Patent Application
20150239070
The present application is based on Japanese patent application No. 2014-036371 filed on Feb. 27, 2014, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
This invention relates to a joining material.
2. Description of the Related Art
A hybrid integrated circuit is disclosed in JP-H05-109919, the hybrid integrated circuit including a ceramics substrate, a wiring layer joined on the ceramics substrate, a power element disposed on the ceramics substrate, wherein the wiring layer is formed by joining a flat clad plate having a three-layered structure of Cu/Invar/Cu on the ceramics substrate with solder so that the flat clad plate is configured to function as a wire for supplying a large electric current for the power element.
In the hybrid integrated circuit, a chip terminal and a welding lead are joined by solder reflow on a solder layer formed on the flat clad plate via a Ni plated layer.
Conventionally, an element of lead (Pb) has been included in the solder that is a joint material used also in the hybrid integrated circuit described in JP-H05-109919. However, from around 2003, a movement of regulating the use of lead of which harmfulness to the human body is pointed out has spread with a focus on Europe, and development of a lead-free alternative material that does not include lead has been pursued.
A solder is divided into three groups of high temperature, middle temperature and low temperature according to the melting point. Of these, as to the high temperature solder, there was no lead-free high temperature solder that satisfies all of the market requirements of heat resistance at 260 degrees C., high thermal conductivity, joining reliability and low cost.
Consequently, the development of the lead-free high temperature solder satisfying all of the market requirements has been required, and as a developed product, there is a lead-free joint material disclosed in JP-2012-071347.
The joint material disclosed in JP-2012-071347 is configured to be melted from an interface between Zn and Al, thus it shrinks due to surface tension before wetting on the substrate. When it shrinks, diffusion unevenness occurs, or local wetting occurs at thin part of an outermost layer comprised of Cu or the like, the thin part coming into contact with a material to be joined, and shrinkage is carried out with a focus on the above-mentioned occurrence areas, thus there has been room for improvement in that a center position of mounting position is sometimes displaced from a center position when the joint material is supplied to the material to be joined.
It is an object of the invention to provide a joining material that can prevent the position displacement from the supplying position in case of using the specific joint material.
(1) According to one embodiment of the invention, a joining material comprises:
In the above embodiment (1) of the invention, the following modifications and changes can be made.
According to one embodiment of the invention, a joining material can be provided that can prevent the position displacement from the supplying position in case of using the specific joint material.
The preferred embodiments according to the invention will be explained below referring to the drawings, wherein:
[Configuration of Joining Material]
(Configuration of Composite Material 3)
The composite material 3 includes the first metal material having a thermal expansion coefficient of not more than 5, and the second metal material formed on the first metal material (both surfaces thereof), the second metal material having a thermal expansion coefficient higher than the first metal material.
As the first metal material having a thermal expansion coefficient of not more than 5, as shown in
The composite material 3 is configured to have a thermal expansion coefficient of preferably 5 to 15, and more preferably 7 to 13 by selecting a type (thermal expansion coefficient) or adjusting a thickness of the first and the second metal material. If the composite material 3 is configured to have a structure of Cu/Invar/Cu as shown in
The first metal material has a thickness of preferably 40 to 1200 μm, more preferably 80 to 400 μm. In addition, the second metal material has a thickness of preferably 20 to 2400 μm, more preferably 40 to 800 μm. The composite material 3 has the whole thickness of preferably 100 to 3000 μm, more preferably 200 to 1000 μm. It is preferable that the thickness ratio of the second metal material/the first metal material/the second metal material is configured to be (10 to 40)/(20 to 80)/(10 to 40). For example, in case of Cu/Invar/Cu, it is preferable that the thickness ratio is configured to be 1/1/1.
(Configuration of Solder Material 5)
The solder material 5 is a lead-free solder having a melting point of not less than 260 degrees C., and has a laminated structure configured such that a Zn based metal material including Zn as a main component, a first Al based metal material including Al as a main component, and a first X based metal material including Cu, Au, Ag or Sn as a main component are laminated in the order starting from the composite material 3. It is preferable that the solder material 5 is a lead-free solder having a melting point of not less than 350 degrees C. and not more than 400 degrees C.
The solder material 5 can be also configured to have a laminated structure configured such that a second Al based metal material including Al as a main component is further laminated between the composite material 3 and the Zn based metal material, and can be also configured to have a laminated structure configured such that a second X based metal material including Cu, Au, Ag or Sn as a main component is further laminated between the composite material 3 and the second Al based metal material.
The solder material 5A having a plate-like shape shown in
The solder material 5B having a plate-like shape shown in
The solder material 5C having a plate-like shape shown in
In the embodiment, the solder material 5B or the solder material 5C of the four-layer structure or the three-layer structure is more preferable than the solder material 5A of the five-layer structure.
The Zn based metal material 51 is configured to include Zn as a main component (a component included therein most, the same shall apply hereinafter), and it is preferable that the content of Zn is not less than 90% by mass. Namely, it is preferable that the Zn based metal material 51 is a single Zn, or a Zn alloy including impurities of not more than 10% by mass.
The first and second Al based metal material 52 is configured to include Al as a main component, and it is preferable that the content of Al is not less than 90% by mass. Namely, it is preferable that the first and second Al based metal material 52 is a single Al, or a Al alloy including impurities of not more than 10% by mass.
The first and second X based metal material is configured to include Cu, Au, Ag or Sn as a main component, and it is preferable that the content of Cu, Au, Ag or Sn is not less than 90% by mass. In particular, it is preferable that the first and second X based metal material is the Cu based metal material 53 shown in the drawing, including Cu as a main component and having the Cu content of not less than 90% by mass. Namely, it is preferable that the first and second X based metal material is a single Cu, or a Cu alloy including impurities of not more than 10% by mass. For example, pure copper such as oxygen-free copper, tough pitch copper, a dilute copper alloy including sulfur of 3 to 15 ppm by mass, oxygen of 2 to 30 ppm by mass and Ti of 5 to 55 ppm by mass or the like can be used.
As to the five-layer structure of X/Al/Zn/Al/X, for the purpose of generating sufficient liquid phase at the time of melting and enhancing wettability, it is preferable that the five-layer structure has the whole thickness of not less than 20 μm. In addition, in order to lower thermal resistance of the joining part and ensure reliability, it is preferable that the five-layer structure has the whole thickness of not more than 300 μm.
In case of the four-layer structure of X/Al/Zn/Al, it is preferable that the four-layer structure has the whole thickness of not less than 18 μm and not more than 299 μm. In addition, in case of the three-layer structure of X/Al/Zn, it is preferable that the three-layer structure has the whole thickness of not less than 15 μm and not more than 297 μm.
It is preferable that the ratio of (total layer thickness of Al)/(layer thickness of Zn) falls within the range of 1/60 to ⅓. In addition, for the purpose of uniformly melting the whole of the laminated material, it is preferable that the ratio of layer thickness of Al, Zn, Al (Al:Zn:A1) falls within the range of (1:6:1) to (1:60:1). Furthermore, in terms of uniformity of the melted structure, it is more preferable that the ratio (Al:Zn:A1) falls within the range of (1:8:1) to (1:30:1). In case of the three-layer structure of X/Al/Zn, it is preferable that the ratio of layer thickness of Al, Zn (Al:Zn) falls within the range of (1:3) to (1:60).
In addition, the X based metal material is needed to have a thickness of not less than a certain amount so as to have a function that is capable of preventing Zn and Al from being oxidized. On the other hand, the X based metal material results in being melted into a Zn—Al alloy produced by reaction of Zn and Al so as to be melted, and constituting a Zn—Al—Cu alloy, in this case, it is preferred to minimize an influence imparted by the element X on hardness and melting point of the Zn—Al alloy. Consequently, the X based metal material is needed to be thinner than Zn and Al. The layer thickness ratio [(Al+Zn+Al):(X+X)] is preferably [(1):(0.0002 to 0.2)] and more preferably [(1):(0.0005 to 0.1)]. In case of the three-layer structure of X/Al/Zn, it is preferable that the layer thickness ratio [(Zn+A1):(X)] is [(1):(0.0001 to 0.1)], and in case of four-layer structure of X/Al/Zn/Al, it is preferable that the layer thickness ratio [(Al+Zn+Al):(X)] is [(1):(0.0001 to 0.1)].
The solder material 5 shown in
[Manufacturing Method of Joining Material]
Next, a manufacturing method of the joining material according to the embodiment will be explained.
The composite material 3 can be obtained as a clad material by holding both surfaces of the first metal material (for example, Invar 1) with the second metal materials (for example, Cu 2) so as to integrate by a cold rolling process, an extrusion process or the like.
The solder material 5 (5A to 5C) can be manufactured by a clad rolling method, a plating method, or vapor deposition method. Details thereof can be manufactured by a method described in the above-mentioned JP-2012-71347 A1, thus the explanation will be omitted. Further, the solder material 5B, 5C can be also obtained by removing the X based metal material, or the X based metal material and the Al based metal material formed on the one surface of the solder material 5A by brushing with a brush after the solder material 5A has been manufactured.
The Ni plated layer 4 is formed on the composite material 3 manufactured by the above-mentioned method and the solder material 5B is joined on the Ni plated layer 4 by the clad rolling method or the like, thereby the joining material 10B can be obtained. It is preferable that the joining surface of the solder material 5B with the Ni plated layer 4 is washed so as to remove foreign substance and the like on the surface by brushing with a brush or the like before joining. The same can be said about the case in which the solder material 5A, 5C is used. Consequently, it is preferable that the following solder material is used as the solder material 5B, 5C in terms of being capable of preventing oxidation until the joining and obtaining a washing effect of the joining surface, the solder material being obtained by removing the X based metal material, or the X based metal material and the Al based metal material formed on the one surface of the solder material 5A by brushing with a brush or the like after the solder material 5A has been manufactured.
According to the embodiment of the invention, in case of using a specific joint material, namely in case of using a joint material having a laminated structure configured such that a Zn based metal material including Zn as a main component, an Al based metal material including Al as a main component, and an X based metal material including Cu, Au, Ag or Sn as a main component are laminated, the composite material 3 is located as the upper layer of the solder material 5 of the specific joint material, thus even if it becomes locally wet at the time of melting, it does not shrink, consequently a joining material can be provided that is capable of preventing position displacement from the supplying position. In addition, the composite material 3 and the solder material 5 are integrally formed preliminarily, thus there is a merit of process omission, consequently a joining material can be provided that is capable of dispensing with a solder paste.
Although the invention has been described with respect to the specific embodiments for complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art which fairly fall within the basic teaching herein set forth.
For example, the joining material according to the embodiment of the invention can be formed in various shapes such as a plate-like shape, a linear shape of which cross section is circular, elliptical or rectangular shape.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-036371 | Feb 2014 | JP | national |
