JPS6349598B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a bonding material having an appropriate liquidus temperature and a bonding method using the same. [Technical Background of the Invention and Problems Therewith] In general, a joining material used for joining a plurality of parts is required to have excellent workability and high joining strength. In recent years, there has also been a demand for low working temperatures, that is, low melting temperatures, from the viewpoints of energy saving during bonding, reduction of thermal stress applied to objects to be bonded, and reduction of furnace contamination. Now, silver (hereinafter referred to as Ag) is a bonding material that can be stably applied regardless of the atmosphere used.
Ag with 28% by weight (hereinafter referred to as wt%) of copper (hereinafter referred to as Cu) added to
-Cu eutectic alloy (JIS, BAg-8) is mainly used. However, this alloy has a melting temperature of
Since the temperature is as high as 779℃, the actual bonding work temperature must be selected to be a high temperature exceeding 800℃, and there are many cases where the objects to be bonded cannot withstand the heat stress. Then, set this bonding working temperature to 750
℃ or less, the melting temperature of the joining alloy needs to be several tens of degrees lower than 730℃, preferably 700℃ or less. Therefore, as one of the techniques for lowering the melting point of such bonding materials, for example, BAg-2 (35%
Ag-26%Cu-21%Zn-18%Cd, liquidus temperature approx. 700
°C) is known. However, although this bonding material is effective in lowering the melting temperature, it contains high vapor pressure elements such as zinc and cadmium (hereinafter referred to as Zn and Cd, respectively), which may cause contamination of the inner wall of the bonding furnace and Contamination and effects on the human body have also been pointed out. Furthermore, as another technique for lowering the melting point of bonding materials, a method is known in which indium and tin (hereinafter referred to as In and Sn, respectively) are used to eliminate the effects of Cd on the human body. For example, JP-A-50
-74551 (Ag=45~60, Cu=15~25, Zn=19
~29, Sn=0.5~4, In=0.5~5), JP-A-51-
No. 62164 (Ag=25~37, Cu=35~72, P (phosphorus)
=1~7, or In=1~7, Zn=1~
27 type 1 or 2), JP-A-51-117148 (Ag=
18~48, Cu=15~40, Zn=20~35, Sn=0.5~7
Or In=0.5~7, Mn (manganese)=0.15
~2, Li (lithium) = at least 2 of 0.15 ~ 5
species), JP-A-51-128664 (Ag=30~50, Cu=
10~25, Zn=10~25, Cd=15~30 with In, Sn, Ga
(gallium) and Ge (germanium) (1 to 12% for one type, and 1 to 15% for two types). However, these bonding materials
Although In and Sn have low vapor pressure characteristics, they both have the same drawback as the above in that they contain high vapor pressure elements such as Zn. Furthermore, as another technique for lowering the melting point of bonding materials, Ag-Cu-Sn-In4 elements, which are based on Ag and Cu and co-added with Sn and In, are used as bonding materials in Japanese Patent Application Laid-Open No. 51-132147. No. 44-11009. In other words, the former is Ag
=70~47wt%, Cu=25~40wt%, Sn=2~6wt
%, In=3 to 7 wt%, and is intended to be a silver solder alloy that can be joined in atmospheric gas or vacuum, and has good workability. However,
In this alloy composition range, Sn = 6wt%, In = 7wt% is the most likely to be expected to lower the melting point.
% alloy, the welding temperature is over 750°C, and although a certain degree of bonding strength can be obtained, the thermal stress on the objects to be welded becomes significant, making it virtually difficult to obtain favorable welding results. , Sn, In is more than Sn=6wt%, In=7wt%
However, as stated in the same publication, it has the disadvantage of reduced workability. On the other hand, the latter is a Ag and Cu eutectic alloy with Sn + In = 30 ~
60 wt%, Sn = 15 to 30 wt%, In = 15 to 30 wt%, and Sn/In = 1/1. The main purpose is to add it to crystal bonding alloys. However, this bonding material uses a large amount of Sn and In compared to CdO, which has poor wettability, so it has the disadvantage that it is extremely difficult to process the alloy into wire rods or thin plates. ing. [Object of the invention] The present invention was made in consideration of the above circumstances, and its purpose is to create a material that can be used at a moderately low bonding temperature (750 to 500°C) and has excellent workability. The object of the present invention is to provide a bonding material that is economical and causes less thermal stress to objects to be bonded, and a bonding method using the same. [Summary of the Invention] In order to achieve the above object, the present invention combines 1 to 5 weight percent of tin, 7 to 20 weight percent of indium, 53.9 to 66.1 weight percent of silver, and 21.1 to 25.9 weight percent of copper. When joining the first part to be joined at a welding temperature higher than 750°C and the second joint part to be joined at a welding temperature of 750 to 500°C sequentially by brazing, at least A bonding material having the above composition is used as the bonding material for the second bonding location. [Embodiments of the invention] First, in order to achieve the above-mentioned purpose,
It is thought to be a good idea to utilize elements based on Ag and Cu that have low vapor pressure characteristics. The bonding operation is not only carried out in the atmosphere or atmospheric gas, but also in a vacuum. Especially in the latter case,
As mentioned earlier, the contamination of the furnace, objects to be joined, etc. due to the evaporation of high vapor pressure components is significant, so the vapor pressure at the temperature of 750°C to 800°C, where bonding work is normally performed, is set at 1×10 ^- from the viewpoint of suppressing evaporation. It is considered necessary to be lower than ³ Torr. And 1× at 800℃
As an element with a vapor pressure lower than 10 ^-3 Torr,
Preferred elements include In (6×10 ⁻⁴ Torr) and Sn (6×10 ⁻⁷ Torr), respectively. On the other hand, Zn, which is commonly used as a bonding material, has a
10 ⁺² Torr, Cd is 1×10 ⁺³ Torr, which is not preferable. Therefore, it is considered advantageous to use In and Sn, which can lower the liquidus temperature of the Ag-Cu alloy and have low vapor pressure properties. This low vapor pressure bonding material can be used, for example, in structures made up of many parts that need to be bonded, precision parts with extremely small air gaps allowed in electronic components, or objects to be bonded with complex structures. When it is necessary to confirm whether each internal component or joint part is reliably joined, it is preferable to adopt a manufacturing method in which the parts are joined in stages. To meet these demands, new bonding materials are required that have low vapor pressure properties, low melting points, and a certain degree of processability. According to experiments on commonly known Ag-Cu-Sn-based bonding materials, there is a tendency for poor fluidity of the brazing material to occur depending on conditions such as the bonding atmosphere, and therefore, when bonding precision parts such as electronic components, It was observed that the surface of the objects to be bonded was not wet in some places, and when it was applied to areas requiring airtightness, poor airtightness was observed in some cases. These are thought to be due to the selective oxidation phenomenon of Sn in the bonding material, and before the Ag-Cu-Sn alloy melts, moisture released from the bonding alloy itself or adsorption on the object to be bonded and its vicinity. It is thought that the joining alloy itself was oxidized during the temperature rising process due to gases, moisture, etc., which deteriorated the wettability of the parts to be joined. Also, according to experiments with Ag-Cu-In based bonding materials, contrary to the above, the wettability is rather good, so if one surface of the parts to be bonded is wetted first, the bonding material does not spread to the opposite surface to be bonded. In some cases, there appears to be a lack of bonding material, and as a result, it is not possible to obtain enough wetting to cover both opposing surfaces, and in some cases, wetting is too good and unnecessary bonding occurs when bonding minute parts such as electronic components. In some cases, the bonding material may be used excessively. Therefore, when there is little flare and insufficient strength or airtightness is required, airtightness may be poor. Based on this knowledge, the present invention uses Ag-Cu
−Ag−Cu to take advantage of the advantages of Sn and Ag−Cu−In.
-We investigated various Sn-In alloys and developed a new bonding alloy with high industrial value in terms of low melting point and workability. This point will be specifically explained below with reference to FIGS. 1 and 2. FIGS. 1 and 2 are cross-sectional views showing the side where two parts are joined using the joining material according to the present invention. In the figure,
The B part 7 is bonded to the bonding material 5 at the first bonding point 4.
The part A 6 is soldered to the side surface of the part A 6 in advance by soldering, and finally the part A 6 is soldered to the main body base 1 at the second joining location 2 using the joining material 3. In this case, in Figures 1 and 2,
When welding the second joint 2 that is to be joined at a welding temperature of 750 to 500°C, the part B 7 at the joint of the first joint 4 that is to be joined at a welding temperature higher than 750°C may fall or shift. In order to prevent It is preferable. On the other hand, in a configuration where the gap 8 between the main body base 1 and the A part 6 cannot be sufficiently secured due to the structure, the second
When the vapor pressure of the bonding material 3 used for the bonding point 2 is high, it may be deposited on the surface of the B component 7, and if the bonding material 3 oozes out during bonding, the The surfaces may become undesirably contaminated by the bonding material. Therefore, the seepage property is an important measure for evaluating bonding materials, especially when precision parts are bonded. Note that it is important that the bonding material does not contain elements with high vapor pressure. Now, especially the second method applied to such joining conditions.
As a guideline for selecting the joining material 3 for joining the joint 2 of the Ag-Cu -Sn-In joint alloys were evaluated.

【table】

[Table] The outline of the production of the Ag-Cu-Sn-In joint alloy used in this evaluation is as follows. In other words, each sample with each composition shown in the attached table was weighed, and approx.
After vacuum melting in a refractory crucible at 850-900°C, it is cast to obtain a material with a diameter of 20 mm and a length of 200 mm. next,
After hot forging at 450 to 700°C, a thin plate with a thickness of 85 μm and a width of 50 mm is finally produced by a combination of cold rolling, hot rolling, and heat treatment. and,
At this time, we evaluated the workability such as the degree of surface cracks, and as shown in Table 1, In = 16.2%, Sn = 6.5
% (Comparative Example 2), In=32%, and Sn=2.3% (Comparative Example 4), it was difficult to roll. Therefore, for these two types, a lumpy material with cracks was used as the evaluation material, and for the other types, a disk with a diameter of 2.4 mm was taken from a thin plate with a thickness of 85 μm and a width of 50 mm and placed at the second joint point 2. This is the bonding material used. Note that the bonding material used for the first bonding portion 4 was a normal eutectic silver solder. Next, in Figure 1, 72%Ag-Cu
B part 7 at 820℃ using silver wax (melting point 779℃)
After joining the A part 6 to the A part 6, the A part 6 and the main body base 1 are joined at the second joining part 2. Evaluation results of each joining material will be described. The bonding temperature for each bonding material is also listed in the table as a preferred temperature. As the bonding results are shown in the table, the amount of Sn is
At 0.5wt% (Comparative Example 1), the above-mentioned Ag-Cu-In
The properties (defects) of the system are strongly manifested, and the seepage distance near the joint surface extends to more than 2 mm, indicating that it is not suitable as a joining material in a short gap, and the tensile strength of the joint is also low. It can be seen that the weight is less than 20 kg, which is an undesirable composition. On the other hand, the Sn content is 1.0wt% (Example 1) and the Sn content is 2.0wt% or 5.0wt% (Examples 2 and 3).
In this case, the exudation distance is 1 mm or less, which indicates that it is a joining material suitable for joining precision parts, and the tensile strength is also 25 Kg or more, 30 Kg or more, and the working temperature is 750° C. or less, which is a preferable range. However, when the Sn content reaches 6.5wt% (Comparative Example 2), although the tensile strength and seepage distance are sufficient,
The workability of the material is not good, so the amount of Sn is 1 to 5wt.
Ideally within %. Also, the amount of In is 5.1wt when the amount of Sn is around 2wt%
% (Comparative Example 3), the tensile strength of the joint is 25
While the level is low below Kg, the In content is 7wt%
(Example 4), 750°C when 20wt% (Example 5)
The melting point below can be secured, and the tensile strength and processability maintain satisfactory values.
It can be seen that when the In amount is 32 wt% (Comparative Example 4), the low melting point property is sufficient, but the tensile strength and workability are inferior. Therefore, the amount of In is 7~
A range of 20wt% is ideal. In addition, when vacuum-sealing the A part 6 with the B part 7 attached, the bonding material of the present invention has a low vapor pressure, so it is preferable that there is no contamination due to adhesion to the surface of the B part 7, especially when the gap is short. It is an extremely effective bonding material. As mentioned above, the bonding material of this example is Sn
=1~5wt%, In=7~20wt%, Ag=53.9~
Since the composition is 66.1wt% and Cu = 21.1 to 25.9wt%, the components of the bonding material do not contaminate other component surfaces, making it economical and highly reliable. It is possible to obtain materials with high In addition, when performing the above-mentioned joining using the joining material of the present invention, it is possible to perform the joining work in the atmosphere, in an atmospheric gas, or in a vacuum, but in particular, the first joining point is exposed to an atmospheric gas. (Hydrogen, etc.) Medium, 2nd
It is particularly effective to perform the first and second joints in a vacuum, or to perform both the first and second joints in a vacuum. Further, in this case, when performing the process in a vacuum, it is preferable to perform the process in a high vacuum of 10 ^-4 Torr or more. [Effect of the invention] As explained above, according to the present invention, Sn=1
~5wt%, In=7~20wt%, Ag=53.9~66.1wt
%, Cu=21.1~25.9wt% constitutes the bonding material,
In addition, the first bonding process is performed at a bonding temperature higher than 750℃.
When joining the joint part by brazing sequentially to the second joint part to be joined at a joining temperature of 750 to 500°C, the joining material having the above composition is used as the joining material for at least the second joint part. Since we decided to use
500°C), is economical as a material with excellent workability, and can provide a bonding material that causes less thermal stress on workpieces, as well as a bonding method using the same.

[Brief explanation of drawings]

FIGS. 1 and 2 are cross-sectional views showing an example of joining two parts using the joining material of the present invention. 1...Body base, 2...Second joint location, 3,
5...Joining material, 4...First joint location, 6,7
...A, B parts, 8...Gap.

Claims (1)

[Claims] 1. 1 to 5% by weight of tin, 7% by weight of indium.
~20 weight percent, 53.9 to 66.1 weight percent silver, and 21.1 to 25.9 weight percent copper. 2 The first step is to bond at a bonding temperature higher than 750℃.
In a joining method of sequentially brazing a joining point and a second joining point which is joined at a welding temperature of 750 to 500°C, at least the joining material used for the second joining point contains 1 to 5% tin by weight. %, indium 7 to 20 weight %, silver 53.9 to 66.1 weight %, copper 21.1 to 25.9 weight %.