Plating pretreatment agent and metal plating method using...

Coating processes – With pretreatment of the base – Preapplied reactant or reaction promoter or hardener

Reexamination Certificate

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C427S305000, C427S437000, C427S438000, C427S212000, C106S001050, C106S001110

Reexamination Certificate

active

06780467

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a plating pretreatment agent used for the metal plating of surfaces of low-conductivity materials, mirror-surface articles, powders and the like by electroless plating, and a metal plating method using this agent.
BACKGROUND ART
The electroless metal plating method is one method for forming metal coating films on substrates that do not possess conductivity. In performing electroless plating, a method known as activation in which a precious metal such as palladium or the like is caused to adhere to a substrate beforehand (as a catalyst is generally used as an electroless plating pretreatment. In the past, methods in which Pd is adsorbed by an immersion treatment in an aqueous solution of PdCl
2
following a treatment with a hydrochloric acid aqueous solution of SnCl
2
, and methods in which Pd is supported on the surface by means of a colloid solution of Sn and Pd, have been used as such activation methods. Such methods involve numerous problems such as the use of highly toxic Sn, the need for a complicated treatment process and the like. Recently, therefore, various methods which use a silane coupling agent that has functional groups capable of forming a complex with precious metals such as Pd or the like that constitute catalysts for electroless plating have been proposed as methods for supporting such precious metals on the surface being treated (Japanese Patent Publication No. S59-52701, Japanese Patent Application Laid-Open No. S60-181294, Japanese Patent Application Laid-Open No. S61-194183, Japanese Patent Publication No. H3-44149). Among these methods, there are methods in which separate treatments are performed using a plating catalyst fixing agent and a plating catalyst, i.e., methods in which the precious metal ions that constitute the catalyst are supported after a coupling agent has been adsorbed on the article to be plated. In such cases, however, depending on the material of the article being plated, it is sometimes difficult to form a uniform plating film with good adhesion, possibly due to modification of the surface of the article being plated by the coupling agent treatment, or due to the fact that the precious metal ions cannot be efficiently supported. Furthermore, depending on the material of the article being plated and the plating conditions, it has also been impossible in some cases to obtain a uniform plating film in the case of using a mixed solution of an aminosilane coupling agent and palladium chloride, either for the above-mentioned reasons or because the palladium does not show a sufficient catalytic activity.
DISCLOSURE OF THE INVENTION
In view of the foregoing, it is an object of the present invention to provide a metal plating method using a novel electroless plating that allows ideal electroless plating to be performed even on materials which have difficulties in the application of conventional electroless plating. Another object of the present invention is to provide a metal plating pretreatment agent for use in the above-mentioned electroless plating. In particular, the present invention makes it possible to accomplish uniform plating with good adhesion even using a plating solution with a weak reducing power such as a copper plating solution or the like.
As a result of diligent research conducted in order to solve the above-mentioned technical problems, the present inventors discovered that electroless plating can be performed in an ideal manner and by means of a simple process even on materials to be plated in which it has been difficult to use conventional electroless plating, by subjecting the article that is to be plated to a surface treatment with a pretreatment agent which has been prepared by capturing a metal with a silane coupling agent which has a metal-capturing functional group or groups in its molecule, and then adding a reducing agent. This discovery led to the perfection of the present invention.
Specifically, the present invention provides:
(1) A method for metal plating which is characterized in that the method comprises treating an article to be plated with a pretreatment agent, which has been prepared by capturing a metal with a silane coupling agent having a metal-capturing functional group in its molecule, then adding a reducing agent and performing electroless plating.
(2) The method for metal plating according to (1) above, which is characterized in that the metal-capturing functional group is an amine.
(3).The method for metal plating according to (1) above, which is characterized in that the metal-capturing functional group is an imidazole.
(4) The method for metal plating according to (1) above, which is characterized in that the metal is provided in the form of a palladium compound.
(5) The method for metal plating according to (1) which is characterized in that the silane coupling agent having a metal-capturing functional group in its molecule is a silane coupling agent obtained by the reaction of an azole compound and an epoxysilane type compound.
(6) The method for metal plating according to (1) above, which is characterized in that the reducing agent is dimethylamine borane.
(7) The method for metal plating according to (1) above, wherein the metal plating is copper or nickel.
(8) A pretreatment agent for metal plating which is characterized in that this agent has been prepared by capturing a metal with a silane coupling agent having a metal-capturing functional group in its molecule, and then adding a reducing agent.
The present invention is characterized in that a specified silane coupling agent, i.e., a silane coupling agent in which a metal constituting a catalyst with a high activity is captured by a metal-capturing functional group, is used, and a reducing agent is added to this coupling agent.
BEST MODE FOR CARRYING OUT THE INVENTION
In the metal plating pretreatment agent of the present invention, the activity of the catalyst can be increased by the addition of a reducing agent, so that reduction can be accomplished using even a plating solution with a weak reducing power.
Nitrogen-containing heterocyclic compounds such as imidazoles or the like, including primary amines, secondary amines and tertiary amines, can be used as the metal-capturing functional groups.
In the present invention, precious metals are desirable as the metals that constitute high-activity catalysts; examples of precious metal compounds that can be used include chlorides, hydroxides, oxides, sulfates and amine complexes (ammonium salts or the like) of palladium, silver, platinum, gold and the like, which show catalytic activity when copper, nickel or the like is deposited on the surface of the article being plated from an electroless plating solution. Among these compounds, palladium chloride is especially desirable. The capture of the precious metal by the above-mentioned silane coupling agent is accomplished by mixing solutions of the respective compounds. The same solvent as that used for the pretreatment agent (described later) can be used as the solvent of the above-mentioned solutions.
The silane coupling agent with a metalcapturing functional group that is used in the present invention may be any silane coupling agent that has the above-mentioned metal-capturing functional group or groups; there are no particular restrictions on this coupling agent. Silane coupling agents which have nitrogen-containing heterocyclic azole compounds such as imidazole or the like are especially desirable.
As a result of the presence of nitrogen-containing hetero-rings in the molecule, an electron state and orientation that effectively manifest the activity of the plating catalyst can be obtained through the conjugate and aromatic properties of the nitrogen-containing hetero-rings; furthermore, since the agent is a silane coupling agent, tight adhesion of the agent to an article being plated can be realized.
Examples of such nitrogen-containing heterocyclic azole compounds include imidazole, oxazole, thiazole, selenazole, pyrazole, isooxazole, isothiazole, triazole, oxadiazole, thiadiazole, tetr

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