JPH0419177B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an improvement in a method of metallizing a glass surface using electroless plating, and particularly to a method in which a pretreatment step prior to metallization by electroless plating is improved. [Prior art] For example, when forming electrodes on a glass substrate,
A metallization method using electroless plating is widely used. During metallization, in order to uniformly and firmly adhere the metal thin film to the glass surface, the glass surface is polished in advance to make it uneven, or chemical treatment is performed using an aqueous solution of nitric acid, sulfuric acid, or hydrofluoric acid. Etching is being done. [Problems to be Solved by the Invention] However, in the conventional glass metallization method described above, even if irregularities are formed on the surface or chemical etching is applied, the adhesion strength of the metal film due to electroless plating is insufficient. was not sufficient. In addition, when performing pretreatment using a strong acid,
When the concentration of strong acid is increased, steam containing the strong acid tends to accumulate in the surrounding area, which tends to cause corrosion of surrounding equipment and causes environmental pollution. Furthermore, glass is difficult to be etched even with strong acids, and therefore requires etching operations using highly concentrated strong acids at high temperatures and over long periods of time. Further, as mentioned above, the adhesion strength is not necessarily sufficient, and as a result, a phenomenon called "puffer" where the formed metal thin film encapsulates liquid such as plating solution and stretches, tends to occur. When "blowfishing" occurs, not only is the metal thin film partially not formed, but the plating solution contained therein leaks, causing a decrease in the concentration of the plating solution and contamination of the cleaning solution. Therefore, when a large number of glass substrates are sequentially electrolessly plated, it is difficult to uniformly form a metal thin film on the surface. Therefore, an object of the present invention is to provide a method for metallizing a glass surface, which can perform pretreatment in a short time and easily increase adhesion strength without using dangerous chemicals for a long time. It is in. [Means for Solving the Problems] The method for metallizing the glass surface of the present invention involves mechanically roughening the glass surface, forming a metal thin film on the glass surface by electroless plating, and then forming the metal thin film on the glass surface by electroless plating. The method includes a step of heat-treating the glass surface to firmly adhere, diffuse, or react with the glass surface, a step of chemically etching the thin film, and a step of metallizing the glass surface by electroless plating after etching. That is, in this invention, a metal thin film is temporarily formed by electroless plating even in the pretreatment step of the final step of metallizing the glass surface by electroless plating, and this metal thin film is chemically coated after heat treatment. It is characterized by etching. As the glass to which this invention is applied, acid-resistant glass such as Pyrex (trade name of Corning Inc.) can be exemplified. Mechanical roughening of the glass surface preferably includes:
It is done to a roughness of #400 to #2000. As a result, a thin metal film can be formed uniformly in the pretreatment process, and therefore the chemical etching performed later can be uniformly performed. Further, as the material constituting the metal thin film formed in the pretreatment step, any material capable of electroless plating, such as copper or nickel, can be used. The thickness of the metal thin film formed in the pretreatment process is approximately 0.1 to 0.5 μm, preferably 0.3 μm in chemical analysis film thickness.
That's about it. This is because if the thickness is less than 0.1 μm, it will be difficult to uniformly metalize the glass surface even if the subsequent process is carried out, whereas if the thickness exceeds 0.5 μm, smudges will occur as the metal thin film grows. Because it does. The heat treatment performed after the formation of the metal thin film is as follows:
In order to firmly adhere, diffuse or react the metal thin film to the glass, the process is carried out in an oxidizing atmosphere, neutral atmosphere or reducing atmosphere. In addition, the heat treatment temperature is
It is carried out at a temperature of 400-800°C. This is because glass deforms when the temperature exceeds 800°C. Therefore, this temperature range varies depending on the heat resistance of the target glass, and is not necessarily critical. However, on the low temperature side, it is preferable to heat at a temperature of 400° C. or higher in order to ensure the diffusion or reaction of the metal thin film into the glass substrate. When performing chemical etching for heat treatment,
For example, dilute hydrochloric acid, dilute nitric acid or hydrofluoric acid aqueous solution can be used, and this etching can be carried out at a temperature of 100° C. or less and in a short time of about 10 minutes. The metallization applied after etching is the same as the conventional method, and is carried out by electroless plating as usual. Alternatively, a metal thin film may be formed by electrolytic plating after electroless plating. [Operations and Effects] In the present invention, a thin metal film is formed on the glass surface in a pretreatment step prior to the intended metallization. This thin film formed in the pretreatment step is then chemically etched to facilitate subsequent metallization. When the glass surface itself is chemically etched to form a fairly thick thin metal film in one treatment, as in the conventional method, as mentioned above, the adhesion strength is weak, and as the film thickness increases, blemishes occur. However, the present invention can solve such problems. That is, since the thin film once formed is etched rather than the glass surface, chemical etching can be carried out in a short time without using a highly concentrated strong acid. Therefore, low concentration acids such as dilute nitric acid, dilute hydrochloric acid, and hydrofluoric acid aqueous solutions can be used, and therefore work can be carried out in a safer environment and does not cause environmental pollution problems. . Further, since the thin film is formed thin and removed by chemical etching, there is almost no reduction in electrical conductivity of the finally formed metal thin film. Furthermore, since the metal thin film can be easily etched, the processing time for chemical etching can be significantly reduced compared to conventional methods, and therefore the processing time for the entire metallization method can also be significantly reduced. This invention is suitable for applications where a strong and uniform metal thin film is required to be formed on the glass surface, such as when forming electrodes on a glass substrate, but it also requires metallization of the glass surface. It should be pointed out that it can be used for general purposes. [Description of Examples] A 1 mm thick Pyrex glass substrate (#7740: Corning Co., Ltd. product) was prepared as a glass substrate to be metallized. The surfaces of the prepared glass substrates were polished to polishing roughnesses of #400, #600, #1000, and #2000, respectively. After polishing, each glass substrate was degreased and cleaned, and then etched using a 0.5% hydrofluoric acid aqueous solution at a temperature of 60° C. for 9 minutes. Next, the surface of this glass substrate is sensitized and activated,
A copper thin film with a thickness of 0.3 μm (thickness is based on chemical analysis film thickness) was formed by electroless copper plating method. After copper plating, each glass substrate was heat treated in an oxidizing atmosphere at a temperature of 500 to 800°C for 30 minutes. After heat treatment, each glass substrate was treated with 0.5% hydrofluoric acid and
Etching was performed by immersion in an aqueous solution containing 1.5% hydrochloric acid at a temperature of 60° C. for 9 minutes. Thereafter, sensitization and activation were performed again. Next, electroless copper plating was applied again to a film thickness of 3.5 μm (according to chemical analysis film thickness).
Finally, the plated glass substrate was heat treated at a temperature of 600° C. for 30 minutes in a nitrogen stream. The electrical conductivity of the copper thin film formed on the surface of the glass substrate obtained as described above was measured at the measurement frequency.
Measured at 3.045GHz. The results are shown in Table 1 below.

[Table] From Table 1 above, for those that were not polished in the pre-treatment process, the heat treatment temperature was 500
It can be seen that "pufferfish" is produced at ~600℃. Therefore, it can be seen that if the glass surface is roughened in advance to #400 or higher, a thin film that does not cause any scratches can be reliably formed, and the desired electrical conductivity can therefore be achieved. Next, we measured the thickness of the copper thin film finally formed on each glass substrate, and found that it was 3.53 μm ± 0.14 μm.
(Based on chemical analysis film thickness). The adhesion strength of the formed copper thin film is shown in Table 2 below.

[Table] *2: Degree of polishing before etching The density strength in Table 2 is the value measured by soldering a lead wire to a thin film with an area of 2 x 2 mm and pulling the lead wire with a tensile tester. It is. From Table 2, in the case of non-polishing, even if heat treatment was performed at 700 to 800°C, the adhesion strength was insufficient and could not be measured. It can also be seen that the adhesion strength is the highest when polished with #400 to 600, and especially when polished with #400 to 600 and heat treated at 600°C. In the above-mentioned embodiment, the etching performed after mechanically roughening the glass surface and before the first electroless plating cleans the roughened glass surface and removes the roughened surface. This is to remove the polishing powder left after polishing. If polishing powder remains on the glass surface and the next electroless plating is performed in this state, the polishing powder will decompose the plating bath, shortening the life of the plating bath. Become. Etching is performed to avoid such problems, and if the polishing powder is sufficiently removed by cleaning after polishing, there is no need to perform such etching.

Claims (1)

[Claims] 1. Mechanically roughening the glass surface, forming a metal thin film on the glass surface by electroless plating, and then firmly adhering, diffusing or reacting the metal thin film to the glass surface. 1. A method for metallizing glass, comprising: a step of heat-treating the thin film; a step of chemically etching the thin film; and a step of metallizing the glass surface by electroless plating after the etching.