JPS6119782A - Copper colloid catalyst solution - Google Patents

Abstract

PURPOSE:To provide a catalyst solution for electroless plating good in the precipitation property to the through-hole wall of a plastic laminate plate, constituted of an aqueous copper colloid solution with predetermined pH containing copper metal particles and gelatin in specific concn. CONSTITUTION:This catalyst solution for electroless plating comprises an aqueous copper colloid solution with pH 2-4 containing 0.3g/l or more of copper metal particles and 0.8g or more per 1g of copper metal particles of gelatin. In preparing this aqueous solution, 1.2g or more per 1g of a divalent copper ion of dimethylaminoborane is added to an aqueous solution with pH 1-2 and temp. of 40-70 deg.C containing the divalent copper ion and 0.8g or more per 1g of the divalent copper ion of gelatin. After the divalent copper ion was reduced to metal copper, the pH of this aqueous solution is adjusted to 2-4. The aforementioned catalyst solution by this nethod is used, for example, in the preparation of a printed wiring board and the electroless copper plating coating to the through- hole wall of a copper clad epoxy resin laminated plate can be perfectly performed.

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a copper colloidal catalyst solution for electroless plating and a method for producing the same, particularly for activating an electrically insulating material such as plastic to prepare it for a metal coating process by electroless plating. The present invention relates to a copper colloidal catalyst solution for

(Prior Art) In general, in the electronics industry, it is widely practiced to coat plastics with metals by electroless plating to make them conductive. For example, in the production of printed wiring boards, after through-holes are formed at desired positions on the surface of a copper-clad epoxy resin laminate, a catalyst for non-remission plating is adsorbed onto the walls of the through-holes, and then electroless plating such as electroless copper plating is performed. It is recommended that a metal coating be applied to the wall surface of the through hole to make the wall surface conductive.

Palladium metal is generally used as a catalyst for electroless plating, and palladium metal is formed on the wall surface of the through hole by bringing the wall surface of the through hole into contact with a mixed colloidal aqueous solution of stannous chloride and palladium chloride, and then washing with water. Palladium metal and a tin compound are simultaneously adsorbed onto the wall surface of this through hole. In order to serve as a catalyst for electroless plating, the tin compound adsorbed at the same time as the palladium metal must be removed by immersion in a hydrochloric acid solution or a fluoroboric acid solution to expose the palladium metal. However, when immersed in the above acid aqueous solution,
Palladium metal may also be removed at the same time as the tin compound is removed. In particular, palladium metal is easily removed from the glass surface of the through-hole wall of a copper-clad epoxy resin laminate, and the presence of abrasives causes poor electroless copper plating deposition on the through-hole wall.

(Object of the Invention) It is an object of the present invention to provide a novel catalyst liquid for electroless plating that eliminates the drawbacks of the conventional catalyst liquid for electroless plating, and a method for producing the same.

(Structure of the Invention) The catalyst solution for electroless plating of the present invention has a concentration of copper metal particles of 0.3 g/Q or more and 0.8 gelatin per 1 g of copper metal particles.
P) Containing 12 to 4 g or more of copper colloid aqueous solution, the copper colloid aqueous solution having a pH of 1 to 2 containing divalent copper ions and 08 g or more of shizelatin per 1 g of divalent copper ions, and a liquid temperature of 40 to 70°C. 1 per gram of divalent copper ion in an aqueous solution of
, 2 g or more of dimethylamine borane is added to reduce divalent copper ions to metallic copper, and then the pH of the aqueous solution is adjusted to 2 to 4.

In the production of the copper colloidal catalyst solution of the present invention, sulfuric acid steel or hydroxide dihydroxide can be used as the divalent copper ion source, and sulfuric acid and sodium hydroxide, potassium hydroxide, etc. can be used to adjust the pH of the aqueous solution. is used. When divalent copper ions are reduced with dimethylamine borane, bubbles are generated as hydrogen gas is generated, but in order to reduce bubbling in the aqueous solution and make the reduction reaction of divalent copper ions uniform, butyl Even if an antifoaming alcohol such as alcohol is used, the divalent copper ions reduced by dimethylamine borane become copper metal particles, and are protected by gelatin to form colloidal particles (copper colloid). do. Steel colloids are stable below P)J4, and when the pH reaches 4, they coagulate and precipitate. In addition, adsorption to the through-hole walls of a copper-clad epoxy resin laminate is excellent when the pH of the copper colloid catalyst solution is 2 to 4. The film (which is coated with the coating) is easily removed by washing with water, and the copper metal particles remain on the walls of the through-holes, where they act as a catalyst for electroless plating. The appropriate concentration of copper metal particles in the copper colloidal catalyst solution is 0.3 g/λ or more.
J) When s 03 g/β also decreases, the adsorption of copper colloids decreases significantly.

(Example) The present invention will be explained in detail below using examples.

[Example-1] 10 g of gelatin was added to about 700 mjL of pure water, and the gelatin was completely dissolved in the pure water at a liquid temperature of about 60°C. Next, 24.9 g of copper sulfate (CuSO4, 51120) was added and completely dissolved, and the pH of the aqueous solution was adjusted to about 1.8 with an aqueous sulfuric acid solution. Next, a concentration of 100 g/l. Add 100ml of dimethylamine borane aqueous solution of
The copper ions were completely reduced to metallic copper at ℃. In addition, use 20m of butyl alcohol as an antifoaming agent! Added. The temperature of the aqueous solution was cooled to room temperature, and the volume of the aqueous solution was adjusted to IL by adding pure water to produce a concentrated solution of copper colloidal catalyst solution. The concentration of copper metal particles in this solution is 6.3g/L The concentration of gelatin is 10
g/I1. It is.

[Example 2] The concentrated copper colloidal catalyst solution prepared in Example 1 was diluted with pure water to obtain a copper metal particle concentration of 1 g/II=.

Gelatin concentration 1.58 g/I1. A copper colloidal catalyst solution with pH=3 was prepared. A copper-clad jepoxy resin plate with through-holes formed in this copper colloidal catalyst solution was heated to 4.
After soaking at 0°C for about 1 minute, rinse with water for 1 minute, then soak at 25°C.
The sample was immersed in an electroless copper plating solution having a pH of 13 for about 10 minutes, and the deposition properties of electroless copper plating on the walls of the through hole were examined. A cross-sectional observation of the through-hole wall confirmed that the through-hole wall was completely coated with electroless copper plating.

[Example-3] The concentrated solution of the copper colloidal catalyst solution prepared in Example-1 was diluted with pure water, and the concentration of copper metal particles was 0.3 g/λ.

A copper colloidal catalyst solution with a gelatin concentration of 4.76 g/It and a pH of 3 was prepared, and electroless copper plating was performed on a copper-clad epoxy resin laminate using the same procedure as in Example-2.

(Effects of the Invention) As described above, the present invention has excellent deposition properties of electroless copper plating on the walls of through holes, and the practicality of the present invention has been verified.

Claims (2)

[Claims] (1) A copper colloidal catalyst solution for electroless plating consisting of an aqueous solution having a pH of 2 to 4 and containing 0.3 g/l or more of copper metal particles and 0.8 g or more of gelatin per 1 g of copper metal particles. (2) Contains divalent copper ions and 0.8 g or more of gelatin per 1 g of divalent copper ions, pH 1 to 2, and liquid temperature 40 to 7.
An electroless method consisting of the process of adding 12 g or more of dimethylamine borane per 1 g of divalent copper ions to an aqueous solution at 0°C to reduce the divalent copper ions to metallic copper, and then adjusting the pH of the aqueous solution to 2 to 4. A method for producing a copper colloidal catalyst liquid for copper plating.