JPS5946310B2 - Method for preventing oxidation of heat-treated copper coatings - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention provides a method for forming ceramic bodies such as dielectrics, insulators, resistors, and semiconductors by electroless plating, vacuum evaporation, sputtering, ion blating, etc.
The present invention relates to a method for preventing oxidation of a copper coating that has been subsequently heat-treated.

In general, methods for forming a copper film on the surface of a non-conductive material such as a ceramic body include electroless plating, vacuum evaporation, sputtering, and ion blating. It is known that it has uses such as when forming the electrode part of a ceramic capacitor.

The copper film formed by the above-described method is usually subjected to heat treatment after the film is formed in order to achieve densification, metallization, improvement of adhesion, and stabilization. This heat treatment is generally performed in an inert atmosphere to prevent the copper coating from reacting with oxygen. Only by subjecting it to this heat treatment process will the copper coating formed by electroless plating, vacuum evaporation, sputtering, ion blating, etc. become a copper coating with electrical properties close to those of pure copper. This constitutes a highly reliable electronic component. However, when copper coatings formed by electroless plating, vacuum evaporation, sputtering, etc. are subjected to a heat treatment process,
Compared to a copper coating that is not heat-treated, it is more easily oxidized and more susceptible to changes over time.

This is because the copper coating itself is a metal that is inherently susceptible to oxidation, and the high temperature heat treatment imparts catalytic activity to the surface of the copper coating, creating conditions that make it even more susceptible to oxidation.

For this reason, if a heat-treated copper film is used as it is, for example, as an electrode for a capacitor, the conductivity will decrease due to the formation of an oxide film, and if it is left for a while after heat treatment, the solderability will also deteriorate, which is undesirable. A phenomenon is observed. Therefore, the main purpose of the present invention is to prevent oxidation and stabilize the surface of a heat-treated copper film, thereby improving the long-term preservation of the copper film and, ultimately, the preservation of electronic components made of ceramic bodies on which the copper film is formed. The purpose is to enable high reliability.

That is, the gist of the present invention is characterized in that after heat-treating a ceramic body having a copper coating formed on its surface, the surface of the ceramic body is brought into contact with a volatile single-strike hydrogenated hydrocarbon compound. be.

Here, the volatile logenated hydrocarbon compounds are:
Examples include trichrene, perchrene, freon, and chlorobenzene, all of which have a boiling point of -29.8.
It is an existing substance with a low boiling point of ℃~132℃.

To explain the implementation outline of the method of this invention, first, thin film formation techniques such as electroless plating, vacuum evaporation, sputtering, and ion plating are applied to the surfaces of ceramic bodies such as dielectrics, insulators, resistors, and semiconductors. to form a copper coating.

For example, a capacitor can be constructed by using dielectric ceramic as the ceramic body and forming a copper coating on the surface, and a circuit can be constructed by using a ceramic substrate made of alumina, zirconia, holsterite, etc. as the ceramic body and having a copper coating on the surface. By forming a pattern, a circuit board can be constructed.

In addition, various electronic components can be constructed by forming a copper coating on the surface of a ceramic element such as a resistor or a semiconductor. Various electronic components having copper coatings formed on the surfaces of ceramic bodies by various methods are then heat-treated at a temperature of, for example, about 700° C. in an inert atmosphere such as nitrogen.

The heat-treated copper film is metallized at this time, and its adhesion becomes strong, and its electrical properties are also improved, giving it very favorable properties.

However, because the copper coating undergoes a high-temperature thermal history through heat treatment, it is also given catalytic activity, resulting in a very active copper coating that has the same catalytic ability as Raney copper. Such catalytic activity increases as soon as possible after heat treatment, such as trichlene, perchrene,
If it comes into contact with volatile halogenated hydrocarbon compounds such as freon and chlorobenzene, the active sites in the copper coating will disappear due to the poisoning effect of these volatile halogenated hydrocarbon compounds, and the catalyst will be destroyed. The activity disappears, and the copper coating becomes stable and less susceptible to oxidation.

Volatile after heat treatment...The shorter the time until contact with the stogenated hydrocarbon compound, the better, preferably after heat treatment 3
It is preferable to contact within 0 minutes. The method of contacting the heat-treated copper coating with the volatile halogenated hydrocarbon compound is to apply, spray, or immerse the halogenated hydrocarbon compound, or to immerse it in the vapor of the halogenated hydrocarbon compound. There are several methods of exposing the skin, and any method may be used.

The present invention will be described below with reference to embodiments comprising electroless copper plating deposited coatings. Example 1 A titanium oxide dielectric ceramic body having a diameter of 6.5 mm and a thickness of 0.5 mm was immersed in an electroless copper plating solution to form a copper plating film on the entire surface of the ceramic body.

Next, this ceramic body was heated at 700°C in a nitrogen atmosphere.
After cooling, the sample was placed in a stainless steel mesh basket container and exposed to trichlene vapor for 1 minute. After that, the surface of the copper coating was naturally dried. Regarding the ceramic dielectrics obtained in this way, the ceramic dielectrics exposed to trichlene vapor and the ceramic dielectrics not exposed to trichlene vapor were each left in a natural atmosphere for 24 hours, and the surface of the copper coating was observed. Those that were not treated according to the method of this invention began to take on a brown color and their solderability decreased.

However, in the case of the method according to the present invention, no change was observed even when left for one month, and the solderability was also good. Example 2 Strontium titanate-based grain boundary insulated semiconductor porcelain with a diameter of 10.0mTn and a thickness of 0.3m11n was prepared and immersed in an electroless copper plating solution to form a copper plating film on the entire surface of the semiconductor porcelain. did.

Next, this semiconductor porcelain was placed in an inert atmosphere consisting of nitrogen.
Heat treatment was performed at 700°C.

Subsequently, the semiconductor porcelain on which the copper plating film was formed was immersed in the Freon solution for about 1 minute. The semiconductor porcelain was pulled out of this solution and air-dried to stabilize the copper plating film.

Furthermore, when this semiconductor magnetic material was forcibly oxidized under conditions of humidity of 95% and temperature of 40° C., there was no change in color tone of the surface of the copper coating even after 5000 hours, and the solderability was also good.

As is clear from the above embodiments, according to the present invention,
When the surface of a ceramic body with a copper coating formed on its surface by electroless plating is heat-treated and then brought into contact with a volatile halogenated hydrocarbon compound such as trichlene or freon, no oxidation phenomenon is observed on the surface of the copper coating. First, it has good solderability, making it extremely useful as a method for preventing oxidation of copper coatings after heat treatment.

Namely, in the above-mentioned embodiment, an example of a copper coating formed by an electroless plating method was explained, but the same effect can be obtained even if the present invention is applied to a copper coating formed by a vacuum evaporation method, a sputtering method, or an ion plating method. Of course you can get it.

Regarding ceramic bodies, we have described dielectric ceramic bodies and grain-boundary insulated semiconductor porcelain, but this invention can also be applied to other materials made of dielectrics, insulators, semiconductors, and resistors on which copper coatings are formed. A similar effect can be obtained.

Claims (1)

[Scope of Claims] 1. Oxidation prevention of a heat-treated copper coating, which is characterized by bringing the surface of the ceramic body into contact with a volatile halogenated hydrocarbon compound after heat-treating the ceramic body with a copper coating formed on its surface. Law. 2. The heat-treated copper film according to claim 1, wherein the copper coating is formed by any one of electroless plating, vacuum evaporation, sputtering, and ion plating. Method for preventing oxidation of copper coatings. 3. The method for preventing oxidation of a heat-treated copper coating according to claim 1, wherein the ceramic body is any one of a dielectric, an insulator, a resistor, and a semiconductor. 4. The method for preventing oxidation of a heat-treated copper coating according to claim 1, wherein the ceramic body is a dielectric and the copper coating is an electrode for taking out a capacitance. 5. The method for preventing oxidation of a heat-treated copper coating according to claim 1, wherein the heat treatment of the ceramic body is performed in an inert atmosphere.