Connection structure between heat sink and bus bar

Abstract

To provide a connection structure of a heat sink and a bus bar which is excellent in connection reliability and heat dissipation characteristics while preventing an increase in the number of components for connecting the heat sink to the bus bar.SOLUTION: A connection structure of a heat sink and a bus bar, comprises: a heat sink having a base plate that has a first surface and a second surface opposed to the first surface, and a plurality of heat radiation fins erected on the first surface of the base plate; and a bus bar connected to the second surface of the base plate and having a longitudinal direction and a transverse direction. In the connection structure, the second surface of the base plate and the bus bar are connected to each other at a laser welded part formed on the first surface between the heat radiating fins in a linear shape that does not intersect with each other from the first surface side.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a connection structure between a heat sink and a bus bar, in which a heat sink is laser-welded to a bus bar used as a circuit member in a vehicle such as an automobile. [Background technology]

[0002] Automobiles use many electrical components, such as electrically powered electrical devices and sensors that perform various controls, etc. These electrical components are connected to the battery, which serves as the power supply source, via various electric wires such as power lines and signal lines.

[0003] However, in recent years, the number of electrical components used in automobiles has increased, and there is a demand for an increase in the current capacity of electric wires. Therefore, for example, bus bars, which are plate-shaped conductors with a rectangular cross section, are sometimes used as circuit components.

[0004] On the other hand, as the functionality of electrical components increases, there may be areas on the busbar where heat concentrates due to current concentration on the busbar or an increase in the amount of heat generated by the electrical components. Therefore, a heat sink may be thermally connected to the heat-concentrating area of the busbar to dissipate the heat from the heat-concentrating area to the outside. Conventionally, methods for connecting a heat sink to a busbar have been implemented, such as by adhering the heat sink to the busbar with a thermally conductive adhesive, or by inserting a thermally conductive sheet or thermally conductive grease between the busbar and the heat sink and holding the heat sink to the busbar using a holding mechanism such as a screw or a locking member.

[0005] However, using a thermally conductive adhesive, a thermally conductive sheet, a thermally conductive grease, etc. increases the number of parts required to connect the heat sink to the bus bar, resulting in insufficient connection reliability. Furthermore, using a thermally conductive adhesive, a thermally conductive sheet, a thermally conductive grease, etc. increases manufacturing costs.

[0006] Furthermore, as a means for dissipating heat from a heat-concentrating portion of a busbar to the outside, it has been proposed to use a busbar formed by welding a tab terminal member to a pattern portion of the busbar, in which a welded member having at least a first portion perpendicular to the pattern portion and a second portion parallel to the pattern portion is welded to a predetermined position of the pattern portion of the busbar, and the welded member is used as a heat dissipation member (Patent Document 1).

[0007] However, in Patent Document 1, in which most of the current is diverted to the heat dissipation section, the heat dissipation area of the heat dissipation member is small and the heat dissipation characteristics are insufficient, so there was a need for improvement in terms of dissipating heat from the heat-concentrating section of the bus bar to the outside. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-151149 Summary of the Invention [Problem to be solved by the invention]

[0009] In view of the above circumstances, an object of the present invention is to provide a connection structure between a heat sink and a bus bar that has excellent connection reliability and heat dissipation characteristics while preventing an increase in the number of parts required to connect the heat sink to the bus bar. [Means for solving the problem]

[0010] The gist of the configuration of the present invention is as follows. [1] A heat sink including: a base plate having a first surface and a second surface opposite to the first surface; and a plurality of heat dissipation fins provided upright on the first surface of the base plate; a bus bar connected to the second surface of the base plate and having a longitudinal direction and a lateral direction; A connection structure between a heat sink and a bus bar, A connection structure in which the second surface of the base plate and the bus bar are connected by a laser weld formed on the first surface between the heat dissipation fins in a non-intersecting line from the first surface side. [2] The connection structure according to [1], wherein the laser welded portion is formed at an angle of more than 0° with respect to the short-side direction of the bus bar. [3] A connection structure according to [1] or [2], wherein a plurality of the laser welds are formed in parallel on the first surface. [4] The connection structure according to [1] or [2], wherein the laser welded portion is formed along the longitudinal direction of the bus bar. [5] A connection structure according to [3], wherein a plurality of the laser welds are formed parallel to one another on the first surface. [6] A connection structure according to [1] or [2], wherein the reflectivity of the material of the base plate to laser light having a wavelength of 900 nm or more and 1100 nm or less is lower than the reflectivity of the material of the bus bar to laser light having a wavelength of 900 nm or more and 1100 nm or less. [7] The connection structure according to [1] or [2], wherein the material of the base plate includes aluminum or an aluminum alloy, and the material of the bus bar includes copper or a copper alloy. [8] The connection structure according to [1] or [2], wherein the heat dissipation fin is a plate-shaped member or a columnar member. [9] The connection structure according to [1] or [2], wherein the heat dissipation fin is a plate-shaped member. [Effects of the Invention]

[0011] According to one aspect of the present invention, there is provided a connection structure between a heat sink and a bus bar, the connection structure comprising: a base plate having a first surface and a second surface opposite the first surface; a heat sink having a plurality of heat dissipation fins standing on the first surface of the base plate; and a bus bar having a longitudinal direction and a lateral direction and connected to the second surface of the base plate, wherein the second surface of the base plate and the bus bar are connected by laser welds formed on the first surface between the heat dissipation fins in non-intersecting lines from the first surface side, thereby preventing an increase in the number of parts required to connect the heat sink to the bus bar and providing a connection structure between a heat sink and a bus bar that has excellent connection reliability and heat dissipation characteristics.

[0012] Furthermore, according to an aspect of the connection structure between a heat sink and a bus bar of the present invention, the base plate and the bus bar are connected by a laser weld formed on the first surface between the heat dissipation fin and another adjacent heat dissipation fin from the first surface side, thereby making it possible to obtain a connection structure between a heat sink and a bus bar in which scattering of spatter due to welding is prevented.

[0013] According to an aspect of the connection structure between a heat sink and a bus bar of the present invention, a plurality of the laser welds are formed in parallel on the first surface, thereby increasing the area of the laser welds and further improving the connection reliability between the heat sink and the bus bar, while also improving the welding quality of the laser welds.

[0014] According to an aspect of the connection structure between a heat sink and a bus bar of the present invention, the laser welds are formed parallel to one another on the first surface, thereby facilitating the formation of the laser welds.

[0015] According to an embodiment of the connection structure between a heat sink and a bus bar of the present invention, the reflectivity of the material of the base plate to laser light having a wavelength of 900 nm or more and 1100 nm or less is lower than the reflectivity of the material of the bus bar to laser light having a wavelength of 900 nm or more and 1100 nm or less, which makes it easier to form a laser weld and further improves the connection reliability between the heat sink and the bus bar.

[0016] According to the aspect of the connection structure between a heat sink and a bus bar of the present invention, the radiation fins are plate-shaped members, so that scattering of spatter due to welding can be more reliably prevented. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a perspective view illustrating a connection structure between a heat sink and a bus bar according to a first embodiment of the present invention. [Figure 2] FIG. 10 is a perspective view illustrating a connection structure between a heat sink and a bus bar according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] A connection structure between a heat sink and a bus bar according to a first embodiment of the present invention will be described below with reference to the drawings, in which Fig. 1 is a perspective view illustrating the connection structure between a heat sink and a bus bar according to the first embodiment of the present invention.

[0019] As shown in FIG. 1 , a connection structure 1 between a heat sink and a bus bar according to a first embodiment (hereinafter, sometimes simply referred to as the “connection structure 1”) includes a flat base plate 20 and a heat sink 5 having a plurality of heat dissipation fins 10, 10, 10... provided on the surface of the base plate 20. The base plate 20 has a first surface 21 and a second surface 22 opposite the first surface 21, and a plurality of heat dissipation fins 10, 10, 10... are provided upright on the first surface 21 of the base plate 20. A bus bar 30 having a longitudinal direction L1 and a lateral direction L2 is connected to the second surface 22 of the base plate 20. As described above, the connection structure 1 is a structure in which a heat sink 5 is connected to a bus bar 30. The longitudinal direction L1 is the length direction of the bus bar 30, and the lateral direction L2 is the width direction of the bus bar 30 perpendicular to the longitudinal direction L1.

[0020] The base plate 20 is a plate-like member having a longitudinal direction and a lateral direction (width direction), with the longitudinal direction of the base plate 20 extending in a longitudinal direction L1 and the lateral direction of the base plate 20 extending in a lateral direction L2. The shape of the base plate 20 is not particularly limited, but for the sake of convenience of explanation, the heat sink 5 has a rectangular shape in a plan view (as viewed from the first surface 21 side). The bus bar 30 abuts against the second surface 22 of the base plate 20, thereby thermally connecting the bus bar 30 to the heat sink 5. Therefore, the second surface 22 of the base plate 20 functions as a heat-receiving surface of the heat sink 5.

[0021] In the connection structure 1, the heat dissipation fins 10 are plate-shaped members. The heat dissipation fins 10 are erected on the first surface 21 of the base plate 20 at a predetermined angle with respect to the extension direction of the first surface 21. In the heat sink 5, the heat dissipation fins 10 are erected in a direction substantially perpendicular to the extension direction of the first surface 21. Each heat dissipation fin 10 extends from one end to the other end in the longitudinal direction L1 of the base plate 20. In the heat sink 5, each heat dissipation fin 10 extends substantially linearly from one end to the other end in the longitudinal direction L1 of the base plate 20. Each heat dissipation fin 10 extends in a direction substantially parallel to the longitudinal direction L1 of the base plate 20 and substantially perpendicular to the short-side direction L2. Each heat dissipation fin 10 has substantially the same height from one end to the other end in the longitudinal direction L1 of the base plate 20.

[0022] A plurality of heat dissipation fins 10, 10, 10... are arranged in parallel at predetermined intervals on the first surface 21 of the base plate 20 to form a heat dissipation fin group 11. In the heat sink 5, the plurality of heat dissipation fins 10, 10, 10... are arranged in parallel from one end to the other end in the short-side direction L2 of the base plate 20 to form the heat dissipation fin group 11. The fin pitch of the plurality of heat dissipation fins 10, 10, 10... is not particularly limited, and in the heat sink 5, the plurality of heat dissipation fins 10, 10, 10... are arranged in parallel at approximately equal intervals throughout the entire heat dissipation fin group 11.

[0023] 1, in the connection structure 1, laser welds 40 are formed on the first surface 21 between the heat dissipation fins 10 from the first surface 21 side, and the second surface 22 of the base plate 20 and the bus bar 30 are connected at the laser welds 40 formed from the first surface 21 side. As described above, laser welds 40 are formed on the first surface 21 between the heat dissipation fin 10 and another adjacent heat dissipation fin 10 from the first surface 21 side. The laser welds 40 are weld marks formed on the first surface 21 by laser welding from the first surface 21 side.

[0024] The laser welds 40 are formed on the first surface 21 between the heat dissipation fins 10 in the form of non-intersecting lines. The form of the laser welds 40 is not particularly limited as long as they are non-intersecting lines. For example, if the spacing between the fins 10 is wide, multiple laser welds 40 may be formed between the fins 10, or the laser welds 40 may be jagged or spiral (wobbling welded). In the connection structure 1, the laser welds 40 extend at an angle greater than 0° with respect to the short-side direction L2 of the bus bar 30. In other words, the laser welds 40 do not extend along the short-side direction L2 of the bus bar 30.

[0025] Specifically, in the connection structure 1, the laser welds 40 are formed along the longitudinal direction L1 of the bus bar 30. That is, since each heat dissipation fin 10 extends along the longitudinal direction L1 of the base plate 20, the laser welds 40 are formed along the longitudinal direction L1 of the bus bar 30. Furthermore, since each heat dissipation fin 10 extends in a substantially linear manner from one end to the other end of the base plate 20 in the longitudinal direction L1, the laser welds 40 are formed in a substantially linear manner along the longitudinal direction L1 of the bus bar 30. From the above, the laser welds 40 extend along the extension direction of the heat dissipation fins 10.

[0026] In the connection structure 1, a plurality of laser welds 40, 40, 40... are formed in parallel on the first surface 21. The plurality of laser welds 40, 40, 40... are formed in parallel from one end to the other end of the base plate 20 in the short side direction L2.

[0027] Furthermore, the plurality of laser welds 40, 40, 40 . . . do not intersect, and are formed on the first surface 21 substantially parallel to one another.

[0028] In the connection structure of the present invention, laser welds 40 may be formed all the way between a heat dissipation fin 10 and another adjacent heat dissipation fin 10, or there may be portions between a heat dissipation fin 10 and another adjacent heat dissipation fin 10 where laser welds 40 are formed and portions where laser welds 40 are not formed. In the connection structure 1, there are portions between a heat dissipation fin 10 and another adjacent heat dissipation fin 10 where laser welds 40 are formed and portions where laser welds 40 are not formed.

[0029] In the connection structure 1, the reflectance of the material of the base plate 20 to laser light having a wavelength of 900 nm or more and 1100 nm or less is lower than the reflectance of the material of the bus bar 30 to laser light having a wavelength of 900 nm or more and 1100 nm or less. Examples of laser light having a wavelength of 900 nm or more and 1100 nm or less include a fiber laser and a YAG laser.

[0030] Examples of materials for the base plate 20 include aluminum and aluminum alloys. Examples of materials for the bus bars 30 include copper and copper alloys. The bus bars 30 may be provided with a plating film as needed. Examples of materials for the heat dissipation fins 10 include aluminum and aluminum alloys.

[0031] The width dimension of the heat sink 5 may be the same as or different from the width dimension of the bus bar 30. Furthermore, when the width dimension of the heat sink 5 is different from the width dimension of the bus bar 30, the width dimension of the heat sink 5 may be larger than the width dimension of the bus bar 30, or the width dimension of the bus bar 30 may be larger than the width dimension of the heat sink 5.

[0032] Next, the function of the connection structure 1 will be described.

[0033] When the second surface 22 (heat receiving surface) of the base plate 20 of the heat sink 5 is connected to the heat concentrating portion of the bus bar 30, the heat of the heat concentrating portion of the bus bar 30 is transferred to the base plate 20 of the heat sink 5. The heat transferred from the heat concentrating portion of the bus bar 30 to the base plate 20 is transferred from the base plate 20 to the heat dissipation fins 10, and the heat transferred to the heat dissipation fins 10 is released to the outside of the heat sink 5 by the heat exchange action of the heat dissipation fins 10. By releasing the heat transferred to the heat dissipation fins 10 to the outside of the heat sink 5, the heat of the heat concentrating portion of the bus bar 30 is released to the outside of the connection structure 1, and the heat concentrating portion of the bus bar 30 is eliminated.

[0034] Next, an example of a method for manufacturing the connection structure 1 will be described.

[0035] First, the second surface 22 of the base plate 20 of the heat sink 5 is brought into contact with the heat concentrating portion of the bus bar 30. Next, a laser beam is irradiated from the first surface 21 side, i.e., from the heat dissipation fin 10 side, onto the first surface 21 between the heat dissipation fins 10 along the extension direction of the heat dissipation fins 10 (i.e., the longitudinal direction L1 of the base plate 20), to melt the base plate 20 of the heat sink 5 and the portion of the bus bar 30 that is in contact with the base plate 20, thereby laser welding the heat sink 5 to the bus bar 30. By laser welding the heat sink 5 to the bus bar 30 as described above, a laser weld 40 is formed on the first surface 21 of the base plate 20, extending along the extension direction of the heat dissipation fins 10 (i.e., the longitudinal direction L1 of the base plate 20). The above-described laser welding operation is performed multiple times in the short-side direction L2 of the base plate 20 to form multiple laser welds 40, 40, 40... in parallel on the first surface 21. By forming multiple laser welds 40, 40, 40... in parallel on the first surface 21, the connection structure 1 can be manufactured. Examples of laser welding methods include a fiber laser and a YAG laser.

[0036] The connection structure 1 comprises a base plate 20 having a first surface 21 and a second surface 22, a heat sink 5 having a plurality of heat dissipation fins 10, 10, 10... arranged upright on the first surface 21 of the base plate 20, and a bus bar 30 having a longitudinal direction L1 and a lateral direction L2 and connected to the second surface 22 of the base plate 20, and the second surface 22 of the base plate 20 and the bus bar 30 are connected by laser welds 40 formed on the first surface 21 between the heat dissipation fins 10 in non-intersecting lines from the first surface 21 side.This makes it possible to obtain a connection structure between the heat sink 5 and the bus bar 30 that has excellent connection reliability and heat dissipation characteristics while preventing an increase in the number of parts required to connect the heat sink 5 to the bus bar 30.

[0037] Furthermore, in the connection structure 1, the base plate 20 and the bus bar 30 are connected at a laser weld 40 formed on the first surface 21 between the heat dissipation fin 10 and another adjacent heat dissipation fin 10 from the first surface 21 side, so that a connection structure between the heat sink 5 and the bus bar 30 can be obtained in which the presence of the heat dissipation fin 10 prevents the scattering of spatter caused by welding.

[0038] Furthermore, in the connection structure 1, multiple laser welds 40, 40, 40... are formed in parallel on the first surface 21, thereby increasing the area of the laser welds 40 and further improving the connection reliability between the heat sink 5 and the bus bar 30. Furthermore, in the connection structure 1, the multiple laser welds 40, 40, 40... do not intersect, improving the welding quality of the laser welds 40 and improving the manageability of welding accuracy. Specifically, since the laser welds 40 do not intersect, the same location is not subjected to thermal history due to multiple laser irradiations, thereby suppressing material deterioration and maintaining a consistent weld condition. Since previously welded locations tend to have unevenness, discoloration, or loss of plating, if the laser welds 40 intersect, the laser will be irradiated again on the altered weld surface, easily causing the laser welds 40 to become distorted. Therefore, if the laser welds 40 intersect, it can cause variations in the width and depth of the laser welds 40 and significant spatter.

[0039] Furthermore, in the connection structure 1, the plurality of laser welds 40, 40, 40... are formed on the first surface 21 substantially parallel to one another, which makes it easy to form the plurality of laser welds 40, 40, 40...

[0040] Furthermore, in the connection structure 1, the reflectivity of the material of the base plate 20 to laser light having a wavelength of 900 nm or more and 1100 nm or less is lower than the reflectivity of the material of the bus bar 30 to laser light having a wavelength of 900 nm or more and 1100 nm or less, which makes it easier to form the laser weld 40 and further improves the connection reliability between the heat sink 5 and the bus bar 30.

[0041] Furthermore, in the connection structure 1, the heat dissipation fins 10 are plate-shaped members, so that scattering of spatter due to welding can be prevented more reliably.

[0042] Next, a connection structure between a heat sink and a bus bar according to a second embodiment of the present invention will be described with reference to the drawings. The connection structure between a heat sink and a bus bar according to the second embodiment has major components in common with the connection structure between a heat sink and a bus bar according to the first embodiment, and therefore the same components as those in the connection structure between a heat sink and a bus bar according to the first embodiment will be described using the same reference numerals. Note that Fig. 2 is a perspective view illustrating the connection structure between a heat sink and a bus bar according to the second embodiment of the present invention.

[0043] In the connection structure 1 between a heat sink and a bus bar according to the first embodiment, the heat dissipation fins 10 are plate-shaped members. However, as shown in FIG. 2, in the connection structure 2 between a heat sink and a bus bar according to the second embodiment (hereinafter, sometimes simply referred to as the "connection structure 2"), the heat dissipation fins 10 are columnar members.

[0044] The connection structure 2 includes a flat base plate 20 and a heat sink 6 having heat dissipation fins 10, 10, . . . which are a plurality of columnar members provided on a first surface 21 of the base plate 20.

[0045] A plurality of heat dissipation fins 10, 10, 10... are arranged in parallel at predetermined intervals on the first surface 21 of the base plate 20 to form a heat dissipation fin group 11. In the heat sink 6, the plurality of heat dissipation fins 10, 10, 10... which are columnar members are arranged in parallel from one end to the other along the longitudinal direction L1 of the base plate 20, and the plurality of heat dissipation fins 10, 10, 10... which are columnar members are arranged in parallel from one end to the other along the lateral direction L2 of the base plate 20 to form the heat dissipation fin group 11. The fin pitch of the plurality of heat dissipation fins 10, 10, 10... is not particularly limited, and in the heat sink 6, the plurality of heat dissipation fins 10, 10, 10... are arranged in parallel at approximately equal intervals throughout the entire heat dissipation fin group 11.

[0046] In the connection structure 2, the laser welds 40 are also formed along the longitudinal direction L1 of the bus bar 30. The plurality of heat dissipation fins 10 are arranged in parallel from one end to the other along the longitudinal direction L1 of the base plate 20, and accordingly, the laser welds 40 are formed along the longitudinal direction L1 of the bus bar 30. The plurality of heat dissipation fins 10 are arranged in parallel in a substantially linear manner from one end to the other in the longitudinal direction L1 of the base plate 20, and therefore, the laser welds 40 are formed in a substantially linear manner along the longitudinal direction L1 of the bus bar 30. As described above, the laser welds 40 extend in the direction in which the plurality of heat dissipation fins 10 are arranged in parallel.

[0047] In the connection structure 2, a plurality of laser welds 40, 40, 40... are also formed in parallel on the first surface 21. The plurality of laser welds 40, 40, 40... are formed in parallel from one end to the other end of the base plate 20 in the short-side direction L2.

[0048] Also in the connection structure 2, the plurality of laser welds 40, 40, 40 . . . do not intersect, but are formed on the first surface 21 substantially parallel to one another.

[0049] As described above, in the connection structure between a heat sink and a bus bar of the present invention, the form of the heat dissipation fins 10 erected on the base plate can be selected appropriately depending on the conditions of use of the connection structure.

[0050] The connection structure 2 also comprises a base plate 20 having a first surface 21 and a second surface 22, a heat sink 6 having a plurality of heat dissipation fins 10, 10, 10... arranged upright on the first surface 21 of the base plate 20, and a bus bar 30 having a longitudinal direction L1 and a lateral direction L2 and connected to the second surface 22 of the base plate 20, and the second surface 22 of the base plate 20 and the bus bar 30 are connected by laser welds 40 formed on the first surface 21 between the heat dissipation fins 10 in non-intersecting lines from the first surface 21 side.This makes it possible to obtain a connection structure between the heat sink 6 and the bus bar 30 that has excellent connection reliability and heat dissipation characteristics while preventing an increase in the number of parts required to connect the heat sink 6 to the bus bar 30.

[0051] Next, other embodiments of the connection structure between a heat sink and a bus bar of the present invention will be described. In the connection structures of the above-described embodiments, multiple laser welds 40, 40, 40... are formed along the short-side direction L2 of the base plate 20, but instead, there may be only one laser weld 40. Also, in the connection structures of the above-described embodiments, the laser weld 40 is formed in a substantially linear shape, but instead, the laser weld 40 may be formed in a linear shape with a curved portion.

[0052] Furthermore, in the connection structures of the above-described embodiments, the laser welds 40 extend along the longitudinal direction L1 of the bus bar 30, but instead, the laser welds 40 may extend at a predetermined angle relative to the longitudinal direction L1 of the bus bar 30. Furthermore, in the connection structures of the above-described embodiments, the laser welds 40 are formed over the entire length of the base plate 20 in the longitudinal direction L1, but instead, the laser welds 40 may be formed in a partial range of the base plate 20 in the longitudinal direction L1. [Explanation of symbols]

[0053] 1, 2 Connection structure between heat sink and bus bar 5, 6 Heat sink 10 Heat dissipation fin 20 base plate 21 First Side 22 Second Side 30 Busbar 40 Laser welded section

Claims

1. a heat sink including: a base plate having a first surface and a second surface opposite to the first surface; and a plurality of heat dissipation fins provided upright on the first surface of the base plate; a bus bar connected to the second surface of the base plate and having a longitudinal direction and a lateral direction; A connection structure between a heat sink and a bus bar, A connection structure in which the second surface of the base plate and the bus bar are connected by a laser weld formed on the first surface between the heat dissipation fins in a non-intersecting line from the first surface side.

2. The connection structure according to claim 1 , wherein the laser weld is formed at an angle of more than 0° with respect to the short-side direction of the bus bar.

3. The connection structure according to claim 1 or 2, wherein a plurality of the laser welds are formed in parallel on the first surface.

4. 3. The connection structure according to claim 1, wherein the laser welded portion is formed along the longitudinal direction of the bus bar.

5. The connection structure according to claim 3 , wherein a plurality of the laser welds are formed on the first surface in parallel to one another.

6. 3. The connection structure according to claim 1, wherein the reflectivity of the material of the base plate to laser light having a wavelength of 900 nm or more and 1100 nm or less is lower than the reflectivity of the material of the bus bar to laser light having a wavelength of 900 nm or more and 1100 nm or less.

7. The connection structure according to claim 1 or 2, wherein the material of the base plate includes aluminum or an aluminum alloy, and the material of the bus bar includes copper or a copper alloy.

8. 3. The connection structure according to claim 1, wherein the heat dissipation fin is a plate-like member or a column-like member.

9. 3. The connection structure according to claim 1, wherein the heat dissipation fin is a plate-like member.

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