JPS62130283A - Method for coating cu on ceramic base plate - Google Patents

Abstract

PURPOSE:To obtain a ceramic base plate of a Cu coating which is high in bonding strength for the ceramic base plate at high temp. and excellent in heat resistance by interposing Ni plating between the above-mentioned base plate and Cu in case of plating Cu on the ceramic base plate by means of electroless plating. CONSTITUTION:After degreasing a ceramic base plate, electroless plating is performed and thereafter electroless Cu plating is performed. In this method, since Ni plating is interposed between the ceramic base plate and Cu, Ni which is small in thermal expansion difference and thermal conduction difference for ceramic is excellent in adhesive force on the ceramic base plate at high temp. Also since the thermal expansion difference and the thermal conduction difference between Ni and Cu are remarkably smaller than that between Cu and ceramic, the adhesive force on Cu is excellent. Therefore the bonding strength of Cu for the ceramic base plate at high temp. is made high and Cu coating excellent in heat resistance is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an improvement in a method for coating a ceramic substrate, which is a material for making a printed wiring board, with Cu.

(Prior art) Conventionally, in order to coat a ceramic substrate with Cu,
After degreasing the ceramic substrate, electroless CU plating was applied.

(Problems to be Solved by the Invention) By the way, a ceramic substrate coated with Cu using the conventional Cu coating method described above has the following steps: pattern formation by photoresist → patterned Cu plating → patterned Ni plating - patterned Au plating → photoresist removal - Cu
A printed wiring board is created by forming the required wiring diagram through each etching process, and then resistors, capacitors, transistors, ICs, and LSIs are placed at the required positions on this printed wiring board.
In order to mount other parts, these are soldered (260℃
, about 20 seconds), the electroless Cu plating layer may peel off from the ceramic substrate, resulting in a problem that the bonding portion between the ceramic substrate and the electroless Cu plating layer has poor heat resistance.

This is because the electroless Cu plating layer is heated by the soldering described above, but since there is a large difference in thermal expansion and thermal conductivity between the ceramic and Cu, the electroless Cu plating is heated by the soldering described above. This is because the Cu material rapidly cools down and contracts, reducing the adhesion force at the interface with the ceramic, and thus weakening the adhesive strength of Cu.

Therefore, the present invention aims to provide Cu for ceramic substrates at high temperatures.
The objective is to obtain a Cu-coated ceramic base fabric with high adhesive strength and excellent heat resistance.

(Means for Solving the Problems) A method of coating a ceramic substrate according to the present invention to solve the above problems includes degreasing the ceramic substrate, applying electroless Ni plating, and then applying electroless Cu plating. It is characterized by this.

(Function) As described above, in the method of coating a ceramic substrate with Cu of the present invention, Ni plating is interposed between the ceramic substrate and Cu. It has good adhesion to the ceramic substrate, and since the difference in thermal expansion and thermal conductivity between Ni and Cu is much smaller than that of ceramic, the adhesion with Cu is good. Therefore, C for ceramic substrates at high temperatures
The adhesive strength of U increases, resulting in a Cu coating with excellent heat resistance.

(Example) To explain one example of the method of Cu coating on a ceramic substrate according to the present invention, a 96% alumina substrate measuring 80+u in length, 801 in width and 0.8 am in thickness was degreased with alkali, and then coated with electroless Ni on both sides. Plating, in this example N1-81%
was coated with 0.5 μm of Cu by electroless plating, and then coated with 2 μm of Cu by electroless plating.

On this Cu-coated alumina substrate, the required wiring figure is formed and printed through the following steps: pattern formation with photoresist → pattern Cu plating → pattern Ni plating → pattern Au plating, removal of photoresist, and Cu and Ni etching. Arrangement! After making the JA temporary, and then soldering the IC onto the wiring to mount the IC at the desired position on this printed wiring board, the electroless Cu plating layer that is the base of the wiring in the IC mounting area was heated (260℃). °C, 20
Even if the film was applied for several seconds), it did not peel off from the alumina substrate due to the presence of the electroless Ni plating layer. Also 500℃,
Even after being exposed to a harsh high temperature atmosphere for 30 minutes, no abnormalities in appearance such as blisters were observed.

Although the ceramic substrate in the above embodiment is an alumina substrate, it is not limited to this. Further, the electroless Ni plating is N1-B, but N1-P may also be used.

Furthermore, the thickness of electroless plating is preferably 0.1 to 1 μm.

(Effects of the Invention) As can be seen from the above explanation, the method of coating Cu on a ceramic substrate of the present invention is a method for coating a ceramic substrate with electroless Cu.
Before plating, electroless Ni plating is pre-plated, so the electroless CU plating that is applied afterwards is due to the difference in thermal expansion between the ceramic substrate and the electroless Cu plating.
Since the difference in thermal conductivity is small, it is well attached to the ceramic substrate through the electroless Ni plating. Therefore, the adhesive strength of Cu to ceramic substrates at high temperatures increases, and electroless Cu plating never peels off in high-temperature atmospheres, such as when soldering onto wiring for mounting components after manufacturing printed wiring boards. It is possible to obtain a Cu-coated ceramic substrate for printed wiring boards that is highly reliable and has excellent heat resistance without causing any damage.

Claims (1)

[Claims] A method for coating a ceramic substrate with Cu, the method comprising degreasing the ceramic substrate, applying electroless Ni plating, and then applying electroless Cu plating.