JPH0664980A - Method for jointing ceramic to metal - Google Patents

Abstract

PURPOSE:To provide a method so designed that the wettability of an adhesive to a metallized pattern formed on the surface of a ceramic is improved to accomplish firm jointing of a metal to the metallized pattern. CONSTITUTION:A metallized pattern composed of silver and palladium is formed on the surface of a ceramic, and a gold layer >=3mum thick is provided on the surface of this metallized pattern, and then, a metal is jointed through a gold- based adhesive to the surface of the gold layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for joining ceramics and a metal, and more particularly to a ceramics having a metallized pattern formed of silver and palladium formed on the surface thereof and a metal with high strength. The present invention relates to a method for joining ceramics and metal.

[0002]

2. Description of the Related Art Conventionally, when bonding metal to a metallized pattern formed on the surface of ceramics,
As the bonding material, tin-lead solder having a melting point of 183 ° C, gold-germanium solder having a eutectic composition having a melting point of 356 ° C, gold-silicon solder having a eutectic composition having a melting point of 370 ° C, and melting point of 780 ° A bonding material such as a silver braze having a eutectic composition of C, a silver-copper-indium braze, a silver-copper-tin braze, and a silver-indium braze was used.

Here, particularly when the ceramic is used as a substrate for electronic parts, the ceramic is
For example, after the metal such as the lead electrode is joined, the ceramic may be further heat-treated in a die bonding step for attaching the IC, and the so-called low temperature in which the ceramic used is fired at 850 to 1000 ° C. In the case of being a fired ceramic, the melting point of the above-mentioned joining material having a melting point of 370 ° C. is taken into consideration in order to prevent the strength characteristics of the ceramic from being impaired by the heat at the time of joining with a metal. It has been widely practiced to bond metals to ceramics by using a brazing material such as gold-silicon solder having a eutectic composition or silver-copper-indium solder, silver-copper-tin solder, or silver-indium solder. It was

[0004]

However, here,
When the metallized pattern formed on the surface of the ceramic is one using silver and palladium as its material, the method for forming the metallized pattern is the surface of the ceramic at 800 to 900 ° C. in the atmosphere. Since this is a method of baking a paste composed of silver and palladium on the surface of the metallized pattern, an oxide of silver and palladium is formed on the surface of the metallized pattern, and the oxide forms a bonding material such as gold-based solder or silver-based solder. The wetting property is deteriorated, and as a result, the joining strength of the metal to be joined is weakened, and the joining method has poor reliability.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object thereof is to improve the wetting property of the above-mentioned bonding material to a metallized pattern and to bond a metal to the metallized pattern. It is to provide a method of joining ceramics and metal with high strength.

[0006]

As a result of various tests and studies, the present inventors have found that a gold layer is further formed on a metallized pattern using silver and palladium formed on the surface of ceramics. The inventors have found that the wetting property of the bonding material to the metallized pattern is improved and the bonding with a metal is performed with high strength, and the present invention has been completed.

That is, according to the present invention, a metallized pattern made of silver and palladium is formed on the surface of ceramics,
A gist of a method of joining a ceramic and a metal is to further form a gold layer having a thickness of 3 μm or more on the surface of the metallized pattern and to join a metal to the surface of the gold layer using a gold-based joining material. .

According to the method for joining ceramics and metal according to the present invention, the metal is joined on the metallized pattern using silver and palladium through the gold layer which is very strong against oxidation as described above. Therefore, the gold layer is
The effect of the above-mentioned surface oxidation of the metallized pattern is removed, and a gold-based bonding material is well wetted to the surface of the gold layer, and the metal can be bonded with high strength.

The gold layer formed on the metallized pattern has a thickness of 3 μm or more as described above. This is because if the thickness of the gold layer is less than 3 μm, the effect of improving the wetting property of the above-mentioned joining material is small and the joining strength of metal is also weak. If the thickness of the gold layer is 3 μm or more, the thickness of the gold layer has no influence on the bonding strength of the metal and there is no upper limit. However, considering the manufacturing cost, the thickness is preferably within 10 μm.

The gold layer is preferably formed by a thick film method in which gold or a powder containing gold as a main component is applied to the surface of the metallized pattern and then sintered. This is because when the ceramic forming the gold layer is a low temperature fired ceramic which has alumina as a first component and is fired at 850 to 1000 ° C., the gold plating bath generally used for the ceramic is used. This is because if the dipping method is adopted, the alkaline component of the ceramic will be attacked, and a ceramic substrate that can be put to practical use cannot be obtained.

Further, as the gold-based bonding material used in the present invention, gold-silicon solder having a eutectic composition with a melting point of 370 ° C. is desirable. This has good wettability with the gold layer, and when used in low-temperature fired ceramics fired at 850 to 1000 ° C., does not impair the strength characteristics of the ceramics, and after bonding with a metal. This is because, even if the ceramics are further heat-treated in the die bonding process or the like, the bonding will not be broken.

Further, in the present invention, the metal bonded to the ceramics is preferably an alloy of nickel and iron such as Kovar or 42 alloy. This is because it is well compatible with the above-mentioned gold-based bonding material, particularly gold-silicon solder having a eutectic composition with a melting point of 370 ° C., and can bond with high strength.

The ceramics for which the above-mentioned joining method according to the present invention can be carried out is not limited in any way.
It is particularly effective when the present invention is applied to the low temperature fired ceramics fired in (1).

This is because low temperature fired ceramics have been used in recent years.
It has begun to be used as a substrate for electronic parts for mounting electronic parts such as resistors and capacitors, and the action and effect of the above-described joining method according to the present invention is effectively exhibited.
This is because it is possible to manufacture the electronic component substrate.

[0015]

EXAMPLES Examples of the present invention will be given below together with comparative examples.
The present invention will be described in detail.

First, in order to investigate the effect of the gold layer overlying the metallized pattern made of silver and palladium formed on the surface of the ceramics, alumina was used as the first component of the ceramics sample to be bonded, and it was fired at 900 ° C. A ceramic substrate with a width of 50 mm, a length of 50 mm and a thickness of 1.0 mm is prepared, and 2.0 m is placed on the ceramic substrate.
850 ° C with a paste (TR-4865) made of Tanaka Kikinzoku Kogyo Co., Ltd. and composed of silver and palladium in a size of m square.
Bake, and on top of that, a gold paste (TR made by Tanaka Kikinzoku Kogyo Co., Ltd.) with various thicknesses shown in Table 1
-1301) was baked at 850 ° C to prepare a ceramic sample.

Next, on the gold surface of the above-mentioned ceramic sample, gold-3.15 wt% silicon solder (melting point 370 ° C.) of 2 mm square and 50 μm thick manufactured by Tanaka Denshi Kogyo Co., Ltd.
2 mm in width, 10 mm in length, and 0.5 mm in thickness, which are made by Sumitomo Special Metals Co., Ltd. (KV-
2) and 42 alloy were overlapped with each other at the tip of 2 mm, heated at 400 ° C. in an argon atmosphere, and both were soldered.

Then, in order to evaluate the joining condition of the soldered joined sample, the above-mentioned joined Kovar or 4
The test was conducted by bending the unbonded part of 2 alloy outward by 90 °, sandwiching this bent part, and peeling off Kovar or 42 alloy in a direction perpendicular to the substrate at a speed of 0.5 mm / min. The strength per unit area (kgf / mm ² ) was calculated from the breaking strength, and the value was evaluated as “bonding strength”. The results are shown in Table 1.

[0019]

[Table 1]

From the results shown in Table 1, those without a gold layer (Comparative Example 1) or those with a gold layer formed less than 3 μm (Comparative Examples 2 and 3) have weak bonding strength and practical strength. It was found that the value of ² kgf / mm ² was not satisfied. In addition, a gold layer having a thickness of 3 μm or more (Examples 1 to 1)
In the case of 7), the bonding strength exceeds ² kgf / mm ² and can be practically used, but the subsequent bonding strength does not depend on the thickness of the gold layer, and when considering the manufacturing cost, It has been found that the thickness of the gold layer is preferably 10 μm or less.

Next, as a method for forming a gold layer on the metallized pattern made of silver and palladium formed on the surface of the ceramic, a method by plating was carried out.

In the method of implementation, as a ceramic sample, a ceramic containing alumina as the first component and fired at 900 ° C. is used, and a paste (silver and palladium made by Tanaka Kikinzoku Kogyo KK TR-
4865) at 850 ° C. to form a gold layer having a thickness of 3 μm on the sample, the sample was treated with potassium gold cyanide (10 g / l), potassium dihydrogen phosphate (96 g).
/ L), citric acid (24 g / l), EDTA-cobalt potassium (2 g / l), dipotassium hydrogen phosphate (80 g
/ L).

As a result of carrying out the above-mentioned plating method, it was found that the alkaline component in the ceramics was attacked by the gold plating bath, and it was not possible to obtain a ceramics substrate for practical use.

[0024]

As described above, according to the method for joining the ceramic and the metal according to the present invention, the wetting property of the gold-based joining material on the metallized pattern made of silver and palladium formed on the surface of the ceramic is improved. It is improved, and it becomes possible to bond a metal to ceramics with high strength, and the application of ceramics as a substrate for electronic parts can be expanded.

Claims (5)

[Claims] 1. A metallized pattern made of silver and palladium is formed on the surface of ceramics, a gold layer having a thickness of 3 μm or more is further formed on the surface of the metallized pattern, and a gold layer is formed on the surface of the gold layer. A method for joining ceramics and metal, which comprises joining metals using a system-based joining material. 2. The gold layer formed on the surface of the metallized pattern is formed by a thick film method in which gold or a powder containing gold as a main component is applied to the surface of the metallized pattern and then sintered. The method for joining ceramics and a metal according to claim 1, wherein 3. The melting point of the gold-based bonding material is 370 ° C.
2. The method for joining ceramics and metal according to claim 1, wherein the solder is a gold-silicon solder having the eutectic composition. 4. The method for joining ceramics and metal according to claim 1, wherein the metal to be joined to the ceramics is a nickel-iron alloy such as Kovar or 42 alloy. 5. The method for joining a ceramic and a metal according to claim 1, wherein the ceramic is a ceramic having alumina as a first component and fired at 850 to 1000 ° C.