JPS6248365B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preventing oxidation of a copper coating formed on a ceramic body, and particularly to a method for preventing oxidation of a copper coating formed as an electrode or a conductive part in an electric circuit element including a ceramic body. It is about law.

A specific suitable example of a conductive film on a ceramic body is the electrode part of a ceramic capacitor, and silver, which has high conductivity, is generally used. Such silver electrodes were formed by applying silver paste onto a ceramic body and baking it. However, with the rise in the price of silver materials, the cost of such silver electrodes has increased as a percentage 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. One approach is the electroless plating method, which is a method for forming metal coatings.
Various studies were conducted on vacuum evaporation, sputtering, ion plating, etc. 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. In other words, the specific resistance of the nickel electrode itself is 7.24×
10 ^-6 Ω・cm, and the specific resistance of silver is 1.62×10 ^-6 Ω・cm
higher than that. Therefore, there was a problem that the frequency characteristics at high frequencies deteriorated. Also,
Nickel plated electrodes also have a problem of poor solderability. Furthermore, as a means of lowering the specific resistance of the nickel-plated electrode, a method of soldering the entire surface was also found. 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 a next step, there was a further desire to develop an inexpensive and highly conductive electrode that could replace the nickel electrode mentioned above. Therefore, a new copper plating electrode using electroless copper plating method was attempted. However, this copper electroless plating electrode also had major problems. That is, a copper-plated electrode formed by electroless plating has the property of being easily oxidized as it is. for example,
When a copper coating 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 such oxidation leads to a decrease in electrical conductivity and also decreases solderability. Note that the same phenomenon is observed not only in copper electrodes formed by electroless plating, but also in copper electrodes formed by vacuum evaporation, sputtering, ion plating, and the like.

Therefore, oxidation prevention treatment is required for the copper coating, which is easily oxidized.

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.

Yet another object of the invention is to enable long-term storage of copper coatings.

That is, to summarize the present invention, the present invention is characterized in that the surface of a ceramic body on which a copper coating is formed is brought into contact with a halogenated hydrocarbon compound.

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 electroless plating, vacuum evaporation, sputtering, or ion plating. For example, a codenser 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. Note that although dielectrics and insulators are mentioned here as ceramic bodies, the purpose of dielectrics is to construct capacitors by utilizing their dielectric constant.
On the other hand, insulators do not have a large dielectric constant like dielectrics, and are used as circuit boards by making use of their insulating properties and forming circuit patterns on their surfaces.

As described above, the copper coating formed on the surface of the ceramic body by various methods is exposed as soon as possible to the step of contacting with a halogenated hydrocarbon compound, which is a feature of the present invention. That is, it is more preferable that the time from the formation of the copper coating to the contact with the halogenated hydrocarbon compound be as short as possible. If possible, it is preferable to contact within 30 minutes after forming the copper coating. According to such a contact process using a halogenated hydrocarbon compound, the active sites in the copper coating disappear due to the poisoning effect of the halogenated hydrocarbon compound, and the catalytic activity disappears, making the copper coating stable and preventing oxidation. become less likely to be

The halogenated hydrocarbon compound is preferably trichlorethylene, perchlorethylene,
At least one selected from the group including fluorocarbon, chlorobenzene, methyl chloride, methylene chloride, chloroform, and carbon tetrachloride is used. Any of the following methods may be used to bring such a halogenated hydrocarbon compound into contact with the copper coating. That is, there are methods of applying the halogenated hydrocarbon compound, methods of spraying, methods of dipping, and methods of exposing to the vapor of the halogenated hydrocarbon compound.

In another preferred embodiment of the present invention, in the step of contacting the halogenated hydrocarbon compound, a halogenated hydrocarbon compound solution in which a fatty acid such as stearic acid or a higher fatty acid ester such as wax is dissolved is used.

Usable fatty acids or fatty acid esters include not only stearic acid and wax, but also fatty acids such as palmitic acid and lanolic acid, and fatty acid esters. According to this example,
A monomolecular film of fatty acids or fatty acid esters is formed on the surface of the copper coating, thereby further preventing oxidation and aging of the copper coating. From this viewpoint, 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 yet another preferred embodiment of the invention, the step of contacting the halogenated hydrocarbon compound is carried out with a solution of the halogenated hydrocarbon compound in which the polymer compound is dissolved.

Examples of usable polymer compounds include:
Polyethylene, polypropylene, polyvinyl chloride, polyester resin, polyvinyl acetate, polyvinyl formal, polystyrene, polyvinyl butyral, polyurethane, MMA, ABS, SBR,
Examples include 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.

In addition, as another preferred embodiment mentioned above, a method of bringing a halogenated hydrocarbon compound in which a fatty acid, a higher fatty acid ester, and a polymer compound are dissolved into contact with the copper coating is a method of applying this solution. , how to spray,
There are methods such as immersion in a solution, but any method may be used.

The present invention will be explained below based on detailed examples.

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. After this was once dried, it was placed in a stainless steel mesh basket container and exposed to chloroform vapor for 1 minute. Furthermore, the surface of the copper coating was dried.

The ceramic dielectric thus obtained,
Ceramic dielectrics that had not been subjected to the above treatment were left in a natural atmosphere for 24 hours.
When the surface of the copper film was observed, it was found that the surface of the copper film that had not been treated according to the present invention began to take on a brown color and its solderability decreased. On the other hand, when the product according to the present invention was left for one month, no change was observed, and the solderability was also good.

Example 2 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 plating solution, and a copper plating film was formed on the entire surface of the ceramic body.
After this was once dried, it was placed in a stainless steel mesh basket container and exposed to trichlorene vapor for 1 minute. Furthermore, the surface of the copper coating was dried.

The ceramic dielectric thus obtained,
Ceramic dielectrics that had not been exposed to trichlene vapor were left in a natural atmosphere for 24 hours, and the surfaces of the copper coatings were observed; those that had not been treated by the method of this invention began to turn brown and had poor solderability. It also decreased. On the other hand, when the method of the present invention was used and left for one month, no change was observed and the solderability was good.

Example 3 Strontium titanate-based grain boundary insulated semiconductor porcelain with a diameter of 10.0 mm and a thickness of 0.3 mm was prepared and immersed in an electroless copper plating solution to form a copper plating film on the entire surface of the semiconductor porcelain. After this was once dried, 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 dried to stabilize the copper plating film.

Furthermore, when this semiconductor porcelain was forcibly oxidized under the conditions of 95% humidity and 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.

Example 4 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, after drying the copper plating film on this ceramic body, it was placed in a stainless steel mesh basket container and sprayed with Triclean containing 1% by weight of wax. After this, the surface of the copper coating was dried.

The ceramic dielectric thus obtained,
Ceramic dielectrics that had not been sprayed with trichlene containing melted wax were left in a natural atmosphere for 24 hours, and the surfaces of the copper coatings were observed, and it was found that those that had not been treated with the method of this invention began to turn brown. , solderability also decreased. On the other hand, 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 5 Strontium titanate-based grain boundary insulated semiconductor porcelain with a diameter of 10.0 mm and a thickness of 0.3 mm was prepared and immersed in an electroless copper plating solution to form a copper plating film on the entire surface of the semiconductor porcelain. The copper plating film was then dried.

Subsequently, the semiconductor porcelain on which the copper plating film was formed was immersed for about 1 minute in a Freon solution containing 1% by weight of stearic acid. The semiconductor porcelain was pulled out of this solution and dried to stabilize the copper plating film.

Furthermore, this semiconductor porcelain is heated at a humidity of 95% and a temperature of 40°C.
When the copper coating was forcibly oxidized under the following conditions, there was no change in color tone on the surface of the copper coating even after 5000 hours, and the solderability was also good.

Example 6 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, the surface of the copper plating film was dried. Subsequently, the container was placed in a stainless steel net basket container, and a trichlene solution containing 1% by weight of polyethylene was sprayed onto the container. After this, the surface of the copper coating was dried.

The ceramic dielectric thus obtained,
Ceramic dielectrics that had not been sprayed with trichlene, a solution of polyethylene, were left in a natural atmosphere for 24 hours and the surface of the copper coating was observed. The solderability also deteriorated. On the other hand, when the method of the present invention was used and left for one month, no change was observed and the solderability was good.

Example 7 Strontium titanate-based grain boundary insulated semiconductor porcelain with a diameter of 10.00 mm and a thickness of 0.3 mm was prepared and immersed in an electroless copper plating solution to form a copper plating film on the entire surface of the semiconductor porcelain. The surface of the copper coating was then dried.

Subsequently, the semiconductor porcelain on which the copper plating film was formed was immersed for about 1 minute in a Freon solution containing 1% by weight of polypropylene. The semiconductor porcelain was pulled out of this solution and dried to stabilize the copper plating film.

Furthermore, when this conductor porcelain 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.

Example 8 Strontium titanate-based grain-boundary insulated semiconductor porcelain with a diameter of 10.0 mm and a thickness of 0.3 mm was prepared, and this semiconductor porcelain was installed on the anode side of a two-diameter sputtering device, while on the cathode side. A metallic copper target was placed. Next, once the inside of the vacuum chamber is brought to a high vacuum state, the degree of vacuum is set to 5 × 10 ^-2 to 5 × 10 ^-4 torr, for example, 5 × 10 ^-3 torr, while injecting argon gas, and the target is heated per unit area. A DC voltage was applied between the cathode and the anode so that a power of, for example, 6 W/cm ² was supplied.

In this way, a copper coating was formed on the surface of the semiconductor ceramic by sputtering, and then Freon gas was introduced into the vacuum chamber to bring Freon into contact with the surface of the copper coating.

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

Example 9 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 body was placed in a vacuum chamber of a vacuum evaporation apparatus, and the vacuum chamber was further evacuated from an air supply/exhaust port so that the vacuum level within the chamber was 5.times.10.sup. ^-5 to 5.times.10.sup. ^-6 torr. 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.

The ceramic body with the copper coating formed on its surface was taken out of the vacuum chamber, placed in a stainless steel mesh basket container, and then exposed to chloroform vapor for 1 minute. Furthermore, the surface of the copper coating was dried.

The ceramic bodies obtained in this way and the ceramic bodies not treated with chloroform were each left in a natural atmosphere for 24 hours, and the surface of the copper coating was observed, and it was found that the chloroform treatment according to the present invention had not been carried out. The product 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 10 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 vacuum chamber is brought to a high vacuum through the supply/exhaust port of the vacuum chamber, and argon gas is introduced through the gas supply port to bring the inside of the chamber to 10 ^-1 ~
The gas pressure was adjusted to 10 ^-4 torr. Continued cathode,
A high voltage was applied between the anodes to cause a glow discharge, and further plasma was generated. Next, the copper that 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 the copper film. was attached to the surface of semiconductor porcelain.

The semiconductor porcelain with the copper coating formed on its surface was taken out of the vacuum chamber, placed in a stainless steel mesh basket, and then immersed for 1 minute in a chlorofluorocarbon solution containing 1% by weight of naphthenic acid soap. The semiconductor porcelain was pulled out of this solution and dried to stabilize the copper coating.

When the semiconductor porcelain with the copper coating thus obtained was forcibly oxidized under the conditions of 95% humidity and 40°C, there was no change in the color tone of the copper coating surface even after 5000 hours, and the solderability was also poor. It was good and warm.

Next, a method for manufacturing a ceramic capacitor as an example of a ceramic electric circuit element to which the method of the present invention is applied will be described. The method of the present invention is used in part of the manufacturing process of this ceramic capacitor.

Referring to Figure 1, the ceramic capacitor is
For example, it includes a disc-shaped ceramic body 1. Electrodes 2 facing each other are formed on both main surfaces of the ceramic body 1, respectively. This electrode 2 is made of a copper film. Lead wires 4 are connected to each electrode 2 with solder 3, respectively. The lead wire 4 is led out in the radial direction, for example. The structure configured in this way is covered with an insulating resin 5, as shown by the imaginary line. of course,
The lead wire 4 is configured to be exposed from the insulating resin 5 by a predetermined length from its tip.

An example of the process for manufacturing the ceramic capacitor shown in FIG. 1 is shown in FIG. Referring to Figure 4,
In the first step 11, a ceramic body is prepared. As a second step 12, the ceramic body is subjected to pretreatment for electroless plating. This pretreatment includes degreasing, activation, and cleaning steps. As a third step 13, electroless copper plating is applied to the surface of the pretreated ceramic body. As a result, a copper plating film is formed on the entire surface of the ceramic body. In a fourth step 14, the ceramic body on which the copper coating is formed is washed with water. As a fifth step 15, the copper coating is contacted with a halogenated hydrocarbon compound. In this step 15, the various halogenated hydrocarbon compounds or halogenated hydrocarbon compound solutions that are brought into contact with the copper coating are used. Furthermore, any of various contact methods may be employed.

At the end of the fifth step 15, an intermediate product as shown in FIG. 2 has been obtained. That is, the copper coating 6 is formed on the entire surface of the ceramic body. A sixth step 16 is carried out in order to make the entire copper coating on this intermediate the counter electrode for the capacitor. The state after this sixth step 16 is executed is shown in FIG. That is, in the sixth step 16, the end face of the outer periphery of the intermediate product shown in FIG. 2 is polished to expose the ceramic body 1 from this end face. Thereby, the entire surface copper coating 6 becomes the counter electrodes 2 facing each other. The structure shown in FIG. 3 corresponds to the ceramic body 1 and counter electrode 2 in FIG. next,
The seventh step 17 and the eighth step 18 are carried out in sequence to obtain a ceramic capacitor as shown in FIG.

As is clear from the above embodiments, according to the present invention, when the surface of the copper coating of a ceramic body having a copper coating formed on its surface is brought into contact with a halogenated hydrocarbon compound, the oxidation phenomenon on the surface of the copper coating is prevented. It is extremely useful as a method for preventing oxidation of copper coatings, as it has no visible oxidation and has good solderability.

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

[Brief explanation of the drawing]

FIG. 1 is a side view showing a ceramic capacitor as an example of a ceramic electric circuit element including a ceramic body, FIG. 2 is a perspective view showing a ceramic body with a copper coating formed on the entire surface by electroless plating, and FIG. 3 is a perspective view showing a ceramic capacitor main body in which a counter electrode is formed by polishing the end face of the ceramic body shown in FIG. 2, and FIG. 4 is a block diagram showing the manufacturing process of a ceramic capacitor as an embodiment of the present invention. It is. DESCRIPTION OF SYMBOLS 1... Ceramic body, 2... Electrode, 3... Solder, 4... Lead wire, 5... Insulating resin.

Claims (1)

[Scope of Claims] 1. A method for preventing oxidation of a copper coating on a ceramic body, which comprises bringing the copper coating formed on the surface of the ceramic body into contact with a halogenated hydrocarbon compound. 2 The halogenated hydrocarbon compound is at least one selected from the group including trichlorethylene, perchloroethylene, fluorocarbon, chlorobenzene, methyl chloride, methylene chloride, chloroform, and carbon tetrachloride. A method for preventing oxidation of a copper coating on a ceramic body according to item 1. 3. The halogenated hydrocarbon compound on the ceramic body according to claim 1, wherein at least one compound selected from the group including fatty acids and higher fatty acid esters is dissolved therein. Method for preventing oxidation of copper coatings. 4. 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. 5. The copper coating on the ceramic body according to claim 1, wherein the copper coating is formed by any one of electroless plating, vacuum evaporation, sputtering, and ion plating. Antioxidant method. 6. The method for preventing oxidation of a copper coating on a ceramic body according to claim 1, wherein the ceramic body is any one of a dielectric, an insulator, a resistor, and a semiconductor. 7. A method for preventing oxidation of a copper coating on a ceramic body according to claim 1, wherein the ceramic body is a dielectric and the copper coating is an electrode for taking out a capacitance.