Hitachi, Ltd.

Osamu Miyazawa

Hitoshi Yokono

Akira Tomizawa

Jiro Ushio

Hitoshi Oka

Tokio Isogai

Isamu Tanaka

Akira Matsuo

Naoya Kanda

Hiroaki Okudaira

Setsuo Ando

Naoko Matsuura

Hiroshi Kikuchi

Toshihiko Ohta

Kenji Nakamura

Haruo Suzuki

Toyofusa Yoshimura

Nobuo Nakagawa

Masao Sekibata

The present invention relates to an electroless gold plating solution, a method of plating by using the same, and an electronic device plated with gold by using the same. According to the present electroless gold plating solution, the plating solution components contain no cyanide ions, the amount of a reducing agent used is small, and gold plating can be carried out without causing the gold plating on conducting paths having a fine interval between them to short-circuit the conducting paths. Therefore, according to the method of gold plating by using said electroless gold plating solution, a plating method that is safe in the plating work and in the treatment of its waste liquor can be accomplished. The method has a feature that the method can provide an electronic device on which parts can be mounted highly densely, and wherein the joint reliability to the parts is high.

Electroless gold plating solution, method of plating with gold by using

Electronic device plated with gold by means of an electroless gold

An electroless gold plating solution comprising a thiosulfato gold(I) complex, a thiosulfate, thiourea, a pH regulator and a stabilizer. The electroless gold plating solution shows a plating rate and a plating solution stability comparable to those of conventional gold plating solutions containing cyanide ions, and requires a smaller amount of reducing agent to be used therein. Further, the electroless gold plating solution is safe because it does not contain cyanide ions.

Electroless gold plating solution

Before Au-plating onto the metallic surface of an electronic part, Ni-plating and then Co-plating are applied to form a primer coating for Au-plating. But in the steps of Ni and Co-platings, hydrogen gas produced during the plating is occluded into a plating layer. On the other hand, when a pellet connected onto an Au-plated metal, an Au-Si alloy is formed, but hydrogen gas in the plating layer remains as voids in the Au-Si alloy during a subsequent heating step of the electronic part, resulting in a serious defect. This invention of a plating method is characterized by annealing after Au-plating of an electronic part to eliminate the residual gas.

Plating process for an electronic part

During recyclic use of a chemical copper plating solution, counter anions to copper ions, anions formed by oxidation of a reducing agent, and carbon dioxide by absorption of carbon dioxide from air, which all have an inhibiting effect upon the plating, and also sodium ions having no inhibiting effect are accumulated in the plating solution. These accumulated ions can be removed by electrodialysis. Particularly, regeneration can be satisfactorily regenerated by adjusting the pH of used chemical plating solution to 2-11 before the electrodialysis, and using a selectively monovalent anion permeable membrane as an anion exchange membrane at the electrodialysis.

Process for regenerating chemical copper plating solution

The pH of a chemical copper plating solution is exactly measured for a prolonged time by utilizing a copper oxide prepared by etching metallic copper in an 0.1-1 N inorganic acid then oxidizing the etched metallic copper in an aqueous 0.1-1 N alkali metal hydroxide solution as a main electrode for pH measurement or reducing agent concentration measurement in terms of pH. A combination of the pH measurement with well known procedures for measuring concentrations of cupric ions and a complexing agent exactly measures the pH and the concentrations of a reducing agent, cupric ions and a complexing agent for a continuation of longer time than the conventional procedures.

Method for automatically controlling composition of chemical copper

When an amine compound having at least two polyolefin glycol chains in one molecule is used as a stabilizer, and an alkylene diamine compound, at least one hydrogen atom in the respective amino groups thereof being substituted by CH.sub.2 COOX (wherein X is H or Na) and another hydrogen atom in the respective amino group thereof being substituted by CH.sub.2 OH, is used as a complexing agent for cupric ions and a nitrogen-containing cyclic compound is used as a complexing agent for cuprous ions in an electroless copper plating solution comprising water, a water-soluble copper salt, a complexing agent for cupric ions, a reducing agent, a pH-controlling agent and a stabilizer, or an electroless copper plating solution comprising water, a water-soluble copper salt, a complexing agent for cupric ions, a reducing agent, a pH-controlling agent, a stabilizer and a complexing agent for cuprous ions, the plating rate of the electroless copper plating solution, mechanical strength of plating film, and stability of the plating solution are improved.

Electroless copper plating solution

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Yokosuka, Japan

Osamu Miyazawa