JPS5934157B2 - Method for preventing oxidation of copper coating on ceramic body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preventing oxidation of a copper coating on a ceramic body.

In particular, the present invention relates to a method for preventing oxidation of a copper coating formed as an electrode or conductive part in a ceramic electric circuit element including a ceramic body. A suitable example for explaining the background of this invention is a ceramic capacitor, which is one of ceramic electric circuit elements.

The electrodes of ceramic capacitors generally used highly conductive silver.Such silver electrodes were formed by applying silver paste onto the ceramic body and baking it.However, With the rise in the price of silver materials,
The cost of such silver electrodes has been increasing as a proportion of the total cost of ceramic capacitors. This has been a factor in increasing the overall cost of ceramic capacitors. Against this background, attention has turned to the development of inexpensive electrodes.

As one approach, various studies have been made on methods for forming metal films, such as electroless plating, vacuum evaporation, sputtering, and ion plating. In addition, as another approach, studies have been made to use inexpensive metals instead of silver for the electrodes. Therefore, the first attempt was to create a nickel-plated electrode using an electroless plating method.

The Nickelmetsuki electrode was able to achieve its intended purpose as an inexpensive alternative to silver electrodes. However, it has become clear that the use of nickel plated electrodes as electrodes of ceramic capacitors has the following problems. That is, the specific resistance of the nickel electrode itself is Z24 x 10-6 Ω·T, which is higher than the specific resistance of silver, which is 1.62 x 10-6 Ω·I. Therefore, there was a problem that the frequency characteristics at high frequencies deteriorated. Additionally, the Motsukermetsuki electrode has a problem in that it has poor solderability. Furthermore, an attempt was made to solder the entire surface of the nickel plated electrode as a means of lowering its resistivity. However, when soldering the entire surface of the electrode, a large amount of highly active flux must be used. Therefore, unnecessary flux must be cleaned after soldering. Furthermore, when soldering, for example, the ceramic is immersed in a solder bath, stress is applied to the ceramic, causing cracks to form in the ceramic. As the next step,
There has been a further desire for the development of an inexpensive and highly conductive electrode that can replace the nickel electrode as described above.

In addition, instead of wet plating using electroless plating, methods for forming metal films using dry plating methods such as vacuum evaporation, sputtering, and ion plating were also investigated. Therefore, a new copper plating electrode using a copper dry plating method was attempted.

However, the copper-plated electrode formed by this copper dry plating process has a property that it is easily oxidized as it is. The tendency of the copper coating to be easily oxidized brings about the following drawbacks.

For example, when a copper film is used as an electrode of a ceramic capacitor, an undesirable phenomenon is observed in which the formation of an oxide film as a result of oxidation leads to a decrease in electrical conductivity and also decreases solderability. Therefore, it is necessary to perform oxidation prevention treatment on the copper coating formed by the dry plating method.

Therefore, a primary object of the present invention is to provide a method for preventing oxidation of copper coatings formed on ceramic bodies.

Another object of the present invention is to make it possible to improve the reliability of a copper coating used as an electrode of a ceramic electric circuit element including a ceramic body.

Another object of the invention is to enable long-term preservation of copper coatings. To summarize this invention, which has been made to achieve the above object, a copper coating is formed on a ceramic body by a dry plating method. Afterwards, a halogenated hydrocarbon compound is flowed into the vacuum chamber of the dry plating device, and the copper coating is brought into contact with the halogenated hydrocarbon compound.

According to this invention, no oxidation phenomenon is observed on the surface of the copper coating.
The solderability is also good, and oxidation prevention of the copper coating is advantageously realized. Furthermore, if the method of this invention is adopted, oxidation will not proceed even if the copper coating is left in vacuum at a temperature at which oxidation does not occur, so there is no need to take special cooling measures to prevent oxidation. do not have.

In addition, if the copper coating has come into contact with the rogenated hydrocarbon compound, it will not be oxidized when taken out into the atmosphere, even if the copper coating is in a high temperature state. Therefore, there is no need for extra time for cooling the copper coating after deposition as in the conventional method, and there is an advantage that the processing time for forming the copper coating is shortened. Examples of the above-mentioned dry plating method include a vacuum evaporation method, a sputtering method, and an ion plating method. A ceramic body is housed in a vacuum chamber of various dry plating devices compatible with such a method, and copper particles are scattered under predetermined vacuum conditions to form a copper coating on the ceramic body. After the copper coating is formed, the rogenated hydrocarbon compound is flowed into the vacuum chamber, or it is flowed into the vacuum chamber in the form of a gas or mist, and the copper coating is formed on the ceramic body. The active sites present on the copper coating are reduced by the poisoning action of the halogenated hydrocarbon compound, resulting in no catalytic activity, and the copper coating becomes more stable and less susceptible to oxidation. Further, the halogenated hydrocarbon compound may be introduced at the same time as external atmospheric gas is introduced into the vacuum chamber to bring the vacuum chamber to dog pressure after the formation of the copper coating. The point is that after the formation of the copper coating, the logenated hydrocarbon compound may be introduced into the vacuum chamber, and it is preferable to carry out the treatment as soon as possible after the formation of the copper coating, in order to prevent the oxidation of the copper coating. As the halogenated hydrocarbon compound, at least one selected from the group including trichrene, perchrene, chlorofluorocarbon, chlorobenzene, methyl chloride, methylene chloride, chloroform, and carbon tetrachloride is preferably used.

In another preferred embodiment, in the step of contacting the halogenated hydrocarbon compound, a solution of the halogenated hydrocarbon compound in which a surfactant is dissolved is used. Surfactants that can be used include, for example, anionic surfactants such as naphthenic acid soaps, cationic surfactants such as alkyloxazolines, nonionic surfactants such as polyethylene glycol esters, or taurine condensation co-sols.
-Ampholytic surfactants such as citric acid esters may be exemplified. That is, any surfactant may be used as long as it is soluble in the halogenated hydrocarbon compound. Therefore, it should be pointed out that the type of surfactant is not limited to the above-mentioned examples. If a logenated hydrocarbon compound containing this surfactant is used in the contact process, a monomolecular film of the surfactant will be formed on the surface of the copper coating, compared to the case where no surfactant is included, thereby increasing the copper The effect of preventing the oxidation of the film from changing over time becomes more pronounced. In yet another preferred embodiment of the present invention, in the step of contacting the logenated hydrocarbon compound, a solution of the beaten genated hydrocarbon compound in which fatty acids such as stearic acid and higher fatty acid esters such as wax are dissolved is used. .

Usable fatty acids or fatty acid esters are not limited to stearic acid and wax, and may also include fatty acids such as palmitic acid and lanolic acid, fatty acid esters, and the like. According to this preferred embodiment, a monomolecular film of fatty acids or fatty acid esters is formed on the surface of the copper coating, thereby preventing oxidation and aging of the copper coating. This will make it even more preventable. From this point of view, the fatty acid or fatty acid ester used in this example may be selected, and any fatty acid or fatty acid ester that can easily form a monomolecular film on the surface of the copper coating may be used. In another embodiment of the invention, the step of contacting the logenated hydrocarbon compound is carried out with a solution of the logenated hydrocarbon compound in which the polymeric compound is dissolved.

Examples of usable polymer compounds include polyethylene, polypropylene, polyvinyl chloride, polyester resin, polyvinyl acetate, polyvinyl formal, polystyrene, polyvinyl butyral, polyurethane, and MM.
AlABS. Examples include SBR, neoprene, and chlorinated rubber. According to this example, the phenomenon of forming a film of a polymer compound on the surface of the copper coating occurs more than in the example in which no polymer compound is used, so that the effect of preventing oxidation and preventing aging of the copper coating is further enhanced. can get. A general overview of preferred embodiments of the invention will now be described.

First, a ceramic element such as a dielectric, an insulator, a resistor, or a semiconductor is prepared. Next, a copper coating is formed on the surface of the ceramic body using a thin film forming technique such as vacuum evaporation, sputtering, or 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. Furthermore, a circuit board can be constructed by using ceramic such as alumina, zirconia, or holsterite as the ceramic body and forming a circuit pattern made of a copper film on the surface. 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. In this way, various electronic components with copper coatings formed on the surface of ceramic bodies by various methods are then flowed into vacuum chambers used to carry out the various methods. When brought into contact, the active sites are annihilated and the catalytic activity is eliminated before the copper coating is exposed to the atmosphere, resulting in a copper coating that is resistant to oxidation.

The present invention will be explained in detail below based on examples.

Example 1 Strontium titanate-based grain-boundary insulated semiconductor porcelain with a diameter of 10.0 m71L and a thickness of 0.3 m1 was prepared, and this semiconductor porcelain was installed on the 1 side of a DC bipolar sputtering device, while the cathode A metallic copper target was set up on the side.

Next, once the inside of the vacuum chamber is brought to a high vacuum state, the degree of vacuum is increased to 5 x 10-2 to 4 x 10-2 while injecting argon gas.
4T0rr, for example 3.times.10@-3 T0rr, and a DC voltage was applied between the cathode and the anode so that power of, for example, 6W/C7i per unit area was supplied to the target. In this way, a copper film is formed on the surface of the semiconductor ceramic by sputtering, and then trichlorofluoromethane, a type of chlorofluorocarbon, is flowed into the vacuum chamber from the gas supply port, and the trichlorofluoromethane is brought into contact with the surface of the copper film. I let it happen. Regarding the obtained semiconductor porcelain,
When left in a natural atmosphere, no change was observed even after one month, and the solderability was good. Nah}
In addition to the method described above, trichlorofluoromethane gas may be introduced through a leak valve of a vacuum chamber.

Example 2 A ceramic body made of a titanium oxide dielectric having a diameter of 6.5 mm and a thickness of 0.5 mm was prepared.

Next, this ceramic element body is placed in a vacuum chamber of a vacuum evaporation device, and the inside of the vacuum chamber is further reduced to 5×10−5 to 5×10−5.
The air was evacuated through the air supply and exhaust ports to a degree of vacuum of 6T0rr. Subsequently, electricity was applied to the heating source heater to heat the copper, which was the evaporation source, to evaporate the copper and form a copper coating on the ceramic body. Thereafter, the valve of the supply/exhaust port was opened, and at the same time, chloroform was flowed in from the port in the form of a mist to bring the chloroform into contact with the surface of the copper coating.

For the ceramic bodies obtained in this way and the ceramic bodies not treated with chloroform, each
When the surface of the copper coating was observed after being left in a natural atmosphere for 4 hours, it was found that the copper coating surface, which had not been subjected to the chloroform treatment according to the present invention, began to turn brown and its solderability decreased.

However, when the method of this invention was left for one month, no change was observed and the solderability was good. Example 3 A ceramic body of a titanium oxide derivative having a diameter of 6.5 mm and a thickness of 0.5 mm was prepared.

Thereafter, a copper coating was formed on the surface of the ceramic body in the same manner as in Example 2, and then, at the same time as the valve of the supply and exhaust port of the vacuum evaporation device was opened, trichlene in which polyethylene glycol ester was dissolved was introduced in gaseous form. It was brought into contact with the surface of the copper coating.

The thus obtained ceramic body and the ceramic body which had not been treated with trichlene in which a surfactant was dissolved were left in a natural atmosphere for 24 hours, and the surface of the copper coating was observed. For those that were not treated by this method, the brown color began to fade and the solderability also decreased.

On the other hand, in the case of the method of this invention, no change was observed even after leaving it for one month, and the solderability was good. Example 4 Strontium titanate-based grain boundary insulated semiconductor porcelain having a diameter of 10.0 mm and a thickness of 0.3 mm was prepared.

Next, this semiconductor porcelain was placed on the cathode side of the ion plating apparatus, and on the other hand, copper as a coating material was placed on the anode side. After this, the inside of the tank is made into a high vacuum through the supply and exhaust ports of the vacuum tank.
Further, argon gas was introduced from the gas supply port to adjust the gas pressure in the tank to 10-1 to 10-4T0rr. Subsequently, a high voltage was applied between the cathode and anode to cause a glow discharge, and further plasma was generated. Next, the copper, which is the film forming material, is heated to evaporate the copper, and the copper is collided with ionized or excited argon gas in the plasma to perform charge exchange, scattering the copper particles as ionized particles or particle groups, and forming copper particles. The coating was applied to a semiconductor porcelain coating. Furthermore, the valves at the supply and exhaust ports of the vacuum chamber were opened, and a chlorofluorocarbon solution in which naphthenic acid soap had been dissolved was flowed into the vacuum chamber in the form of a mist, so that the chlorofluorocarbon in which naphthenic acid soap had been dissolved was brought into contact with the copper coating.

When the semiconductor porcelain having the copper coating thus obtained 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 improved. It was also good.

Example 5 Diameter 6.5m7! A titanium oxide dielectric ceramic body having a thickness of 0.5 mm was prepared.

Thereafter, a copper coating was formed in the same manner as in Example 1, and a mist of trichlene in which wax had been dissolved was flowed into the vacuum chamber to contact the surface of the copper coating.

The thus obtained ceramic body and the ceramic body which had not been treated with trichlene containing melted wax were left in a natural atmosphere for 24 hours, and the copper coating was observed. No change was observed, and the solderability was good.

However, the products that were not produced by the method of this invention began to lose their brown color and their solderability also deteriorated. Example 6 Strontium titanate-based grain boundary insulated semiconductor porcelain was used as the ceramic body, and the size was 10.0 m in diameter.
A piece with m1 thickness of 0.3 mm was prepared.

This semiconductor porcelain was treated in the same manner as in Example 1 to form a copper coating on its surface, and a chlorofluorocarbon solution in which stearic acid had been dissolved was flowed in gaseous form into a vacuum chamber through a leak valve to coat the surface of the copper coating. This chlorofluorocarbon was contacted. When the semiconductor porcelain thus obtained was forcibly oxidized at a humidity of 9,570 degrees and a temperature of 40 degrees Celsius, there was no change in color tone on the surface of the copper coating even after 5,000 hours, and the solderability was also good. .

Example 7 A titanium oxide dielectric ceramic body having a diameter of 6.5 mm and a thickness of 0.5 mm was prepared.

This ceramic body was treated in the same manner as in Example 2 to form a copper coating on its surface, and a trichlene solution in which polyethylene was dissolved was made into a mist and flowed in from the air supply and exhaust port of the vacuum chamber to form a copper coating on the surface of the copper coating. Triclean was contacted.

Regarding the ceramic dielectric thus obtained, 1
When the copper coating surface was observed after being left in a natural atmosphere for several months, no changes were observed and the solderability was good.

Example 8 Strontium titanate-based grain boundary insulated semiconductor porcelain was used as the ceramic body, and the size was 10.0 m71 in diameter.
One with a thickness of 0.3 mm was prepared.

This semiconductor porcelain was treated in the same manner as in Example 4 to form a copper coating on its surface, and a chlorofluorocarbon solution in which polypropylene was dissolved was flowed in gaseous form through the supply and exhaust ports to bring the chlorofluorocarbon into contact with the surface of the copper coating. I let it happen. When the semiconductor porcelain thus obtained was forcibly oxidized under conditions of 95% humidity and 40°C, there was no change in color tone on the surface of the copper coating even after 5000 hours, and the solderability was also good. It was hot. Example
9. A multilayer ceramic capacitor body measuring 4.5 mm x 2.0 mm x 1.5 mm was prepared.

This was treated in the same manner as in Example 1 to form a copper film on the surface of the multilayer ceramic capacitor body, and then about 2 CC of carbon tetrachloride was flowed in a mist form into the vacuum chamber from the gas supply port to form a copper film. Carbon tetrachloride was brought into contact with the surface.

When the multilayer ceramic capacitor thus obtained was left in a natural atmosphere, no change was observed in the copper coating even after one month, and the solderability was good.

Example 10 An alumina substrate of 10 mm x 20 mm x 0.6 mm was prepared.

A copper film was formed on the surface of the alumina substrate in the same manner as in Example 2, and then, at the same time as the valve of the supply and exhaust port of the vacuum evaporation equipment was opened, about 3 CC of methylene chloride was flowed in a mist to coat the surface of the copper film. Methylene chloride was contacted.

When the alumina substrate thus obtained was left in a natural atmosphere, no change was observed in the copper coating even after one month, and the solderability was good.

Example 11 Diameter 6.5m TL1 Thickness 0.5m77! A high-frequency ceramic body made of titanium oxide was prepared.

This ceramic body was installed on the cathode side of high-frequency ion plating, and the inside of the vacuum chamber was 2×10-6T0rr.
The air was evacuated through the air supply and exhaust ports to achieve a vacuum level of .

Subsequently, electricity was applied to the heating source heater to heat and evaporate the copper serving as the evaporation source, and the evaporated copper was positively ionized to form a copper coating on the ceramic body. Thereafter, at the same time as the valve of the supply/exhaust port was opened, about 2 cc of perchloren was flowed in from the port in the form of a mist, and the perchloren was brought into contact with the surface of the copper coating.

When the ceramic body thus obtained was left in a natural atmosphere, no change was observed in the copper coating even after one month, and the solderability was good.

Example 12 8m77I x 5m771 x 1mm (7) SnO2-Ti
An O2-based ceramic resistor was prepared.

This ceramic resistor was treated in the same manner as in Example 1 to form a copper film on its surface, and then approximately 2 cc of chlorobenzene was flowed into the vacuum chamber from the gas supply port in the form of a mist to bring the copper film into contact with the chlorobenzene. I let it happen.

When the ceramic resistor thus obtained was left in a natural atmosphere, no change was observed in the copper coating even after one month, and the solderability was good.

Example 13 A cylindrical TiO2-ZrO2-ZnO ceramic dielectric having a height of 7m7n (outer diameter 7mm, inner diameter 3mm) was prepared.

This ceramic dielectric was treated in the same manner as in Example 1 to form a copper film on its surface, and then approximately 2 CC of methyl chloride was flowed into the vacuum chamber from the gas supply port in the form of a mist to form a copper film. brought into contact with.

When the ceramic resistor thus obtained was left in a natural atmosphere, no change was observed in the copper coating even after one month, and the solderability was good.

The resulting ceramic dielectric is an NCO (voltage controlled oscillator)
It is used as a dielectric resonator that forms part of the

As is clear from the above embodiments, according to the present invention, after a copper coating is formed on a ceramic body by a dry plating method, a logenated hydrocarbon compound is introduced into a vacuum chamber of a dry plating device. Since the copper coating is made to come into contact with the rogenated hydrocarbon compound, no oxidation phenomenon is observed on the surface of the copper coating, and it has good solderability, making it an effective method for preventing oxidation of copper coatings. It is extremely useful.

In addition, according to the method of the present invention, the process can be carried out immediately after the step of forming the copper coating, so the process can be carried out in the same vacuum chamber, and there is no need to leave it in an oxidizing atmosphere, allowing for rapid oxidation prevention treatment. .

In the above embodiments, dielectric ceramic bodies and grain-boundary insulated semiconductor porcelain were explained, but the present invention can be applied to other dielectrics, insulators, semiconductors, and resistors with copper coatings formed thereon. A similar effect can be obtained by applying

Further, in manufacturing a ceramic capacitor having an electrode made of a copper film, after carrying out the method of this invention,
Since a ceramic body with a copper coating formed on the entire ceramic body is used as a counter electrode, for example, when a disk-shaped ceramic body is used, it is of course necessary to remove unnecessary copper coating on the circumferential side.

Claims (1)

[Claims] 1. After a copper film is formed on a ceramic body by a dry plating method, a halogenated hydrocarbon compound is flowed into a vacuum chamber of a dry plating device, and the copper film and the halogenated hydrocarbon compound are brought into contact with each other. A method for preventing oxidation of a copper coating on a ceramic body. 2. A method for preventing oxidation of a copper coating on a ceramic body according to claim 1, wherein the dry plating method is any one of a vacuum evaporation method, a sputtering method, and an ion plating method. 3. A method for preventing oxidation of a copper coating on a ceramic body according to claim 1, wherein the halogenated hydrocarbon compound is introduced into the vacuum chamber in the form of a gas or mist. 4. A method for preventing oxidation of a copper coating on a ceramic body according to claim 1, wherein the halogenated hydrocarbon compound is introduced at the same time as external atmospheric gas is introduced into the vacuum chamber. 5 Examples of halogenated hydrocarbon compounds include trichlene,
Preventing oxidation of the copper coating on the ceramic body according to claim 1, which is made of at least one member selected from the group including perchloren, chlorofluorocarbon, chlorobenzene, methyl chloride, methylene chloride, chloroform, and carbon tetrachloride. Law. 6. A method for preventing oxidation of a copper coating on a ceramic body according to claim 1, wherein the halogenated hydrocarbon compound has a surfactant dissolved therein. 7. Oxidation of a copper coating on a ceramic body according to claim 1, wherein the halogenated hydrocarbon compound has at least one selected from the group containing fatty acids and higher fatty acid esters dissolved therein. Prevention method. 8. A method for preventing oxidation of a copper coating on a ceramic body according to claim 1, wherein the halogenated hydrocarbon compound has a polymer compound dissolved therein.