JPS609591B2 - Method for preventing oxidation of heat-treated copper coatings - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for forming a ceramic body such as a resistor, an insulator, a resistor, or a semiconductor by an electroless plating method, a vacuum evaporation method, a sputtering method, an ion plating method, 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 plating. It is known that it can be used in forming electrode parts of ceramic capacitors.

Then, the copper coating formed by the above method is densified,
In order to improve metallization, adhesion, and stability, a heat treatment is usually performed after the film is formed. This heat treatment is generally performed in an inert atmosphere to prevent the copper coating from reacting with oxygen. By subjecting it to this heat treatment process, the copper coating formed by electroless plating, vacuum evaporation, sputtering, ion plating, etc. becomes a copper coating with electrical properties close to those of pure steel, making it highly reliable. It constitutes a digital electronic component. However, when copper coatings formed by electroless coating, 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 easily oxidized, and the high-temperature heat treatment imparts catalytic activity to the surface of the steel coating, creating conditions that make it 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 it is also said that if the heat-treated copper film is left alone, the solderability will deteriorate. An unfavorable phenomenon was observed. Therefore, the main purpose of this invention is to "prevent the oxidation of the heat-treated copper coating surface and stabilize it, thereby improving the long-term preservation of the copper coating and increasing the reliability of electronic components made of ceramic bodies on which the copper coating is formed." The goal is to make it possible.

That is, the gist of the present invention is that after heat-treating a ceramic body with a copper coating formed on its surface, the surface of the ceramic body is evaporated with a dissolved polymeric compound made of one of polyethylene, polypropylene, and polystyrene. This method is characterized by contacting with a halogenated hydrocarbon compound solution.

Here, examples of volatile halogenated hydrocarbon compounds include trichrene, perchrene, freon, and chlorobenzene, all of which have a boiling point of -29.8°C.
It is an existing substance with a low boiling point of o~13〆○.

To explain the outline of the implementation of the method of this invention, first, a dielectric material,
On the surface of ceramic bodies such as insulators, resistors, and semiconductors,
The copper coating is formed using thin film forming techniques such as electroless plating, vacuum evaporation, sputtering, and ion plating.

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 with a copper coating on the surface by using a ceramic substrate such as alumina, zirconia, or holsterite as the ceramic body. 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 in an inert atmosphere such as nitrogen at a temperature of, for example, about 700 qo.

At this time, the heat-treated steel coating is metallized, and its adhesion becomes strong, and its electrical properties are also improved, giving it very favorable properties.

However, since the copper coating undergoes a high-temperature thermal history through heat treatment, the copper coating is also given catalytic activity, resulting in a copper coating that has the same catalytic ability as Raney steel. Such catalytic activity is activated as soon as possible after heat treatment to dissolve high molecular compounds such as trichrene, perchrene, freon, and chlorobenzene.

When brought into contact with a solution of halogenated hydrocarbon compounds, the active sites of the copper coating disappear due to the action of these volatile halogenated hydrocarbon compounds and the catalytic activity disappears, making the steel coating stable and preventing oxidation. It becomes. Further, by forming a film of a polymer compound on the surface of the copper coating, oxidation and change in elevation of the copper coating can be prevented. After the heat treatment, the time period until the polymer compound is brought into contact with the dissolved volatile halogenated hydrocarbon compound is preferably as short as possible, preferably within 30 minutes after the heat treatment. As the polymer compound used, any one of polyethylene, polypropylene, and polystyrene is used. Among these, wax-like polyethylene with a molecular weight of 500 to 2,500 is used.

Also, polypropylene and polystyrene have a molecular weight of 500~
3000 are used. heat-treated copper coating,
Methods for contacting with a volatile halogenated hydrocarbon compound solution in which a polymer compound is dissolved include coating, spraying, and dipping with this solution, and any method may be used.

The present invention will be described below with reference to embodiments comprising electroless copper plating deposits.

Example 1 A titanium oxide dielectric ceramic body having a diameter of 6.5 mm and a thickness of 0.5 ribs was immersed in an electroless steel plating solution, and a copper lacquer coating was formed on the entire surface of the ceramic body.

Next, this ceramic body was heated for 7000 min in a nitrogen atmosphere.
After being subjected to heat treatment at a temperature of 0, after cooling, it was placed in a container made of a stainless steel mesh basket, and a trichlene solution containing 1% by weight of polyethylene having a molecular weight of 1000 was sprayed thereon. After that, the surface of the copper coating was naturally dried.

The ceramic dielectric bodies thus obtained were left in a natural atmosphere for 2 hours, and the ceramic body was sprayed with trichlene containing dissolved polyethylene, and the ceramic dielectric body was not subjected to such treatment.
When the surface of the copper coating was observed, it was found that those not treated according to the method of the present invention began to take on a brown color and the solderability decreased.

However, with the method of this invention, no change was observed even when left for one month, and the solderability was good. Example 2 Strontium titanate-based grain boundary insulated semiconductor porcelain with a diameter of 10. A piece with a thickness of 0.3 was prepared and immersed in an electroless steel plating solution to form a copper lacquer coating on the entire surface of the semiconductor porcelain.

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

Subsequently, 1% by weight of polypropylene with a molecular weight of 1000
The semiconductor porcelain on which the copper coating was formed was immersed in the dissolved Freon solution for about 1 minute. The semiconductor porcelain was pulled out of this solution and air-dried to stabilize the copper lacquer coating.

Furthermore, when this semiconductor porcelain was forcibly oxidized under conditions of humidity of 95% and temperature of 4000, there was no change in color tone of the surface of the copper coating even after 5000 hours, and the solderability was also good.

Example 3 A strontium titanate-based grain boundary insulated semiconductor porcelain coated with a copper plating film was used in the same manner as in Example 2, and then heat treated at 700° C. in an inert atmosphere containing nitrogen.

Subsequently, the semiconductor porcelain on which the copper-plated film was formed was immersed for about 1 minute in a Freon solution containing 1% by weight of polystyrene having a molecular weight of 1000. Thereafter, when the copper coating was treated in the same manner as in Example 2, there was no change in color tone on the surface of the copper coating, and the solderability was also good.

As is clear from the above embodiments, according to the present invention, after heat-treating the surface of the copper coating of a ceramic body on which a copper coating is formed by an electroless finishing method, polyethylene, polypropylene, or polystyrene is used. When a polymer compound consisting of one type of polymer is brought into contact with a volatile halogenated hydrocarbon compound such as tricrene or freon, no oxidation phenomenon is observed on the surface of the copper coating, and the solderability is good. It is extremely useful as a method for preventing oxidation of coatings. In addition, in the above-mentioned embodiment, an example of a copper film formed by an electroless plating method was explained, but the present invention can also be applied to a copper film formed by a summer air evaporation method, a sputtering method, or an ion plating method. Needless to say, this method can provide beneficial effects.

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 with copper coatings formed on them. A similar effect can be obtained.

Claims (1)

[Claims] 1. After heat treating a ceramic body with a copper coating formed on its surface, the surface of the ceramic body is subjected to volatile halogenated carbonization in which a polymeric compound made of one of polyethylene, polypropylene, and polystyrene is dissolved. A method for preventing oxidation of a heat-treated copper film, which method comprises contacting a heat-treated copper film with a hydrogen compound solution. 2. The heat-treated copper coating 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 as claimed in 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 as claimed in claim 1, wherein the heat treatment of the ceramic body is carried out in an inert atmosphere.