JPH0563334A - Manufacture of ceramic wiring board - Google Patents

Abstract

PURPOSE:To obtain a manufacturing method wherein a copper layer can be formed on the surface of a ceramic board in a short time, and the obtained copper layer on the ceramic board surface is excellent in high temperature thermal resistance. CONSTITUTION:In the manufacturing method of a ceramic wiring board wherein a copper layer is formed on the surface of a ceramic board, the forming process of the copper layer consists of the following; a process for forming a first copper layer on the ceramic board surface by electroless plating, and a process for forming a second copper layer on the first copper layer by electroplating using plating solution composed of only sulfuric acid and copper sulfate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a ceramic wiring board used as an electronic material.

[0002]

2. Description of the Related Art A wiring board formed by firing a resistor on a substrate is required to have a high temperature heat resistance because the resistor is fired at a temperature of 600 ° C. or higher. In such applications, a ceramic wiring board manufactured by forming a copper layer on the surface of a ceramic substrate having excellent high temperature heat resistance is used. In this conventional method for manufacturing a ceramic wiring board, the copper layer is formed by electroless plating, which is excellent in high temperature heat resistance because electrolytic plating lacks high temperature heat resistance. However, in order to form a thick copper layer by electroless plating, it is necessary to perform electroless plating for a very long time, and there is a need for a method of forming a copper layer with excellent high temperature heat resistance in a shorter time. It is the current situation.

[0003]

In view of the above circumstances, the problem to be solved by the present invention is to find a method capable of forming a copper layer having excellent high temperature heat resistance on the surface of a ceramic substrate in a short time.

[0004]

According to the present invention, in a method for manufacturing a ceramic wiring board by forming a copper layer on the surface of a ceramic substrate, the step of forming the copper layer is performed by electroless plating on the surface of the ceramic substrate. And a step of forming a second copper layer on the first copper layer by electrolytic plating using a plating solution containing only sulfuric acid and copper sulfate. It is a method of manufacturing a wiring board.

Examples of ceramic substrates to which the present invention is applied include alumina substrates and silicon nitride substrates.

In the step of forming the first copper layer on the surface of the ceramic substrate by electroless plating in the present invention, the electroless copper plating method conventionally used can be used as it is without any particular limitation. For example, the first copper layer is obtained by immersing a ceramic substrate to which a catalyst is applied in an electroless plating solution containing copper sulfate, ethylenediamine tetracomplex, formalin, polyethylene glycol, caustic soda, etc. for an appropriate time, and then taking it out and drying it. Is formed. Since the formation of this first copper layer by electroless plating is intended to provide a conductive material necessary for forming a copper layer on the ceramic substrate by electrolytic plating in the next step, the surface of the ceramic substrate is It only needs to be completely covered, and it does not need to be formed thicker. Therefore, it is sufficient that the thickness of this first copper layer is at most 3 μm. And, this first copper layer by this electroless plating has a porous structure,
Therefore, when exposed to high temperatures, the volatile components contained in the ceramic substrate can escape through this first copper layer, and even if exposed to high temperatures, peeling or blistering occurs in the first copper layer. It also has difficult advantages.

In the present invention, the first obtained as described above
On the copper layer, a step of forming a second copper layer by electrolytic plating using a plating solution containing only sulfuric acid and copper sulfate. The composition of this plating solution is a feature of the present invention, and in electroplating generally performed, an oxyethylene-based surfactant called a brightening agent, a sulfur compound and safranine for increasing the denseness of the plating film in the plating solution. It is normal to add a mixture of dyes, but in the present invention, it was confirmed that it is effective for improving the high temperature heat resistance that the obtained copper layer has a porous structure. Electrolytic plating is carried out by using a plating solution containing only sulfuric acid and copper sulfate without adding a brightening agent. Since electrolytic plating has an advantage that a thicker copper layer can be formed in a shorter time than electroless plating, a second copper layer is formed by electrolytic plating on the first copper layer formed by electroless plating having a required thickness. The formation of the layer can complete the formation of the copper layer in a shorter time than the case where all the copper layers having the same thickness are formed by electroless plating.

In the present invention, when the second copper layer is formed,
It is also possible to perform a so-called pattern plating method in which a resist having a reverse pattern of the conductor pattern is applied on the first copper layer and the second copper layer is formed by electrolytic plating only on the portion where there is no resist.

[0009]

The function of forming a second copper layer by electrolytic plating using a plating solution consisting of sulfuric acid and copper sulfate alone without adding a brightening agent is a porous structure excellent in high temperature heat resistance in a short time. It functions to form a copper layer.

[0010]

EXAMPLES (Example) An alumina substrate having a thickness of 1 mm, which had been subjected to through-holes and was sintered, was immersed in phosphoric acid heated to 300 ° C. for 5 minutes to roughen the substrate surface, followed by thorough washing with water and drying. did. The dried substrate was immersed in an electroless copper plating solution to form a first copper layer having a thickness of 1 μm on the surface of the substrate. Next, the substrate on which the first copper layer was formed was electroplated under the following electrolytic plating conditions to form a second copper layer on the first copper layer. In this case, the formation of the first copper layer and the second
The total time required to form the copper layer was 90 minutes, and the total thickness of the first copper layer and the second copper layer was 35 μm.

Electrolytic plating conditions Composition of plating solution: Copper sulfate 75 g / l Sulfuric acid 180 g / l Current density: 2 A / dm ² Energization time: 75 minutes A copper layer was formed on the surface of the ceramic substrate thus obtained. When the high temperature heat resistance of the substrate was examined, no peeling or blistering occurred in the copper layer even after heat treatment in a nitrogen atmosphere at 700 ° C. for 10 minutes.

Then, a conductor pattern was formed by a method using a dry film using the substrate on which the above copper layer was formed, and a ceramic wiring board could be manufactured.

Comparative Example 1 An alumina substrate having a through hole and a thickness of 1 mm was immersed in phosphoric acid heated to 300 ° C. for 5 minutes to roughen the surface of the substrate, followed by thorough washing with water and drying. did. The dried substrate was dipped in the same electroless copper plating solution as in the example to form a 35 μm thick copper layer on the surface of the substrate. In this case, the time required for forming the copper layer was 700 minutes.

The high temperature heat resistance of the thus obtained ceramic substrate having a copper layer formed on the surface thereof was examined, and the copper layer was peeled and swelled even when heat-treated in a nitrogen atmosphere at 700 ° C. for 10 minutes. Did not occur.

Then, a conductor pattern was formed by a method using a dry film using the substrate on which the above copper layer was formed, and a ceramic wiring board could be manufactured.

Comparative Example 2 A 1 μm thick first copper layer was formed on the surface of the substrate in the same manner as in Example 1 by using a 1 mm thick alumina substrate which had been through-holed and sintered. Next, the substrate on which the first copper layer was formed was electroplated under the following electrolytic plating conditions to form a second copper layer on the first copper layer. In this case, the total time required to form the first copper layer and the second copper layer was 90 minutes, and the total thickness of the first copper layer and the second copper layer was 35 μm. ..

Electrolytic plating conditions Composition of plating solution: Copper sulfate 75 g / l Sulfuric acid 180 g / l 0.5N-HCl 3 ml / l Brightener 5 ml / l (The brightener is a brightener for printed board through-hole plating manufactured by Uemura Kogyo Co., Ltd. AC-90 is used) Current density: 2 A / dm ² Energization time: 75 minutes The high temperature heat resistance of the thus obtained ceramic substrate on which a copper layer is formed is 400 ° C. nitrogen atmosphere. There was no peeling or blistering on the copper layer even after heat treatment for 10 minutes in the atmosphere, but 1
When heat-treated for 0 minutes, peeling and blistering occurred on the copper layer.

Also in this case, a ceramic wiring board could be manufactured by forming a conductor pattern by a method using a dry film using the above-mentioned substrate on which the copper layer was formed.

[0019]

As is clear from the comparison between the example and the comparative example, according to the present invention, a copper layer can be formed on the surface of a ceramic substrate in a short time, and the copper layer on the surface of the obtained ceramic substrate has a high temperature. Since it has excellent heat resistance, the present invention is useful for manufacturing a ceramic wiring board.

Claims (1)

[Claims] 1. A method for manufacturing a ceramic wiring board by forming a copper layer on the surface of a ceramic substrate, wherein the step of forming the copper layer comprises forming a first copper layer on the surface of the ceramic substrate by electroless plating. And a step of forming a second copper layer on the first copper layer by electrolytic plating using a plating solution containing only sulfuric acid and copper sulfate.