JP5079746B2 - Electroless nickel plating method - Google Patents

Description

The present invention relates electroless nickel plating method using the non-conductive nickel plating bath.

  Electroless nickel plating is a type of electroless plating, and is a technique for depositing a metallic nickel film on an object to be plated with electrons released by oxidation of a reducing agent contained in a plating bath. In this way, unlike the electroplating method, this method does not require energization, so that it is easier to apply plating to fine parts than with electronickel plating, and complex electrical and electronic parts can be plated. (Patent Documents 1 to 4).

  Examples of the electroless nickel plating bath include an acidic bath and an alkaline bath. In general, sodium hypophosphite is used as a reducing agent in an acidic bath. In the alkaline bath, sodium hypophosphite or a borohydride compound is used as a reducing agent, and ammonium chloride, sodium hydroxide, or hydrazine is used as an alkali source.

JP 2008-280551 A JP 2008-274444 A JP 2008-266668 Gazette JP 2008-248318 A

However, the conventional electroless nickel plating has a problem in that when the pH is increased, phosphorus ions in the plating bath are reduced, whereby the deposition rate is lowered and a plating film having low adhesion is formed. Further, when the plating bath becomes high temperature, it is difficult to form a dense plating film, and the plating bath itself is easily decomposed naturally, so that there is a problem that the stability of the plating bath itself is lowered.
Therefore, the present invention provides an electroless nickel plating bath capable of forming a plating film with excellent adhesion that can solve the above-described problems, and an electroless nickel plating method using the electroless nickel plating bath. The purpose is to provide.

The present invention has been made to solve the above-mentioned problems. In 1 L of water, 110 to 130 g / L of hypophosphorous acid, 98 to 120 g / L of nickel sulfate, 45 to 60 g / L of sodium acetate, nitric acid The object to be plated is immersed in an electroless nickel plating bath in which 0.005 to 0.025 g / L of lead, 0.003 to 0.023 g / L of thiourea, and 70 to 95 g / L of malic acid are dissolved , The electroless nickel plating method is characterized in that a nickel plating film having a silver color on the surface of the object to be plated and having a glossy mirror surface is formed . Furthermore, the above electroless nickel plating bath, and sodium hydroxide was dissolved 30 to 50 g / L as a p H buffering agent, it is desirable to adjust the PH4.8～5.3.

[Action]
By setting it as the said structure, the plating film excellent in adhesiveness is obtained. In addition, this plating film is a silver color, The surface becomes a mirror surface which has glossiness. Also, the plating bath when the p H 4.8 to 5.3, further adhesion of the plated coating is improved. The used plating bath is diluted 10 times or more with water, or disposed of after adjusting pH using caustic soda, slaked lime or quicklime.

〔effect〕
According to the present invention, a plating film having excellent adhesion can be obtained.

Electron micrograph of the plating film surface of the object to be plated in the example The electron micrograph in which the magnification is different from the electron micrograph in FIG. Explanatory drawing which shows the result table of the adhesion test (thermal shock test) of the to-be-plated object in an Example Explanatory drawing which shows the result table of the adhesion test (bending test) of the to-be-plated object in an Example Appearance photograph of the object to be plated in the example where the bending test was performed Appearance photograph of the object to be plated in the comparative example subjected to a bending test

Hereinafter, the procedure of the plating process will be described.
[Preparation of electroless nickel plating bath]
In 1 liter of ordinary water filled with pure water or non-boiling water, 110-130 g of hypophosphorous acid, 98-120 g of nickel sulfate, 45-60 g of sodium acetate, 0.005-0.025 g of lead nitrate, 0.003 to 0.023 g of thiourea, 70 to 95 g of malic acid, and 30 to 50 g of caustic soda are dissolved, and the solution is stirred while being heated to about 90 ° C. (86 ° C. to 93 ° C.), pH 4.8 to An electroless nickel plating bath is prepared by adjusting to 5.3.

[Degreasing of iron plate]
Polished iron plate (8cm x 0.3cm x 10cm) is immersed in 30-35% dilute hydrochloric acid solution for 45 seconds to 6 minutes at room temperature for acid degreasing, or immersed in alkaline solution for 1-6 minutes at 50 ° C. Then, after alkaline degreasing and acid degreasing, ultrasonic cleaning is further performed for 2 to 5 minutes, and finally, washing with water or ultrasonic water washing and hot water washing are performed. By acid degreasing, the oil can be removed, and the surface of the iron plate as the object to be treated is subjected to charge adjustment. Further, by performing ultrasonic cleaning, extremely fine deposits and oil can be removed.

[Plating treatment]
The iron plate is immersed in the electroless nickel plating bath at a plating bath temperature of 90 ° C. for 20 to 60 minutes for electroless plating treatment. Thereafter, the plated iron plate is taken out of the electroless nickel plating bath and naturally dried for 20 minutes or dried in an electric furnace to obtain an object to be plated.
The plated film of the object to be plated is excellent in decorativeness because it has a glossy silver color and has a finish close to a mirror surface. Further, there is an advantage that interference color does not appear even if the thickness of the plating film is set thin. Further, the object to be plated is excellent in hardness and corrosion resistance. In addition, the electroless nickel plating bath of the present invention is economically advantageous because it can obtain the object to be plated regardless of the number of turns.

〔Example〕
Using the object to be plated as a sample, the surface of the plating film was observed with an electron microscope (see FIGS. 1 and 2). FIG. 1 shows that the plating film of the sample has a small particle size and a small number of particles arranged on the surface of the plating film. For this reason, it turns out that the plating film of the sample concerning the present invention is densely formed.

  Using the object to be plated as a sample, a plating film adhesion test was conducted by a thermal shock test according to JIS H8504. As a result, in this sample, no peeling or blistering of plating was observed, and it was found that the adhesion was excellent (see FIG. 3).

  Using the object to be plated as a sample, a plating film adhesion test was performed by a bending test according to JIS H8504. As a result, in this sample, no peeling or blistering of plating was observed, and it was found that the adhesion was excellent (see FIGS. 4 and 5).

[Comparative Example]
As a comparative example, an iron plate subjected to a galvanizing process according to the prior art was prepared, and the iron plate was fixed to a backing metal and bent by 90 °. As a result, the coating peeled off on the iron plate (see FIG. 6).

  The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the gist of the present invention.

Claims (2)

1 L of water, 110-130 g / L of hypophosphorous acid, 98-120 g / L of nickel sulfate, 45-60 g / L of sodium acetate, 0.005-0.025 g / L of lead nitrate, 0 of thiourea 0.003 to 0.023 g / L, the object to be plated is immersed in an electroless nickel plating bath in which malic acid is dissolved in an amount of 70 to 95 g / L. The surface of the object to be plated is silver, and the surface is glossy. An electroless nickel plating method comprising forming a nickel plating film which is a mirror surface . Furthermore, above electroless nickel plating bath, and sodium hydroxide was dissolved 30 to 50 g / L as a p H buffering agent, an electroless nickel plating method regulatory claims 1 described PH4.8～5.3.