JP2012138306A - Joined body, method for producing joined body, and battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a joined body excellent in bond strength and high in reliability; a method for producing the joined body; and a battery pack.SOLUTION: A joined body 10 according to an embodiment includes a first metallic member 1, a second metallic member 2 and a junction 3. The first metallic member 1 contains Al, while the content of Cu is less than 5.7% by weight. The second metallic member 2 contains Cu, while the content of Al is less than 9.4% by weight. The junction 3 joins the first metallic member 1 with the second metallic member 2. Further, the junction 3 contains at least one element selected from the group consisting of Si, Ni, Mn, Co, Zn, Ge, Au, Ag and Pd.

Description

  Embodiments described herein relate generally to a bonded body, a manufacturing method of the bonded body, and a battery pack.

  Examples of the method for joining different metal materials include melt welding methods such as laser welding and TIG arc welding. In these methods, alloying is performed by heating the joint to a melting temperature of one or both of the materials to be joined. At that time, a brittle intermetallic compound may be formed depending on the alloy system, and a sufficient joint strength may not be obtained in a joint portion containing such a brittle intermetallic compound.

When an aluminum (Al) material and a copper (Cu) material are directly welded by a fusion bonding method, a eutectic reaction occurs at 548 ° C. at a composition of Al-33 wt% Cu when the molten portion is solidified. A lamellar eutectic structure is formed in the part. This lamellar structure includes an α (Al) phase in which Cu is dissolved in Al and a θ (CuAl ₂ ) phase. Since this θ (CuAl ₂ ) phase is brittle, a joint including a large amount of this phase is remarkably inferior in joint strength. Therefore, the joined body including such a joined portion has low reliability.

Japanese Patent Laid-Open No. 10-137952

  The problem to be solved by the present invention is to provide a bonded body having excellent bonding strength and high reliability, a method for manufacturing the bonded body, and a battery pack using the bonded body.

  The joined body according to the embodiment includes a first metal member, a second metal member, and a joint portion. The first metal member contains Al, and the Cu content is less than 5.7% by weight. The second metal member contains Cu and the Al content is less than 9.4% by weight. The joining portion joins the first metal member and the second metal member. Further, the bonding portion includes at least one element selected from the group consisting of Si, Ni, Mn, Co, Zn, Ge, Au, Ag, and Pd.

  The manufacturing method of the joined body which concerns on embodiment is related with the manufacturing method of the said joined body. The manufacturing method includes a step of arranging a bonding material between the first metal member and the second metal member. The first metal member contains Al, and the Cu content is less than 5.7% by weight. The second metal member contains Cu and the Al content is less than 9.4% by weight. The bonding material includes at least one element selected from the group consisting of Si, Ni, Mn, Co, Zn, Ge, Au, Ag, and Pd. Moreover, the manufacturing method includes a step of melting the bonding material and forming a welded portion. Further, the manufacturing method includes a step of obtaining a joined body in which a joined portion including the at least one element is formed between the first metal member and the second metal member by solidifying the melted portion.

  The battery pack according to the embodiment includes a plurality of unit cells and a bus bar. Each of the plurality of unit cells includes an electrode terminal. The electrode terminal contains Al and the Cu content is less than 5.7% by weight. The bus bar electrically connects the electrode terminals of the plurality of unit cells. Moreover, a bus bar contains Cu and content of Al is less than 9.4 weight%. The electrode terminal is joined to the bus bar via the joint. The junction includes at least one element selected from the group consisting of Si, Ni, Mn, Co, Zn, Ge, Au, Ag, and Pd.

FIG. 1 is a schematic cross-sectional view of the joined body according to the first embodiment. FIG. 2 is a schematic view showing one step of the method of manufacturing the joined body according to the third embodiment. FIG. 3 is a schematic view showing one process of a modification of the method for manufacturing a joined body according to the third embodiment. FIG. 4 is a schematic cross-sectional view of a joined body obtained by the method for producing the joined body of FIG. FIG. 5 is an exploded perspective view schematically showing the battery pack according to the fourth embodiment. 6 is a partially enlarged view of the battery pack of FIG. FIG. 7 is a schematic plan view of the battery pack of FIG. 5 as viewed from above. FIG. 8 is a schematic cross-sectional view of a joined body obtained in a comparative example.

  Hereinafter, embodiments will be described with reference to the drawings. In the following description, constituent elements that exhibit the same or similar functions are denoted by the same reference numerals throughout the drawings, and redundant descriptions are omitted.

  Moreover, the electrical conductivity (unit:% IACS) of each member in the following description is the relative electrical conductivity of each member when the electrical conductivity of the international standard annealed copper wire is 100% IACS. The electrical conductivity of the international standard annealed copper wire is 1.72 μΩ · cm at a temperature of 20 ° C.

(First embodiment)
The joined body according to the first embodiment includes a first metal member, a second metal member, and a joint portion. The first metal member contains Al, and the Cu content is less than 5.7% by weight. The second metal member contains Cu and the Al content is less than 9.4% by weight. The joining portion joins the first metal member and the second metal member. Further, the bonding portion includes at least one element selected from the group consisting of Si, Ni, Mn, Co, Zn, Ge, Au, Ag, and Pd.

  The first metal member contains Al and has a Cu content of less than 5.7% by weight (including 0% by weight).

  This is because when the Cu content is 5.7% by weight or more, a brittle Cu (Al) intermetallic compound is formed, and the electrical conductivity is greatly reduced while the strength of the first metal member does not increase so much. .

  In actual applications, in the case where it is necessary to ensure the mechanical properties of the first metal member even if the electrical conductivity is somewhat sacrificed, the first metal member can contain inevitable impurities as an alloy element. Examples of inevitable impurities of the first metal member include Si, Fe, Cu, Mn, Mg, Zn, and Cr. The content of inevitable impurities is at least one selected from the group consisting of Al contained in the first metal member and Si, Ni, Mn, Co, Zn, Ge, Au, Ag, and Pd contained in the joint. What is necessary is just to set so that it may not have big influence on formation of the solid solution or intermetallic compound with these elements. In order to obtain excellent electrical conductivity in addition to high bonding strength, the Al content in the first metal member is desirably 99.5% by weight or more. In such a first metal member, the content of inevitable impurities is 0.5% by weight or less, and the electrical conductivity can be 60% IACS or more.

  Examples of the first metal member include 1050 aluminum material, 1080 aluminum material, and 1100 aluminum material.

  The second metal member 2 contains Cu, and the Al content is less than 9.4% by weight (including 0% by weight).

  When the Al content is 9.4% by weight or more, a brittle (Al) Cu intermetallic compound is formed, and the electrical conductivity is greatly reduced while the strength of the second metal member does not increase so much. .

  In actual applications, if it is necessary to ensure the mechanical properties of the second metal member even if the electrical conductivity is somewhat sacrificed, inevitable impurities can be included as alloy elements. Examples of the inevitable impurities of the second metal member include oxygen, P, Zn, Sn, Fe, Al, and Pb. The content of inevitable impurities is at least one selected from the group consisting of Cu contained in the second metal member and Si, Ni, Mn, Co, Zn, Ge, Au, Ag, and Pd contained in the joint. What is necessary is just to set so that it may not have big influence on formation of the solid solution or intermetallic compound with these elements. In order to obtain excellent electrical conductivity in addition to high bonding strength, it is desirable that the Cu content in the second metal member be 99.9% by weight or more. In such a second metal member, the content of inevitable impurities is 0.1% by weight or less, and the electrical conductivity can be 90% IACS.

  An example of such a second metal member is oxygen-free copper.

  The junction includes at least one element selected from the group consisting of Si, Ni, Mn, Co, Zn, Ge, Au, Ag, and Pd. Hereinafter, in order to avoid unnecessary duplication, at least one element selected from the group consisting of Si, Ni, Mn, Co, Zn, Ge, Au, Ag, and Pd included in the bonding portion is referred to as a “bonding element”. .

  The joined body having the above configuration is excellent in joining strength for the reason described in detail below.

  Each element that can be selected as a bonding element included in the bonding portion has higher reactivity between the element and Al and higher reactivity between the element and Cu than reactivity between Al and Cu.

  Table 1 shows the reactivity of each of Al and Cu with each bonding element.

  In Table 1, an element in the column marked with “◯” in the row of Al is an element in which the reactivity between the element and Al is higher than the reactivity between Al and Cu, that is, solid solution with Al. An element having a wide range and an element in a row where “「 ”is written has a reactivity of the element with Al more than the reactivity of an element in the row with“ ◯ ”and Al. It is an element that is high, that is, has a wider solid solution range with Al. Similarly, an element in the column marked with “」 ”in the Cu row is an element in which the reactivity between the element and Cu is much higher than the reactivity between Al and Cu, that is, the solid solution range of Cu. Is an extremely wide element.

  From Table 1, the reactivity between Al and each element that can be selected as a bonding element is higher than the reactivity between Al and Cu, and the reactivity between Cu and each element that can be selected as a bonding element is between Cu and Al. It can be seen that it is higher than the reactivity. That is, when Al, Cu, and a bonding element coexist, Al and Cu react with the bonding element preferentially over each other. For this reason, the 1st metal member and the 2nd metal member can be firmly joined via this joined part, suppressing reaction of Al and Cu by using a joined part containing a joining element. Thereby, a highly reliable joined body can be obtained.

  Hereinafter, the joined body according to the first embodiment will be described with reference to FIG.

  FIG. 1 is a schematic cross-sectional view of the joined body according to the first embodiment.

  The joined body 10 shown in FIG. 1 includes a first metal member 1, a second metal member 2, and a joint portion 3 that joins the first metal member 1 and the second metal member 2.

  The shapes of the first metal member 1 and the second metal member 2 can be appropriately selected by those skilled in the art depending on the application.

  The joint portion 3 includes a first region 31 adjacent to the first metal member 1, a second region 32 adjacent to the second metal member 2, and a third region located between the first region 31 and the second region 32. 33.

  The first region 31 included in the joint portion 3 is made of Al derived from the first metal member 1 adjacent to the first region 31, and Si, Ni, Mn, Co, Zn, Ge, Au, Ag, and Pd. It contains at least one element selected from the group. The first region 31 does not contain Sn.

  The second region 32 included in the joint portion 3 is made of Cu derived from the second metal member 2 adjacent to the second region 32 and Si, Ni, Mn, Co, Zn, Ge, Au, Ag, and Pd. It contains at least one element selected from the group. The second region 32 does not contain Sn.

  The third region 33 included in the junction 3 mainly includes at least one element selected from the group consisting of Si, Ni, Mn, Co, Zn, Ge, Au, Ag, and Pd. The third region 33 does not contain Sn.

  As described above, the junction 3 extends from the first region 31 to the third region 33, and includes at least one selected from the group consisting of Si, Ni, Mn, Co, Zn, Ge, Au, Ag, and Pd. Contains elements.

  As described above, the first region 31 includes Al derived from the first metal member 1 and a bonding element. Since Al has high reactivity with the bonding element, it can form a solid solution and / or an intermetallic compound together with the bonding element. Therefore, it is preferable that the first region 31 included in the bonded portion 3 of the bonded body 10 in FIG. 1 includes a solid solution of Al and a bonding element and / or an intermetallic compound.

  As described above, the second region 32 includes Cu derived from the second metal member 2 and a bonding element. Since Cu has high reactivity with the bonding element, it can form a solid solution and / or an intermetallic compound together with the bonding element. Therefore, it is preferable that the second region 32 included in the bonding portion 3 of the bonded body 10 in FIG. 1 includes a solid solution of Cu and a bonding element and / or an intermetallic compound.

  The bonding element forms a solid solution and / or intermetallic compound with Al and Cu, respectively, so that Al derived from the first metal member 1 and Cu derived from the second metal member 2 form a solid solution or an intermetallic compound. Consumed and less directly reacts with Cu derived from the second metal member 2 and Al derived from the first metal member 1, respectively. Thus, since formation of a coarse and brittle Al (Cu) intermetallic compound is suppressed, excellent bonding strength and high reliability can be obtained in the bonding portion 3.

  The joined body 10 in FIG. 1 includes the joint portion including the coarse and fragile intermetallic compound composed of Al and Cu by using the joint portion 3 including the first region 31 and the second region 32. The bonding strength can be improved as compared with the bonded body.

  Each element that can be selected as a bonding element is highly reactive with Al. However, as shown in Table 1, among these, especially Mn, Zn, Ge and Ag have very high reactivity with Al. Therefore, if the bonding part 3 contains at least one element selected from the group consisting of Mn, Zn, Ge and Ag as a bonding element, a solid solution with Al and / or an intermetallic compound are more easily formed. As a result, a more reliable bonded body can be provided.

  Further, selecting at least one element selected from the group consisting of Ni, Mn, Co, Zn, Ge and Ag as a bonding element is easy to form a solid solution with Al and / or an intermetallic compound, and Cu and This is not only advantageous in that a solid solution and / or an intermetallic compound is easily formed, but is also preferable from an economical viewpoint.

  Furthermore, as described above, the junction 3 does not contain Sn. So-called soldering in which a metal member is joined using a material containing Sn, that is, an Sn-based solder material, has an advantage that it can be performed at a relatively low temperature because the melting point of the Sn-based solder material is low. However, when the joined body obtained by joining the metal members using the Sn-based solder material is compared with the joined body according to the first embodiment, as is apparent from Table 2 below, the latter is electrically conductive. It is superior to the former in terms of properties and mechanical strength. In the case of a joined body that can be exposed to high temperatures, the low melting point of the Sn-based solder material can be a drawback.

  That is, the joined body according to the first embodiment is superior to the joined body obtained using the Sn-based solder material at least in terms of electrical conductivity and mechanical strength.

  As described above, according to the first embodiment, it is possible to obtain a bonded body that has excellent bonding strength, high reliability, and excellent electric conductivity.

(Second Embodiment)
Hereinafter, the joined body according to the second embodiment will be described.

  The joined body according to the second embodiment further includes Ti and B in the joint portion of the joined body according to the first embodiment.

  More specifically, it is desirable that Ti and B are uniformly dispersed with a Ti (B) intermetallic compound having a particle diameter of 1 μm or less in the joint. Such a fine Ti (B) intermetallic compound can refine the crystal grains of the joint as solidification nuclei during the melting and solidification process of the joining material, thereby improving the joining strength.

  Although the specific reason is unclear, the inventors of the present invention formed the fine Ti-B phase while inhibiting the reaction between Al and Cu during the formation of the joint, and the formed joint. It was discovered that the crystal structure was further refined.

  The joined body including such a joined portion can further improve the joining strength, and can further increase the reliability.

  Thus, according to the second embodiment, it is possible to obtain a bonding material with further improved bonding strength.

(Third embodiment)
The third embodiment relates to a method for manufacturing a joined body. The manufacturing method includes a first metal member having a Cu content of less than 5.7% by weight and containing Al and a second metal member having an Al content of less than 9.4% by weight and containing Cu. A step of disposing a bonding material containing at least one element selected from the group consisting of Si, Ni, Mn, Co, Zn, Ge, Au, Ag, and Pd. Further, the manufacturing method includes a step of melting the bonding material to form a melted portion. Furthermore, the manufacturing method includes the step of obtaining a joined body in which a joined portion including the at least one element is formed between the first metal member and the second metal member by solidifying the molten portion. Including.

  The joined body according to the first embodiment and the second embodiment can be manufactured by, for example, the joined body manufacturing method according to the third embodiment.

  Hereinafter, a method for manufacturing a joined body according to the third embodiment will be described with reference to FIG.

  FIG. 2 is a schematic view showing one step of the method of manufacturing the joined body according to the third embodiment. In FIG. 2, the first metal member 1, the second metal member 2, and the bonding material 3 ′ are shown as sectional views thereof.

  In the method according to the present embodiment, first, the first metal member 1 and the second metal member 2 are faced with a gap provided at least at a part between them. More specifically, the first metal member 1 and the second metal member 2 each having a notch at each end are abutted at these ends.

  Next, a bonding material 3 ′ is disposed between the first metal member 1 and the second metal member 2. More specifically, the wire-like bonding material 3 ′ is inserted into a gap formed by two notches provided at the end of the first metal member 1 and the end of the second metal member 2.

  The bonding material 3 ′ includes at least one element selected from the group consisting of Si, Ni, Mn, Co, Zn, Ge, Au, Ag, and Pd, that is, a bonding element. Further, the bonding material 3 ′ may further contain Ti and B. Further, the bonding material 3 ′ does not contain Sn. That is, the bonding material 3 ′ is not Sn solder.

  Next, the bonding material 3 ′ disposed between the first metal member 1 and the second metal member 2 is melted. Melting can be performed by heating, for example. Examples of the heating method include laser welding, electron beam welding, MIG arc welding, and TIG arc welding, which can perform local melt welding. Moreover, heating can be performed with welding apparatuses, such as a laser beam welding apparatus, an electron beam welding apparatus, a MIG arc welding apparatus, and a TIG arc welding apparatus, for example. When manufacturing a small joined body, the laser beam welding apparatus and electron beam welding apparatus which can make a heating spot small are preferable.

  FIG. 2 shows an example in which the bonding material 3 ′ is melted using the laser beam welding apparatus 4.

  The laser beam welding device 4 and / or the molten bonding material 3 ′ further melts the part 31 ′ of the first metal member 1 and the part 32 ′ of the second metal member 2 in contact with the bonding material 3 ′. The molten bonding material 3 ′, the molten portion 31 ′ of the first metal member 1, and the molten portion 32 ′ of the second metal member 2 are mixed with each other to form a molten portion.

  Next, this molten part is solidified. During solidification, a eutectic reaction occurs between the elements present in the melted portion.

  As described above, the melting portion is formed of the molten bonding material 3 ′, the molten portion 31 ′ of the first metal member 1, and the molten portion 32 ′ of the second metal member 2. Therefore, the melting part contains a bonding element derived from the bonding material 3 ′, Al derived from the first metal member 1, and Cu derived from the second metal member 2. Note that Al and Cu are unevenly distributed in a portion near the first metal member 1 and a portion close to the second metal member 2 from which they originate, respectively.

  As described in the first embodiment, Al and Cu are more reactive with the bonding element than with each other. Therefore, Al and Cu cause a eutectic reaction preferentially with the bonding element rather than each other, and can form a solid solution and / or an intermetallic compound together with the bonding element. The presence of the bonding element in the molten portion containing Al and Cu allows Al and Cu to react with the bonding element to form a solid solution and / or an intermetallic compound, respectively. And the formation of an intermetallic compound that is brittle.

  When the solidification of the molten part is completed, a joined body in which a joined part including a joining element derived from the joining material 3 ′ is formed between the first metal member 1 and the second metal member 2 can be obtained.

  Thus, according to the present embodiment, the joined body according to the first embodiment, that is, the joined body having excellent joining strength and high reliability can be manufactured.

  In the present embodiment, when the bonding material 3 ′ further including Ti and B is used, a bonded body including a bonded portion in which the Ti—B phase is dispersed can be manufactured. That is, according to the present embodiment, the joined body according to the second embodiment can also be manufactured.

  In addition, in the manufacturing method of the joined body demonstrated referring FIG. 2, although each butt | matching which butt | matches each edge part of the 1st metal member 1 and the 2nd metal member 2 is performed, the joining method is as follows. There is no particular limitation. For example, at least a part of the first metal member 1 can be overlap-bonded so that at least a part of the second metal member 2 is overlapped, or a butt joint in which one end is pressed against the other surface.

  The form of the bonding material 3 ′ can be appropriately selected by those skilled in the art according to the shape of the first metal member 1, the shape of the second metal member 2, and the bonding method of these metal members. As a form of the bonding material 3 ′, for example, a bar shape, a sheet shape, or a line shape can be cited in addition to the wire shape.

  A method for arranging the bonding material 3 ′ between the first metal member 1 and the second metal member 2 can also be appropriately selected by those skilled in the art.

  If the end portions are to be abutted, for example, the end portion of the first metal member 1 may be abutted against the end portion of the second metal member 2 with the sheet-like bonding material 3 ′ interposed therebetween. it can.

  In the case where the second metal member 2 is superimposed on a part of the first metal member 1, for example, a sheet-like bonding material 3 ′ is placed on the first metal member 1, and the second metal is placed thereon. The member 2 can be overlapped. Alternatively, a groove is provided on the surface of the first metal member 1, a linear, rod-like or wire-like bonding material 3 'is inserted into the groove, and the second metal member 2 is stacked thereon. You can also.

  Further, since the bonding material 3 ′ only needs to include the bonding element and be disposed between the first metal member 1 and the second metal member 2, for example, the surface of the first metal member 1 or the second metal member 2. A part of the metal layer containing the bonding element provided at least in part can be used as the bonding material 3 ′.

  Here, one of such modifications will be described in detail with reference to the drawings.

  FIG. 3 is a schematic view showing one process of a modification of the method for manufacturing a joined body according to the third embodiment. FIG. 4 is a schematic cross-sectional view of a joined body obtained by the method of manufacturing the joined body of FIG.

  3 is the same as the method for manufacturing a joined body described with reference to FIG. 2 except that the surface of the first metal member 1 is covered with the metal layer 34. is there.

  The metal layer 34 is coated on the surface of the first metal member 1 for the purpose of improving, for example, corrosion resistance and electrical conductivity.

  The metal layer 34 includes a bonding element. The bonding element can be contained in the metal layer 34 in the form of an alloy or a compound. The bonding element included in the metal layer 34 may be the same as or different from the bonding element included in the bonding material 3 ′.

  The metal layer 34 may be a single layer or may have a laminated structure of two or more layers. The effect can be further exhibited by using a laminated structure of two or more layers.

  The formation method of the metal layer 34 is not specifically limited. The metal layer 34 can be formed on the first metal member 1 by, for example, electroless plating, electroplating, physical vapor deposition, chemical vapor deposition, powder application, and thermal spraying.

  The thickness of the metal layer 34 depends on the purpose of providing the metal layer 34, but is not particularly limited. The thickness of the metal layer 34 can be, for example, within a range of 0.1 μm or more and 100 μm or less for a single layer, and within a range of 0.1 μm or more and 500 μm or less for a plurality of layers. Can do. For example, when formed by a plating method, the thickness of the metal layer 34 is preferably in the range of 3 μm or more and 5 μm or less, and when formed by a powder coating method, the thickness of the metal layer 34 is 30 μm or more, It is preferable that it exists in the range of 50 micrometers or less.

  Moreover, when comprised by multiple layers, the thickness of the metal layer 34 can also be made into the sum total of the appropriate thickness of each metal layer.

  At least a part of the surface of the metal layer 34 facing the second metal member 2 is, for example, a part of the first metal member 1 by the bonding material 3 ′ melted by the laser beam welding device 4 and / or the laser beam welding device 4. Melts with 31 '. The molten metal layer 34, the bonding material 3 ', the molten portion 31' of the first metal member 1, and the molten portion 32 'of the second metal member 2 form a molten portion.

  As the melted portion solidifies, the first metal member 1, the second metal member 2, the first metal member 1, and the second metal member 2 whose surfaces are covered with the metal layer 34 as shown in FIG. The joined body 10 including the joint portion 3 in which the melted portion is solidified is obtained.

  When the molten part solidifies, a eutectic reaction occurs between the elements contained in the molten part.

  The part adjacent to the first metal member 1 in the melted portion mainly includes Al derived from the first metal member 1, a bonding element derived from the bonding material 3 ′, and a bonding element derived from the metal layer 34. . Since the portion adjacent to the first metal member 1 in the melted portion thus contains Al and a bonding element that are highly reactive with each other, these elements cause a eutectic reaction during solidification. As a result, the first region 31 formed by solidifying the portion adjacent to the first metal member 1 in the melted portion contains a solid solution of Al and a bonding element and / or an intermetallic compound. Thereby, when the 1st field 31 is formed, reaction of Al and Cu of the 1st metal member 1 can be controlled.

  Moreover, the part adjacent to the 2nd metal member 2 among melt | fusion parts becomes the 2nd area | region 32 like the manufacturing method of the joining material demonstrated using FIG. 2 by solidifying. Further, in the melted portion, the portion sandwiched between the portion adjacent to the first metal member 1 and the portion adjacent to the second metal member 2 is solidified to produce the bonding material described with reference to FIG. Similar to the method, it becomes the third region 33.

  Therefore, according to the method for manufacturing a joined body shown in one step in FIG. 3, the joined body according to the first embodiment can be manufactured.

  In addition, according to the method for manufacturing a joined body shown in FIG. 3, for example, the metal layer 34 provided for the purpose of improving the corrosion resistance and the electrical conductivity can be contributed to the joining, so that the corrosion resistance and the electrical conductivity are further improved. A joined body can be manufactured with few processes.

  Furthermore, in the manufacturing method of the joined body shown in FIG. 3, the joined body according to the second embodiment can be manufactured by using the joining material 3 ′ further including Ti and B.

  3, the metal layer 34 is provided on the first metal member 1, but the metal layer may be provided on the second metal member 2, or the first metal member 1 may be provided. A metal layer can also be provided on both the member 1 and the second metal member 2.

  As described above, according to the third embodiment, a bonded body having excellent bonding strength and high reliability can be obtained.

(Fourth embodiment)
Next, a battery pack according to the fourth embodiment will be described.

  The battery pack according to the fourth embodiment includes a plurality of unit cells and a bus bar. Each of the plurality of unit cells includes an electrode terminal. The electrode terminal contains Al and the Cu content is less than 5.7% by weight. The bus bar electrically connects the electrode terminals of the plurality of unit cells. Moreover, a bus bar contains Cu and content of Al is less than 9.4 weight%. The electrode terminal is joined to the bus bar via the joint. The junction includes at least one element selected from the group consisting of Si, Ni, Mn, Co, Zn, Ge, Au, Ag, and Pd.

  In the battery pack according to the fourth embodiment, one of the first to third embodiments may be applied, or a plurality may be applied in combination.

  FIG. 5 is an exploded perspective view of the battery pack 51 according to the fourth embodiment. FIG. 6 is a partially enlarged view of the battery pack 51 of FIG. FIG. 7 is a view of the battery pack 51 of FIG. 5 as viewed from directly above.

  The battery pack 51 shown in FIGS. 5 to 7 includes a plurality of unit cells 52. Each unit cell 52 includes a positive electrode terminal 56 and a negative electrode terminal 57 made of a first metal member.

  The positive terminal 56 of one unit cell 52 is electrically connected in series to the negative terminal 57 of another unit cell 52 via a bus bar 55 made of a second metal member. However, the positive terminal 56 of the unit cell 52 positioned at one end of the series of electrical connections and the negative terminal 57 of the unit cell 52 positioned at the other end are not connected to the bus bar. The battery pack 51 is used by connecting a positive electrode terminal and a negative electrode terminal that are not connected to the bus bars of the unit cells located at both ends to an electric device.

  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 of the curved portion 553. ing. In addition, an opening 554 for fitting the positive terminal 56 or the negative terminal 57 is provided at the center of the two flat portions 552 of the bus bar 55. Further, the bus bar 55 has a needle-like connection pin 551 protruding vertically from one flat surface portion 552. The connection pin 551 is made of a second metal member.

  The positive electrode terminal 56 and the negative electrode terminal 57 of each unit cell 52 are laser welded to the peripheral edge of the opening 554 of the corresponding bus bar 55 to form joints 56a and 57a.

  These unit cells 52 are accommodated in a battery case 54. On the battery case 54, a positive electrode terminal 56, a negative electrode terminal 57, a part of a curved portion 553 of the bus bar 55, and a connection pin 551 are provided. A battery cover 53 is formed on which a window for exposing the portion is formed. A control board 58 is attached to the upper surface of the battery pack 51. A plurality of holes 581 are formed in the control substrate 58. The connection pin 551 is fitted in the hole 581 so as to penetrate the control board 58 through the hole 581. A circuit (not shown) made of metal (for example, oxygen-free copper) is formed on the surface of the control board 58.

  In the battery pack 51 according to the present embodiment, the joined body according to the first embodiment or the second embodiment is applied to the joined portions 56a and 57a between the bus bar 55 and the positive electrode terminal 56 and the negative electrode terminal 57, respectively. Yes.

  In the battery pack 51 according to the present embodiment, the joining portions 56a and 57a are formed by the method according to the third embodiment, for example. First, the positive electrode terminal 56 and the negative electrode terminal 57 made of the first metal member are fitted into the corresponding opening 554 of the bus bar 55 with at least a partial gap provided therebetween. Next, a linear bonding material 3 ′ including a bonding element is inserted along the gap. Thereafter, the linear bonding material 3 ′ is melted by a laser beam, and a part of the positive electrode terminal 56 and the negative electrode terminal 57 adjacent to the bonding material 3 ′ and the opening 554 of the bus bar 55 adjacent to the bonding material 3 ′. A part of the periphery of the film is melted to form a melted portion. The melted portion is solidified by cooling to obtain joined portions 56a and 57a.

  As described above, the joined body according to the first and second embodiments and the joined body manufactured by the method according to the third embodiment can improve joint strength and increase reliability. it can. Since the battery pack 51 according to the present embodiment to which these joined bodies are applied includes such joint portions 56a and 57a having excellent joint strength, the battery pack 51 has high performance and high reliability.

  As the fourth embodiment, a battery pack having a configuration in which the electrode terminal is made of the first metal member and the bus bar is made of the second metal member has been described. However, as a matter of course, the battery pack having a configuration in which the electrode terminal is made of the second metal member and the bus bar is made of the first metal member, the joined body according to the first embodiment or the joined body according to the second embodiment, or The joined body manufactured by the method according to the third embodiment can also be applied. In FIG. 5, the unit cells 52 are connected in series, but the present invention can also be applied to a battery pack in which the unit cells 52 are connected in parallel.

  As described above, according to the fourth embodiment, a battery pack having high performance and high reliability can be realized.

(Example)
Examples will be described below.

Example 1
In this example, a joined body having the same structure as the joined body 10 shown in FIG. 1 was manufactured.

  First, the first metal member 1 and the second metal member 2 were prepared.

  As the first metal member 1, an Al material containing 0.2% by weight of Si, 0.3% by weight of Fe, and the balance of Al was used. This Al material had a thickness of 3 mm, a width of 15 mm, a length of 50 mm, and an electric conductivity of 61% IACS.

  As the second metal member 2, an oxygen-free copper material containing less than 10 ppm of oxygen, 0 wt% Al, and 99.97 wt% Cu was used. This Cu material had a thickness of 3 mm, a width of 15 mm, a length of 50 mm, and an electrical conductivity of 101% IACS.

  One end of each of the first metal member 1 and the second metal member 2 was chamfered at 60 ° by a notch.

  Next, the 1st metal member 1 and the 2nd metal member 2 were faced | matched by the edge part which gave the chamfer. Thereby, the space | gap formed of the said notch part was provided between the 1st metal member 1 and the 2nd metal member 2. As shown in FIG.

  Next, a linear bonding material 3 ′ was inserted into the gap provided by the butt.

  As the bonding material 3 ′, a wire material containing 10 wt% Ni and the remaining Ag was used. This wire had a diameter of 2.8 mm and a length of 15 mm. This bonding material 3 'was manufactured by producing a sintered body in which Ni was uniformly dispersed in Ag by powder metallurgy, and then subjecting this to extrusion and drawing.

  After the bonding material 3 ′ was inserted, the bonding material 3 ′ was melted by YAG laser welding. The part 31 ′ of the first metal member 1 and the part 32 ′ of the second metal member 2 ′ were also melted by the heat of the molten bonding material 3 ′ and / or the YAG laser. Due to this melting, a melting portion was formed between the first metal member 1 and the second metal member 2.

  Next, this molten part was solidified by cooling. Accordingly, the joined body 10 including the first metal member 1, the second metal member 2, and the joint portion 3 that joins the first metal member 1 and the second metal member 2, similar to the joined body 10 illustrated in FIG. 1. Got.

  Next, the obtained bonded body 10 was subjected to (i) cross-sectional observation and composition analysis of the bonded portion; and (ii) tensile strength analysis of the bonded body.

(I) Cross-sectional observation and composition analysis of joint part The obtained joined body 10 was cut | disconnected, and the cross section which passes along the 1st metal member 1, the 2nd metal member 2, and the junction part 3 was obtained. The obtained cut surface was polished with sand paper and then subjected to bubbling. Thereafter, the cross section subjected to polishing was observed with an optical microscope, and then composition analysis was performed with EPMA.

  As a result of cross-sectional observation with an optical microscope, the joined portion of the obtained joined body 10 is connected to the first region 31 adjacent to the first metal member 1 and the second metal member 2 in the same manner as the joined body 10 shown in FIG. It was found to include the adjacent second region 32 and the third region 33 sandwiched between the first region 31 and the second region 32.

  As a result of component analysis by EPMA, the first region 31 includes (Ag) Al solid solution, (Ag) Al intermetallic compound, (Ni) Al intermetallic compound, and (Ag, Ni) Al intermetallic compound. I found out. Moreover, it turned out that the 2nd area | region 32 contains the (Ni, Ag) Cu solid solution. Furthermore, it turned out that the 3rd area | region 33 contains Ag base material with which Ni particle | grains were disperse | distributed.

  Moreover, in the analysis by EPMA, the Cu (Al) intermetallic compound formed by direct reaction of Al and Cu was not observed in the joint part 3.

(Ii) Strength Analysis A JIS-Z2201 metal material tensile test piece 13B was prepared from the obtained joined body 10 and both ends of the tensile test piece, that is, the first metal member 1 side and the second metal member 2 side. The ends of each were fixed to a holder of a tensile strength tester, and the tensile strength of the joined body 10 was measured according to a metal material tensile test method of JIS-Z2241.

  The obtained bonded body 10 broke at 80 MPa in the third region 33 of the Ag base material in which Ni particles were dispersed.

(Example 2)
In this example, a joined body was manufactured by the same method as in Example 1 except that different materials were used as the first metal member 1, the second metal member 2, and the joining material 3 ′.

  In this example, as the first metal member 1, 0.3 wt% Si, 0.7 wt% Fe, 0.25 wt% Cu, 1.2 wt% Mn, 1.2 A 3004Al alloy material consisting of wt% Mg, 0.25 wt% Zn, and the balance Al was used. This Al alloy material had a thickness of 3 mm, a width of 10 mm, a length of 50 mm, and an electrical conductivity of 38% IACS.

  Further, as the second metal member 2, a Cu—Ni—Sn alloy composed of 1.0 wt% Ni, 0.9 wt Sn, and the remaining Cu was used. This alloy had a thickness of 3 mm, a width of 10 mm, a length of 50 mm, and an electrical conductivity of 40% IACS.

  Further, a wire rod containing 30 wt% Co and the remaining Ag was used as the bonding material 3 ′. This wire had a diameter of 2.8 mm and a length of 10 mm. This bonding material 3 'was manufactured by producing a sintered body in which Co was uniformly dispersed in Ag by powder metallurgy, and then subjecting this sintered body to extrusion and drawing.

  As in Example 1, the obtained bonded body 10 was subjected to (i) cross-sectional observation and composition analysis of the bonded portion; and (ii) tensile strength analysis of the bonded body.

  As a result of cross-sectional observation with an optical microscope, the joined portion of the obtained joined body 10 is connected to the first region 31 adjacent to the first metal member 1 and the second metal member 2 in the same manner as the joined body 10 shown in FIG. It was found to include the adjacent second region 32 and the third region 33 sandwiched between the first region 31 and the second region 32.

  As a result of component analysis by EPMA, it was found that the first region 31 contained (Ag) Al solid solution, (Co) Al intermetallic compound, and (Ag, Co) Al intermetallic compound. Moreover, it turned out that the 2nd area | region 32 contains the (Co, Ni, Ag) Cu solid solution. Furthermore, it turned out that the 3rd area | region 33 contains Ag base material with which Co particle | grains were disperse | distributed.

  Although the first metal member 1 contains a small amount of Cu, in the analysis by EPMA, Cu (Al) formed by a direct reaction between Al and Cu in the joint 3 of the obtained joined body 10. No intermetallic compound was observed.

  A metal material tensile test piece 13B of JIS-Z2201 is prepared from the obtained joined body 10, and both ends of the tensile test piece, that is, the end portion on the first metal member 1 side and the end portion on the second metal member 2 side are formed. Each was fixed to a holder of a tensile strength tester, and the tensile strength of the joined body 10 was measured according to a metal material tensile test method of JIS-Z2241.

  The obtained bonded body 10 was broken at 150 MPa in the third region 33 of the Ag base material in which Co particles were dispersed.

Example 3
In this example, a joined body was manufactured in the same manner as in Example 1 except that different materials were used as melting means for the joining material 3 ′ and the joining material 3 ′.

  In this example, an Ag wire having a diameter of 2.8 mm was used as the bonding material 3 ′. This bonding material 3 'was manufactured by casting an Ag ingot having a purity of 99.7% by weight, and then subjecting it to extrusion and drawing.

  The bonding material 3 ′ was melted using an electron beam.

  In the same manner as in Example 1, the obtained bonded body 10 was subjected to (i) composition analysis of the bonded portion; and (ii) tensile strength analysis of the bonded body.

  As a result of cross-sectional observation with an optical microscope, the joined portion of the obtained joined body 10 is connected to the first region 31 adjacent to the first metal member 1 and the second metal member 2 in the same manner as the joined body 10 shown in FIG. It was found to include the adjacent second region 32 and the third region 33 sandwiched between the first region 31 and the second region 32.

  As a result of component analysis by EPMA, it was found that the first region 31 contained (Ag) Al solid solution and (Ag) Al intermetallic compound. Moreover, it turned out that the 2nd area | region 32 contains the Cu (Ag) solid solution. Furthermore, it turned out that the 3rd area | region 33 contains Ag base material.

  In the analysis by EPMA, a Cu (Al) intermetallic compound formed by a direct reaction between Al and Cu was not observed in the joint 3 of the joined body 10 obtained.

  On the other hand, as a result of testing the obtained bonded body 10 with a tensile tester, the bonded body 10 was broken at 60 MPa in an Ag base material.

Example 4
In this example, a joined body was manufactured in the same manner as in Example 1 except that different materials were used as melting means for the joining material 3 ′ and the joining material 3 ′.

  In this example, a wire containing 3 wt% Pd and the remaining Ag was used as the bonding material 3 ′. This wire had a diameter of 2.8 mm and a length of 15 mm. This bonding material 3 'was manufactured by casting an ingot composed of 3% by weight of Pd and the balance of Ag, and then subjecting it to extrusion and drawing.

  The bonding material 3 ′ was melted using an electron beam.

  In the same manner as in Example 1, the obtained bonded body 10 was subjected to (i) composition analysis of the bonded portion; and (ii) tensile strength analysis of the bonded body.

  As a result of cross-sectional observation with an optical microscope, the joined portion of the obtained joined body 10 is connected to the first region 31 adjacent to the first metal member 1 and the second metal member 2 in the same manner as the joined body 10 shown in FIG. It was found to include the adjacent second region 32 and the third region 33 sandwiched between the first region 31 and the second region 32.

  As a result of component analysis by EPMA, the first region 31 includes (Ag) Al solid solution, (Ag) Al intermetallic compound, (Pd) Al intermetallic compound, and (Ag, Pd) Al intermetallic compound. I found out. Moreover, it turned out that the 2nd area | region 32 contains the (Ag, Pd) Cu solid solution. Further, it was found that the third region 33 includes an Ag base material in which Pd is dissolved.

  In the analysis by EPMA, a Cu (Al) intermetallic compound formed by a direct reaction between Al and Cu was not observed in the joint 3 of the joined body 10 obtained.

  On the other hand, as a result of testing the obtained bonded body 10 with a tensile tester, the bonded body 10 was broken at 100 MPa in an Ag base material in which Pd was dissolved.

(Example 5)
In this example, a joined body was manufactured in the same manner as in Example 3 except that a different joining material 3 ′ was used.

In this example, an Ag (Ti, B) wire having a diameter of 2.8 mm was used as the bonding material 3 ′. This bonding material 3 ′ is composed of an Ag powder having a particle size of 10 to 25 μm and a purity of 99.7% by weight, and a TiB ₂ powder having a particle size of 1 μm or less of 99.5: 0.5. The mixture was sintered at a% ratio, and the mixture was sintered. Thereafter, the sintered body was subjected to extrusion and drawing.

  In the same manner as in Example 1, the obtained bonded body 10 was subjected to (i) composition analysis of the bonded portion; and (ii) tensile strength analysis of the bonded body.

  As a result of cross-sectional observation with an optical microscope, the joined portion of the obtained joined body 10 is connected to the first region 31 adjacent to the first metal member 1 and the second metal member 2 in the same manner as the joined body 10 shown in FIG. It was found to include the adjacent second region 32 and the third region 33 sandwiched between the first region 31 and the second region 32. Further, the crystal grains contained in the joint 3 were extremely fine compared to the joint 3 of the joined body of Example 3.

As a result of component analysis by EPMA, it was found that the first region 31 contained (Ag) Al solid solution and (Ag) Al intermetallic compound. Moreover, it turned out that the 2nd area | region 32 contains the Cu (Ag) solid solution. Further, the third region 33 was found to contain Ag substrate TiB ₂ is dispersed.

  In the analysis by EPMA, a Cu (Al) intermetallic compound formed by a direct reaction between Al and Cu was not observed in the joint 3 of the joined body 10 obtained.

On the other hand, as a result of testing the obtained bonded body 10 with a tensile tester, the bonded body 10 was broken at 85 MPa in an Ag base material in which TiB ₂ was dispersed.

  The strength of the joined body obtained in this example is higher than that of the joined body obtained in Example 3. The crystal grains contained in the joined portion 3 are extremely fine, thereby improving the joint strength. It is considered a thing.

(Example 6)
In this example, a joined body having the same structure as the joined body 10 shown in FIG. 4 is formed in the same manner as in Example 1 except that a metal layer is provided on the surface of the first metal member 1. Manufactured.

  In this example, a Pd metal layer having a thickness of 3 μm was formed on the surface of the first metal member 1 by electroless plating.

  In the same manner as in Example 1, the obtained bonded body 10 was subjected to (i) composition analysis of the bonded portion; and (ii) tensile strength analysis of the bonded body.

  As a result of cross-sectional observation using an optical microscope, the joined portion of the obtained joined body 10 is connected to the first region 31 adjacent to the first metal member 1 and the second metal member 2 in the same manner as the joined body 10 shown in FIG. It was found to include the adjacent second region 32 and the third region 33 sandwiched between the first region 31 and the second region 32.

  As a result of component analysis by EPMA, the first region 31 includes (Ag) Pd solid solution in addition to the solid solution and the intermetallic compound included in the first region 31 of the joint portion 3 of the joined body 10 obtained in Example 1. I found out. Moreover, it turned out that the 2nd area | region 32 contains the Cu (Ni) solid solution. Furthermore, it turned out that the 3rd area | region 33 contains Ag base material with which Ni particle | grains were disperse | distributed.

  In the analysis by EPMA, a Cu (Al) intermetallic compound formed by a direct reaction between Al and Cu was not observed in the joint 3 of the joined body 10 obtained.

  On the other hand, as a result of testing the obtained joined body 10 with a tensile tester, the joined body 10 was broken at 80 MPa in the first metal member 1.

(Comparative example)
In this example, the joined body 10 shown in FIG. 8 was manufactured by the same method as in Example 6 except that the bonding material 3 ′ was not used.

  As shown in FIG. 8, the obtained joined body 10 includes a first metal member 1, a second metal member, and a joint portion 3 sandwiched between the first metal member 1 and the second metal member 2. It was.

  In the same manner as in Example 1, the obtained bonded body 10 was subjected to (i) composition analysis of the bonded portion 3 and (ii) tensile strength analysis of the bonded body.

  As a result of cross-sectional observation using an optical microscope, it was found that the joined portion 3 of the obtained joined body 10 includes a plurality of void defects having a size of several tens of μm to several hundreds of μm.

As a result of analysis by EPMA, a eutectic structure of lamellar and coarse α (Al) phase and θ (CuAl ₂ ) phase was observed in the joint 3 other than the void defect of the obtained joined body 10.

  On the other hand, as a result of testing the obtained joined body with a tensile tester, the joined body 10 was broken at 20 MPa in the joint portion 3 on the first metal member 1 side.

(Consideration of results)
The bonding materials obtained in Examples 1 to 6 did not contain a coarse θ phase composed of Cu and Al in the bonding portion. On the other hand, the bonding material obtained in the comparative example contained a coarse θ phase composed of Cu and Al in the bonding portion.

  The tensile strengths of the bonding materials obtained in Examples 1 to 6 were superior to the tensile strength of the bonding materials obtained in the comparative examples. This proves that the bonding material including the bonding portion where the coarse θ phase does not exist has higher strength than the bonding material including the bonding portion where the θ phase exists.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 10 ... Bonded body, 1 ... 1st metal member, 2 ... 2nd metal member, 3 ... Joint part, 3 '... Joining material, 31 ... 1st area | region, 32 ... 2nd area | region, 33 ... 3rd area | region, 4 ... Laser beam welding apparatus, 51 ... Battery pack, 52 ... Unit cell, 53 ... Battery cover, 54 ... Battery case, 55 ... Bus bar, 551 ... Connecting pin, 552 ... Bus bar flat part, 553 ... Bus bar curved part, 554 ... Opening of bus bar, 56 ... Positive terminal, 56a ... Junction between positive terminal and bus bar, 57 ... Negative terminal, 57a ... Junction between negative terminal and bus bar, 58 ... Control board, 581 ... Hole formed in control board .

Claims (7)

A first metal member having a Cu content of less than 5.7% by weight and containing Al;
A second metal member having an Al content of less than 9.4% by weight and containing Cu;
A joining portion for joining the first metal member and the second metal member;
The joined portion includes at least one element selected from the group consisting of Si, Ni, Mn, Co, Zn, Ge, Au, Ag, and Pd.   The joined body according to claim 1, wherein the joint further includes Ti and B.   At least one of the first metal member and the second metal member is at least one element selected from the group consisting of Si, Ni, Mn, Co, Zn, Ge, Au, Ag, and Pd and a solid solution, or The joined body according to claim 1, wherein an intermetallic compound is formed.   The first metal member 1 contains 99.5% by weight or more of Al, and the second metal member 2 contains 99.9% by weight or more of Cu. The joined body according to item 1. It is a manufacturing method of the joined object given in any 1 paragraph of Claims 1 thru / or 4,
Between the first metal member containing less than 5.7% by weight of Cu and containing Al and the second metal member containing less than 9.4% by weight of Al and containing Cu, Si, Ni Arranging a bonding material containing at least one element selected from the group consisting of Mn, Co, Zn, Ge, Au, Ag and Pd;
Melting the bonding material to form a molten portion;
Obtaining a joined body in which a joined part including the at least one element is formed between the first metal member and the second metal member by solidifying the molten part. Manufacturing method.   6. The manufacturing method according to claim 5, wherein the formation of the melted portion is performed by a melt welding method selected from a laser welding method, an electron beam welding method, a MIG arc welding method, and a TIG arc welding method. A plurality of unit cells each having an electrode terminal containing Cu, the Cu content being less than 5.7% by weight;
Electrically connecting the electrode terminals of the plurality of unit cells, the Al content is less than 9.4 wt%, comprising a bus bar containing Cu,
The electrode terminal is bonded to the bus bar via a bonding portion including at least one element selected from the group consisting of Si, Ni, Mn, Co, Zn, Ge, Au, Ag, and Pd. A battery pack characterized by

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