JP2002004060A - Electroless gold plating bath - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electroless gold plating bath which is stable after being used for plating and with which a having an excellent appearance can be obtained. SOLUTION: The electroless gold plating bath contains, as a complexing agent, at least one of aliphatic sulfide compounds selected from oxyalkylene type sulfide compounds, each containing an oxyethylene group, an oxypropylene group or an oxy(hydroxyethylene) group or these groups in the repeated state, bonding to one side or both sides of a monosulfide or a disulfide in the molecule and carboxylic acid-type sulfide compounds, each having a carboxy group or carboxy groups bonding to an alkylene chain or alkylene chains bonded to one side or both sides of a monosulfide or a disulfide. For example, in the case of each oxyalkylene type sulfide compound, the sulfide-based compound forms a complex effectively with a gold ion by synergic electron-donating functions of the sulfur atom in the sulfide group and oxygen atoms in the repeated oxyalkylene chain, and thereby the plating bath is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an electroless gold plating bath which provides an excellent bath stability and plating film appearance.

[0002]

BACKGROUND OF THE INVENTION Conventionally, electrical contact portions of electronic parts are often provided with a surface coating of a noble metal having good corrosion resistance and excellent electrical characteristics, and gold electroplating is often used industrially. Have been. However, in electroplating,
It has been difficult to form a gold-plated film with a uniform thickness on parts with fine and complex shapes, or on parts with design restrictions due to high-density mounting, or on electrically isolated fine parts. . On the other hand, electroless plating has an advantage that a plating film can be formed without energization, and a film can be formed without trouble even on a fine and complicated part or an electrically isolated portion.

[0003] The above-mentioned electroless plating can be further classified into two types, displacement plating and reduction plating. That is, in the displacement plating method, when the base metal is eluted into the bath, metal ions in the bath are precipitated as metal due to the difference in oxidation-reduction potential between the metal in the bath and the metal of the object to be plated (base). The reduction plating method is a method of depositing metal ions in a plating bath by the action of a reducing agent.

[0004]

2. Description of the Related Art (1) Prior art 1 (Japanese Patent Laid-Open No. 2-107780)
No.) Gold complexing agents such as thiosulfuric acid, sulfurous acid, or salts thereof,
Hypophosphites, borohydride compounds, thioureas, reducing agents such as borane, and Cu ²⁺ , Ni ²⁺ ,
An electroless gold plating bath containing a polyamine such as ethylenediamine which forms a complex with an impurity ion such as Fe ²⁺ and a concealing complexing agent such as a polycarboxylic acid such as EDTA is disclosed.

(2) Prior art 2 (JP-A-5-156460) A substituted gold plating bath containing a soluble gold salt such as sodium chloroaurate and mercaptosuccinic acid is disclosed.

[0006]

Basically, gold has a precious noble redox potential, so that the gold plating bath is easily decomposed, and it is not easy to stabilize gold ions in the bath. The bath containing the agent is more likely to be unstable. Actually, if the sulfite or thiosulfate of the above-mentioned prior art 1 is used alone, the above stabilizing effect is not sufficient, and there is a problem that the color tone unevenness occurs in the plating film obtained from the bath. On the other hand, the mercapto succinic acid of the prior art 2 has a bath stabilizing effect, but is expensive.

It is a technical object of the present invention to newly develop a gold plating bath which is excellent in bath stability and obtains a film having a good appearance by using a different kind of compound different from the above prior arts 1 and 2. And

[0008]

SUMMARY OF THE INVENTION The present applicant has previously disclosed in Japanese Patent Application No. 10-367107 (hereinafter referred to as "prior art") an opaque complexing agent and a specific surfactant such as an amphoteric surfactant. And at least one basic nitrogen in a molecule such as 2,2'-dibenzothiazolyl disulfide, 2,2'-dipyridyl disulfide, 2,2'-dithiodianiline, and 2-ethylthioaniline. A substituted gold plating bath containing an aromatic sulfide compound having atoms has been proposed. In this case, one point of attention is that the sulfide-based compound belongs to the sulfur-containing compound in common with the mercaptosuccinic acid of prior art 2 which is a mercaptan.

The present inventors have conducted extensive research on other sulfide-based compounds starting from the aromatic sulfide-based compound proposed in the above-mentioned prior art, and as a result, have found that the aromatic sulfide-based compound is adjacent to both sides or one side of a mono- or disulfide bond. When a specific aliphatic sulfide compound such as an oxyalkylene type sulfide compound having an oxyethylene group, an oxypropylene group or an oxy (hydroxypropylene) group singly or repeatedly in a molecule is contained in a gold plating bath, a substitution type, reduction The stability of the bath is effectively increased regardless of the type,
The present inventors have found that the appearance of a gold film obtained from a plating bath is also improved, and completed the present invention.

That is, the present invention relates to an oxyalkylene-type sulfide system having a single or repeated oxyethylene group, oxypropylene group or oxy (hydroxypropylene) group in both or one side of a mono- or disulfide bond. Electroless gold plating containing, as a complexing agent, at least one aliphatic sulfide compound selected from the group consisting of carboxylic acid sulfide compounds having a carboxyl group on both or one side of a compound or a mono- or disulfide bond. It is a bath.

A second aspect of the present invention is the electroless gold plating bath according to the first aspect, further comprising a reducing agent.

The present invention 3 provides the above-mentioned invention 1 or 2, further comprising at least one concealing complexing agent selected from the group consisting of oxycarboxylic acids, amine compounds, nitrogen-containing heterocyclic compounds and ammonium compounds. An electroless gold plating bath characterized by containing.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is an electroless gold plating bath containing a specific aliphatic sulfide compound, and includes both substitution type and reduction type gold plating baths. The soluble gold salt as a supply source of gold is a gold salt capable of supplying monovalent or trivalent gold ions into a plating bath, and specifically, potassium chloroaurate, sodium chloroaurate, gold chloride Examples thereof include ammonium phosphate, gold potassium sulfite, gold sodium sulfite, gold ammonium sulfite, gold potassium thiosulfate, gold sodium thiosulfate, and gold ammonium thiosulfate. The content of the soluble gold salt in the bath was 0.001 to 0.001 in terms of metal.
20 g / L, preferably 0.5 to 10 g / L.

The above-mentioned specific aliphatic sulfide-based compound shows an action of complexing and stabilizing gold ions in a plating bath and can be classified into the following compounds (a) and (b). (a) Oxyalkylene-type sulfide compound A sulfide compound having an oxyethylene group, an oxypropylene group or an oxy (hydroxypropylene) group singly or repeatedly in the molecule, adjacent to both sides or one side of a mono- or disulfide bond. (b) Carboxylic acid type sulfide compound A sulfide compound having a carboxyl group in the alkylene chain on both sides or one side of a mono- or disulfide bond.

The oxyalkylene type sulfide compound (a) includes the following. _{(1) H- (OCH 2 CH} 2) 3 -S- (CH 2 CH 2 O) 3 bis represented by -H (triethylene glycol) thioether _{(2) H- (OCH 2 CH} 2) 6 -S _{- (CH 2 CH 2 O)} 6 bis represented by -H (hexaethylene glycol) thioethers _{(3) H- (OCH 2 CH} 2) 10 -S- (CH 2 CH 2 O) 10 -H
Bis (decaethylene glycol) thioether represented by the formula (4) H- (OCH ₂ CH ₂ ) ₁₂ -S- (CH ₂ CH ₂ O) ₁₂ -H
(5) H- (OCH ₂ CH ₂ ) ₁₅ -S- (CH ₂ CH ₂ O) ₁₅ -H
(6) H- (OCH ₂ CH ₂ ) ₂₀ -S- (CH ₂ CH ₂ O) ₂₀ -H
Bis (icosaethylene glycol) thioether represented by the formula (7) H- (OCH ₂ CH ₂ ) ₃₀ -S- (CH ₂ CH ₂ O) ₃₀ -H
(8) H- (OCH ₂ CH ₂ ) ₄₀ -S- (CH ₂ CH ₂ O) ₄₀ -H
Bis (tetracontaethylene glycol) thioether represented by the formula (9) H- (OCH ₂ CH ₂ ) ₅₀ -S- (CH ₂ CH ₂ O) ₅₀ -H
Bis (pentacontaethylene glycol) thioether represented by the formula (10) 2,2'-thiodiglycol represented by HOCH ₂ CH ₂ -S-CH ₂ CH ₂ OH (11) HOCH ₂ CH ₂ CH ₂ -S -CH ₂ CH ₂ CH 3,3'- thiodiglycol propanol (12) represented by _{2 OH H- (OCH 2 CH 2} ) 5 -S-S- (CH 2 CH 2 O) 5 -
Bis (ω-hydroxypentaethoxy) disulfide represented by H (13) H- (OCH ₂ CH ₂ ) ₁₂ -SS- (CH ₂ CH ₂ O) ₁₂
Bis (ω-hydroxydodecaethoxy) disulfide represented by -H (14) H- (OCH ₂ CH ₂ ) ₂₀ -SS- (CH ₂ CH ₂ O) ₂₀
Bis (ω-hydroxyicosaethoxy) disulfide represented by -H (15) H- (OCH ₂ CH ₂ ) ₅₀ -SS- (CH ₂ CH ₂ O) ₅₀
Bis (ω-hydroxypentacontaethoxy) disulfide represented by -H (16) H- (OCH ₂ CH (OH) CH ₂ ) ₈ -S- (CH ₂ CH
(OH) CH ₂ O) ₈ bis represented by -H (oct glycerol) thioether _{(17) H- (OC 3 H} 6) 5 - (OC 2 H 4) 15 -S- (C 2 H 4 O)
_{15 - (C 3 H 6 O} ) 5 bis represented by -H (pentadecalactone glycol pentaethylene glycol) thioethers _{(18) H-OCH 2 CH} (OH) CH 2 - (OC 2 H 4) 10 -S −
_{(C 2 H 4 O) 10} -CH 2 CH (OH) CH 2 bis represented by OH (decaethylene glycol mono glycerol) thioether _{(19) H- (OC 2 H} 4) 10 - (OC 3 H ₆ ) ₃ -S- (C ₃ H ₆ O) <sub>3
- (C 2 H 4 O)</sub> 10 bis represented by -H (tripropylene glycol decamethylene glycol) thioethers _{(20) H- (OC 3 H} 6) 5 - (OC 2 H 4) 15 -S-S- (C ₂ H _{4
O) 15 - (C 3 H} 6 O) 5 bis represented by -H (.omega.-hydroxy penta propoxy pentadecanoyl ethoxy) disulfide _{(21) H-OCH 2 CH} (OH) CH 2 - (OC 2 H 4) ₁₀ -S-
_{S- (C 2 H 4 O)} 10 -CH 2 CH (OH) CH 2 bis represented by OH (.omega.-hydroxy-mono-glycerophosphate carboxymethyl deca ethoxy) disulfide _{(22) H- (OC 2 H} 4) 20 -(OC ₃ H ₆ ) ₅ -SS- (C ₃ H _{6
O) 5 - (C 2 H} 4 O) bis represented by ₂₀ -H (.omega.-hydroxy equalize ethoxylated pentaerythritol propoxylate) disulfide _{(23) H- (OC 2 H} 4) 5 -S-CH 2 CH 2 - S- (C ₂ H
₄ O) S represented by ₅ -H, S'-bis (pentaethylene glycol) ethylene dithioether _{(24) H- (OC 2 H} 4) 15 -S-CH 2 CH 2 -S- (C 2 H _Four
O) ₁₅ S represented by -H, S'-bis (pentadecalactone ethylene glycol) ethylene dithioether _{(25) H- (OC 2 H} 4) 30 -S-CH 2 CH 2 CH 2 -S- (C
₂ H ₄ O) S represented by ₃₀ -H, S'-bis (triacontanyl ethylene glycol) propylene dithio ether _{(26) H- (OC 3 H} 6) 3 - (OC 2 H 4) 20 -S- CH ₂ CH ₂
S represented by —S— (C ₂ H ₄ O) ₂₀ — (C ₃ H ₆ O) ₃ —H,
S'- bis (tripropylene glycol equalize Sa ethylene glycol) ethylene dithioether _{(27) H- (OCH 2 CH} 2) 2 -S- (CH 2 CH 2 O) bis represented by ₂ -H (diethylene glycol) thioether _{(28) HOCH 2 CH (OH} ) CH 2 -S-CH 2 CH (OH)
CH represented by bis (monoglycerol) at ₂ OH thioether _{(29) H- (OCH 2 CH} (OH) CH 2) 3 -S- (CH 2 CH
Bis (triglycerol) thioether represented by (OH) CH ₂ O) ₃ -H (30) H- (OCH ₂ CH ₂ ) ₄₁ -SS- (CH ₂ CH ₂ O) ₄₁
Bis (ω-hydroxyphentetracontaethoxy) disulfide represented by -H (31) H- (OC ₃ H ₆ ) _5- (OC ₂ H ₄ ) ₂₀ -SS- (C ₂ H _{4
O) 20 - (C 3 H} 6 O) 5 bis represented by -H (.omega.-hydroxy penta propoxycarbonyl alkoximinoalkyl Cosa ethoxy) disulfide _{(32) H- (OCH 2 CH} (OH) CH 2) 3 -S-S − (CH ₂
Bis (ω-hydroxytriglyceroxy) disulfide represented by CH (OH) CH ₂ O) ₃ -H (33) H- (OCH ₂ CH (OH) CH ₂ ) ₁₀ -SS- (CH ₂
Bis (ω-hydroxydecaglyceroxy) disulfide represented by CH (OH) CH ₂ O) ₁₀ —H (34) HOCH ₂ CH ₂ —S—CH ₂ CH ₂ —S—CH ₂ CH ₂
S represented by OH, S'-bis (monoethylene glycol) ethylene dithioether _{(35) H- (OC 2 H} 4) 10 -S-C 3 H 6 -S- (OC 2 H 4) 10
S represented by -H, S'-bis (decamethylene glycol) propylene dithio ether _{(36) H- (OCH 2 CH} 2) 5 -S-CH 2 CH (OH) CH 2
_{-S- (CH 2 CH 2 O)} 5 S represented by -H, S'-bis
(Pentaethylene glycol) -2-hydroxypropylene dithioether _{(37) H- (OC 3 H} 6) 2 -S-CH 2 CH (OH) CH 2 -S
_{- (C 3 H 6 O)} S represented by ₂ -H, S'-bis (dipropylene glycol) -2-hydroxypropylene dithioether _{(38) H- (OCH 2 CH} 2) 20 -S-CH 2 CH ₂ -S- (C
H ₂ CH ₂ O) ₂₀ S represented by -H, S'-bis (equalizing sub ethylene glycol) ethylene dithioether (39) 2 represented by _{CH 3 -S-CH 2 CH 2} OH ( methylthio) ethanol

In the above formulas (1) to (9), an oxyethylene group (C ₂ H ₄ O) is repeated in the molecule at adjacent positions on both sides of the monosulfide bond, and the above formulas (10) to (11) )) Has an oxyethylene group or an oxypropylene group (C ₃ H ₆ O) in a single molecule at adjacent positions on both sides of the monosulfide bond. Above
In (12) to (15), the molecule has a repeating oxyethylene group at adjacent positions on both sides of the disulfide bond, and the above formula (16)
Oxygen is added to the adjacent position on both sides of the monosulfide bond.
It has a repeating (hydroxypropylene) group (CH ₂ CH (OH) CH ₂ O) in the molecule. In the above formula (17), a repeating oxyethylene group and a repeating oxypropylene group are present in the molecule at adjacent positions on both sides of the monosulfide bond, and in the above formula (20), oxyethylene groups are present at adjacent positions on both sides of the disulfide bond. In the above formula (21), the repeating of the oxyethylene group and the oxypropylene group are located at adjacent positions on both sides of the disulfide bond.
It has repeating (hydroxypropylene) groups in the molecule. In the above formulas (23) to (25), two monosulfide bonds are contained in the molecule, and one of the monosulfide bonds is bonded to an oxyethylene group, and the other is bonded to an ethylene group or a propylene group. Although the compounds listed in the above formula have many bilaterally symmetric molecular structures around a mono- or disulfide bond, the oxyalkylene-type sulfide-based compound of the present invention may be a compound having a different molecular structure in the left and right, for example, the above formula ( As shown in 39), an alkyl group or the like may be bonded to one side of a mono- or disulfide bond.

The aliphatic sulfide compound of the present invention
That is, the carboxylic acid sulfide compound shown in the above (b)
Is 2,2'-thiodiglycolic acid (HOOCCH_Two
-S-CH_TwoCOOH), 2,2'-thiodipropionic acid
(HOOCCH_TwoCH_Two-S-CH _TwoCH_TwoCOOH)
No.

The above aliphatic sulfide compounds can be used alone or in combination. Among them, 2,2'-thiodiglycol and bis
(Dodecaethylene glycol) thioether, bis (pentadecaethyleneglycol) thioether, 2- (methylthio) ethanol, 2,2'-thiodiglycolic acid and the like are preferred. The content of the aliphatic sulfide compound in the bath is 0.01 to 500 g / L, preferably 1 to 300 g / L.
g / L. Needless to say, the aliphatic sulfide compound may be used in combination with a known gold complexing agent such as a sulfite or a thiosulfate.

The electroless gold plating bath of the present invention contains the present invention 3
As shown, a masking complexing agent can be added. Generally, gold plating is performed on a base metal such as copper, nickel, and palladium. When the base metal is eluted as impurity ions in the bath during the plating operation, the concealment complexing agent functions to conceal or block these. Therefore, the stability of the gold plating bath can be expected to be further improved. The concealing complexing agent is an oxycarboxylic acid, an amine compound, a nitrogen-containing heterocyclic compound, an ammonium compound, or ammonia. Examples of the oxycarboxylic acid include tartaric acid, citric acid, malic acid, and gluconic acid. Can be The amine compound is an aminoacetic acid, an aminopropionic acid, an aminovaleric acid, an aminocarboxylic acid compound such as an amino acid,
The term encompasses compounds such as polyamines such as ethylenediamine and pentaethylenehexamine, and aminoalcohols such as monoethanolamine and diethanolamine.

Specific examples of the aminocarboxylic acid compound among the above amine compounds include ethylenediaminetetraacetic acid (EDTA) and disodium ethylenediaminetetraacetic acid.
(EDTA · 2Na), hydroxyethylethylenediaminetriacetic acid (HEDTA), diethylenetriaminepentaacetic acid
(DTPA), triethylenetetramine hexaacetic acid (TTH
A), ethylenediaminetetrapropionic acid, nitrilotriacetic acid (NTA), iminodiacetic acid (IDA), iminodipropionic acid (IDP), metaphenylenediaminetetraacetic acid,
1,2-diaminocyclohexane-N, N, N ', N'-tetraacetic acid, diaminopropionic acid, glutamic acid, ornithine, cysteine, N, N-bis (2-hydroxyethyl)
Glycine and the like. Specific examples of polyamines, monoamines, amino alcohols and the like among the above amine compounds include ethylenediaminetetramethylenephosphate, diethylenetriaminepentamethylenephosphate,
Examples include aminotrimethylene phosphate, pentasodium aminotrimethylene phosphate, monoethanolamine, diethanolamine, triethanolamine, monopropanolamine, dipropanolamine, and tripropanolamine.

The nitrogen-containing heterocyclic compound includes 1,1
10-phenanthroline, 2,9-dimethyl-1,10-
Phenanthroline, 2,2'-bipyridyl, 2,2 ',
2 ''-terpyridyl, pyridine and the like. The ammonium compound is a concept including an ammonium salt and an alkyl (or aryl) ammonium salt. As the ammonium salt, ammonium sulfate, ammonium chloride, ammonium bromide, ammonium phosphate,
Examples include ammonium hypophosphite, ammonium carbonate, ammonium bicarbonate, ammonium tartrate, ammonium citrate, ammonium oxalate, ammonium formate, ammonium acetate, ammonium borate and the like.
The alkyl (or aryl) ammonium salt is a first to fourth alkyl (or aryl) ammonium in which a hydrogen atom of an ammonium ion (NH ₄ ⁺ ) is substituted with one to four alkyl groups (and / or aryl groups). Salts such as methyl ammonium salt ([CH ₃ NH ₃ ] ⁺ Cl ⁻ ), dipropyl ammonium salt ([(C ₃ H ₇ ) ₂ NH ₂ ] ₂ SO ₄ ), and triethyl ammonium salt ([(C ₂ H ₅ ) ₃ NH] ⁺ CH ₃ S
O ₄ ⁻ ), trimethylbenzylammonium salt ([(CH ₃ ) ₃
N (CH ₂ C ₆ H ₅ )] ⁺ OH ⁻ ), dodecyldimethylbenzylammonium salt ([(CH ₃ ) ₂ (C ₁₂ H ₂₅ ) N (CH ₂ C
₆ H ₅ )] ⁺ Cl ⁻ ), hexadecylpyridinium salt ([(C _{5
H 5 N) -C 16 H 33} ] + I -), and the like octylamine acetate.

The above-mentioned masking complexing agent can be used alone or in combination, and the amount added is 0.001 to 200 g / L.
Preferably it is 0.01 to 100 g / L.

As described above, the electroless gold plating bath of the present invention can be applied irrespective of the substitution type or the reduction type. Therefore, as in the present invention 2, a reducing agent can be contained in the bath. The reducing agent is hypophosphorous acid or its salt, phosphorous acid or its salt, amine borane, borohydride compound, thiourea or its derivative, hydrazine, formaldehyde, ascorbic acid or its salt, glyoxylic acid or its salt And so on. Examples of the hypophosphite include sodium, potassium, calcium, and ammonium salts of hypophosphorous acid. Examples of the amine borane include dimethylamine borane, trimethylamine borane, isopropylamine borane, and morpholine borane. Examples of the borohydride compound include sodium borohydride, potassium borohydride, and the like. Examples of the thiourea derivative include 1,3-dimethylthiourea, trimethylthiourea, and diethylthiourea.
(Eg, 1,3-diethyl-2-thiourea), N, N'-
Diisopropylthiourea, allylthiourea, acetylthiourea, ethylenethiourea, 1,3-diphenylthiourea, thiourea dioxide, thiosemicarbazide, S-methylisothiourea sulfate, tributylthiourea, benzylisothiourea hydrochloride, 1,3-dibutylthio Examples thereof include urea, 1-naphthylthiourea, tetramethylthiourea, 1-phenylthiourea, and 1-methylthiourea. Examples of the hydrazines include hydrazine hydrate, hydrazine sulfate, hydrazine maleate or salts thereof, methylhydrazine, phenylhydrazine, and hydroxyamine.

The above reducing agents can be used alone or in combination. The amount of the reducing agent is 0.001 to 150 g / L, preferably 1 to 150 g / L.
80 g / L.

The gold plating bath of the present invention can further contain various additives such as a surfactant, a pH adjuster and a buffer. Examples of the surfactant include an anionic surfactant, a cationic surfactant, a nonionic surfactant, and an amphoteric surfactant. Examples of the anionic surfactant include an alkyl sulfate, a polyoxyethylene alkyl ether sulfate, a polyoxyethylene alkyl phenyl ether sulfate, an alkylbenzene sulfonate, and an alkylnaphthalene sulfonate. Examples of the cationic surfactant include a quaternary ammonium salt and a pyridinium salt. Examples of the nonionic surfactant include C ₁ -C ₂₀ alkanol, phenol, naphthol, bisphenols, C ₁ -C ₂₅ alkyl phenol, arylalkyl phenol, C ₁ -C ₂₅
C ₂₅ alkyl naphthol, C ₁ -C ₂₅ alkoxyl phosphoric acid (salt), sorbitan esters, polyalkylene glycol, C ₁ -C _{2 2} like ethylene oxide fatty amides (E
O) and / or propylene oxide (PO) from 2 to 300
Those obtained by mole addition condensation are exemplified. Examples of the amphoteric surfactant include carboxybetaine, imidazoline betaine, sulfobetaine, aminocarboxylic acid and the like. Various acids such as hydrochloric acid and sulfuric acid, and various bases such as sodium hydroxide, potassium hydroxide and aqueous ammonia can be used as the pH adjuster. As the buffer,
Ammonium chloride, glycine, boric acids, phosphoric acids and the like can be used.

[0026]

[Function] The stability of Lewis acid / base complex is a general and qualitative concept of hard / soft acid / base.
(That is, the HSAB principle) is known (application of the concept of hard, soft, acid and base to organic chemistry;
Vol. 3, No. 11 (1975)). For example, a base having a large electronegativity, a low polarizability, and a property of strongly retaining valence electrons is called a hard base, and conversely, a small electronegativity, a high polarizability, and relatively weakly retaining valence electrons. A base with a property is called a soft base. Hard bases coordinate to hard acids to form more stable complexes, and soft bases coordinate to soft acids to form more stable complexes. In this case, the gold ion having the property of Lewis acid can be classified as a soft acid, and the aliphatic sulfide compound of the present invention can be classified as a soft base, so that in a gold plating bath, the aliphatic sulfide compound is effective for gold ions. Can be estimated to contribute to stabilization. In particular, it can be assumed that in the oxyalkylene-type sulfide compound, the complexing action to the gold ion is further promoted by the synergistic electron donating function of the sulfur atom of the sulfide group and the oxygen atom of the oxyalkylene group. Further, the aliphatic sulfide-based compound of the present invention has excellent solubility due to the repetition of the oxyalkylene chain and the presence of the carboxyl group (particularly, the solubility of the carboxylic acid-type sulfide-based compound is higher). Becomes better.

[0027]

(1) As shown in the test examples described below, since the electroless gold plating bath of the present invention contains a specific aliphatic sulfide compound as a complexing agent, there is no decomposition after plating and the bath is stable. Excellent in nature. For example, when a sulfite or a thiosulfate, which is frequently used as a complexing agent for gold, is used alone, or when these are used in combination in the presence of a reducing agent, compared to the decomposition of the bath after plating, The aliphatic sulfide compound of the present invention can exhibit a stabilizing effect that is comparable to or better than that obtained when a sulfite and a thiosulfate are used in combination. In general, in an electroless gold plating bath, a reduction plating bath containing a reducing agent tends to be more unstable than a substitution bath containing no reducing agent.However, when the aliphatic sulfide-based compound of the present invention is used, a reduction bath and a substitution bath are used. Regardless of the bath, decomposition after plating can be suppressed smoothly. In addition, the above-mentioned prior art 2
Although the mercaptosuccinic acid of the present invention and the aliphatic sulfide compound of the present invention belong in common to the fact that they belong to the sulfur-containing compound, the stability of the plating bath is clear as compared with Examples 1 to 15 and Comparative Example 2. In this respect, the aliphatic sulfide compound of the present invention can secure the same level as that of mercaptosuccinic acid.

(2) As described in the above (1), since the gold plating bath is stable, the gold plating film obtained from the bath has a uniform color tone and the appearance of the film as shown in the test examples described later. Can maintain a level higher than the practical level.

[0029]

EXAMPLES Examples of the electroless gold plating bath of the present invention will be described in order below, and various test examples of the stability of each gold bath after plating and the appearance of a gold film obtained from the plating bath will be described.
The present invention is not limited to the following examples, test examples, etc.
Of course, any modifications can be made within the scope of the technical idea of the present invention.

Examples 1 to 9 below are examples of a substitution type gold plating bath, and Examples 10 to 15 are examples of a reduction type gold plating bath.
Examples 6 to 9 are examples of the combined use of the aliphatic sulfide compounds of the present invention, or examples of the combination with a known gold complexing agent. Other Examples 1 to 5, 10 to 15 are the examples of the aliphatic sulfide of the present invention. It is a single use example of a system compound. Comparative Example 1 is an example of a substituted gold plating bath using thiosulfate alone as a gold complexing agent, Comparative Example 2
Is an example of a substituted gold plating bath using mercaptosuccinic acid, Comparative Example 3 is an example of a substituted gold plating bath using a combination of thiosulfate and sulfite, and Comparative Example 4 is a thiosulfate and sulfurous acid according to the prior art 2. It is an example of a reduction plating bath using a salt together.

Example 1 A replacement gold plating bath was constructed with the following composition. Sodium chloroaurate (III) 2.0 g / L 2,2'-thiodiglycolic acid 15.0 g / L Adjusted to pH 7.0 with sodium hydroxide Using the above substituted gold plating bath, the following conditions (A) The gold plating film obtained was 0.01 μm
m and a good appearance with a uniform color tone.

Example 2 A replacement gold plating bath was constructed with the following composition. Sodium chloroaurate (III) 5.0 g / L 2,2'-thiodiglycol 12.5 g / L Adjusted to pH 6.0 with sodium hydroxide Using the above substituted gold plating bath, under the following conditions (A) As a result of gold plating, the resulting gold plating film was 0.04μ
m and a good appearance with a uniform color tone.

Example 3 A replacement gold plating bath was constructed with the following composition. Sodium chloroaurate (III) 3.0 g / L 2- (methylthio) ethanol 10.0 g / L Trisodium citrate 40.0 g / L Betaine lauryldimethylaminoacetate 0.1 g / L pH 6.0 with sodium hydroxide Adjustment As a result of performing gold plating under the condition (A) described below using the above-described substituted gold plating bath, the obtained gold plating film was 0.02 μm.
m and a good appearance with a uniform color tone.

Example 4 A replacement gold plating bath was constructed with the following composition. Sodium chloroaurate (III) 2.0 g / L Bis (dodecaethylene glycol) thioether 80.0 g / L Adjusted to pH 5.0 with sodium hydroxide Using the above substituted gold plating bath, gold plating under the following conditions (A) As a result, the obtained gold plating film was 0.04 μm.
m and a good appearance with a uniform color tone.

Example 5 A replacement gold plating bath was constructed with the following composition. Sodium chloroaurate (III) 2.0 g / L bis (pentadecaethylene glycol) thioether 100.0 g / L Trisodium citrate 45.0 g / L Adjusted to pH 5.0 with hydrochloric acid As a result of gold plating under the condition (A), the obtained gold plating film was 0.03 μm.
m and a good appearance with a uniform color tone.

Example 6 A replacement gold plating bath was constructed with the following composition. Sodium chloroaurate (III) 2.0 g / L 2,2'-thiodiglycol 10.0 g / L Bis (pentadecaethylene glycol) thioether 70.0 g / L Polyethylene glycol (PEG1000) 0.1 g / L Hydrochloric acid The pH was adjusted to 4.0. As a result of performing gold plating under the condition (A) described below using the above-described substituted gold plating bath, the resulting gold plating film was 0.04 μm.
m and a good appearance with a uniform color tone.

Example 7 A replacement gold plating bath was constructed with the following composition. Sodium chloroaurate (III) 3.0 g / L 2,2'-thiodiglycolic acid 10.0 g / L Bis (dodecaethylene glycol) thioether 40.0 g / L Trisodium citrate 50.0 g / L Hydrochloric acid pH5 Adjusted to 0.0 Using the above-described replacement gold plating bath, gold plating was performed under the following conditions (A).
m and a good appearance with a uniform color tone.

Example 8 A replacement gold plating bath was constructed with the following composition. Sodium chloroaurate (III) 5.0 g / L bis (pentadecaethylene glycol) thioether 40.0 g / L Sodium sulfite 5.0 g / L Trisodium citrate 40.0 g / L Amidopropyl betaine laurate 0.05 g / L L Adjusted to pH 7.0 with hydrochloric acid As a result of performing gold plating under the following conditions (A) using the above-described substituted gold plating bath, the resulting gold-plated film was 0.03 μm.
m and a good appearance with a uniform color tone.

Example 9 A replacement gold plating bath was constructed with the following composition. Sodium chloroaurate (III) 4.0 g / L 2,2'-thiodiglycol 10.0 g / L Sodium thiosulfate 8.0 g / L Disodium malate 50.0 g / L Adjusted to pH 5.0 with hydrochloric acid As a result of performing gold plating under the following conditions (A) using a displacement gold plating bath, the resulting gold plated film was 0.05 μm thick.
m and a good appearance with a uniform color tone.

Example 10 A replacement gold plating bath was constructed with the following composition. Sodium chloroaurate (III) 2.0 g / L 2,2'-thiodiglycolic acid 30.0 g / L Sodium ascorbate 20.0 g / L Adjusted to pH 7.0 with sodium hydroxide Using the above substituted gold plating bath As a result of gold plating under the condition (B) described later, the obtained gold plating film was 0.05 μm.
m and a good appearance with a uniform color tone.

Example 11 A reduction-type gold plating bath was constructed with the following composition. Sodium chloroaurate (III) 4.0 g / L 2,2'-thiodiglycol 12.5 g / L Sodium hypophosphite 8.0 g / L α-naphthol polyethoxylate (EO15) 0.1 g / L Water The pH was adjusted to 6.0 with sodium oxide. As a result of performing gold plating under the condition (B) described below using the reduced gold plating bath, the resulting gold-plated film was 0.06.
It had a film thickness of μm and exhibited a good appearance with a uniform color tone.

Example 12 A reduction type gold plating bath was constructed with the following composition. Sodium chloroaurate (III) 5.0 g / L 2- (methylthio) ethanol 10.0 g / L Trisodium citrate 40.0 g / L Glyoxalic acid monohydrate 8.0 g / L Adjusted to pH 5.0 with hydrochloric acid As a result of performing gold plating under the condition (B) described below using the reduced gold plating bath, the obtained gold plating film was 0.08.
It had a film thickness of μm and exhibited a good appearance with a uniform color tone.

Example 13 A reduction-type gold plating bath was constructed with the following composition. Sodium chloroaurate (III) 3.0 g / L bis (dodecaethylene glycol) thioether 80.0 g / L Sodium ascorbate 20.0 g / L Octylamine polyethoxylate (EO8) 0.1 g / L Sodium hydroxide pH 4 The gold plating film obtained was 0.06 as a result of performing gold plating under the condition (B) described below using the above-mentioned reduced gold plating bath.
It had a film thickness of μm and exhibited a good appearance with a uniform color tone.

Example 14 A reduction-type gold plating bath was constructed with the following composition. Sodium chloroaurate (III) 5.0 g / L bis (pentadecaethylene glycol) thioether 100.0 g / L thiourea 5.0 g / L Trisodium citrate 45.0 g / L Adjusted to pH 5.0 with hydrochloric acid The above reduction As a result of performing gold plating under the condition (B) described below using a mold gold plating bath, the obtained gold plated film was 0.10.
It had a film thickness of μm and exhibited a good appearance with a uniform color tone.

Example 15 A reduction-type gold plating bath was constructed with the following composition. Sodium chloroaurate (III) 3.0 g / L bis (dodecaethylene glycol) thioether 95.0 g / L Sodium tartrate dihydrate 25.0 g / L Adjusted to pH 6.0 with sodium hydroxide As a result of performing gold plating under the condition (B) described below, the obtained gold plating film was 0.07
It had a film thickness of μm and exhibited a good appearance with a uniform color tone.

Comparative Example 1 A replacement gold plating bath was constructed with the following composition. Potassium chloroaurate (III) 1.0 g / L Sodium thiosulfate 10.0 g / L Adjusted to pH 6.0 with sodium hydroxide

Comparative Example 2 A replacement gold plating bath was constructed with the following composition. Potassium chloroaurate (III) 4.0 g / L Mercaptosuccinic acid 7.5 g / L Adjusted to pH 1.5 with hydrochloric acid

Comparative Example 3 A replacement gold plating bath was constructed with the following composition. Potassium chloroaurate (III) 10.0 g / L Sodium sulfite 25.0 g / L Sodium thiosulfate 60.0 g / L Ammonium chloride 10.0 g / L

Comparative Example 4 A reduction-type gold plating bath was constructed with the following composition. Potassium chloroaurate (III) 10.0 g / L Sodium sulfite 25.0 g / L Sodium thiosulfate 60.0 g / L Thiourea 8.0 g / L Ammonium chloride 10.0 g / L

[Plating Conditions] (1) Condition A: Electroless nickel was applied to a copper plate of 25 × 25 mm to a thickness of 5 μm, and this test piece was replaced with each of the substituted gold plating baths of Examples 1 to 9 and Comparative Examples 1 to 3. Immersed in 60
Gold plating was performed at 10 ° C. for 10 minutes. (2) Condition B: A 25 × 25 mm copper plate was coated with electroless nickel at a thickness of 5 μm, and further subjected to displacement gold plating using the bath of Example 1 above.
It was immersed in each of the reduced gold plating baths of Nos. 0 to 15 and Comparative Example 4 and gold-plated at 60 ° C. for 10 minutes.

Therefore, when the plating treatment was performed using the above electroless gold plating bath, the stability of the bath was evaluated based on the change of the plating bath before and after the treatment. << Example of stability test of electroless gold plating bath >> That is, electroless plating was performed using each of the electroless gold plating baths of Examples 1 to 15 and Comparative Examples 1 to 4, and presence or absence of decomposition of the electroless bath after plating. Was visually evaluated for stability. The evaluation criteria are as follows. ：: There was no bath change before or after plating or during plating, the transparent state was maintained, and no decomposition phenomenon was observed. ×: The bath after plating was turbid and precipitated, or gold was deposited on the inner periphery of the plating container, and a decomposition phenomenon of the bath was observed.

The left column of FIG. 1 shows the test results. Each of the electroless plating baths of Examples 1 to 15 was stable without being decomposed regardless of the substitution type or the reduction type. Comparative Example 3 is a substituted gold plating bath using a highly practical thiosulfate and sulfite in combination as a gold complexing agent. Comparative Example 2 is an example based on the prior art 2 described above, but Example 1 was used. Each of the gold plating baths No. to No. 15 showed results comparable to those of Comparative Example 3 or 2 in terms of bath stability. In particular, the reduction-type gold plating bath containing a reducing agent tends to be unstable, and the stability comparison between Comparative Example 3 and Comparative Example 4 confirms this tendency.
Was not decomposed similarly to the substituted gold plating baths of Examples 1 to 9. Therefore, the electroless gold plating bath using the aliphatic sulfide compound of the present invention,
Not only the substitution type, but also the reduced type exhibits excellent bath stability, and in this regard, it can be seen that this is superior to the reduced type gold plating bath using both thiosulfate and sulfite (Comparative Example 4).

<< Appearance test example of gold plating film >> Gold plating film obtained by performing gold plating under the above conditions A and B using each of the electroless gold plating baths of Examples 1 to 15 and Comparative Examples 1 to 4. Was visually evaluated for its appearance. The evaluation criteria are as follows. ：: The color tone of the film was uniform without unevenness. X: The color tone of the film was uneven in density and was not uniform. The thickness of the plating film was described in the examples of each plating bath.

The right column of FIG. 1 shows the test results. Each of the gold films obtained from each of the electroless plating baths of Examples 1 to 15 exhibited a uniform color tone and a good film appearance. This is in good agreement with the bath stability results in the test examples. That is, the appearance of the plating films obtained from Examples 1 to 15 is as follows:
Since there is no inferiority to the film appearance obtained from Comparative Example 3 which is a substituted gold plating bath using a combination of thiosulfate and sulfite,
It became clear that a film appearance of a practical level or higher could be secured.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a table showing test results of bath stability and film appearance of electroless gold plating baths of Examples 1 to 15 and Comparative Examples 1 to 4.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kaoru Tanaka 5-26 Nishiyanagihara-cho, Hyogo-ku, Kobe-shi, Hyogo Ishihara Pharmaceutical Co., Ltd. F term (reference) 4K022 AA02 BA03 BA31 DA01 DB02 DB04 DB07 DB08

Claims (3)

[Claims] 1. An oxyalkylene-type sulfide compound, mono- or disulfide having an oxyethylene group, oxypropylene group or oxy (hydroxypropylene) group in a single or repeated molecule adjacent to both sides or one side of a mono- or disulfide bond. An electroless gold plating bath containing, as a complexing agent, at least one aliphatic sulfide compound selected from the group consisting of carboxylic acid sulfide compounds having a carboxyl group on the alkylene chain on either or both sides of the bond. 2. The electroless gold plating bath according to claim 1, further comprising a reducing agent. 3. The method according to claim 1, further comprising at least one concealing complexing agent selected from the group consisting of oxycarboxylic acids, amine compounds, nitrogen-containing heterocyclic compounds, and ammonium compounds. 3. The electroless gold plating bath according to 2.