JP2011167714A - Solder joined body of aluminum material, solder joining method, and battery pack using the solder joining method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a joined body in which aluminum materials or an aluminum material and a different kind of material are joined, and which has excellent joining strength and reliability. <P>SOLUTION: The joined body contains: a first metal member made of an aluminum material, a second metal member made of an aluminum material or a different kind of metal material, and a connection part connecting the first metal member and the second metal member. The connection part is formed on the surface of the first metal member and includes a metal layer made of at least one kind of first metal element selected from a group composed of Cu, Ni, Co, Zn, Ge, Au, Pd and Sn, and a joining layer formed on the metal layer and made of an Sn based solder containing at least one kind of second metal element capable of forming a solid solution or an intermetallic compound with the at least one kind of first metal element, and the second metal element is selected from a group composed of Cu, Ag, In, Bi, Co and Ti. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a joined body of aluminum materials or between an aluminum material and a different material, a method for producing the joined body, and a battery pack.

  Since metal aluminum is easily oxidized in the air, the surface of the aluminum material is usually covered with a strong oxide film mainly made of alumina. Therefore, when joining aluminum materials or between an aluminum material and a dissimilar metal member, such an oxide film prevents diffusion of the metal element at the joining interface, and sufficient joining strength cannot be obtained.

  Even when a flux is used when soldering an aluminum material, the above-mentioned oxide film cannot be sufficiently removed with the existing flux, and it is difficult to obtain high bonding strength and reliability.

  Therefore, a method of joining by forming a solder layer on the surface of the aluminum material by a liquid phase reaction with the molten solder while immersing the aluminum material in a molten solder bath and destroying the aluminum oxide film by mechanical vibration or the like Has been proposed (Patent Document 1). However, in this method, there is a problem that a part of the aluminum material is melted and the dimensions of the aluminum material are distorted practically. Further, a large amount of molten aluminum diffuses into the solder layer, so that a coarse intermetallic compound is formed between the aluminum and the metal element in the solder layer, and the bonding strength is lowered. Furthermore, when such a method is continuously performed, the concentration of aluminum in the solder bath increases with time, making it difficult to obtain a product with uniform quality.

Japanese Patent Laid-Open No. 8-1322

  An object of the present invention is to provide a bonded body having good bonding strength and excellent reliability when soldering aluminum materials or between an aluminum material and a dissimilar metal member.

  As a result of diligent studies to achieve the above object, the present inventors formed a metal layer composed of a metal element capable of forming a solid solution or intermetallic compound with aluminum on the surface of the aluminum material, and this metal layer By using Sn-based solder containing a metal element that can form a solid solution or intermetallic compound with a metal element contained in the solder, it has good bonding strength by soldering aluminum materials or between aluminum materials and dissimilar materials It was found that a joined body was obtained.

  That is, according to one aspect of the present invention, a first metal member made of an aluminum material, a second metal member made of an aluminum material or a different metal material, the first metal member, and the second metal member And the connection portion is formed on the surface of the first metal member, and is selected from the group consisting of Cu, Ni, Co, Zn, Ge, Au, Pd, and Sn. A metal layer comprising at least one first metal element; and at least one second metal layer formed on the metal layer and capable of forming a solid solution or intermetallic compound with the at least one first metal element. A bonded layer comprising a Sn-based solder containing a metal element, wherein the second metal element is selected from the group consisting of Cu, Ag, In, Bi, Co, and Ti. Provided.

  According to one aspect of the present invention, the surface of the first metal member made of an aluminum material has at least one first selected from the group consisting of Cu, Ni, Co, Zn, Ge, Au, Pd and Sn. Forming a metal layer made of the metal element, and joining the first metal member on which the metal layer is formed and the second metal member made of an aluminum material or a different material via a joining layer The bonding layer is formed on the metal layer and contains at least one second metal element capable of forming a solid solution or intermetallic compound with the at least one first metal element. There is provided a bonding method characterized in that it is made of a system solder and the second metal element is selected from the group consisting of Cu, Ag, In, Bi, Co, and Ti.

  According to one aspect of the present invention, the apparatus includes a plurality of unit cells, a bus bar made of an aluminum material that couples the plurality of unit cells, and a control board, and the bus bar and the control board are connected via a connection portion. The connection portion is formed on the surface of the bus bar, and is at least one kind selected from the group consisting of Cu, Ni, Co, Zn, Ge, Au, Pd and Sn. A metal layer comprising one metal element and at least one second metal element formed on the metal layer and capable of forming a solid solution or an intermetallic compound with the at least one first metal element. A battery pack, wherein the second metal element is selected from the group consisting of Cu, Ag, In, Bi, Co, and Ti. Provided.

  According to the present invention, a bonded body excellent in bonding strength and reliability can be obtained.

FIG. 1 is a cross-sectional view showing a joined body according to one embodiment of the present invention. FIG. 2 is a cross-sectional view showing a joined body according to one embodiment of the present invention. FIG. 3 is an exploded perspective view showing a battery pack according to one embodiment of the present invention. FIG. 4 is a partially enlarged view of FIG. FIG. 5 is a plan view of the battery pack of FIG. 3 viewed from above. 6 is a cross-sectional view of the battery pack of FIG.

  The joined body of the present invention is obtained by connecting a first metal member made of an aluminum material and a second member made of an aluminum material or a dissimilar metal member via a specific connecting portion.

  The first metal member is made of an aluminum material. The aluminum material may contain a small amount of an additive element, but is substantially composed of aluminum, and is referred to as so-called pure aluminum. Examples thereof include 1050 aluminum, 1080 aluminum, and 1100 aluminum.

  The second metal member is made of the same aluminum material or different metal member as the first metal member, and the different metal member is made of a (different) metal material other than pure aluminum. The dissimilar metal material can be selected from the group consisting of an aluminum alloy, Fe, Cu, Ni, Co, Zn, Ge, Au, Pd and Sn, and an alloy of two or more thereof. The second metal member is preferably oxygen-free copper or aluminum material.

  The connecting portion that connects the first metal member and the second metal member includes a metal layer formed (directly) on the surface of the first metal member. The metal layer is made of at least one first metal element selected from the group consisting of Cu, Ni, Co, Zn, Ge, Au, Pd, and Sn. Any of these first metal elements can form a solid solution or an intermetallic compound with aluminum constituting the first metal member. The metal layer may be a single layer or a laminate of two or more layers. Although there is no restriction | limiting in particular in the thickness of a metal layer, It is preferable that it is 0.1-500 micrometers. If the thickness of the metal layer is less than 0.1 μm, the effect may be insufficient, and a thickness exceeding 500 μm is uneconomical. Particularly when the metal layer is a single layer, a thickness of 0.1 to 100 μm is preferable, and a thickness of 1 to 10 μm is more preferable. The metal layer may be formed only on the surface region of the first metal member facing the second metal member, or may be formed on another surface. For example, the metal layer can be formed on the entire surface of the first metal member.

  The metal layer can be formed by a method such as electroless plating, electroplating, physical vapor volume (PVD) (deposition), chemical vapor volume (CVD), or the like.

  In addition, the connection portion further includes an Sn-based solder layer formed on the metal layer. The Sn-based solder includes at least one second element that can form a solid solution or an intermetallic compound with at least one first metal element. This second metal element is selected from the group consisting of Cu, Ag, In, Bi, Co and Ti and combinations thereof. The second metal element is blended in an amount capable of forming a solid solution or intermetallic compound with the first metal element contained in the metal layer. The thickness of the bonding layer made of Sn solder is not particularly limited, but is preferably 50 to 200 μm.

  As described above, the metal layer can have a multilayer structure of two or more layers. In that case, the layer in contact with the first metal member (aluminum material) is a solid solution or metal with aluminum among the first metal elements. The intermetallic compound is more easily formed by a metal element, for example, Zn and / or Pd, and the layer in contact with the bonding layer made of Sn-based solder is a metal element in the Sn-based solder among the first metal elements. A solid solution or an intermetallic compound can be formed of a metal element that is more easily formed, for example, Ni and / or Co.

  Further, when the second metal member contains aluminum, the metal layer can be formed also on the surface of the second metal member. In this case, the connecting portion is formed on the metal layer formed on the first metal member, the bonding layer made of Sn-based solder formed on the metal layer, and the second metal member formed on the bonding layer. A second metal layer in contact with the surface of the substrate. When the second metal member does not contain aluminum, the bonding layer made of Sn-based solder constituting the connection portion is in direct contact with the second metal member.

  By the way, as described above, since the second metal element contained in the Sn-based solder is a metal element that can form a solid solution or intermetallic compound with the first metal element, the first metal element to be used is used. Is a dissimilar metal element, but in addition to the dissimilar metal element, it can contain the same metal element as the first metal element. That is, the Sn-based solder to be used always includes a metal element different from the first metal element (which can form a solid solution or intermetallic compound with the first metal element) as the second metal element. In addition to the metal, the same metal element as the first metal element may be included. Does the Sn-based solder consist of a second metal element different from the first metal element (which can form a solid solution or intermetallic compound with the first metal element) and the remaining Sn (and inevitable impurities)? A second metal element different from the first metal element (which can form a solid solution or an intermetallic compound with the first metal element), a second metal element of the same type as the first metal element, and the remainder Sn (and inevitable impurities).

Table 1 below shows combinations of the first metal element and the second metal element that can form a solid solution or an intermetallic compound.

  When the Sn-based solder contains a plurality of second metal elements different from the first metal element, each of the second metal elements can form a solid solution or an intermetallic compound with the first metal element It is particularly preferred that

  For example, when the first metal element is Cu, Ni, Co, Zn, Ge, Au, Pd and / or Sn, at least one second metal element selected from the group consisting of Cu, Co and Ti is used. Sn-based solder containing Sn (and inevitable impurities), specifically Cu-Sn solder (0.7 wt% Cu and remaining Sn; melting point 227 ° C), Cu-Co-Sn solder (0.7 Wt% Cu, 0.2 wt% Co and the balance Sn; melting point 217.5 ° C), or Cu-Co-Ti-Sn solder (eg 0.3-1.2 wt% Cu, 0.01-1 wt% Co, 0.01-1 wt) % Ti and the balance Sn, preferably 0.5 to 0.7 wt% Cu, 0.1 to 0.3 wt% Co, 0.1 to 0.3 wt% Ti and the balance Sn) etc. are suitable.

  For example, when the first metal element is Zn, Ge, Au, Pd and / or Sn, it contains at least one second metal element selected from the group consisting of Cu, Ag, Co and Ti, and the balance Sn solder consisting of Sn (and inevitable impurities), specifically Cu-Ag-Co-Ti-Sn solder (e.g. 0.3-1.2 wt% Cu, 0.3-4.0 wt% Ag, 0.01-1.0 wt% Co) 0.01 to 1.0 wt% Ti and the balance Sn, preferably 0.5 to 0.7 wt% Cu, 3.0 to 3.5 wt% Ag, 0.1 to 0.3 wt% Co, 0.1 to 0.3 wt% Ti and the balance Sn) are suitable. is there.

  For example, when the first metal element is Au, Pd and / or Sn, it contains at least one second metal element selected from the group consisting of Cu, Ag, In, Co and Ti, with the balance being Sn Sn solder consisting of (and inevitable impurities), specifically Cu-Ag-In-Co-Ti-Sn solder (e.g. 0.3-1.2 wt% Cu, 0.3-4.0 wt% Ag, 2.0-6.0 wt% In) 0.01-1.0 wt% Co, 0.01-1.0 wt% Ti and the balance Sn, preferably 0.5-0.7 wt% Cu, 3.0-3.5 wt% Ag, 4.0-5.2 wt% In, 0.1-0.3 wt% Co, 0.1 ~ 0.3 wt% Ti and the balance Sn) etc. are suitable.

  For example, when the first metal element is Pd and / or Sn, it contains at least one second metal element selected from the group consisting of Cu, Ag, Bi, Co, and Ti, with the balance being Sn (and Sn solder composed of inevitable impurities), specifically Cu-Ag-Bi-Co-Ti-Sn solder (e.g. 0.3 to 1.2 wt% Cu, 0.3 to 4.0 wt% Ag, 2.0 to 6.0 wt% Bi, 0.01 -1.0 wt% Co, 0.01-1.0 wt% Ti and the balance Sn, preferably 0.5-0.7 wt% Cu, 3.0-3.5 wt% Ag, 4.0-5.0 wt% Bi, 0.1-0.3 wt% Co, 0.1-0.3 Weight% Ti and the balance Sn) are suitable.

  That is, the joined body of the present invention first removes the oxide film present on the surfaces of the first metal member and the second metal member by etching or the like, and removes the oxide film on the surface of the first metal member. In addition, a metal layer composed of at least one first metal element can be formed, and then the first metal member and the second metal member can be solder-bonded by Sn-based solder. . Here, as described above, the bonding layer made of Sn-based solder is in direct contact with the metal layer formed on the surface of the first metal member, while being in direct contact with the second metal member or the second metal member. It is in direct contact with a similar metal layer formed on the surface of the metal member.

  By the way, heat treatment is performed on the first metal member and / or the second metal member on which at least one metal layer is formed, and at the interface between the first metal member and / or the second metal member and the metal layer. It is possible to promote the diffusion of the metal elements contained in both, and to further improve the bonding strength and reliability. In the case where the metal layer includes a plurality of layers, the diffusion of the metal element between the metal layers can be promoted by heat treatment. A preferable temperature for such heat treatment is 150 to 350 ° C, more preferably 250 to 300 ° C.

Note that the joined body of the present invention is preferably manufactured under conditions such that a new oxide film is not formed on the surface of the metal member, and specifically manufactured under an inert atmosphere such as H ₂ , Ar, or He. However, the present invention is not limited to this.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of a joined body 11 according to one embodiment of the present invention. In FIG. 1, a first metal member 20 and a second metal member 30 are joined via a connecting portion 40. The connection portion 40 includes a metal layer 401 and a bonding layer 402 made of Sn-based solder. The metal layer 401 is formed on the surface of the first metal member 20, and the bonding layer 402 is in contact with the metal layer 401.

  FIG. 2 is a cross-sectional view of the joined body 12 according to one embodiment of the present invention. In FIG. 2, the first metal member 20 and the second metal member 30 are both made of an aluminum material and are connected via a connecting portion 40. The connecting portion 40 is a joint composed of metal layers 401 and 403 respectively formed on opposing surface regions of the first metal member and the second metal member, and Sn-based solder disposed between the metal layers 401 and 403. Layer 402.

  On the other hand, according to another aspect of the present invention, it includes a plurality of unit cells, a bus bar made of an aluminum material connecting the plurality of unit cells, and a control board, and the bus bar and the control board are connected in the present invention. A battery pack connected via the unit is provided.

  The battery pack of the present invention will be described below with reference to the drawings.

  FIG. 3 is an exploded perspective view of the battery pack 51 of the present invention. 4 is a partially enlarged view of FIG. 3, and FIG. 5 is a view of the battery pack 51 of FIG. 3 as viewed from directly above. FIG. 6 is a cross-sectional view of the battery pack 51 of FIG.

  3 to 6, the battery pack 51 includes a plurality of unit cells 52. The positive electrode 56 of one unit cell is electrically connected in series with the negative electrode 57 of another unit cell via a bus bar 55 made of aluminum, and the positive electrode of the unit cell positioned at both ends of the series of electrical connections or One of the negative electrodes exists without being connected to the bus bar. The positive or negative electrodes of the unit cells at both ends are connected to an electric device for use. The bus bar 55 has a shape in which an inverted U-shaped structure is formed in the center of the flat plate, and has a central inverted U-shaped curved portion 553 and flat portions 552 that are present on both sides across the curved portion 553, An opening 554 for fitting the positive electrode 56 or the negative electrode 57 is provided at the center of the flat portion 552. Further, the bus bar 55 has a needle-like aluminum connection pin 551 protruding vertically from the flat portion 552. The positive electrode 56 and the negative electrode 57 and the peripheral edge of the opening 554 of the bus bar are laser-welded to form joints 56a and 57a. These unit cells 52 are accommodated in a battery case 54. On the battery case 54, a battery cover 53 in which a window from which a positive electrode 56, a negative electrode 57, and a part of the bus bar 55 (551) are exposed is formed. Is covered. A control board 58 is attached to the upper surface of the battery pack 51. A hole 581 for fitting the connection pin 551 is formed in the control board 58. A circuit (not shown) made of metal (for example, oxygen-free copper) is formed on the surface of the control board 58. The metal layer (not shown) of the present invention described above is formed on the entire surface of the bus bar 55, or at least the bus bar pin 551, and the bus bar pin 551 fitted with the circuit portion of the control board 58 and the hole 581. Are connected via the connection portion of the present invention, that is, the solder joint portion 59.

  That is, according to this invention, the battery pack excellent in the joining strength and reliability of a solder joint part is provided.

  Next, the present invention will be described with reference to examples and comparative examples.

[Example 1]
An electroless Ni-plated metal layer having a thickness of 5 μm was formed on the surface of a first metal member made of a 1050 aluminum material having a thickness of 3 mm, a width of 10 mm, and a length of 50 mm.

  Next, a Cu-Co-Sn solder sheet (0.7 wt% Cu, 0.2 wt% Co and the remaining Sn) having a thickness of 0.1 mm, a width of 10 mm, and a length of 10 mm was added to the first metal member and a thickness of 3 mm, width 10 mm, length 50 mm inserted between the second metal member made of an oxygen-free copper material, after dropping the flux, the first metal member and the second metal member in a nitrogen gas atmosphere at 245 ° C Metal members were joined to produce a joined body.

  The obtained joined body was subjected to a shear test at a tensile rate of 10 mm / min. As a result, the shear strength was 52 MPa, and shear fracture occurred in the joining layer. The void defect rate which is inversely proportional to the electrical conductivity was 5.0%.

[Example 2]
Electroless Ni-plated metal with a thickness of 5 μm on the surface of the first metal member made of 1050 aluminum material and the second metal member made of 1050 aluminum material each having a thickness of 3 mm, a width of 10 mm, and a length of 50 mm A layer was formed.

  Next, a Cu-Co-Sn solder sheet (0.7 wt% Cu, 0.20 wt% Co and the remaining Sn) having a thickness of 0.1 mm, a width of 10 mm, and a length of 10 mm was added to the first metal member and the second metal member. The first metal member and the second metal member were joined in a nitrogen gas atmosphere at 245 ° C. after being inserted between the metal members and dropping the flux, thereby producing a joined body.

  As a result of conducting a shear test on the obtained joined body at a tensile rate of 10 mm / min, the shear strength was 50 MPa, and shear fracture occurred in the joining layer. The void defect rate, which is inversely proportional to the electrical conductivity, was 5.5%.

[Example 3]
Other than using a Cu-Co-Ti-Sn solder sheet (0.75 wt% Cu, 0.2 wt% Co, 0.1 wt% Ti and the remaining Sn) after forming a 3 μm metal layer of Cu by electroless plating Produced a joined body in the same manner as in Example 2.

  The obtained bonded body had a shear strength of 55 MPa, and shear fracture occurred in the bonding layer. The void defect rate which is inversely proportional to the electrical conductivity was 5.0%.

[Example 4]
A 3 μm metal layer made of Ni was formed by electroplating, and a Cu-Ag-Co-Ti-Sn solder sheet (0.5 wt% Cu, 3.0 wt% Ag, 0.2 wt% Co, 0.1 wt% Ti and the balance) A joined body was produced in the same manner as in Example 2 except that Sn) was used.

  The obtained bonded body had a shear strength of 52 MPa, and shear fracture occurred in the bonded layer. The void defect rate, which is inversely proportional to the electrical conductivity, was 5.5%.

[Example 5]
A 5 μm metal layer made of Co is formed by electroplating, and a Cu-Ag-In-Co-Ti-Sn solder sheet (0.7 wt% Cu, 3.0 wt% Ag, 4.0 wt% In, 0.1 wt% Co, A joined body was produced in the same manner as in Example 2 except that 0.1 wt% Ti and the remaining Sn) were used.

  The obtained bonded body had a shear strength of 48 MPa, and shear fracture occurred in the bonding layer. The void defect rate, which is inversely proportional to the electrical conductivity, was 7.0%.

[Example 6]
A 1 μm metal layer made of Au is formed by electroplating, and a Cu-Ag-Bi-Co-Ti-Sn solder sheet (0.5 wt% Cu, 3.0 wt% Ag, 6.0 wt% Bi, 0.1 wt% Co, A joined body was produced in the same manner as in Example 2 except that 0.1 wt% Ti and the remaining Sn) were used.

  The obtained bonded body had a shear strength of 50 MPa, and shear fracture occurred in the bonding layer. The void defect rate which is inversely proportional to the electrical conductivity was 6.0%.

[Comparative Example 1]
For comparison, an example of a joined body in which a layer of molten Zn—Sn solder is formed instead of the metal layer of the present invention on the surfaces of the first metal member and the second metal member is shown.

  A Zn-Sn solder bath (9.0 wt.) In which a first metal member made of 1050 aluminum material having a thickness of 3 mm, a width of 10 mm, and a length of 50 mm and a second metal member made of aluminum material are melted at 300 ° C. % Zn and the remaining Sn) for 30 seconds, and a layer of Zn-Sn solder (9.0 wt% Zn and the remaining Sn) having a thickness of 5 μm on the surfaces of the first metal member and the second metal member, respectively. ) Was formed.

  Next, a Cu-Sn solder sheet (0.7 wt% Cu and the remaining Sn) having a thickness of 0.1 mm, a width of 10 mm, and a length of 10 mm is inserted between the first metal member and the second metal member. After dropping the flux, the first metal member and the second metal member were joined in a nitrogen gas atmosphere at 245 ° C. to produce a joined body.

  The obtained joined body was subjected to a shear test at a tensile rate of 10 mm / min. As a result, it was found that the shear strength was 10 MPa. Shear fracture occurred at the interface between the first and second metal members and the Zn-Sn solder layer, and at the interface between the Zn-Sn solder layer and the Cu-Sn solder layer. The void defect rate was 20%.

[Comparative Example 2]
For further comparison, examples of joined bodies (Comparative Examples 2 to 4) in the case where the first metal element and the second metal element are selected in combination including a pair that does not form a solid solution or an intermetallic compound are shown.

  A bonded body was prepared in the same manner as in Example 2 except that a 3 μm metal layer made of Cu was formed by electroless plating and an Ag-Sn solder sheet (3.5 wt% Ag and the remaining Sn) was used. did.

  The obtained bonded body had a shear strength of 35 MPa and a void defect rate of 15%.

[Comparative Example 3]
A 3 μm metal layer made of Ni was formed by electroplating and the same as in Example 2 except that an Ag—In—Sn solder sheet (3.0 wt% Ag, 4.0 wt% In and the balance Sn) was used. The joined body was produced by the method.

  The obtained bonded body had a shear strength of 32 MPa and a void defect rate of 15%.

[Comparative Example 4]
A 5 μm metal layer made of Co was formed by electroplating, and an Ag—Bi—Sn solder sheet (3.0 wt% Ag, 6.0 wt% Bi and the remaining Sn) was used, and the same as in Example 2. The joined body was produced by the method.

  The obtained bonded body had a shear strength of 30 MPa and a void defect rate of 12%.

[Consideration of results]
From the comparison between Example 2 and Comparative Example 1, the bonding strength is remarkably improved by forming a film composed of the first metal element on the surfaces of the first metal member and the second metal member. Became clear.

  From the comparison between Examples 2 to 6 and Comparative Examples 2 to 4, when the first metal element and all the second metal elements are selected in a combination capable of forming a solid solution or an intermetallic compound, the first metal Compared to the case where the element and the second metal element are selected as a combination including a pair that does not form a solid solution or an intermetallic compound, the electrical strength estimated from the bonding strength and the void defect rate may be significantly improved. It became clear.

11, 12: joined body, 20: first metal member, 30: second metal member, 40: connecting portion, 401, 403: metal layer, 402: joining layer, 51: battery pack, 52: unit cell, 53: Battery cover, 54: Battery case, 55: Bus bar, 551: Connection pin, 552: Plane part, 553: Curved part, 554: Opening part, 56: Positive electrode, 57: Negative electrode, 56a: Joining of positive electrode and bus bar Part, 57a: Joint between negative electrode and bus bar, 58: Control board, 581: Hole, 59: Solder joint

Claims (15)

  Including a first metal member made of an aluminum material, a second metal member made of an aluminum material or a dissimilar metal material, and a connecting portion for connecting the first metal member and the second metal member, The connecting portion is formed on the surface of the first metal member and is made of at least one first metal element selected from the group consisting of Cu, Ni, Co, Zn, Ge, Au, Pd, and Sn. A junction comprising a metal layer and an Sn-based solder which is formed on the metal layer and contains at least one second metal element capable of forming a solid solution or an intermetallic compound with the at least one first metal element. And a second metal element selected from the group consisting of Cu, Ag, In, Bi, Co, and Ti.   The joined body according to claim 1, wherein the Sn-based solder includes Cu and Co as the second metal element.   The joined body according to claim 2, wherein the Sn-based solder further contains Ti as the second metal element.   The Sn-based solder further includes Ag as the second metal element, and the first metal element is selected from the group consisting of Zn, Ge, Au, Pd, and Sn. The joined body described.   5. The joined body according to claim 4, wherein the Sn-based solder further includes In as the second metal element, and the first metal element is selected from the group consisting of Au, Pd, and Sn. .   The joined body according to claim 4, wherein the Sn-based solder further includes Bi as the second metal element, and the first metal element is selected from the group consisting of Pd and Sn.   The joined body according to claim 1, wherein the metal layer has a laminated structure of two or more layers.   The joined body according to any one of claims 1 to 7, wherein the second metal member is made of an aluminum material, and the metal layer is formed on a surface of the second metal member.   The joined body according to any one of claims 1 to 8, wherein a heat treatment is performed on the first metal member on which the metal layer is formed.   The joined body according to claim 8 or 9, wherein a heat treatment is performed on the second metal member on which the metal layer is formed.   11. The joined body according to claim 1, wherein the metal layer has a thickness of 0.1 μm or more and 100 μm or less, and the metal layer is formed of a single layer.   The joined body according to claim 1, wherein the metal layer has a thickness of 0.1 μm or more and 500 μm or less, and the metal layer includes a plurality of layers.   The joined body according to any one of claims 1 to 12, wherein the metal layer is formed by electroless plating, electroplating, physical vapor deposition, or chemical vapor deposition. A metal layer made of at least one first metal element selected from the group consisting of Cu, Ni, Co, Zn, Ge, Au, Pd and Sn is formed on the surface of the first metal member made of an aluminum material. Process,
Joining the first metal member on which the metal layer is formed and the second metal member containing an aluminum material or a dissimilar material via a joining layer, and the joining layer is formed on the metal layer. Formed of Sn solder containing at least one second metal element that can form a solid solution or an intermetallic compound with the at least one first metal element, and the second metal element comprises: A bonding method characterized by being selected from the group consisting of Cu, Ag, In, Bi, Co, and Ti.   A battery pack comprising a plurality of unit cells, a bus bar made of an aluminum material for connecting the plurality of unit cells, and a control board, wherein the bus bar and the control board are connected via a connecting portion, The connecting portion is formed on the surface of the bus bar, and a metal layer made of at least one first metal element selected from the group consisting of Cu, Ni, Co, Zn, Ge, Au, Pd and Sn, A bonding layer made of Sn-based solder containing at least one second metal element formed on the metal layer and capable of forming a solid solution or intermetallic compound with the at least one first metal element. The battery pack is characterized in that the second metal element is selected from the group consisting of Cu, Ag, In, Bi, Co, and Ti.

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