Compositions: coating or plastic – Coating or plastic compositions – Metal-depositing composition or substrate-sensitizing...
Reexamination Certificate
2000-06-29
2002-07-09
Klemanski, Helene (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Metal-depositing composition or substrate-sensitizing...
C106S001260
Reexamination Certificate
active
06416571
ABSTRACT:
FIELD OF INVENTION
The present invention relates to a pyrophosphoric acid bath for use in copper-tin alloy plating capable of performing copper-tin alloy plating appropriate for applications to ornamentation and lead-free solder plating without containing a cyanic ion and a copper-tin alloy coating obtained by using the cyanide-free pyrophosphoric acid bath.
DESCRIPTION OF THE RELATED ART
Nickel (Ni) plating has conventionally been widely used in plating of ornamentation. However, the Ni plating has a problem of Ni allergy which causes skin eruption or inflammation to an individual who puts on an ornament having an Ni coating so that copper-tin (Cu—Sn) alloy plating has been reviewed in recent years to take the place of the Ni plating. A Cu—Sn alloy coating has smoothness and corrosion resistance so that it has a property capable of substituting the Ni coating as a base coating for gold, silver or chromium plating.
Copper-lead (Cu—Pb) alloy plating which essentially contains lead has also conventionally been widely used as solder or solder plating. However, solder or solder plating which does not contain lead has recently been required so as to prevent a global environmental pollution.
Plating bathes for use in industrial Cu—Sn alloy plating are mostly those containing a cyanic ion such as a cyanide-stannic acid bath, tin pyrophosphate-copper cyanide bath and the like. Due to a severe sewage treatment regulation, treatment of waste water from those bathes is costly. There is also a problem from the standpoint of an operation in a safe environment. Therefore, a Cu—Sn alloy plating bath without containing a cyanic ion (hereinafter referred to simply as “cyanide-free”) is required.
As a cyanide-free Cu—Sn alloy plating bath, a pyrophosphoric acid bath has conventionally been known. A pyrophosphoric acid plating is performed by energizing a bath containing copper pyrophosphate, stannous pyrophosphate, a complexing agent (for example, an alkali metal salt of pyrophosphoric acid) and other additives; however, since there is no appropriate brightener suitable for the pyrophosphoric acid bath, a coating to be obtained has neither silver-white gloss nor stable color tone, namely, is not fully satisfactory for ornamentation. Furthermore, the pyrophosphoric acid bath for use in Cu—Sn alloy plating has a narrow optimum current density range so that the metal alloy tends to be deposited in a spongy state; thus, the cyanide-free bath which is industrially applicable has not been put to practical use.
Therefore, the applicant of the present invention has previously proposed in Japanese Laid-Open Patent Publication (JP-A) No. 10-102278 a pyrophosphoric acid bath for use in Cu—Sn alloy plating which contains a reaction product of an amine derivative and an epihalohydrin in a 1:1 weight ratio and an aldehyde derivative (formaldehyde, paraformaldehyde or metaformaldehyde) and, when necessary, further contains a surface tension adjusting agent as a cyanide-free pyrophosphoric acid bath by which Cu—Sn alloy plating for ornamentation can safely be performed in an industrial scale in place of Ni plating. According to the cyanide-free pyrophosphoric acid bath described above, color tones of the deposited film can easily be changed between from silver-white to copper colored and also a glossy, beautiful coating having a stable color tone and a film can be obtained. However, since an aldehyde derivative used as a gloss auxiliary has a hygienic problem in an operational environment and a ratio of tin contents can not be raised more than about 60% at the maximum, the proposed bath can not be used for the solder plating.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to solve the above-described problems of a cyanide-free pyrophosphoric acid bath which contains a reaction product of an amine derivative and an epihalohydrin and an aldehyde derivative to be used for substituting Ni plating and to provide a cyanide-free pyrophosphoric acid bath for use in Cu—Sn alloy plating capable of performing lead-free solder plating.
Under the above circumstances, the present inventors have conducted an intensive study and found that not only the above-described problems are solved by employing a cationic surfactant in place of the aldehyde derivative as an additive described in JP-A No. 10-102278, but also, by adjusting a ratio of Cu ion and Sn ion contents of the said bath, both color tone and film become stable, the film can be obtained the color of which is changeable between from glossy, beautiful silver-white to copper colored and further to light black and the present invention can be used as lead-free solder plating since the tin content can substantially be increased in the alloy coating. Thus, the present invention has been accomplished on the basis of this finding.
Namely, the present invention provides a pyrophosphoric acid bath for use in Cu—Sn alloy plating and a Cu—Sn alloy coating as follows:
1) A pyrophosphoric acid bath for use in Cu—Sn alloy plating without containing a cyanic ion, comprising a reaction product (A) of an amine derivative and an epihalohydrin in a 1:1 mole ratio and a cationic surfactant (B) as additives.
2) The pyrophosphoric acid bath for use in Cu—Sn alloy plating described in 1) above, further comprising a surface tension adjusting agent (C).
3) The pyrophosphoric acid bath for use in Cu—Sn alloy plating described in 1) above, further comprising a bath stabilizer (D).
4) The pyrophosphoric acid bath for use in Cu—Sn alloy plating described in any one of 1) to 3) above, further comprising an N-benzylpyridinium derivative (E).
5) The pyrophosphoric acid bath for use in Cu—Sn alloy plating described in 1) above, wherein the reaction product (A) of an amine derivative and an epihalohydrin in a 1:1 mole ratio is a reaction product of at least one amine derivative selected from the group consisting of ammonium, ethylenediamine, diethylenetriamine, diethylenediamine (piperazine), n-propylamine, 1,2-propanediamine, 1,3-propanediamine, 1-(2-aminoethyl)piperazine, 3-diethylaminopropylamine, dimethylamine, hexamethylenetetramine, tetraethylenepentamine, triethanolamine, hexamethylenediamine and isopropanolamine, and epichlorohydrin in a 1 to 1 mole ratio.
6) The pyrophosphoric acid bath for use in Cu—Sn alloy plating described in 1) above, wherein the cationic surfactant (B) is selected from the group consisting of betaine-type surfactants and quaternary ammonium salt-type surfactants.
7) The pyrophosphoric acid bath for use in Cu—Sn alloy plating described in 2) above, wherein the surface tension adjusting agent (C) is selected from the group consisting of gelatin, gum arabic, polyvinylalcohol, polyethyleneglycol, polypropyleneglycol and acetyleneglycol.
8) The pyrophosphoric acid bath for use in Cu—Sn alloy plating described in 3) above, wherein the bath stabilizer (D) is selected from the group consisting of organic sulfonic acids and the salts thereof.
9) The pyrophosphoric acid bath for use in Cu—Sn alloy plating described in 4) above, wherein N-benzylpyridinium derivative (E) is a reaction product of a pyridine derivative and benzyl chloride in a 1:1 mole ratio.
10) A Cu—Sn alloy coating which can be obtained by using the pyrophosphoric acid bath for use in Cu—Sn alloy plating described in any one of 1) to 9) above.
DETAILED DESCRIPTION
The present invention will be described in detail below.
A pyrophosophoric acid bath according to the present invention is prepared by compounding the above-described components (A) and (B) and, when necessary, further components (C), (D) and (E) as additives into a known fundamental bath composition of a pyrophosphoric acid bath for use in Cu—Sn alloy plating.
The fundamental composition of the pyrophosphoric acid bath contains a Cu ion, an Sn ion and an alkali metal salt (potassium salt or sodium salt) of pyrophosphoric acid for forming a water-soluble complex salt. As a source of the Cu ion, copper pyrophosphate can favorably be utilized; as a source of the Sn ion, stannous pyrophosphate, stannous chloride, stannous sulfate
Hatta Asao
Kaneko Mitsuru
Kunii Mitsuharu
Klemanski Helene
LaPointe Dennis G.
Mason & Assoc., PA
Nihon New Chrome Co., Ltd.
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