Battery pack

Abstract

A battery pack is provided with: a battery block in which a plurality of battery cells are arranged at fixed positions; a circuit board connected to the battery cells of the battery block; and a lead plate connected to a lead connection portion provided on the surface of the circuit board. The circuit board is a multilayer substrate in which a plurality of insulating layers and a wiring pattern are laminated into a plurality of layers, and a reflective copper foil that reflects a laser beam is disposed at a position in which the insulating layers and the wiring pattern are laminated into a plurality of layers. And a reflective copper foil which is positioned on the rear surface side of the first insulating layer on the surface of which the lead connection part is disposed, faces a fusion region where the lead connection part and the lead plate are fused, and is closely attached to the rear surface of the insulating layer of the laminated structure by a laser reflecting surface of the reflective copper foil which reflects a laser beam on the surface, the laser reflecting surface being covered by the insulating layer.

Description

Technical Field

[0001] This disclosure relates to a battery pack constructed by being electrically connected to a circuit board via laser welding. Background Technology

[0002] In order to power electrical equipment using rechargeable secondary battery cells such as lithium-ion secondary batteries, battery packs and power supply devices using multiple secondary battery cells are used as power sources for electric vehicles such as electric bicycles, electric cars, and electric scooters, or as power sources for portable devices such as power tools and electric cleaners, and are used in various fields. Such battery packs widely adopt the following structure: the secondary battery cells are positioned in a fixed position using a battery holder, and the lead plate connected to the electrodes of the secondary battery cells is exposed from the battery holder and soldered to the surface of the circuit board for electrical connection (e.g., Patent Document 1).

[0003] Brazing makes it difficult to maintain a consistently stable electrical connection. This is because the structure for connecting a leadboard to a circuit board via brazing requires the leadboard to maintain a fixed contact state with the lead connector on the circuit board. In this state, the solder melts, and the molten solder adheres tightly to both the lead connector and the leadboard, maintaining this contact state while cooling the molten solder. However, in brazing, the molten solder contacts the surfaces of the lead connector and the leadboard, and cooling occurs while still in contact, making it difficult to maintain a consistently stable electrical connection.

[0004] Brazing that provides a consistently stable electrical connection requires the following conditions (1) to (3).

[0005] (1) Keep the lead wire connection and the lead wire plate in contact;

[0006] (2) The solder at the contact position between the lead connector and the lead plate is heated and melted, or the heated and melted solder is supplied to the contact position, and the lead connector and the lead plate are heated by the molten solder, so that the surface temperature of the heated lead connector and the lead plate is higher than the melting temperature of the solder, so that the molten solder flows and seals the surface of the lead connector and the lead plate.

[0007] (3) Furthermore, the lead wire connection and the lead plate are not misaligned, and the molten solder that is in close contact with the surface of the lead wire connection and the lead plate is cooled.

[0008] Stable brazing requires meeting the above requirements. Therefore, it is necessary to keep the lead connection and the lead plate in contact, ensuring that the surface temperature of the lead connection and the lead plate being brazed is higher than the melting temperature of the solder. This allows the solder to flow along the surface of the lead connection and the lead plate and adhere tightly. Furthermore, the molten solder flows along the surface and remains in the adhered position, allowing the molten solder to cool and harden. In the connection structure of Patent Document 1, to meet the requirement of (1), the lead plate and the lead connection of the circuit board are kept in a locked state for brazing. This connection structure uses a pin that is bent into a unique shape, and the pin and the lead plate are kept in a locked state for brazing. The above-mentioned stacked structure can connect and braze the lead plate and the circuit board without misalignment. However, since the pin is bent into a complex shape and the lead plate is locked to the pin for brazing, there is a problem of labor-intensive component processing and brazing.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent Application Publication No. 2013-247100 Summary of the Invention

[0012] The connection structure in Patent Document 1 allows for the misalignment of the lead connector and lead plate, but the solder-based electrical connection has inherent problems that cannot be eliminated in principle. It does not directly connect the components to be connected via electrodes, but rather through solder, thus potentially resulting in a mechanical connection without electrical connection. These problems can be eliminated by replacing soldering with laser welding, which melts the metals of both components to achieve an electrical connection. However, laser welding involves a laser beam melting the lead connector and lead plate to be fused together, leading to the following issues: the laser beam melting the two components can partially melt the circuit board, causing unexpected short circuits and melting other components. The drawback of laser beams penetrating circuit boards can be prevented by placing components that are not melted by the laser beam, such as thick metal plates or ceramics, on the back of the circuit board to block the laser beam. However, this method has the following disadvantages: it is laborious to place the components that block the laser beam at the point where the laser beam penetrates, and it is even more difficult to place the components that block the laser beam between the stacked insulating layers in multilayer boards.

[0013] One of the objectives of this disclosure is to provide a battery pack that reliably and stably connects the circuit board and the lead plate without requiring a dedicated component to eliminate the problem of laser beams penetrating the circuit board, thus avoiding the drawbacks of laser beams penetrating the circuit board.

[0014] One aspect of this disclosure relates to a battery pack comprising: a battery block in which multiple battery cells are arranged in fixed positions; a circuit board connected to the battery cells of the battery block; and a lead plate connected to a lead connection portion disposed on the surface of the circuit board. The circuit board is a multilayer substrate formed by stacking multiple insulating layers and wiring patterns into multiple layers. Furthermore, a reflective copper foil for reflecting laser beams is disposed on the circuit board at a position opposite to the back side of a first insulating layer on which the lead connection portion is disposed and to a welding area where the lead connection portion and the lead plate are fused. The laser reflecting surface of the reflective copper foil for reflecting laser beams is in close contact with the back side of the stacked insulating layer, and the laser reflecting surface is covered by the insulating layer.

[0015] The above battery pack has the following advantages: it eliminates the need for special components to eliminate the problem of laser beams penetrating the circuit board, and it can avoid the drawbacks of laser beams penetrating the circuit board by laser welding the circuit board and lead plate to achieve a reliable and stable electrical connection. Attached Figure Description

[0016] Figure 1 This is a schematic perspective view of a battery pack according to one embodiment of the present disclosure.

[0017] Figure 2 This is a simplified exploded 3D view of the battery pack.

[0018] Figure 3 It is a roughly enlarged cross-sectional view showing the welded area formed by laser.

[0019] Figure 4A It is a schematic plan view representing the wiring pattern.

[0020] Figure 4B It is a schematic plan view representing the wiring pattern.

[0021] Figure 5 This is a schematic cross-sectional view of a battery pack according to other embodiments of this disclosure.

[0022] Figure 6 This is a schematic cross-sectional view of a battery pack according to other embodiments of this disclosure. Detailed Implementation

[0023] The manner of this disclosure can be determined by the following composition and features.

[0024] One embodiment of the present disclosure relates to a battery pack comprising: a battery block in which a plurality of battery cells are arranged in a fixed position; a circuit board connected to the battery cells of the battery block; and a lead plate connected to a lead connection portion disposed on the surface of the circuit board. The circuit board is a multilayer board formed by stacking a plurality of insulating layers and wiring patterns into a plurality of layers. Furthermore, a reflective copper foil for reflecting a laser beam is disposed on the circuit board at a position opposite to the back side of a first insulating layer on which the lead connection portion is disposed, and opposite to a welding area where the lead connection portion and the lead plate are fused together. The laser reflecting surface of the reflective copper foil for reflecting a laser beam is in close contact with the back side of the stacked insulating layer, and the laser reflecting surface is covered by the insulating layer.

[0025] The above battery pack has the following advantages: it eliminates the need for dedicated components to eliminate the problem of laser beam penetration through the circuit board, and allows for reliable and stable electrical connection by laser welding of the circuit board and lead plate, avoiding the drawbacks of laser beam penetration. This is because the above battery pack uses copper foil provided on the circuit board connecting the lead plate as reflective copper foil to reflect the laser beam, thereby laser welding the lead connection portion of the circuit board and the lead plate. In this specification, "lead plate" is not specifically defined as a lead plate that is entirely made of metal, but is used broadly to include leads to which plate-shaped connection terminals are connected to the ends of leads.

[0026] Another embodiment of the battery pack disclosed herein may involve a multilayer substrate of the circuit board having a second insulating layer stacked on the back side of the first insulating layer, and a reflective copper foil disposed between the first insulating layer and the second insulating layer. The above battery pack has the advantage that the laser beam penetrates only the first insulating layer where lead connections are provided and does not penetrate other insulating layers below the first insulating layer (below the second insulating layer).

[0027] Another embodiment of the battery pack disclosed herein may involve, based on any of the above methods, making the reflective copper foil a floating island that is not connected to copper foil of other wiring patterns. The above battery pack has the following advantages: since the reflective copper foil is made into a floating island, even if the laser beam melts the lead plate, lead connection portion, and metal of the wiring pattern and electrically connects them to the reflective copper foil, no disadvantages caused by such electrical connection will occur.

[0028] Another embodiment of the battery pack disclosed herein may involve, based on any of the above methods, a circuit board having one or more reflective copper foils, such that at least one or more reflective copper foils are floating islands not connected to copper foils of other wiring patterns. The above battery pack has the following advantages: by providing multiple reflective copper foils, and furthermore, by making one or more reflective copper foils floating islands, the drawback of laser beams penetrating the circuit board can be more reliably prevented, thereby improving safety.

[0029] Another embodiment of the battery pack disclosed herein may involve, based on any of the above embodiments, having the lead connection portion of the circuit board as a metal plate electrically connected to the circuit board via a wiring pattern copper foil fixed to the surface of the first insulating layer of the circuit board. The above battery pack has the advantage that, since a metal plate is provided on the copper foil on the surface of the circuit board as the lead connection portion, the lead plate can be stably electrically connected to the circuit board via the metal plate.

[0030] Another embodiment of the battery pack disclosed herein may involve, based on any of the above embodiments, having the lead connection portion be a metal plate soldered to copper foil of a wiring pattern. The above battery pack has the advantage that, since the metal plate soldered to copper foil of a wiring pattern is used as the lead connection portion, the lead plate can be stably electrically connected to the circuit board via this metal plate.

[0031] Another embodiment of the battery pack disclosed herein may involve, based on any of the above-described methods, a copper foil removal area where no copper foil is present directly below the welding area of ​​the metal plate where the lead connection portion and the lead plate are welded, provided by the wiring pattern on the surface of the circuit board. The above-described battery pack has the following advantages: by providing a copper foil removal area where no copper foil (surface copper foil) is present directly below the welding area by the wiring pattern (surface wiring pattern) on the surface of the circuit board, melting of the copper foil (surface copper foil) and flow of molten copper foil (surface copper foil) down into the through-hole can be prevented, thus avoiding electrical connection with the reflective copper foil on the back side of the insulating layer.

[0032] Another embodiment of the battery pack disclosed herein may involve, based on any of the above-described methods, having a metal plate for the lead connection portion that is thicker than the copper foil of the wiring pattern. The above-described battery pack has the advantage that, since the lead plate can be connected to the circuit board via a metal plate thicker than the copper foil, the lead plate and the circuit board can be reliably connected.

[0033] Another embodiment of the battery pack disclosed herein may be, based on any of the above methods, wherein the metal plate of the lead connection portion is a metal plate with a nickel-plated surface.

[0034] Another embodiment of the present disclosure relates to a battery pack in which, based on any of the above methods, the battery block includes a battery holder that arranges a plurality of battery cells in a fixed position, the battery holder arranges a circuit board in a fixed position, one end of a lead plate is laser-welded to a lead connection portion, and the other end is connected to a battery cell.

[0035] Another embodiment of the battery pack disclosed herein may include, based on any of the above methods, an outer casing for housing the circuit board and the battery pack, the outer casing having an output terminal, one end of the lead plate being laser-welded to the lead connection portion, and the other end being connected to the output terminal.

[0036] The embodiments of this disclosure will now be described with reference to the accompanying drawings. Furthermore, in the following description, terms indicating specific directions or positions (e.g., "upper," "lower," and other terms including these terms) will be used as needed, but these terms are used to facilitate understanding of the invention with reference to the drawings, and the technical scope of this disclosure is not limited by the meaning of these terms. Additionally, portions marked with the same reference numerals shown in the various drawings represent the same or equivalent parts or components.

[0037] Furthermore, the embodiments shown below are specific examples illustrating the technical concept of this disclosure and are not intended to limit this disclosure to these embodiments. Additionally, the dimensions, materials, shapes, and relative arrangements of the constituent components described below are not intended to limit the scope of this disclosure unless specifically stated otherwise; they are merely illustrative. Furthermore, the content described in one embodiment or example can be applied to other embodiments or examples. Additionally, the size and positional relationships of the components shown in the accompanying drawings are sometimes exaggerated for clarity.

[0038] The battery pack 100 disclosed herein can utilize a structure in which a lead plate 3 is laser-welded to a circuit board 2 connected to a secondary battery cell 1 for electrical connection. In particular, it can utilize a battery pack 100 in which a plurality of secondary battery cells 1 are arranged in a fixed position using a battery holder 12 as a battery block 10, the circuit board 2 is connected to the battery block 10, and the lead plate 3 is laser-welded to the circuit board 2.

[0039] [Implementation Method 1]

[0040] The battery pack 100 according to Embodiment 1 of this disclosure is shown in Figures 1-4B In these figures, Figure 1 This is a schematic perspective view of the battery pack 100 according to Embodiment 1. Figure 2 This is a rough exploded 3D view of the battery pack 100. Figure 3 This is an enlarged schematic diagram of the welded area formed by laser. Figure 4A , Figure 4B It is a schematic plan view representing the wiring pattern.

[0041] (Battery pack 100)

[0042] Figure 1 or Figure 2The battery pack 100 shown includes: a battery block 10 in which multiple secondary battery cells 1 are arranged in fixed positions by battery holders 12; a circuit board 2 connected to the secondary battery cells 1 of the battery block 10; and an outer casing 15 for housing the circuit board 2 and the battery block 10. Output terminals 16 are disposed on the surface of the outer casing 15. The circuit board 2 and a lead plate 3 are electrically connected by laser welding. The lead plate 3, electrically connected to the circuit board 2, connects the circuit board 2 to the secondary battery cells 1, the output terminals 16, etc.

[0043] (Circuit board 2)

[0044] Figure 1 The battery block 10 shown has a circuit board 2 mounted on the surface (upper surface in the figure) of a plastic battery holder 12 that holds the secondary battery cell 1 in a fixed position. The circuit board 2 may include, for example, a current detection circuit for detecting the charging and discharging current, a circuit for detecting and calculating the full charge and remaining capacity of the secondary battery cell 1 based on battery information such as voltage and temperature, a control circuit for controlling the charging and discharging of the secondary battery cell 1, or a protection circuit for monitoring whether the battery is functioning properly. The circuit board 2 in the figure is formed in a rectangular shape, but it can also be in a shape other than a rectangle. The circuit board 2 is a multilayer substrate with multiple insulating layers 21 stacked on top of each other, and the insulating layers 21 are preferably made of resin such as glass epoxy resin. Furthermore, this disclosure does not limit the type, structure, manufacturing method, or process of the insulating layers.

[0045] The circuit board 2 of the multilayer substrate has multiple insulating layers 21 and wiring patterns 22 (wiring layers) alternately stacked. Regarding the multiple insulating layers 21, for example, the substrate layer and the prepreg layer can be alternately stacked in a manner where a prepreg layer sandwiches a substrate layer. Additionally, a resist layer or similar material can be provided to protect the surface. Figure 3 The circuit board 2 shown in the enlarged cross-sectional view is a multilayer substrate with three insulating layers 21 stacked on top of each other. A second insulating layer 21B is stacked on the back side of the first insulating layer 21A, and a third insulating layer 21C is stacked on the back side of the second insulating layer 21B. In the case of a multilayer substrate with three insulating layers 21 stacked on top of each other, the second insulating layer 21B in the middle is composed of a substrate layer, and the first insulating layer 21A and the third insulating layer 21C sandwiched between the upper and lower sides can be composed of prepreg layers. The circuit board 2 in the figure has three insulating layers stacked from the surface side where the lead connection portion 31 is provided: the first insulating layer 21A, the second insulating layer 21B, and the third insulating layer 21C. Figure 3The circuit board 2 shown has copper foil 23 forming a wiring pattern 22 between each insulating layer 21. The wiring pattern 22 between the upper and lower insulating layers 21 is sandwiched between the upper and lower insulating layers 21 and is in close contact with the surfaces (upper and lower surfaces) of the upper and lower insulating layers 21. The wiring pattern 22 is disposed on the surface including the upper and lower surfaces (upper and lower surfaces) of the insulating layers 21. The wiring pattern 22 between each insulating layer 21 is sandwiched and in close contact with the lower surface of the upper insulating layer 21 and the upper surface of the lower insulating layer 21. Figure 3 The circuit board 2 shows a copper foil 23 with three layers of wiring patterns 22, including the wiring pattern 22 (surface wiring pattern 22a) on the surface where the lead connection portion 31 is provided, the wiring pattern 22 between the first insulating layer 21A and the second insulating layer 21B, and the wiring pattern 22 between the second insulating layer 21B and the third insulating layer 21C. However, the circuit board of the multilayer board disclosed herein is not limited to the number of insulating layers and wiring patterns. For example, it is possible to have three or more insulating layers, and it is possible to have wiring patterns (copper foil) of, for example, four, six, eight, or even more layers of wiring patterns.

[0046] The circuit board 2 of the multilayer substrate is fabricated by laminating multiple insulating layers 21 in a tightly packed state. Wiring patterns 22 of copper foil 23 are provided on the upper and lower surfaces of the circuit board 2 and between the stacked insulating layers 21. The copper foil 23 is prevented from contacting air by the insulating layers 21 tightly packed to its surface, thus preventing oxidation of the copper foil 23 surface. The surface of the unoxidized copper foil 23 has high reflectivity to laser beams, preventing melting of the copper foil 23 caused by the laser beam. The battery pack 100 of this disclosure effectively utilizes the unique physical property of copper surface to efficiently reflect laser beams, preventing the disadvantage of laser beams melting and penetrating the circuit board 2. In particular, by effectively utilizing the copper foil 23 provided as wiring patterns 22 in the circuit board 2, the copper foil 23 reflects laser beams, thereby preventing the circuit board 2 from melting and penetrating due to laser beams. The structure that effectively utilizes the copper foil 23 of the circuit board 2 to prevent the laser beam from penetrating the circuit board 2 has the following advantages: the insulating layer 21, which is closely attached to the surface of the copper foil 23, effectively prevents the oxidation of the surface of the copper foil 23, and effectively maintains the reflectivity of the laser beam on the surface of the copper foil 23 stably and at a high level. Therefore, the structure that uses the copper foil 23, which is already provided as a wiring pattern 22 in the circuit board 2, as a component to prevent the laser beam from penetrating the circuit board 2 has the following advantages: it eliminates the need to provide dedicated components between the insulating layers 21 to prevent the defects caused by the laser beam, and it can eliminate the obstacle of the circuit board 2 caused by the laser beam with a simple structure that effectively utilizes a portion of the copper foil 23 of the wiring pattern 22. Moreover, it can prevent the defects caused by the laser beam, and laser welding can be performed to reliably and stably connect the circuit board and the lead plate.

[0047] Figure 3 The circuit board 2 shown in the enlarged cross-sectional view has a lead connection portion 31 provided on the surface of the first insulating layer 21A. The lead connection portion 31 shown in this figure is electrically connected by brazing a metal plate 32 to a copper foil 23 (surface copper foil 23a) of a wiring pattern 22 (surface wiring pattern 22a) provided on the surface of the circuit board 2. The metal plate 32 is thicker than the copper foil 23; for example, the film thickness of the copper foil 23 can be 0.01 mm or more and 0.06 mm or less, and the thickness of the metal plate 32 can be, for example, 13 times or more, preferably 15 times or more, of the copper foil, for example, about 1 mm. The lead plate can be stably electrically connected to the circuit board via a metal plate thicker than the copper foil. In order to stably laser weld the lead plate 3 and reduce resistance, the metal plate 32 can, for example, be an aluminum plate with a nickel-plated surface. However, the metal plate can also be other metal plates such as iron with a nickel-plated surface, or the entire plate can be a nickel plate.

[0048] Figure 3 In the enlarged cross-sectional view of the circuit board 2, a reflective copper foil 24, which reflects the laser beam, is provided as part of the wiring pattern 22 at a position between the first insulating layer 21A and the second insulating layer 21B, opposite to the welding area where the lead plate 3 is laser-welded to the lead connection portion 31. The laser-reflecting surface 24a of the reflective copper foil 24 (the upper surface of the reflective copper foil 24 in the figure) is tightly adhered to the back side of the first insulating layer 21A stacked on it, thereby preventing surface oxidation. The reflective copper foil 24, maintained in an unoxidized state, has a high reflectivity to the laser beam, efficiently reflecting the laser beam without melting, thus preventing the laser beam from penetrating the circuit board 2. The laser welding of the lead plate 3 utilizes the reflective copper foil 24 to reflect the laser beam, thus avoiding the disadvantage of penetrating the circuit board 2. In laser soldering of leadboard 3, for example, a YAG laser can be used. However, the reflectivity of YAG laser on the unoxidized copper surface is as high as about 90%, and copper only absorbs about 10% of the laser beam energy, which is about 1 / 3 of that of nickel. This disclosure effectively utilizes the unique physical properties of the circuit board 2 with wiring pattern 22 provided with copper foil 23, that is, the copper foil 23 provided on the printed circuit board, namely the unique physical property that the copper foil 23 is not melted by the laser beam, to prevent the drawbacks caused by the laser beam penetrating the circuit board 2.

[0049] The circuit board 2 has a reflective copper foil 24 disposed on the back side of the first insulating layer 21A on which the lead connection portion 31 is disposed, and opposite to the welding area where the lead connection portion 31 and the lead plate 3 are fused. The reflective copper foil 24 is disposed on the back side of the first insulating layer 21A, that is, on the surface (upper or lower surface) of the back side of the insulating layer 21 containing the back side of the first insulating layer 21A or the back side of the insulating layer 21 that is lower than the first insulating layer 21A. The reflective copper foil 24 is disposed in close contact with the back side of any insulating layer 21. The reflective copper foil 24 is preferably disposed on the back side of the insulating layer 21 at a shallow position close to the surface of the insulating layer 21 on which the lead connection portion 31 is disposed. The laser beam is reflected by the reflective copper foil 24, and the laser beam does not travel to depths below the reflective copper foil 24. By placing the reflective copper foil 24 on the back side of the shallow insulating layer 21, the penetration depth of the laser beam can be suppressed to a shallower depth, the range in which interlayer short circuits may occur can be limited, and the drawbacks caused by the laser beam penetrating the circuit board 2 can be prevented. Figure 3 The circuit board 2 has a reflective copper foil 24 disposed on the back side (lower surface side) of the first insulating layer 21A. The laser beam is reflected by the laser reflecting surface 24a of the reflective copper foil 24, thereby preventing it from traveling deeper than the first insulating layer 21A and penetrating through it.

[0050] The first insulating layer 21A, in Figure 3 In this case, a reflective copper foil 24 is set on the back using a wiring pattern 22 of copper foil 23. For example... Figure 4B As shown, the reflective copper foil 24 is like an island that exists independently of the land, and is not connected to the copper foil 23 of other wiring patterns 22. Figure 4A The copper foil 23 shows the wiring pattern 22 on the surface of the circuit board 2 (the surface of the first insulating layer 21A) connected to the lead connection portion 31. Figure 4B The diagram shows a case where the reflective copper foil 24 of the wiring pattern 22 on the back side of the first insulating layer 21A is a floating island 25, with non-connection portions 26 formed around it. The non-connection portions 26 separate the floating island 25 from the copper foil 23 of other wiring patterns 22, making it non-connected. This ensures that the reflective copper foil 24 of the floating island 25 is not connected to the copper foil 23 of other wiring patterns 22 in the same layer. The reflective copper foil 24 of the floating island 25 prevents the disadvantage caused by the molten metal, such as the copper foil 23 on the lead connection portion 31 or surface, penetrating the insulating layer 21 and electrically connecting to the reflective copper foil 24 during the laser welding of the lead board 3. The reflective copper foil 24 is designed to prevent itself from being melted by the irradiated laser beam, rather than preventing the laser beam from melting and penetrating the first insulating layer 21A. Sometimes the laser beam penetrating the first insulating layer 21A melts the metal of the lead connection portion 31, or melts the wiring pattern 22 due to its heat. The molten metal flows down through the through hole and is electrically connected to the reflective copper foil 24 provided on the back side.

[0051] The drawbacks caused by the connection of molten metal such as lead connector 31 to reflective copper foil 24 can be eliminated by making reflective copper foil 24 a floating island 25. In the multilayer substrate, copper foil 23 is configured with an optimal wiring pattern 22 on both the surface and back of the first insulating layer 21A, but the wiring pattern 22 of copper foil 23 is not configured to electrically connect lead connector 31 and reflective copper foil 24. This is because even if molten metal penetrating the insulating layer 21 electrically connects lead connector 31 and reflective copper foil 24, the electrical connection caused by the molten metal cannot be as stable as a through-hole provided through the insulating layer 21 of the multilayer substrate, and it will not form a circuit structure that electrically connects the wiring patterns 22 on both sides at the location where the molten metal penetrates the insulating layer 21. Therefore, when the laser beam electrically connects lead connector 31 and reflective copper foil 24, normal operation of the circuit board 2 becomes impossible. Assuming a circuit structure in which the lead connection portion 31 is connected to the power line on the front side in the wiring pattern 22 where the reflective copper foil 24 on the back side of the first insulating layer 21A is connected to the ground wire, the disadvantage of molten metal short-circuiting the output terminal 16 to the ground wire would occur. With the floating island 25, even if the lead connection portion 31 is electrically connected to the reflective copper foil 24 due to molten metal, it will not connect to other circuits, ensuring the normal operation of the circuit board 2.

[0052] The reflective copper foil 24 has a laser-reflecting surface 24a that reflects the laser beam. Taking into account the size of the lead connection portion 31 and the offset of the laser beam's irradiation position, the laser-reflecting surface 24a is designed to be large and shaped enough to cover at least the area irradiated by the laser beam. The reflective copper foil 24 of the floating island 25 has a laser-reflecting surface 24a, and a non-connection portion 26 is formed around the floating island 25 that is not connected to the copper foil 23 of other wiring patterns 22. The non-connection portion 26 is designed to ensure that even if the lead connection portion 31 is electrically connected to the reflective copper foil 24 by molten metal caused by the laser beam, the reflective copper foil 24 is not connected to the copper foil 23 of other wiring patterns 22 on the same layer. Therefore, the reflective copper foil 24 of the floating island 25 can reliably avoid the disadvantage of the laser beam penetrating the circuit board 2.

[0053] The copper foil 23 of the wiring pattern 22 disposed on the surface of the circuit board 2 connected to the lead connection portion 31, i.e., the surface of the first insulating layer 21A, is referred to as the surface copper foil 23a of the surface wiring pattern 22a. The area of ​​the surface copper foil 23a that is directly below the stacking direction of the plurality of insulating layers 21 including the fusion area, and that includes the portion connected to the lead connection portion 31 or is located directly above the reflective copper foil 24, is referred to as the connecting copper foil 23b. The connecting copper foil 23b may be configured to have the same or different shape, size, or area as the reflective copper foil 24. For example, the connecting copper foil 23b may be configured to have a smaller area or a different shape than the reflective copper foil 24. The connecting copper foil 23b may be configured to have a shape in which the surface copper foil 23a of the surface wiring pattern 22a directly below the fusion area where the lead connection portion 31 and the lead plate 3 are fused by the laser beam is removed. Figure 4A The connecting copper foil 23b has a copper foil removal area 23c of the surface copper foil 23a that does not have a surface wiring pattern 22a directly below the fusion area. By making the connecting copper foil 23b smaller than the reflective copper foil 24, and especially by having a copper foil removal area 23c of the surface copper foil 23a that does not have a surface wiring pattern 22a directly below the fusion area, it is possible to prevent or reduce the melting of the surface copper foil 23a of the surface wiring pattern 22a due to the laser beam or its heat, and the flow of the molten surface copper foil 23a down into the through hole, thereby avoiding or suppressing electrical connection with the reflective copper foil 24 disposed on the back side of the insulating layer 21.

[0054] By configuring the connecting copper foil 23b to be in a shape, size, and area that allows for stable connection of the lead wire connection portion 31, the lead board 3 can be stably electrically connected to the circuit board 2 via the lead wire connection portion 31. The connecting copper foil 23b can be configured, for example, to be a shape that surrounds the area excluding the area directly below the fusion area, or a shape that partially surrounds the area, such as a straight line, curve, or plane. Figure 4A The connecting copper foil 23b is configured as two parallel straight lines extending in the left-right direction, excluding the area directly below the fusion welding zone. This connecting copper foil 23b can prevent the surface copper foil 23a from melting and flowing down into the through hole, and can stably connect the lead plate 3 to the circuit board 2 via the lead connection part 31.

[0055] [Implementation Methods 2 and 3]

[0056] The battery packs 200 and 300 involved in embodiments 2 and 3 of this disclosure are shown respectively. Figure 5 and Figure 6 . Figure 3 The circuit board 2 of the battery pack 100 shown has a reflective copper foil 24 provided on the wiring pattern 22 on the back side of the first insulating layer 21A, that is, between the first insulating layer 21A and the second insulating layer 21B. However, the reflective copper foil 24 can be provided on the wiring pattern 22 on the back side of the insulating layer 21, which is lower than the first insulating layer 21A. Figure 5The reflective copper foil 24 is disposed on the back side of the second insulating layer 21B. That is, in Figure 5 In this circuit, a reflective copper foil 24 is provided on the wiring pattern 22 between the second insulating layer 21B and the third insulating layer 21C. Furthermore, although not shown, the reflective copper foil can be provided on the back side of any insulating layer lower than the first insulating layer, such as the back side of the third insulating layer, or an insulating layer located lower than it. By providing the reflective copper foil 24 on the back side of any insulating layer 21 lower than the first insulating layer 21A, the drawback of the laser beam penetrating the circuit board 2 can be avoided, and the design freedom of the wiring pattern 22 can be increased. Additionally, the depth to which the laser beam penetrates the insulating layer 21 can be adjusted. As described above, when the reflective copper foil 24 is disposed on the back side of any insulating layer 21 lower than the first insulating layer 21A, in the wiring pattern disposed on the back side of the insulating layer between the lead connection portion 31 and the reflective copper foil 24, by setting it to a copper foil removal area that is directly below the welding area where the lead connection portion 31 and the lead plate 3 are welded together by a laser beam, the copper foil 23 of the wiring pattern 22 in the middle can be prevented from melting due to the laser beam or its heat used when the lead plate 3 is welded to the lead connection portion 31. Therefore, it is possible to avoid or suppress the melting of the copper foil 23 of the middle wiring pattern 22 and the molten copper foil 23 penetrating the insulating layer 21 and electrically connecting to the reflective copper foil 24. Furthermore, since, as described above, when there is a copper foil removal area in the middle wiring pattern 22, it is possible to avoid or suppress the electrical connection between the copper foil 23 of the middle wiring pattern 22 and the reflective copper foil 24, it is also preferable to set a structure in which the copper foil 23a of the surface wiring pattern 22a does not have a copper foil removal area 23c, but the connecting copper foil 23b is provided on the entire back side of the metal plate 32.

[0057] The circuit board 2 of the battery pack 300 can be provided with multiple reflective copper foils 24. These multiple reflective copper foils 24 are located opposite to the welding area where the lead connection portion 31 and the lead plate 3 are welded together by irradiating a laser beam, and each reflective copper foil 24 can be disposed between multiple insulating layers 21. When multiple reflective copper foils 24 are provided, it is preferable that the reflective copper foil 24 closest to the surface of the multilayer substrate is disposed on the back side of a shallow insulating layer 21 (e.g., the back side of the first insulating layer 21A). This is because the penetration depth of the laser beam can be suppressed to a shallower depth, and multiple reflective copper foils 24 can be disposed below the shallowest reflective copper foil 24. When multiple reflective copper foils 24 are provided, their shapes, sizes, etc., can be the same or different.

[0058] Multiple reflective copper foils 24 can be used to make all or any of the reflective copper foils floating islands 25. Figure 6In the figure, four layers of reflective copper foil 24 are stacked. The reflective copper foil 24 is disposed on the back side of the first insulating layer 21A, the back side of the second insulating layer 21B, the back side of the third insulating layer 21C, and the back side of the fourth insulating layer 21D. Furthermore, in... Figure 6 In this configuration, all reflective copper foils 24 are arranged as floating islands 25. By arranging multiple reflective copper foils 24 as floating islands 25, the drawback of laser beams penetrating the circuit board 2 can be more reliably prevented, thus improving the safety of the battery pack. Furthermore, as described above, the circuit board 2 of the multilayer substrate can effectively utilize a portion of the existing wiring pattern 22. In either the configuration of the reflective copper foils 2 or their arrangement as floating islands 25, the following advantages are available: by simply changing the shape of a portion of the existing wiring pattern 22 of the circuit board 2, without configuring other dedicated components, the drawback of laser beams penetrating the circuit board 2 can be reliably prevented without increasing costs, ensuring further improvement in safety. Especially as the requirements for high density and thinness increase, in circuit boards with 10 or more, dozens of, or even 100 layers, ensuring the reliability and safety of preventing laser beams from laser welding from penetrating the circuit board becomes even more important.

[0059] Industrial availability

[0060] The battery pack disclosed herein can be used effectively as a battery pack that can reliably and stably connect the circuit board and the lead plate by avoiding the drawback of the laser beam of laser welding penetrating the circuit board.

[0061] [Explanation of reference numerals in the attached figures]

[0062] 100, 200, 300, 900… battery packs

[0063] 1…Secondary battery unit

[0064] 2…Circuit board

[0065] 3…leadboard

[0066] 10… battery blocks

[0067] 12… Battery Holder

[0068] 15…Outer casing

[0069] 16… Output terminals

[0070] 21…Insulation layer

[0071] 21A…First Insulation Layer

[0072] 21B…Second Insulation Layer

[0073] 21C…Third Insulation Layer

[0074] 21D…Fourth Insulation Layer

[0075] 22… Wiring pattern

[0076] 22a… Surface wiring pattern

[0077] 23…copper foil

[0078] 23a… Surface copper foil

[0079] 23b… Connecting copper foil

[0080] 23c… Copper foil removal area

[0081] 24…Reflective copper foil

[0082] 24a…Laser reflector

[0083] 25… Floating Island

[0084] 26…Non-connecting parts

[0085] 31… Lead wire connection part

[0086] 32… metal plate

Claims

1. A battery pack, comprising: A battery block is formed by arranging multiple battery cells in fixed positions; The circuit board connected to the plurality of battery cells of the battery block; and A lead plate connected to a lead connection portion disposed on the surface of the circuit board. The circuit board is a multilayer substrate formed by stacking multiple insulating layers including a first insulating layer and wiring patterns. Furthermore, the circuit board has a reflective copper foil for reflecting laser beams disposed at a location opposite to the welded area where the lead connection portion is disposed on the back side of the first insulating layer. The laser-reflecting surface of the reflective copper foil, which reflects the laser beam from a surface opposite to the back side of any of the plurality of insulating layers, is in close contact with the back side of any of the insulating layers in the stacked structure. The laser reflective surface is covered by any of the insulating layers.

2. The battery pack according to claim 1, The plurality of insulating layers of the circuit board include a second insulating layer stacked on the back side of the first insulating layer. The reflective copper foil is disposed between the first insulating layer and the second insulating layer.

3. The battery pack according to claim 1, The reflective copper foil is a floating island that is not connected to the copper foil of the wiring pattern.

4. The battery pack according to claim 1, The circuit board has one or more of the aforementioned reflective copper foils. The one or more reflective copper foils are floating islands that are not connected to the copper foils of the wiring pattern.

5. The battery pack according to claim 1 or 4, The lead connection portion is a metal plate electrically connected to the copper foil of the wiring pattern disposed on the surface of the first insulating layer of the circuit board.

6. The battery pack according to claim 5, The lead connection portion is a metal plate that is brazed onto the copper foil of the wiring pattern.

7. The battery pack according to claim 5, A copper foil removal area is provided directly below the welding area of ​​the metal plate on the surface of the circuit board, in the stacking direction of the plurality of insulating layers, where the copper foil of the wiring pattern is not present.

8. The battery pack according to claim 5, The metal plate of the lead connection is a metal plate that is thicker than the copper foil of the wiring pattern.

9. The battery pack according to claim 5, The metal plate of the lead wire connection is a nickel-plated metal plate.

10. The battery pack according to claim 1, The battery block includes a battery holder that positions the plurality of battery cells in a fixed location. The battery holder positions the circuit board in a fixed location. One end of the lead plate is laser-welded to the lead connection portion, and the other end is connected to the corresponding battery cell among the plurality of battery cells.

11. The battery pack according to claim 1, It has an outer casing for housing the circuit board and the battery pack. The outer casing has output terminals. One end of the lead plate is laser-welded to the lead connection part, and the other end is connected to the output terminal.

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