JPH0123551B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides SnO ₂ ,
The present invention relates to an electroless plating method on a substrate on which an n-type semiconductor layer such as In ₂ O ₃ or TiO ₂ is formed.

Conventionally, when performing electroless plating on an insulator substrate,
Various treatments have been applied to improve the adhesion of plating films. For example, the surface of an insulator substrate may be mechanically polished, or chemically polished using hydrofluoric acid and chromium mixed acid, or both may be treated, followed by immersion in SnCl ₂ solution, water washing, and PdCl ₂
The plating film was formed through a process of immersion in a solution, washing with water, and immersion in an electroless plating solution. However, improving adhesion has been a problem with electroless plating on insulating substrates.

However, by forming an n-type semiconductor layer on an insulating substrate, the adhesion of the plating film has been significantly improved. The plating process in this case was also the same as described above. However, although the adhesion of the plating film has improved, another problem in electroless plating on an insulator, that the plating surface becomes cloudy, remains unsolved. The white cloudy areas are areas where the plating film is unevenly applied.
In addition, although these parts were not visible to the naked eye, many pinholes were observed under a transmission microscope.

This unevenness seems to be related to the thickness of the palladium layer on the surface of the insulator substrate, and it appeared that the palladium layer was not uniform on the surface of the insulator substrate that was still wet with water. Therefore, after soaking in PdCl ₂ and rinsing with water, a blowing force was applied by rotation to forcibly blow away the excess palladium in an attempt to obtain a palladium surface as uniform as possible. The plated body obtained by the electroless plating method of the present invention has very few pinholes, no plating unevenness, and has an extremely glossy and uniform plated surface.

In order to use plating for exterior parts and decoration, it is essential that it has a uniform luster, and that there are no pinholes makes it possible to use electroless plating for light-shielding parts such as optical shutter parts and photomasks. This is a condition for use.

The electroless plating process of the present invention is as follows.

Vapor deposition or sputtering on an insulating substrate
SnO ₂ , TiO ₂ ,
After forming an n-type semiconductor layer such as In ₂ O ₃ , the surface was cleaned by ultrasonic cleaning with an alkaline aqueous solution, for example, a 3% KOH aqueous solution. Thereafter, it was washed with water, neutralized with an acidic aqueous solution, for example, a 3% aqueous H ₂ SO ₄ solution, and washed with water. Next, the usual pretreatment for electroless plating was performed.

That is, the insulating substrate was immersed in an acidic aqueous solution of stannous chloride and washed with water. This is called sensitizing, and divalent tin ions are adsorbed onto the substrate surface. Next, the insulating substrate was immersed in an aqueous palladium chloride solution and washed with water. This is called activating, and the divalent tin ions in the previous sensitizing release electrons to divalent palladium ions to become valent tin ions, and the divalent palladium ions form metal palladium on the surface of the insulator substrate. It precipitates out.

Sn ² + Pd ²⁺ →Sn ⁴⁺ Pd ⁰ ...(1) This metal palladium is said to act as a catalyst nucleus for subsequent plating. However, according to recent research reports, it is said that the reaction is not as simple as the one shown in equation (1) above, but that a colloid of tin and palladium serves as the catalytic core.

After drying the insulating substrate thus obtained by blowing off excess catalyst nuclei with a spinner,
It was immersed in a predetermined electroless plating bath maintained at an appropriate temperature. Examples of electroless plating baths include nickel plating baths, cobalt plating baths, copper plating baths, and the like.
The plating film thus obtained did not become cloudy and had extremely few pinholes.

This will be explained in detail below using examples.

Example A SnO ₂ film was formed on borosilicate glass (80×120 mm) using CVD. This glass substrate was placed in an aqueous solution of 3% KOH at 65°C and subjected to ultrasonic cleaning.
Thereafter, it was washed with water, neutralized with a 3% H ₂ SO ₄ aqueous solution, and washed with water. Then add SnCl ₂ aqueous solution (SnCl ₂ 1g/,
The glass substrate was immersed in HCl1c.c./) for 5 minutes, washed with water, and then immersed in a PdCl ₂ aqueous solution (Redshumer, manufactured by Kanigen Co., Ltd.) for 5 minutes, and dried with a spin dryer after washing with water. When it was immersed for 10 minutes in an electroless Metzkel bath (Schumer S680, manufactured by Kanigen Co., Ltd.) kept at 45°C, a beautiful mirror-like nickel plating film with no clouding was obtained.

Comparative example The same insulator substrate as in the above example was prepared in the same process.
Immersion in PdCl ₂ aqueous solution was performed. Immediately after washing the insulating substrate with water, it was immersed in a similar electroless nickel bath for 10 minutes, resulting in a thin white cloudy appearance on the plated surface.

As can be seen from the above, it was found that a beautiful glossy plating film could be obtained by drying the insulating substrate before being immersed in a nickel bath. There were almost no pinholes in the plated body obtained by the process according to the present invention, but quite a lot were observed in the conventional process without a drying step.

Application Example A panel for imprinting the date on a camera was made using an electroless nickel plating body formed in the same manner as in the above example. Figure 1 shows its outline. Reference numerals 1 and 2 are front and rear substrates each made of borosilicate glass and having a thickness of 0.4 mm. 3,
4 is a transparent electrode (SnO ₂ ) formed into a predetermined pattern by CVD. 5 is a nickel plating film formed by the same method as in the example,
It has a thickness of 2000 Å. 6 is a sealant made of epoxy resin containing a gapping agent of 10μ, and 7 is a liquid crystal usually used for display bodies.

This panel is used as shown in Fig. 2, and the nickel plating has the purpose of blocking light as indicated by the broken line in the figure.

As described above, according to the present invention, an insulator substrate on which an n-type semiconductor layer is formed is subjected to alkali ultrasonic treatment and acid immersion, and then immersed in a SnCl ₂ solution and a PdCl ₂ solution, and further processed using a spinner. By drying and removing excess catalyst nuclei along with moisture,
It is possible to obtain an electroless plating film that has a uniform and mirror-like surface and does not affect adhesion in any way.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a liquid crystal panel for imprinting the date. 1, 2...Front and back substrate, 3, 4...Transparent electrode, 5
...Nickel plated part, 6...Sealing material, 7...Liquid crystal. FIG. 2 is a diagram showing the date imprinting mechanism of the camera. 8... Lamp (light source), 9... First panel, 10
... Panel support, 11... Photographic film.

Claims (1)

[Claims] 1. After immersing an insulating substrate on which an n-type semiconductor layer is formed in an alkaline solution and irradiating it with ultrasonic waves,
a step of immersing the insulating substrate that has gone through the above step in an acidic solution and then washing it with water; a step of immersing the insulating substrate that has gone through the above step in an aqueous SnCl ₂ solution and then washing it with water; A step of immersing the insulator substrate in a PdCl ₂ aqueous solution and then washing it with water, a step of drying the insulator substrate that has undergone the above step using a spinner, and a step of immersing the insulator substrate that has gone through the above step in an electroless plating solution. An electroless plating method characterized by comprising the steps of plating.