JPS62250179A - Surface treatment of ceramic - Google Patents

Abstract

PURPOSE:To provide electric conductivity to a ceramic substrate by subjecting the surface of the ceramic substrate to degreasing, etching with an acid soln. and electroless plating so as to metallize the surface. CONSTITUTION:The surface of a ceramic member 1 is degreased with an org. solvent contg. chlorine and the member 1 is immersed in an aqueous soln. contg. hydrofluoric acid, nitric acid and other inorg. acid to etch the surface. The surface is then sensitized and activated as usual and a Cu layer 2, an Ni layer 3 and an Ay layer 4 are successively formed by electroless plating. Thus, superior electric conductivity is provided to the ceramic member of Si3N4, SiC Al2O3, ZnO2, Cr2O3- added Al2O3 or the like having high hardness, superior wear, corrosion and heat resistances, so the utilization range can be considerably extended.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of surface treatment on the surface of a substrate made of ceramics.

[Prior art] As is well known, with the development and manufacturing of semiconductor devices,
Today, everything from home appliances to industrial equipment is becoming smaller and lighter.
Higher speed, higher density, and higher reliability.

The demand for low prices is becoming increasingly strong, and technological innovation is constantly being developed.

Among these trends, engineering ceramics have recently been attracting attention.

Engineering ceramics are different from conventional ceramics, and are made with industrially advanced materials such as silicon nitride, silicon carbide, alumina, zirconia, chromium oxide-added alumina, barium titanate, zinc oxide, aluminum alloy, etc.
and? ) Seed sintered ferrite etc.

Although engineering ceramics are typical brittle materials, they have a high reflectivity compared to ducks and plastics, and have excellent wear resistance, corrosion resistance, and 1IIH heat resistance, and depending on the type of additives, they have high thermal conductivity.

In addition, with the increase in the number of communications stations and the development of wide-area communication systems, there is a demand for miniaturization of microwave circuits.

The miniaturization of microwave circuits is based on the wavelength of electromagnetic waves.
In general, it will be as follows, D middle □ ・・・・・・・・・ (1) J
q D: Diameter f of dielectric resonator Resonance frequency C: Speed of light εr: Relative permittivity Two Length L of coaxial resonator L Length of strip line ε-=0.6~0.9εr ...~(31 As shown in the equation, it has been found that a material with a large dielectric constant (Cer) is desirable for downsizing microwave circuits, and secondary ring ceramics are the most promising material in this respect.

As mentioned above, methods have been established to utilize material properties such as high hardness, corrosion resistance, abrasion resistance, heat resistance, and dielectric constant, but in addition to the brittleness of the material.

Electrical conductivity is poor, and by applying surface treatment technology to the surface of a ceramic base material and metallizing it, electrical conductivity can be imparted to the surface of the ceramic base material, further expanding the field of application. is expected.

Examples of such surface treatment techniques include a) screen printing method, b) vacuum evaporation/sputtering method, and c) electroless and electrolytic plating method.

[Problems to be Solved by the Invention] The following problems occur in the surface treatment method for applying a film with good heat resistance and excellent electrical conductivity to the surface of a base material made of ceramics for garden trees as described above. There are several points.

That is, according to the above method (A1), an electronic circuit is printed on the surface of a base material made of ceramics by a screen printing method using a conductive paste of gold, silver, palladium, copper, etc. as a printing ink. The necessary electronic circuit is obtained by baking the ceramic substrate onto the surface of the ceramic substrate at the optimum sintering temperature for each conductivity in the range of 0,000°C.

In addition, in the cell method, after printing the above-mentioned conductive paste on the entire surface of the ceramic base material using a screen printing method, only the required electronic circuit parts are baked at the optimum temperature for each conductive material (for example, using a laser device), and then , unnecessary parts other than the required electronic circuits are melted and removed.

The electrical conductivity of the above conductive paste is on the order of 1G-40-, which is insufficient for the characteristics required for electronic circuit components and microwave circuit components.

According to method 1 above, a base material made of ceramics is placed in a vacuum or sputtering apparatus, and a required metal, for example chromium, is deposited with the required degree of tolerance.

Nickel, copper, gold, titanium, aluminum.

This involves heating and melting an alloy, etc., and depositing it on a ceramic substrate.

In the above method, the metallized layer is relatively thick, e.g.
It takes a long time (approximately 5 hours or more) to form a film of 000 Å or more, and even if it can be made thick, it is only a few μm thick, making it difficult to put into practical use.In addition, it is applicable to products with complex shapes. There are limits to what you can do.

If method 1) is used, the required electroless plating is performed on the surface of the ceramic base material using hfA after pretreatment.
Then, the required electrolytic plating is performed.

Such a method is proposed in detail in Japanese Patent Publication No. 54-24405.

However, according to the above-mentioned Japanese Patent Publication No. 54-24405, in a method in which copper is electrolessly plated on a ceramic substrate and then electrolytically plated on the electroless plating soil, the temperature is once at 11°C and once at 20°C.

As a result of changing the curve during plating in the range of 30"G and 40°C, and examining the occurrence of electroless phenomenon from t, it was found that the electroless phenomenon of electroless copper plating depends on the thickness of the copper plating layer and the ceramics used. However, in the case of electroless plating, this phenomenon is caused by the surface area of the product and the metal content in the metal salt added at the time of preparing the plating solution during electroless plating. It is shown by the relationship.

Plating thickness x Specific gravity of metal It is a method that
It is thought that the non-electrostatic phenomenon of electroless plating occurs because a processing method for plating IT+i has not been established.

In addition, in electroless and electrolytic plating methods, the electroless plating method can apply a thick plating, but the long cleavage time can be reduced by the electroplating method, which can be done in a short time.

Although it has the advantage of adding various amounts of money, it cannot be applied if the shape of the product becomes complex.

There was a problem.

This invention was made to solve the above-mentioned problems, and its purpose is to metallize the surface of a ceramic substrate by a relatively simple method. Moreover, it is an object of the present invention to provide a method for providing a treatment layer having desirable heat resistance and electrical conductivity.

[Means for solving problems]

As a result of extensive research, the surface treatment method for the surface of a base material made of ceramics according to the present invention was developed by degreasing the surface of a base material made of ceramics using a conventional method, and then treating the surface with hydrofluoric acid, nitric acid, and an inorganic acid salt. It has been discovered that the above object can be achieved by immersing it in an aqueous solution for a required period of time for etching, and then plating it with electroless copper, electroless nickel, or electroless gold to the required thickness, and has completed the present invention. Ta.

Namely, 1. The method of surface treatment on the surface of a substrate made of ceramics according to the present invention requires obtaining appropriate surface roughness and heat resistance in order to improve the adhesion of the plating film.

Considering the combination of metals to improve electrical conductivity,
Furthermore, it is characterized in that it can be completely plated using electroless plating, which can be plated without considering current distribution so that it can be applied to products with complex shapes.

The history will be explained in detail below.

In the surface treatment method of the present invention, first, degreasing is performed using a chlorinated organic solvent or the like in order to remove fats and oils attached to the surface of a base material made of ceramics.

In the surface treatment method of the present invention, the surface of a ceramic substrate is placed in an aqueous solution containing hydrofluoric acid, nitric acid, and an inorganic acid in order to obtain an appropriate surface roughness for improving the adhesion of the plating film. After soaking and etching for the required time, sensitizing and activating using conventional methods, and then plating with electroless steel, electroless nickel, and electroless gold to form a metallized layer with good heat resistance and electrical conductivity. You get it.

[Function] In this invention, the adhesion of the plating film is ensured by degreasing the plating surface and proper etching, and then the metallizing layer is formed without using any external source, thereby eliminating the fateful problems of electrolytic plating. The film thickness at the irregularities and edges of the article, which is a drawback, can be made nonuniform, and even articles with complex shapes can be plated without using an auxiliary electrode, eliminating plating defects.
Since the ILs portion is equal to fj (fl), the quality is stable.

Furthermore, since the electroless nickel coating and electroless gold plating coating are stable at high temperatures, they are stable even at soldering temperatures and can provide good electrical conductivity.

〔Example〕

In the following, 1′=Ali! [5'lJ This invention will be explained in more detail using an example.

Figure 1 shows the thermal changes in infrared emissivity for various plating specifications, where specimen number 111 (2) is electroless steel plated and ten electrolytic gold plated, and (3: electroless gold plated). Steel plating 10 electroless gold plating, 141, 151 electroless silver plating 10 electroless gold plating, +61.171 electroless silver plating 10 electroless gold plating, 1B+, (91 electroless nickel + electrolytic gold plating Gold plating, tlQ, uυ are electroless nickel plating and electroless gold plating.

The valley specimen was held at a temperature of 200 to 290° C. for 4 hours at each time, and after heating JIF, the infrared emission rate was measured as a guide for stationary grasping, and the change around 0 is illustrated.

As is clear from Fig. 1, at a baking temperature of 290°C, the change in infrared emissivity of each plating specification is '&'; There was little change before and after, which was enough for practical use, and showed the best thermal stability.

FIG. 2 shows the measurement results of the specific resistance values of each electroless plated film. The specific resistance value of each plated film obtained is close to that of pure metal.

In general, the electrical resistance of a film may take into account the skin effect, such as in contact type electronic equipment and electronic equipment commonly used in high frequency bands (for example, quasi-mi'1 wave? tr%).

In the case of a contact type, the electrical At conductivity is determined by the resistance value of the top layer plating film, but in the case of electric equipment used in high frequency bands, the resistance value of the entire plating film JIQJψ must be considered. There's dinner.

As an example, let us explain using the cross-sectional view of the plating film in Fig. 3. In Fig. 0, 11) is ceramic.

(2) is an electroless copper plating layer, (3I is an electroless nickel plating layer, and 141 is an electroless gold plating layer.

As shown in Figure 3, the radiation (Wl), the ceramics (
1) Electroless copper plating (21, electroless nickel (3;
, Considering the example of electroless gold plating (4), the following results are obtained.

Resistance of gold plating film + 41 (R1) j, = + = Resistance of gold plating thick nickel film (3) (R2) ρ2 = Specific resistance value of nickel plating film 12 = Nickel plating thick copper plating film (2) Multiple resistance (R5) ρ5 = Specific resistance value of copper plating film [38 From the relational expression of copper plating thickness 151, 161, +71, the combined resistance formula is as follows.

・・・・・・ta+ becomes.

(From the results of formula 81 and Figure 2, the thickness of electroless nickel plating should be as thin as possible, the thickness of electroless copper plating (2:), and the thickness of electroless gold plating (4) should be as thick as possible. By doing so, the total resistance of the plating film is lowered, and a film with good electrical conductivity can be obtained.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to easily apply plating to articles with complex shapes, which has been desired for many years, and the heat resistance at high temperatures (e.g., 300°C) is improved. Therefore, it is expected that it will be widely used in the future.

For example, it is highly anticipated for surface treatment of three-dimensional circuit components used in the quasi-millimeter wave band, and high reliability can be guaranteed.

[Brief explanation of drawings]

Figure 1 is a diagram showing thermal changes in infrared emissivity for various plating specifications, Figure 2 is a diagram showing the measurement results of specific resistance values of each electroless plating film, and Figure 3 is a cross section of the plating film. It is a diagram. M width-III 1! -h'x 2"IN?
IQI l-+ d-ku'WI WaG Buddha^1c layer・(
31 is an electroless nickel plating layer, and (4) is an electroless gold plating layer.

Claims (1)

[Claims] After degreasing a ceramic article of a desired shape by a conventional method, it is etched by immersing it in an aqueous solution containing hydrofluoric acid, nitric acid, and an inorganic acid salt for a required period of time, and then sensitized and activated by a conventional method. Electroless copper plating, electroless nickel plating, and electroless gold plating of the required thickness are performed in order to form multiple plating layers, and the electroless nickel plating film and electroless gold plating film are coated at high temperature ( 1. A method of surface treatment on ceramics, characterized in that stability against temperatures (for example, 300° C.) and good electrical conductivity are obtained.