JPS6224893A - Low melting point cu-ag alloy brazing filler metal having good wettability - Google Patents

Abstract

PURPOSE:To improve wettability and to stabilize the performance of a brazed part for a long period of time by incorporating a specific ratio each of Ag, Pd and Si and a specific ratio of 1 or 2 kinds of B and Li into a brazing filler metal. CONSTITUTION:The Cu-Ag alloy brazing filler metal contg. 25-65% Ag, 0.5-25% Pd, 0.25-6.5% Si and 0.01-0.8% 1 or 2 kinds of B and Li ad consisting of the balance unavoidable impurities is produced by applying an ordinary melting method and plastic working method. The Cu-Ag alloy brazing filler metal obtd. in such a manner has a low vapor pressure and low m.p. and exhibits good wettability in the stage of brazing; in addition, said metal obviates the generation of the base metal crack arising from the intrusion of solder. The performance of the brazed part is thus stably assured for a long period of time.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is based on the invention that over-brazing is a crack caused by penetration of solder into the crystal grain boundaries of a base metal (hereinafter referred to as base metal cracking due to solder penetration).
The present invention relates to a Cu-Ag based alloy brazing material that does not cause the occurrence of oxidation and has good wettability, low vapor pressure, and low melting point.

[Conventional technology]

Conventionally, when brazing electron tubes and vacuum equipment, for example, when the brazing material is exposed to the atmosphere, a large amount of component evaporation can contaminate the components during brazing and the inner walls of the vacuum furnace. Furthermore, even if the parts are exposed to high temperatures in a vacuum during use, brazing will reduce the degree of vacuum inside the electron tube or vacuum equipment.
A brazing filler metal with a low vapor pressure is used because it may contaminate the inside of the component.

A typical brazing filler metal with this type of low vapor pressure is Cu.
Ag-Cu alloy brazing filler metal (J, I S
-BAg-El) is known. However, when using this heg-Cu alloy brazing filler metal, which has a low vapor pressure, for brazing a base material whose material is a Ni-Fe alloy or a Kovar type alloy, the brazing filler metal constituents A phenomenon appears in which wax tends to penetrate into the grain boundaries of the base metal, and as a result, cracks often occur during or after brazing due to penetration of the solder into the base metal. Therefore, when brazing the base material made of the Ni-Fe alloy or copal type alloy, the Ag-Cu alloy brazing material should be prepared by suppressing the penetration of the brazing material constituents into the grain boundaries of the base material. Pd: 5 to 2 in order to prevent cracking due to penetration of wax into the base material.
An Ag-Cu-Pd alloy brazing filler metal containing 50% is used.

[Problem that the invention seeks to solve]

However, in this Ag-Cu-Pd alloy brazing material,
Currently, the melting point increases in proportion to the Pd content, and the wettability deteriorates, so that it cannot necessarily be said that it is a brazing material with good brazing properties.

[Means for solving problems]

From the above-mentioned viewpoint, the present inventors have developed the above-mentioned conventional Ag
- Focusing on the Cu-Pd alloy brazing filler metal, we conducted research to lower the melting point of this brazing filler metal and improve its wettability. When B and Ll are added, the melting point is lowered and the wettability is significantly improved while maintaining a low vapor pressure without causing cracks in the base material due to penetration. It was discovered that these components have a significant deoxidizing effect, which not only prevents the oxidation of the wax during brazing, but also significantly suppresses the dissolution of gas into the molten solder.

This invention was made based on the above findings, and includes: Ag: 25-65%, Pd: 015-25%, Si: 0.25-6.5%, one of B and Li, or 2&: 0.001~0
．． 8%, has a composition consisting of Cu and unavoidable impurities: residue, has a low vapor pressure and a low melting point, and exhibits good wettability during brazing.
This is a Cu-Ag alloy brazing material that does not cause cracks in the base material due to solder penetration.

Next, in the Cu-Ag alloy brazing material of this invention,
The reason why the component composition range was limited as described above will be explained.

(a) Ag The Ag component has the effect of lowering the melting point of the brazing filler metal and improving the wettability when coexisting with the Cu and Sl components, as well as improving the processability of the brazing filler metal into foil and ultrafine wire. If the content is less than 25%, the desired effect cannot be obtained in the above-mentioned action, and on the other hand, even if the content exceeds 65%, the improvement effect of -1 cannot be obtained due to the above-mentioned action. , its content was determined to be 25-65%. In addition, when performing cold working under severe conditions, it is desirable to contain 35 or more Ag.

(b) pd The Pd component has the effect of suppressing the intrusion of brazing constituents into the grain boundaries of the base material, especially when the component is a Ni-Fe alloy or copal type alloy. However, if the content is less than 0.5 inch, the desired effect cannot be obtained, while if the content exceeds 25 inch, the melting point of the brazing material will rise and the wettability will deteriorate. Therefore, the content was determined to be between 0.05 and 25.0%.

(c) The 5i Sl component has the effect of significantly improving the wettability and lowering the melting point without any effect on the vapor pressure of the brazing filler metal, but if its content is less than 0.25%, the above-mentioned If the content exceeds 6.5%, the workability of the brazing filler metal deteriorates, so the desired effect cannot be obtained.
Its content was determined to be 0.25 to 6.5%. In addition, if it is necessary to perform cold working under severe conditions, 5%
The following Si content is desirable.

(a) S and Ll These components prevent the oxidation of the wax during soldering, forcibly reduce oxides on the surface of the wax liquid material, and further suppress the dissolution of gas into the molten solder. It has a uniform effect, but if its content is less than 1%, the desired effect cannot be ensured, while if it is contained in excess of 0.8%, the processability of the brazing filler metal will be affected. Since this will cause deterioration, its content should be reduced from 0.001 to 0.
It was set as 8q6.

〔Example〕

Next, the Cu-Ag brazing filler metal of the present invention will be explained using examples while comparing it with a conventional example.

By applying the usual melting method and plastic working method, the brazing materials 1 to 15 of the present invention having the component compositions shown in Table 1, respectively.
And conventional brazing materials 1 to 4 were manufactured.

Next, the resulting brazing materials 1 to 15 of the present invention and conventional brazing materials 1 to 4 were given a thickness of 5 in an argon atmosphere at a temperature of 850°C in accordance with JIS-Z3191.
My Kovar alloy (Ni: 29%, Co: 17%, Fe
and unavoidable impurities: remaining) The spread area of the wax on the base material was measured. Also, in the same argon atmosphere, the above brazing filler metal was placed on the above base material, and the temperature was set to 850°C for 2 hours.
The depth of penetration of the brazing filler metal into the base metal grain boundaries after holding for a minute was measured. In addition, in this solder penetration depth measurement, since conventional brazing filler metal 2.3 has a high melting point, its heating temperature was set to 900°C (conventional brazing filler metal 2) and 95°C, respectively.
The temperature was 0°C (conventional brazing filler metal 3). Furthermore, the vapor pressure at a temperature of 5oO<0>C of the solder (in the same state as after brazing) after the measurement of the spread area of the solder was measured. These measurement results are summarized in Table 1.

〔Effect of the invention〕

From the results shown in Table 1, the brazing fillers 1 to 15 of the present invention are as follows:
In addition to having a low vapor pressure equivalent to that of conventional filler metals 1 to 4, they also exhibit superior properties equivalent to or better than conventional filler metal 3, in which the penetration of the filler metal into the grain boundaries of the base material is extremely small. It is clear that it has a low melting point equivalent to Materials 1 and 4, and also exhibits good wettability equivalent to or better than conventional brazing filler metal 4, which has good wettability.

As mentioned above, the Cu-Ag alloy brazing material of the present invention is
In brazing, the intrusion of solder into the grain boundaries of the base material is extremely small, and it has good wettability, low vapor pressure, and low melting point, and also has excellent workability, so covered brazing is used for parts. Brazing can be performed in good condition without being restricted by the material and shape of the parts, and the resulting brazing has industrially useful properties such as stable performance over a long period of time. It is.

Claims (1)

[Claims] Ag: 25-65%, Pd: 0.5-25%, Si: 0.25-6.5%, one or two of B and Li: 0.001-0
．． A low melting point Cu-Ag based alloy brazing filler metal with good wettability, characterized in that it has a composition (weight %) of 8% and the rest consisting of Cu and unavoidable impurities.