern on the metal block in any of the above embodiments. With this configuration, the four corners that fix the metal block to the circuit board can be removed, and the positive electrode tab and negative electrode tab can be fixed to the metal block.

[0015] Furthermore, in other embodiments of the present disclosure, the power supply device is such that, in any of the above embodiments, the positive electrode tab is made of Al, the negative electrode tab is made of Ni, and the metal block is made of nickel, nickel silver plated on the surface, or aluminum.

[0016] Furthermore, in any of the above embodiments, the power supply device is configured such that the solder layer is made of reflow solder.

[0017] Furthermore, in any of the above embodiments, the power supply device is a pouch cell in which the secondary battery cell is a pouch cell.

[0018] The embodiments of this disclosure will be described below with reference to the drawings. However, the embodiments shown below are examples for concretizing the technical concept of this disclosure, and this disclosure is not limited to the following. Furthermore, this specification does not limit the members shown in the claims to the members of the embodiments. In particular, the dimensions, materials, shapes, relative arrangements, etc. of the components described in the embodiments are not intended to limit the scope of this disclosure to those, unless otherwise specifically stated, but are merely illustrative examples. Note that the size and positional relationships of the members shown in each drawing may be exaggerated for clarity of explanation. Furthermore, in the following description, the same name and reference numeral indicate the same or similar members, and detailed explanations will be omitted as appropriate. Furthermore, each element constituting this disclosure may be configured such that multiple elements are made of the same member, with one member serving multiple elements, or conversely, the function of one member may be shared among multiple members.

[0019] The power supply device and its manufacturing method, laser welding method, and laser welding method for metal plates disclosed herein can be used for laser welding metal tabs to soldered metal blocks. As an example, the following describes a method of laser welding the positive and negative metal tabs of a secondary battery cell, such as a pouch cell, to a metal block soldered to a circuit board by reflow soldering. However, this disclosure is not limited to this example and can be appropriately used for welding metal objects such as metal tabs to metal objects such as lead plates or soldered metal blocks. [Embodiment 1]

[0020] Figures 1 to 7 show a power supply device 100 according to Embodiment 1 of the present disclosure. In these figures, Figure 1 is an enlarged perspective view of the main part of the power supply device 100 according to Embodiment 1, Figure 2 is an enlarged plan view of the main part of the power supply device 100 in Figure 1, Figure 3 is a schematic cross-sectional view showing the state in which reflow solder 11 has been applied to the circuit board 2, Figure 4 is a schematic cross-sectional view showing the state in which the metal block 8 is fixed to the circuit board 2 in Figure 3 by reflow, Figure 5 is a schematic cross-sectional view showing the state in which the positive electrode tab 3A and negative electrode tab 3B of the secondary battery cell 1 are fixed to the metal block 8 in Figure 4, Figure 6 is a schematic plan view showing the area on the circuit board 2 of the power supply device 100 according to Embodiment 1 in which the metal block 8 is placed, and Figure 7 is a schematic plan view showing the state in which the positive electrode tab 3A and negative electrode tab 3B have been laser welded to the circuit board 2 in Figure 6. The power supply device 100 shown in Figures 1 to 2 comprises a secondary battery cell 1 and a circuit board 2 connected to the metal tab 4 of the secondary battery cell 1. (Secondary battery cell 1)

[0021] The secondary battery cell 1 can utilize a secondary battery cell with a rectangular shape. In the examples shown in Figures 1 and 2, a thin secondary battery cell called a pouch-side secondary battery cell is used. Any known secondary battery, such as a lithium-ion secondary battery, nickel-metal hydride battery, or nickel-cadmium battery, can be used as appropriate for the secondary battery cell 1.

[0022] Each secondary battery cell 1 has a positive electrode and a negative electrode. The terminals of the positive or negative electrode are preferably provided on one end face of the secondary battery cell 1. In the examples shown in Figures 1 and 2, a positive electrode tab 3A and a negative electrode tab 3B are projected from one end face of the secondary battery cell 1, spaced apart from each other. These electrode tabs are metal tabs 3 made of metal plates. Aluminum or other metals are used for the positive electrode tab 3A. Nickel or other metal plates are used for the negative electrode tab 3B. The material, size, and thickness of the metal plates are appropriately selected according to the required specifications of the secondary battery cell, such as voltage, capacity, and size. For example, the thickness of the metal tab 4 is set to about 0.01 mm to 0.25 mm.

[0023] The secondary battery cell 1 has a battery element 4 with positive and negative electrodes laminated between two insulating films. The secondary battery cell 1 covers both the upper and lower surfaces of the battery element 4 with two insulating films. The two insulating films that cover both surfaces can be used by folding one film over one side of the battery element 4 to create two films that cover both surfaces. The two insulating films join and weld together the laminated portion 5 that is laminated on the outside of the battery element 4. The insulating film is a plastic film that tightly adheres to the laminated portion 5 that is laminated on the outside of the battery element 4, keeping the inside airtight. Note that one insulating film does not need to be a single layer, and may be composed of multiple layers. The battery element 4 of the secondary battery cell 1 is preferably a lithium polymer battery. However, this disclosure does not limit the battery element 4 of the secondary battery cell 1 to a lithium polymer battery, and any secondary battery that can laminate insulating films on both sides of the battery element 4 and join the insulating films on the outside of the battery element 4 can be used.

[0024] The secondary battery cell 1 has a rectangular shape, with insulating films laminated along the outer edge of the battery element 4 to form a laminated section 5. In the laminated section 5 of the secondary battery cell 1, two insulating films are airtightly joined by adhesive, welding, or other methods. Preferably, the secondary battery cell 1 is used by folding one insulating film over one side of the battery element 4 to cover both sides of the battery element 4. In this structure, since the insulating film is folded over along one side of the battery element 4, there is no laminated section 5 on one side of the rectangle, and laminated sections 5 are provided on three sides. However, the secondary battery cell 1 can also have a structure in which laminated sections 5 are provided on the outer circumference of all four sides of the rectangle. This secondary battery cell 1 is manufactured by overlapping two separate insulating films on both sides of the battery element 4 and joining them at the laminated sections 5 on all four sides around the battery element 4. Furthermore, even if the battery element 4 of the secondary battery cell 1 is rectangular, the external shape may differ from a rectangle depending on how the metal tab 3 is removed and how the stacked portion 5 is folded. Therefore, the external shape of the secondary battery cell 1 can also be a shape other than a rectangle, such as a polygon, an oval, a polygon with a partially curved portion, a regular shape, or an irregular shape.

[0025] In the secondary battery cell 1 shown in Figures 1 and 2, the insulating film laminated on the lower surface of the battery element 4 is flat or nearly flat, and the insulating film laminated on the upper surface of the battery element 4 is bent downward along the periphery of the battery element 4 and laminated onto the insulating film on the lower surface to form a terrace portion 6.

[0026] The secondary battery cell 1 has a terrace portion 6 on one side of its outer circumference. The terrace portion 6 is a laminated portion 5 of insulating film that protrudes to the outside of the battery element 4. The terrace portion 6 is arranged in a plane parallel to both sides of the battery element 4. The secondary battery cell 1 has the terrace portion 6 positioned on the bottom side of the battery element 4. Furthermore, the secondary battery cell 1 has side walls 7 connected to both sides of the terrace portion 6. As shown in Figure 1, the side walls 7 are formed by bending the laminated portions 5 that protrude on both sides of the battery element 4 by 90 degrees so that they follow the sides of the battery element 4. In this shape of the terrace portion 6, the side walls 7 on both sides act as reinforcing ribs, which can increase the bending strength of the terrace portion 6.

[0027] The secondary battery cell 1 has positive and negative metal tabs 3 insulated and sandwiched between terrace portions 6, which are part of the laminated portion 5. As shown in Figure 1, the metal tabs 3 are hermetically sandwiched between two insulating films of the terrace portion 6 and extended to the outside of the terrace portion 6. The positive electrode metal tab 3 is made of aluminum, and the negative electrode metal tab 3 is made of nickel. The positive and negative metal tabs 3 are electrically connected by being directly laser-welded to a metal block 8 fixed to the surface of the circuit board 2. (Circuit board 2)

[0028] The secondary battery cell 1 is connected to the circuit board 2 via a positive electrode tab 3A and a negative electrode tab 3B. The circuit board 2 implements a charge / discharge circuit for charging and discharging the secondary battery cell 1, as well as a protection circuit that monitors the voltage and temperature of the secondary battery cell 1 and cuts off the current in case of abnormalities. The circuit board 2 is made of a glass epoxy substrate or a phenolic substrate, etc. (Metal block 8)

[0029] The circuit board 2 has a pair of metal blocks 8. The pair of metal blocks 8 are components for connecting to the positive electrode tab 3A and the negative electrode tab 3B of the secondary battery cell 1, respectively. By constructing the circuit board 2 from insulating material and arranging the metal blocks 8 on the circuit board 2 in this way, metal components such as the metal tabs 3 of the secondary battery cell 1 can be easily connected electrically and mechanically by methods such as welding or soldering. Such metal blocks 8 can be made of nickel, nickel silver, aluminum, etc. The surface of the metal blocks 8 may also be plated with nickel or the like.

[0030] The thickness of the metal block is determined according to the expected current flow and the required electrical resistance, and is, for example, 0.1 mm to 2.0 mm. In order to meet the recent demands for thinner and lighter power supply devices, it is preferable to make the metal block 8 thinner. Furthermore, the thickness of the metal block 8 is 13 times or more, preferably 15 times or more, that of the metal tab 4. (First interface IF1)

[0031] The metal block 8 is fixed to the circuit board 2 by soldering. Therefore, a solder layer 12 is partially formed at the first interface IF1 between the circuit board 2 and the metal block, as shown in Figures 4 to 6. The solder layer 12 is formed on a portion, not the entire, block placement area 10 on the upper surface of the circuit board 2 where the metal block 8 is placed. (Block placement area 10)

[0032] The block placement area 10 is set to be approximately the same size as the footprint of the metal block 8, or slightly larger, depending on the shape of the metal block 8. In examples such as Figure 6, the block placement area 10 is designed as a horizontally elongated rectangle, slightly larger than the metal block 8, to match the horizontally elongated metal block 8. The metal block is not limited to this shape; it may be a vertically elongated rectangle, a square, a polygon, a circle, an ellipse, a track shape, etc. (Solder layer 12)

[0033] Preferably, the solder layer 12 is formed in an island shape along at least a portion of the contours of the positive electrode tab 3A and the negative electrode tab 3B in a plan view of the power supply unit 100. In the example shown in Figure 6, solder layers 12 are provided at each of the four corners of the block arrangement area 10. By providing solder layers 12 at the four rectangular corners in this way, self-alignment can be easily achieved when fixing the metal block 8.

[0034] The solder layers 12 are not limited to being placed at the four corners of the block arrangement area 10, but can also be provided in other patterns that are spaced apart from each other within the block arrangement area. For example, the solder layers 12 may be separated in the center in the short direction and provided as a pair, one above the other, along the long direction, as shown in Figure 10B, or they may be separated in the center in the long direction and provided as a pair, one left and one right, along the short direction, as shown in Figure 10C. In addition to being placed at the four corners as shown in Figure 10A, solder layers 12 may also be provided in the middle along the surrounding contour, as shown in Figure 10D.

[0035] In this manner, it is preferable to provide multiple solder layers 12 in an island-like arrangement, isolated from each other, within the block arrangement region 10 on the circuit board 2 where the metal blocks 8 are placed. (Second interface IF2)

[0036] Furthermore, the metal tabs 3, i.e., the positive electrode tab 3A and negative electrode tab 3B of the secondary battery cell 1, are joined to the upper surface of the metal block 8. Between the metal block 8 and the metal tabs 3, a joint region 20 is partially formed at the second interface IF2 where they face each other, in a plan view, where the metal block 8 and the metal tabs 3 are joined. (Joint region 20)

[0037] The joint region 20, where the metal block 8 and the metal tab 3 are joined, is positioned so as not to overlap with the solder layer 12 in a plan view of the power supply unit 100. By providing the joint region 20 that fixes the metal tab 3 and the metal block 8 in this way, while avoiding the solder layer 12, it is possible to avoid damaging the fixation between the metal block 8 and the circuit board 2 when fixing the positive or negative electrode tabs 3B to the metal block 8, thereby improving reliability.

[0038] The reason for this will be explained with reference to the power supply device 900 related to the comparative example shown in Figures 8 and 9. Figure 8 shows a state in which a metal block 908 is fixed on a circuit board 902 by reflow soldering. As shown by the dashed lines in the figure, reflow solder layers 912 are provided at each of the four corners of the block arrangement area 910. In this state, as shown in Figure 9, consider the case in which a positive electrode tab 903A or a negative electrode tab 903B, which is a metal tab 903, is placed on the upper surface of each metal block 908, and laser welding is performed by scanning a laser beam from the upper surface. In Figure 9, an example is shown in which the trajectory TR for scanning the laser beam is sawtooth-shaped.

[0039] When the scanned laser beam penetrates the metal tab 903 and the metal block 908 and reaches the reflow solder layer 912, there is a concern that the solder layer 192 fixing the metal block 908 and the circuit board 902 at the second interface may be melted, damaged, or penetrated, thereby compromising the reliability of the fixation between the metal block 908 and the circuit board 902. In particular, when the positive electrode tab 903A of the secondary battery cell is made of aluminum, its high reflectivity makes welding difficult, requiring the use of a high-power laser beam. This increases the concern that high-power laser welding may damage the solder layer 912.

[0040] In contrast, the power supply unit 100 according to this embodiment avoids such a situation and ensures the reliability of the joint by setting the joining region 20, which joins the metal block 8 and the metal tab 3, so as not to overlap with the solder layer 12. Specifically, when laser welding the metal tab 3 to the metal block 8, the laser beam is scanned while intentionally avoiding the solder layer 12, thereby preventing the joining region 20 from overlapping with the solder layer 12. This ensures that the joining of the metal tab 4 and the metal block 8, and the joining of the metal block 8 and the circuit board 2 are performed in separate regions, thus avoiding interference between the joinings and maintaining reliability.

[0041] In the example shown in Figure 7, the bonding region 20 is formed in a cross-shaped pattern on the metal block 8. This arrangement allows the four corners that fix the metal block 8 to the circuit board 2 to be removed, and the positive electrode tab 3A and negative electrode tab 3B to be fixed to the metal block 8.

[0042] Furthermore, the joining region 20 is not limited to this example, and is set in a region that does not overlap with the solder layer 12, i.e., in the non-solder region 13, according to the pattern of the solder layer 12 provided in the block arrangement region 10. For example, if the solder layer 12 is set at the four corners of a rectangle, as in the power supply device 100 according to Embodiment 1 shown in Figure 10A, the joining region 20 is set in a cross shape along the non-solder region 13. Also, if the solder layer 12B is set along a pair of long sides of the rectangular block arrangement region 10, as in the power supply device according to Embodiment 2 shown in Figure 10B, a rod-shaped joining region 20B is set in the center of the block arrangement region 10 along the longitudinal direction. Alternatively, if the solder layer 12C is set along a pair of short sides of the rectangular block arrangement region 10, as in the power supply device according to Embodiment 3 shown in Figure 10C, a rod-shaped joining region 20C is set in the center of the block arrangement region 10 along the short direction. Furthermore, as in the power supply device according to Embodiment 4 shown in Figure 10D, if solder layers 12D are set not only at the four corners of the rectangular block arrangement area 10 but also in the middle of the long side, the joining area 20D is set to a pattern in which two crosses are joined side by side.

[0043] Further, the bonding region 20 may be a single region or may be divided into a plurality of regions. For example, as in the power supply device according to Embodiment 5 shown in FIG. 10E, when solder layers 12E are provided along a pair of long sides of a rectangular block arrangement region 10, a plurality of rectangular bonding regions 20E may be provided at intervals along the longitudinal direction in the region sandwiched by the pair of solder layers 12E.

[0044] The bonding region 20, that is, the region where the laser beam is scanned during welding, can be easily set by setting the processing program of the laser processing apparatus. For example, when the reflow solder 11 is applied on the circuit board 2 as shown in FIG. 3, the circuit board 2 is imaged in a plan view, and the region of the solder layer 12 is specified by image processing. Then, a laser beam scanning pattern is set in the non-solder region 13 obtained by removing the solder layer 12 from the block arrangement region 10 so as to avoid the solder layer 12.

[0045] When setting the bonding region 20, it is preferable to set a certain margin instead of matching the contour of the solder layer 12, that is, the outer edge of the non-solder region 13. Thereby, the solder layer 12 and the bonding region 20 can be surely separated, and the risk of impairing the bonding reliability can be reduced.

[0046] For the laser beam scanning, for example, when a cross-shaped bonding region 20 is set as shown in FIG. 7, the laser beam is irradiated in a pulsed manner along the contour of the cross shape. That is, the irradiation marks of the laser beam become dot-shaped, and by connecting these dots, the bonding region 20 along the cross-shaped contour is formed. Further, if necessary, the laser beam can be irradiated along the cross-shaped contour and the laser beam can be appropriately irradiated inside the contour to increase the area of the bonding region 20. Also in this case, it is not always necessary to scan the entire surface inside the contour of the bonding region 20, and the scanning and irradiation positions of the laser beam are determined so that the irradiation marks of the laser beam are appropriately separated. For such a laser processing apparatus used for laser welding, a high-power fiber laser can be preferably used. [Method for manufacturing a power supply device]

[0047] Next, a method for manufacturing a power supply device 100 including a secondary battery cell 1 and a circuit board 2 will be described. First, a circuit board 2 to which a metal block 8 is fixed via a solder layer 12 is prepared.

[0048] Specifically, as shown in FIG. 3, on the circuit board 2, reflow solder 11 is applied to a part of a block placement area 10 where the metal block 8 is to be placed. Next, as shown in FIG. 4, the metal block 8 is placed on top of the reflow solder 11 on the circuit board 2.

[0049] In this state, the circuit board 2 with the metal block 8 placed thereon is passed through a reflow heating furnace to melt and cure the reflow solder, forming a solder layer 12, and fixing the metal block 8 to the circuit board 2 via the solder layer 12. In this way, a circuit board 2 with the metal block 8 fixed as shown in FIG. 6 is prepared.

[0050] Next, as shown in FIG. 5, a positive electrode tab 3A and a negative electrode tab 3B are arranged on the metal block 8. In this state, as shown in FIG. 7, in a plan view of the power supply device 100, a bonding region 20 is set in a region that does not overlap with the solder layer 12, and a laser beam is scanned over the bonding region 20 to weld the positive electrode tab 3A and the negative electrode tab 3B to the metal block 8. In this way, it becomes possible to fix the metal block 8 to the circuit board 2 having the metal block 8 connected to the metal tab 3 by laser welding. Here, by setting the bonding region 20 for fixing the positive electrode tab 3A and the negative electrode tab 3B to the metal block 8 while avoiding the solder region, when fixing the metal tab 3 such as the positive electrode tab 3A or the negative electrode tab 3B to the metal block 8, a situation that impairs reliability such as damage to the fixing to the circuit board 2 on the back side of the metal block 8 can be avoided.

[0051] The power supply device and its manufacturing method, the laser welding method, and the laser welding method for a metal plate according to the present disclosure can be suitably used for connecting a metal tab of a secondary battery cell to a circuit board in a battery pack used for a driving power source of an assist bicycle, a self-propelled robot for home delivery, a home delivery vehicle, an electric cart for a golf course, an electric scooter, a construction machine, a hybrid vehicle, an electric vehicle, or the like. Further, it can be applied not only to the power supply device but also to various contacts that require bonding between metals.

[0052] 100...Power supply unit 1...Secondary battery cell 2...Circuit board 3...Metal tab; 3A...Positive electrode tab; 3B...Negative electrode tab 4...Battery element 5...Laminated section 6...Terrace section 7...Side wall 8...Metal block 10...Block placement area 11...Reflow solder 12...Solder layer 13...Non-solder area 20...Bonding area 900...Power supply unit 902...Circuit board 903...Metal tab; 903A...Positive electrode tab; 903B...Negative electrode tab 908...Metal block 910...Block placement area 912...Solder layer IF1...First interface IF2...Second interface TR...Trajectory for scanning laser beam

Claims

1. A power supply device comprising: a secondary battery cell having a positive electrode tab and a negative electrode tab; and a circuit board having a pair of metal blocks connected to the positive electrode tab and the negative electrode tab of the secondary battery cell, wherein a solder layer is formed on at least a portion of the block arrangement region where the metal blocks and the circuit board face each other; in a plan view of the power supply device, the solder layer is formed in an island shape along at least a portion of the contours of the positive electrode tab and the negative electrode tab; in a plan view of the power supply device, a bonding region is formed where the positive electrode tab and the negative electrode tab and the metal block are joined together at at least a portion of the interface where the positive electrode and the negative electrode tab and the metal block face each other; and in a plan view of the power supply device, the solder layer and the bonding region are arranged so as not to overlap.

2. A power supply device according to claim 1, wherein, in a plan view of the power supply device, the solder layer is formed to overlap the corner of the metal block.

3. A power supply device according to claim 2, wherein the bonding region is formed in a cross-shaped pattern on the metal block.

4. A power supply device according to claim 1, wherein the positive electrode tab is made of Al, the negative electrode tab is made of Ni, and the metal block is made of nickel, or nickel silver plated on the surface or aluminum.

5. A power supply device according to claim 1, wherein the solder layer is made of reflow solder.

6. A power supply device according to claim 1, wherein the secondary battery cell is a pouch cell.

7. A method for manufacturing a power supply device comprising: a secondary battery cell having a positive electrode tab and a negative electrode tab; a circuit board having a pair of metal blocks connected to the positive electrode tab and the negative electrode tab of the secondary battery cell, respectively, the method comprising: applying reflow solder to a part of a block placement area on the circuit board where the metal blocks are placed; placing the metal blocks on top of the reflow solder on the circuit board; passing the circuit board on which the metal blocks are placed through a reflow heating furnace to melt and harden the reflow solder to form a solder layer, and fixing the metal blocks to the circuit board via the solder layer; placing the positive electrode and negative electrode tabs on the metal blocks; and, with the positive electrode and negative electrode tabs placed on the metal blocks, setting a bonding area in a region that does not overlap with the solder layer in a plan view of the power supply device, scanning the bonding area with a laser beam to weld the positive electrode and negative electrode tabs to the metal blocks.

8. A laser welding method for a power supply device comprising: a secondary battery cell having a positive electrode tab and a negative electrode tab; and a circuit board having a pair of metal blocks connected to the positive electrode tab and the negative electrode tab of the secondary battery cell, respectively, the method comprising: preparing the circuit board by placing the metal blocks on top of reflow solder applied to a part of a block placement area on the circuit board, melting and hardening the reflow solder to form a solder layer, thereby fixing the metal blocks via the solder layer; placing the positive electrode and negative electrode tab on the metal blocks; and, with the positive electrode and negative electrode tab placed on the metal blocks, setting a joining area in a plan view of the power supply device that does not overlap with the solder layer, scanning the joining area with a laser beam to weld the positive electrode and negative electrode tab to the metal blocks.

9. A laser welding method for a metal plate, comprising the steps of: applying reflow solder to a part of a block placement area on the circuit board where the metal block is to be placed; placing the metal block on top of the reflow solder on the circuit board; passing the circuit board on which the metal block is placed through a reflow heating furnace to melt and harden the reflow solder to form a solder layer, and fixing the metal block to the circuit board via the solder layer; placing the metal tab on the metal block; and, with the metal tab placed on the metal block, setting a joining area in a plan view that does not overlap with the solder layer, scanning the joining area with laser light to weld the metal tab to the metal block.

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