JPH05331660A - Copper metallizing method - Google Patents

Abstract

PURPOSE:To enable the use of aluminum nitride, etc., which are heretofore difficult to be used as a substrate by improving the adhesive strength between the substrate and a copper plated surface. CONSTITUTION:A zinc acetate soln. is sprayed by a spraying method on the substrate A1 to form the film of zinc oxide A2 thereon. The substrate is then immersed into a Pd soln. and is thereby treated to be deposited with a catalyst. Further, the substrate is immersed into an electroless copper plating liquid and is subjected to copper plating A3. The plated copper is subjected to a heating treatment in the atm. and is converted to copper oxide. The copper oxide surface is then reduced in a hydrogen atmosphere and finally copper A4 is plated by copper electroplating thereon, by which the wiring board for electronic equipment is formed.

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, glass or the like to copper, and particularly when manufacturing a wiring board for electronic equipment, the substrate material such as ceramics or glass and the wiring material metallic copper. The present invention relates to a copper metallizing method for joining and.

[0002]

2. Description of the Related Art When manufacturing a wiring board for electronic equipment,
The following methods are known as a method for joining a substrate material such as ceramics and glass to a wiring material such as metallic copper.

(A) Copper metallizing method FIG. 2 shows an example of steps of a conventional copper metallizing method. First, the substrate B1 is washed and dried, a copper compound paste B2 made of a copper compound, silicon oxide and a solvent is applied and dried. This paste is baked in the air at 1,000 to 1,300 ° C. to form a copper oxide layer, and then the surface of the copper layer is heated to about 300 ° C.
Reduce with hydrogen. Finally, electrolytic copper plating B3 on the reducing surface
Apply.

(B) Copper method (heat-resistant metallizing method) FIG. 3 shows an example of steps of the conventional copper method (heat-resistant metallizing method). First, the substrate C1 is washed and dried, and then the oxidized copper plate C2 is sandwiched between the substrate C1 and the nickel plate C3.
Bake at 1,100 ° C. Finally, electrolytic copper plating C4 is applied to the surface of the nickel plate.

(C) Thick film printing method (copper paste method) A paste prepared by mixing resin, copper powder and glass frit is printed on a substrate and baked at 800 to 900 ° C. in a reducing atmosphere.

(D) Direct plating method A fine uneven surface is formed on the ceramic surface and electroless copper plating is performed.

(E) Sputtering method A Cr or Ti thin film layer is provided on a substrate, and copper is deposited thereon.

[Problems to be Solved by the Invention]

Since the conventional copper metallizing method and copper method (heat resistant metallizing method) require a step of treating at a high temperature of 1,000 ° C. or higher, the difference in thermal expansion between the substrate and copper (copper compound) is internal. It becomes stress and adversely affects the adhesion strength. Therefore, there is a drawback that it cannot be used for anything other than a heat resistant substrate.

For the thick film printing method (copper paste), see 8
Since firing is performed in a reducing atmosphere at a high temperature of 00 to 900 ° C., the firing cost is high, and like the other conventional methods described above, there is a problem that it cannot be used for other than a heat resistant substrate. The direct plating method is a normal temperature process, but it cannot be applied to plating on a smooth substrate because the surface is rough, and the sputtering method can be metalized on a smooth substrate at low temperature, but the equipment is complicated. There was a weak point that productivity was not increased because it was expensive.

[0010]

The present invention comprises a first step of forming a copper oxide layer on a substrate, a second step of reducing the outer surface of the copper oxide layer to metallic copper, and In the first step of the copper metallizing method consisting of the third step of electrolytic copper plating on the metal copper surface, a zinc oxide film is formed on the substrate, electroless copper plating is applied on the zinc oxide film, The present invention relates to a copper metallizing method, characterized in that the copper oxide layer is formed by heat treatment in an oxygen atmosphere.

In the method of the present invention, the processing temperature in each of the above steps is preferably 400 ° C. or lower.

[0012]

According to the method of the present invention, since a baking process at a high temperature is unnecessary, even a substrate other than heat resistant can be used without trouble and the adhesion strength is not lowered. Further, since it is not necessary to make the substrate surface rough, it is possible to metalize even a smooth substrate.

[0013]

EXAMPLES Examples according to the present invention will be shown below. Here, FIG. 1 is a process diagram of a copper metallizing method showing an example of the method of the present invention, and an embodiment will be described along with (a) to (f) of the figure.

(A) Glass substrate (Corning 705
9) was washed and then dried. Any known substrate can be used as the substrate, but examples thereof include ceramics such as ferrite and titanate compounds, and glasses such as quartz glass. Further, aluminum nitride or the like, which has conventionally been difficult to metallize, can also be used. In addition, even if the surface of the substrate is smooth or uneven, it can be metallized.

(B) 250 to 450 by spray method
A zinc acetate (or zinc chloride) solution was sprayed onto the substrate heated to 0 ° C. to form a zinc oxide film having a thickness of 0.6 μm. The heating temperature is preferably 300 to 400 ° C, more preferably 350 to 400 ° C. Other examples of the film deposition method include the sputtering method and the CVD method, but the spray method is relatively easy and low in cost.

(C) Electroless Copper Plating A substrate coated with zinc oxide is dipped in a Pd solution to carry out a catalytic treatment, and then dipped in an electroless copper plating solution to a thickness of 0.
2 micron copper plating was applied.

(D) Copper Oxidation Treatment The plated copper was heat-treated at 200 to 500 ° C. in the atmosphere to obtain copper oxide. This copper oxidation treatment improves the adhesion strength between copper and zinc oxide. The oxidation treatment is not limited to the atmosphere, but may be an oxygen atmosphere. The oxidation treatment temperature is preferably 300 to 400 ° C., more preferably 350 to 400 ° C.
It is 400 ° C.

(E) Copper surface reduction treatment The copper surface was reduced as a pretreatment for electrolytic copper plating in the next step. This reduction was performed by the following method. That is, the metal powder (Zn, Fe,
Sn, Al, etc.) is attached to the copper surface and treated with an acid at room temperature to generate active hydrogen from the metal powder. This hydrogen reduces the copper oxide.

(F) Electrolytic copper plating Copper was plated to a desired film thickness by known electrolytic copper plating.

In order to measure the adhesion strength of the copper metallization to the glass substrate of the wiring board prepared as described above, 2
When a pattern of mm × 2 mm square was prepared and a tensile test was conducted, the substrate was broken before the metallized metal was peeled off. That is, the wiring board according to the present invention has a practically sufficient metallization strength.

As is clear from the above, the wiring board formed by the method of this embodiment was plated with copper, which was significantly stronger than the wiring board formed by the conventional method.

[0022]

As described above, according to the present invention, since the processing temperature of each step is low, most of the ceramics,
Glass or the like can be used as the substrate. Further, a substrate having a smooth surface which cannot be obtained by the conventional low temperature metallization can be used. Further, in the case of zinc oxide, since etching can be easily performed with a copper etching solution, fine pattern wiring can be formed by photo etching. Furthermore, it is possible to perform metallization on an aluminum nitride substrate, which has been difficult to metallize conventionally. Further, since the reduction treatment is performed, the sheet resistance is reduced, and the current density during plating can be increased, so that the plating speed can be increased, the time can be shortened, the variation in plating thickness can be eliminated, and as a result, mass productivity can be improved.

[Brief description of drawings]

FIG. 1 is a process drawing showing an example of a copper metallizing method according to the present invention.

FIG. 2 is a process drawing showing an example of a copper metallizing method according to a conventional technique.

FIG. 3 is a process drawing showing an example of a copper method (heat resistant metallizing method) according to a conventional technique.

[Explanation of symbols]

A1, B1, C1 ... Substrate, A2 ... Zinc oxide film, A3 ... Electroless copper plating layer, A4, B3, C4 ... Electrolytic copper plating layer,
B2 ... Copper compound paste, C2 ... Copper oxide plate, C3 ... Nickel plate

Claims (2)

[Claims] 1. A first step of forming a copper oxide layer on a substrate, a second step of reducing the outer surface of the copper oxide layer to metallic copper, and electrolytic copper plating on the metallic copper surface. Forming a zinc oxide film on the substrate in the first step of the copper metallizing method consisting of the third step of applying, electroless copper plating on the zinc oxide film, and then heat treating in an oxygen atmosphere. Forming a copper oxide layer by a copper metallizing method. 2. The processing temperature of each step according to claim 1 is 4
Copper metallization method at 00 ° C or lower.