Method of electroplating non-conductive materials

Details Method of electroplating non-conductive materials Method of electroplating non-conductive materials

1997-12-09

1999-06-01

Gorgos, Kathryn

Electrolysis: processes, compositions used therein, and methods

Electrolytic coating

Coating predominantly nonmetal substrate

205164, 205210, 427 98, 427125, 427304, 427305, 427306, 4274431, 106 105, 106 111, C25D 554, C25D 556, C25D 534, B05B 310

Patent

active

059085436

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to a method of electroplating the surface of non-conductive materials without involving electroless plating.


PRIOR ART

Various methods are known for plating non-conductive materials such as plastics for decorating purposes or for function-imparting purposes.
Electroless plating methods are commonest for such purposes. Methods industrially available include a method comprising applying Pd-Sn catalyst nuclei onto a substrate of plastics, typically ABS resins, to be electroplated, treating the substrate with a diluted acidic solution, forming an electroconductive metal coating using an electroless copper plating solution or an electroless nickel plating solution, and then electroplating the substrate.
However, electroless plating methods necessitate complicated pretreatments. Further an etectroless plating solution his a drawback that a complicated procedure is involved to strictly control the bath because of its intensive self-decomposing property. In addition, when an electroless copper plating solution is used, various problems arise. For example, highly toxic formalin, i.e. a carcinogen, is widely used as a reducing agent. Moreover, a highly effective complexing agent such as EDTA or the like is used to solubilize copper ions in an alkali solution. In using the complexing agent, considerable labor is entailed for removal of metal ions in disposal of waste water, and a prolonged period of time is taken for the formation of even a very thin copper coating. When an electroless nickel plating solution is used, hypophosphite used as a reducing agent is converted to phosphite on oxidation. The obtained phosphite is legally controlled for regulation of phosphorus. Further, the electroless nickel plating solution is raising an environmental pollution problem as a high COD waste liquor.
In the current situation, it has been reported to carry out a variety of pretreatments prior to electroplating in methods for electroplating a non-conductive material without involving electroless plating. For example, the proposed pretreatment methods include a method treating a substrate with a palladium-tin solution, a method forming an organic electroconductive coating and a method applying carbon black (U.S. Pat. Nos. 3,099,608; 4,683,036; 4,895,739; 4,919,768; 5,007,990; and 4,810,333; Japanese Examined Patent Publication No. 1,381/1991 and International Publication Wo 89/08,375).
However, these methods mostly produce coatings of low electroconductivity and are used for limited applications due to a low depositing rate in electroplating. The methods, for example, are limited to a purpose of electroplating through holes of thin printed boards. In most cases, the methods entail difficulty in forming a desirable coating by electroplating on plastic molded articles having a large area. Further, the methods pose problems of forming an electroplated coating of low adhesion and poor covering power, namely can not assure formation of reliable coating.
In recent years, various researches have been conducted on methods of electroplating non-conductive materials. For example, the following methods have been reported.
U.S. Pat. No. 5,071,517 discloses a method comprising treating a substrate with an aqueous solution of a non-acidic salt containing a dispersion of fine colloids of precious metal and tin to form an electroconductive layer, followed by electroplating. U.S. Pat. No. 5,342,501 discloses a method comprising treating a substrate with a non-acidic tin-palladium catalyst and then with a promoter solution of low basicity to improve the electroconductivity.
U.S. Pat. No. 5,543,182 discloses a method comprising bringing a non-conductive substrate into contact with an activating agent containing a precious metal/IVA Group metal sol and treating the substrate with a solution containing a soluble salt of a metal which is more precious than IVA Group metal, a hydroxide of IA Group metal and a specific complexing agent to form a metallic coating.
Japanese Unexamined Patent Publicat

REFERENCES:
patent: 3099608 (1963-07-01), Radovsky et al.
patent: 4631117 (1986-12-01), Minten et al.
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patent: 5071517 (1991-12-01), Oabayashi
patent: 5342501 (1994-08-01), Okabayashi
patent: 5543182 (1996-08-01), Joshi et al.

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