JPS62263972A - Colloidal solution for copper catalyst for electroless plating and its production - Google Patents

Abstract

PURPOSE:To produce a colloidal soln. of a Cu catalyst causing no defective deposition of plating on a wall having through holes by adding dimethylamineborane to an aqueous soln. contg. Cu ions, a specified amount of gelatin and polyethylene glycol to reduce the Cu ions and by adding sodium hypophosphite. CONSTITUTION:An aqueous soln. of 1-4 pH contg. bivalent Cu ions in the form of copper sulfate or the like, gelatin by >=0.8g per 1g Cu ions and polyethylene glycol having 1,000-10,000 average mol.wt. is prepd. Dimethylamineborane is added to the soln. by >=1.2g per 1g Cu ions to reduce the Cu ions to metallic Cu at 40-70 deg.C. The soln. is then heated to >=70 deg.C and aged for a desired time to perfectly hydrolyze the unreacted dimethylamineborane. After sodium hypophosphite is added and dissolved, the pH of the resulting soln. is adjusted to 2-4 to obtain a colloidal soln. of a Cu catalyst for electroless plating.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a colloidal copper catalyst solution for electroless plating and a method for producing the same, and more particularly to an electrically insulating material.

In particular, the present invention relates to a copper colloid catalyst solution for activating plastics and preparing them for a metal coating process by electroless plating.

[Conventional technology]

Generally, in the electronics industry, plastics are coated with metal by electroless plating to make them conductive. For example, in the production of printed wiring boards, after forming through holes at desired positions on the surface of a copper-clad epoxy resin laminate,
It is practiced to adsorb an electroless plating catalyst on the wall of the through hole, and then apply a metal coating to the wall surface of the through hole by electroless plating such as electroless steel plating to make the wall surface of the through hole conductive.

Palladium metal is generally used as a catalyst for electroless plating, and palladium metal is formed on the walls of the through-holes by contacting the through-hole walls with a mixed colloidal aqueous solution of stannous chloride and palladium chloride, and then washing with water. do. 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.

[Problem that the invention seeks to solve]

In the conventional electroless plating catalyst using palladium metal, when immersed in an acid aqueous solution, the palladium metal may be removed simultaneously with the removal of the tin compound. In particular, palladium metal is easily removed from the glass surface of the through-hole wall of a copper-clad epoxy resin laminate, often causing poor electroless steel plating deposition on the through-hole wall.

An object of the present invention is to provide a novel method for producing a catalyst liquid for electroless plating that eliminates such conventional drawbacks.

[Failure to solve the problem]

The catalyst solution for electroless plating of the present invention has a concentration of copper metal particles of 0.3 g/or more and a gelatin content of 0.3 g/g/g of copper metal particles.
8 g or more of polyethylene glycol with an average molecular weight of 1,000 to 100,000 and 0.8 g or more of a copper colloid aqueous solution with a pH of 2 to 4 containing sodium hypophosphite,
The aqueous copper colloid solution contains divalent copper ions, 0.8 g or more of gelatin per 1 g of divalent copper ions, and 0.8 g or more of gelatin with an average molecular weight of 1.000 to io0. oo.

per gram of divalent copper ion in an aqueous solution of pt-i 1 to 4 containing polyethylene glycol After adding 1.2g or more of dimethylamine borane, the liquid temperature ranges from 40℃ to 70℃.
After reducing copper ions to metal steel within a range not exceeding Manufactured by adjusting to.

In the production of the copper colloidal catalyst liquid of the present invention, steel sulfate or cupric hydroxide can be used as the divalent copper ion source, and sulfuric acid and sodium hydroxide or potassium hydroxide can be used to adjust the pH of the aqueous solution. be done.

Average molecular weight used in the present invention 1,000 to 100,000
The polyethylene glycol controls the rate of reduction of divalent copper ions by dimethylamine borane and contributes to the production of micro steel metal particles, and the amount added is 10.0% per gram of divalent copper ions. S g or more is appropriate. Divalent copper ions become steel metal particles due to dimethylamine borane, and are protected by gelatin to form colloidal particles (copper colloid).
form. Copper colloids are stable at pH 2-4, p
If H is less than 2 or exceeds 4, the copper colloid will coagulate and precipitate.

Hypophosphorous acid used in the present invention protects the copper colloid from oxidation by oxygen (dissolved oxygen) in the air dissolved in the copper colloid catalyst solution, and the amount added is 0, 1-2. ,
Og/l is suitable. If the amount added exceeds 2 g/L, the aggregation of the copper colloid will be promoted, and if the amount added is less than 0.1 g/L, the antioxidant effect of the copper colloid of sodium hypophosphite will be reduced. Decrease.

〔Example〕

Hereinafter, the present invention will be explained in detail using examples.

[Example-1] 10 g of gelatin and 5 g of polyethylene glycol with an average molecular weight of 1,000 were dissolved in approximately 700 nit pure water,
After adding a sulfuric acid aqueous solution while maintaining the temperature at 60°C and adjusting the pi of the gelatin aqueous solution to 1.8, sulfuric acid steel (Cu
80.5H,O)t 24.9 g was dissolved. Next, 118 mA of a dimethylamine borane aqueous solution having a concentration of 7t was added, and the copper ions were completely reduced to metal steel at a liquid temperature of 60°C. Next, the liquid temperature was raised to 75°C and aged for 2 hours to completely hydrolyze unreacted dimethylamine/borane.Then, the liquid temperature was further cooled to room temperature, and 2g of sodium hypophosphite (NaH, POt) was added and dissolved. After this, the p)l of the aqueous solution was adjusted to 2.5 with an aqueous sodium hydroxide solution. Next, the total amount of the aqueous solution was made up to 1 t by adding pure water to produce a copper colloid catalyst liquid.

[Example-2] In place of the polyethylene glycol with an average molecular weight of 1,000 in Example-1, polyethylene glycol with an average molecular weight of 20,000 and 1
Two types of copper colloidal catalyst solutions were produced using 00,000 polyethylene glycol and the same procedure as in Example-1.

[Example-3] The copper colloidal catalyst liquids produced in Example-1 and Example-2 and their 10-fold dilutions were prepared.

Note that the p)I of the 10-fold diluted solution was adjusted to 2.5 with an aqueous sulfuric acid solution. A copper-clad jepoxy resin laminate with through-holes formed in these copper colloidal catalyst solutions was immersed for about 5 minutes at room temperature (25°C), washed with water for 1 minute, and then soaked at a liquid temperature of 25°C and a pH of
It was immersed in an electroless steel plating solution of =13 for about 10 minutes to examine the precipitation of electroless steel plating on the walls of the through hole.

〔Effect of the invention〕

As described above, according to the present invention, by cross-sectional observation of the through-hole walls, the electroless steel plating on the through-hole walls of all samples was completely covered.
Furthermore, the copper colloidal catalyst solution of the present invention was very stable, thus proving the practicality of the present invention.

Claims (2)

[Claims] (1) The concentration of copper metal particles is 0.3 g/l or more, 0.8 g or more gelatin per 1 g of copper metal particles, 0.8 g or more of polyethylene glycol with an average molecular weight of 1,000 to 100,000, and hypochlorite. pH2 with sodium phosphate
A copper colloidal catalyst solution for electroless plating consisting of an aqueous solution of ~4. (2) Divalent copper ion and 0.8 per gram of divalent copper ion
g or more gelatin and 0.8 g or more average molecular weight 1.0
1.2 g per 1 g of divalent copper ion in an aqueous solution of pH 1 to 4 containing polyethylene glycol of 0.0 to 100,000
After adding the above dimethylamine borane, the liquid temperature was 40℃.
After reducing copper ions to metallic copper at a temperature not exceeding 70°C, the solution is further aged at a temperature of 70°C or higher for a desired period of time, and then sodium hypophosphite is added and dissolved, and the pH of the aqueous solution is adjusted to 2 to 70°C. 4. A method for producing a copper colloidal catalyst solution for electroless plating, comprising the steps of: