JP2000192248A - Substituted gold plating bath and metal plating method using the bath - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the plating spreading, abnormal deposition, unequal deposition, etc., at the time of applying gold plating and extend the life of a substituted gold plating bath. SOLUTION: This plating bath contains a soluble gold salt, a complexing agent consisting of sulfite and thiosulfite, a concealing complexing agent consisting of oxycarboxylic acid, such as tartaric acid, an amine compound, such as aminoacetic acid or ethylenediamine and ammonium compd., a pH control agent, an amphoteric surfactant or a mixture composed of the amphoteric surfactant and a nonionic surfactant. The plating bath is characterized in that the sulfite and the thiosulfite are combined as the complexing agent, that the concealing complexing agent is used and that the kind of the surfactant is limited to the mixture of the amphoteric or amphoteric and nonionic system. The stabilization of the gold ions in the plating bath and the suppression of the plating spreading, etc., at the time of gold plating may be simultaneously achieved by the synergistic effect based on the constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a displacement gold plating bath and a gold plating method using the bath. The present invention provides a bath having excellent bath stability and capable of effectively preventing spread of plating and uneven deposition during gold plating.

[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,
Uniform thickness of gold-plated coatings on parts with minute and complicated shapes with minute gaps and recesses, or on places where there are design restrictions due to high-density mounting, or on electrically isolated fine parts Was difficult to form. On the other hand, the electroless plating method has an advantage that a plating film can be formed without energization, and a film can be formed without trouble even on a component having a fine and complicated shape or an electrically isolated portion.

[0003] In the electroless plating method, the metal ions in the bath are dissolved when the base metal is eluted into the bath, due to the difference in the oxidation-reduction potential between the metal in the bath and the metal to be plated (base). And a reduction plating method in which metal ions in a plating bath are precipitated by the action of a reducing agent (or, the deposited metal serves as a catalyst for the reducing agent, and is also called an autocatalytic method). ). However, in contrast to this broad concept, in the narrow sense, the latter reduction plating is often distinguished from the former substitution plating, and is often referred to as electroless plating. (Note that the following usage of electroless plating is basically To the broad concept above).

[0004]

2. Description of the Related Art Generally, the above-described replacement gold plating is suitable for improving the solderability of chip components and improving the adhesion between a nickel base material and a thick gold film formed by a reduction type electroless method. As a substitution type electroless gold plating bath, JP-A-4-371584 discloses an ED which forms a complex salt with a gold sulfite, a thiosulfate, and a base metal eluted in the bath.
A non-cyanide type gold plating bath containing a complexing agent such as TA or a salt thereof and a pH adjusting agent is disclosed (hereinafter referred to as prior art 1). The replacement gold plating bath of the prior art 1 is
Since no cyanide is used, there is no problem in safety at the time of work and waste liquid, and the liquid property is neutral or weakly acidic, the deposition rate is fast regardless of the substitution method, and thick plating is possible. It is stated that there is. However,
If the gold plating bath is applied to a printed circuit board, etc., the coating will spread out at places other than the purpose (for example, resist), causing bleeding, etc. In many cases, precipitation or unevenness in deposition in which the color tone of the film is not uniform occurs.

The following are examples of electroless gold plating baths designed to prevent the spread of plating. (1) Prior art 2 JP-A-6-17258 discloses a soluble salt of gold, a gold complexing agent comprising a macrocyclic polyamine, an aminocarboxylic acid such as ethylenediaminetetraacetic acid and glycine, or a tartaric acid and the like. A surfactant having a polyethylene group or the like is added as a brightener to a plating bath containing a complexing agent capable of coordinating with a base metal ion such as oxycarboxylic acid and various pH adjusters, and lauryl sulfate is added. A gold plating bath of a substitution type or a reduction type in which an anionic surfactant such as a salt or dodecyl sulfate is added as a wetting agent is disclosed. The brightener is used for imparting gloss to the gold film and improving mechanical properties. Further, the wetting agent is used for improving the wettability of the plating solution to the concave portion of the gold film and preventing the generation of pinholes in the gold film.

(2) Prior art 3 JP-A-6-280039 discloses that a water-soluble gold salt such as gold sulfite, a complexing agent such as sulfite, thiosulfate and EDTA, hydrazines and ascorbic acids A reduction type gold plating bath in which a stabilizer such as a nonionic surfactant of polyethylene glycol or polypropylene glycol type is added to a plating bath containing a reducing agent such as an amine borane, thiourea or hypophosphorous acid is disclosed. I have. The electroless gold plating bath is not a substitution type, but a reduction type plating bath containing a reducing agent such as hydrazine or thiourea. The stabilizer is used to prevent the spread of plating and form a good gold plating film only on the metal portion.

[0007]

In the electroless gold plating baths of the above-mentioned prior arts 2 and 3, various surfactants are added for preventing the spread of plating and the generation of pinholes.
Actually, it is not easy to effectively prevent the spread of plating, abnormal deposition, deposition unevenness, and the like. In the displacement gold plating bath, the base metal elutes as the plating reaction progresses, and the bath deteriorates or self-decomposes, or the impurities in the bath accumulate. There is a problem that cannot be continued. An object of the present invention is to provide a substituted gold plating bath that has excellent bath stability over time, prevents the spread of plating, prevents uneven deposition and abnormal deposition, and obtains a gold plating film excellent in shear strength and the like.

[0008]

Means for Solving the Problems In the displacement gold plating bath, the present inventors stabilize gold ions in the bath with a combination of a sulfite and a thiosulfate, and add a surfactant to a specific type of surfactant. The use of a concealing complexing agent that sequesters impurity metal ions in the bath increases the stability of the bath, prevents the spread of plating and prevents uneven deposition when gold is deposited, or gold plating. The inventors have found that the shear strength and the like of the film are improved, and completed the present invention.

That is, the present invention comprises (A) a soluble gold salt, (B)
A complexing agent comprising a sulfite and a thiosulfate, (C) tartaric acid,
Oxycarboxylic acids such as citric acid and malic acid, amino compounds such as aminoacetic acid, ethylenediamine, ethanolamine, ethylenediaminetetraacetic acid, and benzylamine;
Nitrogen-containing heterocyclic compounds such as pyridine, bipyridyl and phenanthroline, ammonium compounds such as ammonium chloride, at least one concealing complexing agent composed of ammonia, (D) a pH adjuster, (E) an amphoteric surfactant, or an amphoteric A displacement gold plating bath containing a mixture of a surfactant and a nonionic surfactant.

[0010] The present invention 2 is characterized in that, in the above-mentioned invention 1, (B)
Characterized in that at least one of a sulfide compound and a sulfinic acid is contained in place of the complexing agent.

[0011] The present invention 3 is characterized in that the above invention 1 or 2 further comprises a buffer.

A fourth aspect of the present invention is characterized in that the plating bath according to any one of the first to third aspects of the present invention further contains a trace amount of at least one of a copper salt and a nickel salt.

[0013] The present invention 5 is a gold plating method characterized in that gold is applied to a copper, nickel or palladium metal surface forming a substrate by the substitutional gold plating bath of any of the present inventions 1-4. is there.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Is a gold salt capable of supplying trivalent or trivalent gold ions, specifically, potassium chloroaurate, sodium chloroaurate, ammonium chloroaurate, gold potassium sulfite, gold sodium sulfite, gold ammonium sulfite, Examples include gold potassium thiosulfate, gold sodium thiosulfate, and gold ammonium thiosulfate. The content of the soluble gold salt in the bath is 0.001 to 20 g / L in terms of metal, preferably 0.5 to 1 g / L.
0 g / L.

The complexing agent is a mixture of a sulfite and a thiosulfate, and acts mainly as a complexing agent for gold ions in a plating bath, and stabilizes gold ions in the bath. It is also conceivable that these salts contribute to reducing trivalent gold ions to monovalent. Examples of the sulfite include sodium sulfite, potassium sulfite, ammonium sulfite, and alkaline earth metal salts. As thiosulfate,
Examples thereof include sodium thiosulfate, potassium thiosulfate, ammonium thiosulfate, and alkaline earth metal salts.
The content of the sulfite and the thiosulfate may be 1 to 300 g / L in the bath as a mixture, preferably 10 to 10 g / L.
0 g / L. If it is less than 1 g / L, the gold plating bath will self-decompose and precipitate, and if it is excessive, the plating rate may be reduced.

Further, as the complexing agent, the above-mentioned sulfite and
And thiosulfates instead of sulfide compounds
Or sulfinic acids can be used. the above
Examples of the sulfide compound include C_TwoH_FiveSC_TwoH_Five, (Is
o-C_ThreeH₇) -S- (iso-C_ThreeH₇), C_TwoH_FiveS- (is
o-C_FourH₉), C₆H_FiveSC₆H_Five, C₆H_FiveSCH_Three, 2-d
Tylthioaniline, 2,2′-dipyridyl sulfide,
HOOCCH _TwoSCH_TwoCOOH, HOOCCH_TwoCH_TwoS
CH_TwoCH_TwoMonosulfide compounds such as COOH, CH
_ThreeSSCH_Three, C_TwoH_FiveSSC_TwoH_Five, C_ThreeH₇SSC_ThreeH₇, C
₆H_FiveSSC₆H_Five2,2'-dibenzothiazolyl disul
Fido, 2- (2-aminoethyldithio) pyridine, 2,
2'-dithiadiazolyl disulfide, 5,5'-di
(1,2,3-triazolyl) disulfide, 2,2'-di
Pyrazinyl disulfide, 2,2'-dipyridyl disulphide
Fido, 2,2'-dithiodianiline, 4,4'-dipyri
Zyl disulfide, 2,2'-diamino-4,4'-dim
Tyldiphenyl disulfide, 2,2'-dipyridazini
Rudisulfide, 5,5'-dipyrimidinyl disulfide
2,2'-di (5-dimethylaminothiadiazolyl)
Disulfide, 5,5'-di (1-methyltetrazolyl)
Disulfide, 2,2'-di (1-methylpyrrolyl) dis
Sulfide, 2-pyridyl-2-hydroxyphenyldis
Sulfide, 2,2'-dipiperidyl disulfide, 2,2
2'-dipyridyl disulfide, 2,6-di (2-pyridyl
Rudithio) pyridine, 2,2'-dipiperazinyldisulf
2,2'-di (3,5-dihydroxypyrimidinyl)
Disulfide, 2,2'-diquinolyl disulfide, 2,2
2'-α-picolyl disulfide, 2,2'-di (8-
(Droxyquinolyl) disulfide, 5,5'-diimidazo
Ryl disulfide, 2,2'-dithiazolyl disulfide
, 2-pyridyl-2-aminophenyl disulfide,
2-pyridyl-2-quinolyl disulfide, 2,2'-
Dithiazolinyl disulfide, 2,2'-dimorpholino
Disulfide, 2,2'-di (8-methoxyquinolyl) di
Sulfide, 4,4'-di (3-methoxycarbonylpyri
(Jill) disulfide, 2-pyridyl-4-methylthiophene
Enyl disulfide, 2-piperazyl-4-ethoxyme
Tylphenyl disulfide, 2,2'-di {6- (2-pyri
(Zirdithio) pyridyl disulfide, 2,2'-diquino
Xalinyl disulfide, 2,2'-dipteridinyl di
Sulfide, 3,3'-diflazanyl disulfide, 3,3
3'-diphenanthrolinyl disulfide, 8,8'-
Diquinolyl disulfide, 1,1'-diphenazinyl di
Sulfide, 2,2'-dipicolyl disulfide,
Tylaminodiethyl disulfide, 2,2'-diperch
Droindolyl disulfide, 2-aminoethyl-2 '
-Hydroxyethyl disulfide, di (2-pyridylti
E) Disulfide compounds such as methane.

Examples of the above sulfinic acids include methanesulfinic acid, ethanesulfinic acid, phenolsulfinic acid, toluenesulfinic acid, and salts thereof. The sulfinic acids have the general formula R (MO) S → O (R is an alkyl group such as methyl or ethyl, a phenyl group or a phenyl group having a substituent such as a methyl group or a hydroxyl group, M is hydrogen or Na, K, It is noted that it is structurally similar to the sulfite represented by the general formula (MO) ₂ S → O. The content of the sulfide compound or the sulfinic acid in the plating bath may be basically the same as the content of the mixture of the sulfite and the thiosulfate, but may be small. However, the sulfide compound and the sulfinic acid can be expected to have the same action as gold sulfonate and thiosulfate, and thus may be used together with a mixture of sulfite and thiosulfate.

The concealing complexing agent is an oxycarboxylic acid, an amine compound, a nitrogen-containing heterocyclic compound, an ammonium compound, ammonia, or the like, which is substituted when substituting gold plating on a base metal such as copper or nickel. The metal impurities in the base material are concealed or blocked by elution into the bath based on the reaction, thereby preventing deterioration of the bath and uneven deposition. Examples of the oxycarboxylic acid include tartaric acid, citric acid, and malic acid. Examples of the amine compound include aminoacetic acid, aminopropionic acid, aminovaleric acid, aminocarboxylic acid compounds such as amino acids, polyamines such as ethylenediamine and pentaethylenehexamine, monoethanolamine and compounds such as aminoalcohols such as diethanolamine. It is an inclusive concept.

Specific examples of the aminocarboxylic acid compound among the above amine compounds include ethylenediaminetetraacetic acid (EDTA) and ethylenediaminetetraacetic acid disodium salt.
(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 concealing complexing agent can be used alone or in combination, and its addition amount is 0.001 to 200 g / L.
Preferably it is 0.01 to 100 g / L. 0.001g
/ L, the amount of impurity metal ions in the bath increases,
The bath will self-decompose. If it exceeds 200 g / L, uneven deposition such as spots will occur.

The surfactant used in the present invention is either an amphoteric surfactant or a mixture of an amphoteric surfactant and a nonionic surfactant. Examples of the amphoteric surfactant include carboxybetaine, imidazoline betaine, sulfobetaine, aminocarboxylic acid and the like. Also, sulfation of a condensation product of ethylene oxide and / or propylene oxide with an alkylamine or diamine,
Alternatively, sulfonated adducts can also be used.

The carboxybetaine has the following general formula:
(a).

Embedded image (In the formula (a), R ₇ is C ₁ -C ₂₀ alkyl, R ₈ and R ₉ are the same or different C ₁ -C ₅ alkyl, and n is an integer of 1-3.)

The above imidazoline betaine has the following general formula
(b).

Embedded image (In the formula (b), R ₁₀ is C ₁ -C ₂₀ alkyl, R ₁₁ is (CH ₂ ) _m
OH or (CH ₂ ) _m OCH ₂ CO ₂ ⁻ , R ₁₂ is (CH ₂ ) _n CO _{2
^{-, (CH 2) n SO}} 3 -, CH (OH) CH 2 SO 3 -, m and n
Represents an integer of 1 to 4. )

Representative carboxybetaines or imidazoline betaines are betaine lauryldimethylaminoacetate, betaine myristyldimethylaminoacetate, betaine stearyldimethylaminoacetate, coconut oil fatty acid amidopropyldimethylaminoacetate betaine, amide propionate betaine, butyric acid Amidopropyl betaine, amidopropyl betaine caprate, amidopropyl betaine laurate, amidopropyl betaine myristate, amidopropyl betaine palmitate, amidopropyl betaine oleate, amidopropyl betaine stearate, amidopropyl betaine palm oil, 2-
Undecyl-1-carboxymethyl-1-hydroxyethylimidazolinium betaine, 2-octyl-1-carboxymethyl-1-carboxyethylimidazolinium betaine, and the like. Sulfated and sulfonated adducts include ethoxylated alkyl. Sulfuric acid adducts of amines and sodium salts of sulfonated lauric acid derivatives can be mentioned.

Examples of the sulfobetaine include coconut oil fatty acid amidopropyldimethylammonium-2-hydroxypropanesulfonic acid, sodium N-cocoylmethyltaurine, sodium N-palmitoylmethyltaurine and the like. Examples of the aminocarboxylic acid include dioctylaminoethylglycine, N-laurylaminopropionic acid, and octyldi (aminoethyl) glycine sodium salt.

[0027] Specific examples of the nonionic surfactants, C ₁ -C ₂₀ alkanols, phenol, naphthol, bisphenol, C ₁ -C ₂₅ alkyl phenols, aryl phenols, C ₁ -C ₂₅ alkyl naphthol, C ₁ ~ C ₂₅ alkoxylated phosphoric acid (salt), sorbitan ester, polyalkylene glycol, C _1-
Etc. C ₂₂ fatty amide ethylene oxide (EO) and /
Or propylene oxide (PO) with those engaged 2-300 mol adduct condensation or, C ₁ -C ₂₅ alkoxylated phosphoric acid (salt)
And the like.

Examples of the C ₁ -C ₂₀ alkanol for addition condensation of ethylene oxide (EO) and / or propylene oxide (PO) include methanol, ethanol, n-butanol, t-butanol, n-hexanol, octanol, decanol and lauryl. Alcohol, tetradecanol, hexadecanol, stearyl alcohol, eicosanol, oleyl alcohol, docosanol and the like can be mentioned. Similarly, as the above bisphenols,
Bisphenol A, bisphenol B, bisphenol F and the like can be mentioned. Examples of the C ₁ -C ₂₅ alkylphenol include mono-, di-, or trialkyl-substituted phenols such as p-methylphenol, p-butylphenol, p-isooctylphenol, p-nonylphenol, p-hexylphenol, and 2,4-diphenol. Butylphenol, 2,4,6-tributylphenol, dinonylphenol, p-dodecylphenol, p-laurylphenol, p-stearylphenol and the like. Examples of the arylalkylphenol include 2-phenylisopropylphenol, cumylphenol,
(Mono, di or tri) styrenated phenol, (mono, di or tri) benzylphenol and the like. Examples of the alkyl group of the C ₁ -C ₂₅ alkyl naphthol include:
Methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, dodecyl, octadecyl and the like,
It may be at any position on the naphthalene nucleus. Examples of the alkylene glycol include polyoxyethylene glycol, polyoxypropylene glycol, and polyoxyethylene polyoxypropylene copolymer.

The above C ₁ -C ₂₅ alkoxylated phosphoric acid (salt)
Is represented by the following general formula (c).

Embedded image (In the formula (c), R _a and R _b are the same or different C ₁ -C ₂₅ alkyl, provided that one may be H. M represents H or an alkali metal.)

As the sorbitan ester, mono,
1,4-, 1,5- or 3,6 di- or triesterified
-Sorbitan, such as sorbitan monolaurate, sorbitan monopalmitate, sorbitan distearate,
Sorbitan dioleate, sorbitan mixed fatty acid ester and the like can be mentioned. Examples of the C ₁ -C ₂₂ aliphatic amide include propionic acid, butyric acid, caprylic acid, capric acid,
Examples include amides such as lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, behenic acid, coconut oil fatty acid, and tallow fatty acid.

Further, as the nonionic surfactant, R ₁ N (R ₂ ) ₂ → O (wherein R ₁ is a C ₅ -C ₂₅ alkyl or RCONHR)
₃ (R ₃ represents C ₁ -C ₅ alkylene) and R ₂ represent the same or different C ₁ -C ₅ alkyl. ) Etc. can be used.

Each of the amphoteric surfactants or nonionic surfactants can be used alone or in combination, and the content of amphoteric surfactants or surfactants combining amphoteric and nonionic surfactants is 0.0001.
To 100 g / L, preferably 0.001 to 50 g / L.

As the pH adjuster, various acids such as hydrochloric acid and sulfuric acid, and various bases such as sodium hydroxide, potassium hydroxide and ammonium hydroxide can be used. Further, a pH buffering agent such as ammonium chloride, glycine, boric acid or phosphate can be added to the substituted gold plating bath of the present invention.

In the displacement plating bath of the present invention, as described in the present invention 4, at least one of a copper salt and a nickel salt contains 0.0.
A small amount can be blended in the range of 0.01 to 5 g / L, preferably 0.01 to 1 g / L. If the amount is excessively mixed, the bath may be deteriorated. Therefore, it is important that the amount does not exceed 5 g / L. These metal salts, in addition to hydrochloride, sulfate, etc.,
Any salt can be used. When a small amount of these salts are added to the bath, they can act in a complex manner with the concealing complexing agent, stabilize the plating rate, and suppress the deposition unevenness and abnormal deposition of the plating film.

The substrate to which the substitutional gold plating bath of the present invention is applied may be a metal such as copper, nickel, iron or the like, or a metal such as an alloy thereof. It can also be applied. Application to a metal base, as shown in Invention 5,
A typical example is to perform substitutional gold plating on a copper, nickel or palladium metal ground. However, it goes without saying that nickel or palladium metal plating may be performed on the base metal, and gold plating may be performed using these metal films as a base material. For example, when performing gold plating using a nickel film as a base, nickel plating is performed on a copper base,
Substitution gold plating can be performed on this nickel film. When gold plating is performed using a palladium film as a base, nickel plating or palladium plating can be applied to a copper base, and gold plating can be applied to the palladium film. Methods such as nickel plating are electric,
Regardless of electroless. Also, after forming a gold film by the replacement gold plating of the present invention, if subjected to a reduction type electroless plating,
It goes without saying that gold can be thickened.

[0036]

The substitution gold plating bath of the present invention is characterized in that a sulfite and a thiosulfate are combined as complexing agents, a masking complexing agent is used, the type of surfactant is amphoteric, or a mixture of amphoteric and nonionic. There is a feature of the configuration in that it is specified. Therefore, the constituents are synergistic to stabilize gold ions in the plating bath, suppress plating spread or abnormal deposition during gold plating, stabilize the plating speed, and improve the strength of the resulting gold plating film. Various actions are performed simultaneously.

[0037]

(1) In the substituted gold plating bath of the present invention, the plating bath does not deteriorate or undergo self-decomposition, as shown in the test examples described later, and the bath stability is excellent. On the other hand, in Comparative Example 5 containing no concealing complexing agent and Comparative Example 6 lacking thiosulfate as a complexing agent, the bath stability was poor.

(2) When gold plating is performed using the displacement plating bath of the present invention, as shown in the test examples described below, plating spread and abnormal deposition do not occur, and the gold film is smoothly formed on the target metal portion. Can be formed and the resulting gold film has no deposition unevenness,
The throwing power is also good. On the other hand, in Comparative Example 4 containing no surfactant, plating spread occurred,
Deposition unevenness was observed in the gold film, and the throwing power was poor.
As described above, the prior art 2 discloses a substituted gold plating bath using a macrocyclic polyamine as a complexing agent and using a nonionic surfactant and an anionic surfactant in combination. Discloses a reduction-type gold plating bath using a hydrazine or thiourea as a reducing agent and containing a nonionic surfactant. The replacement gold plating bath of the present invention is common to the prior arts 2 and 3 in that it is a (broadly defined) electroless plating bath containing a surfactant. The difference is that the addition is limited, or the addition is limited to the combined use of an amphoteric surfactant and a nonionic surfactant. Comparative Example 1 in which the type of surfactant was added in combination with a nonionic surfactant and an anionic surfactant while the composition of the plating bath of the present invention was used as a basis, or sole addition of a nonionic surfactant was performed. In Comparative Example 2, the life of the plating bath and the throwing power of the plating film were good, but during plating, plating spread and abnormal deposition occurred, and deposition unevenness was also observed on the gold plating film. The advantage of the substituted gold plating bath of the present invention is apparent. On the other hand, in Comparative Example 6 in which only a sulfite was contained as a complexing agent, deposition unevenness occurred in the plating film.

(3) In the displacement gold plating bath of the present invention, as shown in the test examples described later, the evaluation of the shear strength of the obtained gold plating film is also good. Therefore, when the gold plating bath of the present invention is applied to high-density mounting and the like, chip components and the like can be firmly mounted on a printed circuit board, and the reliability of products can be improved. On the other hand, in Comparative Examples 1 to 6, good evaluation was not always obtained in terms of shear strength, and the reliability of the product was poor.

[0040]

[Examples] In the following, examples of the replacement gold plating bath will be sequentially described, and the life of the gold plating bath after preparation, the degree of occurrence of plating spread or abnormal deposition during plating, or the shear strength of the obtained gold plating film will be described. Various test examples such as the above will also be described. It should be noted that the present invention is not limited to the following embodiments, and it goes without saying that many modifications can be made within the scope of the technical idea of the present invention.

The following Examples 1 and 3 to 8 are examples using sulfites and thiosulfates as complexing agents, and Example 2 is an example using disulfide compounds in addition to these salts as complexing agents. . Examples 1 to 3 and 7 to 8 are examples of single use of the masking complexing agent, and Examples 4 to 6 are examples of combined use of the masking complexing agent. Examples 1 to 4 and 6 to 8 are examples in which an amphoteric surfactant is used alone as a surfactant, and Example 5 is an example in which an amphoteric surfactant is used in combination with a nonionic surfactant. Example 8 is an example of a trace amount of a specific metal salt. On the other hand, Comparative Example 1 was an example in which a nonionic surfactant and an anionic surfactant were used in combination as surfactants, Comparative Example 2 was an example of using only a nonionic surfactant alone, and Comparative Example 3 was an example in which only an anionic surfactant was used. Comparative Example 4 is a blank example in which no surfactant is added, and Comparative Example 5 is Comparative Example 5.
Is a blank example in which a masking complexing agent is not added, and Comparative Example 6 is a blank example in which only a sulfite is used as a complexing agent and a thiosulfate is not used. Examples 1 to 8 and Comparative Examples 1 to
As described above, the content ratio of each soluble gold salt of No. 6 indicates the number of grams in terms of metal per liter, for example, 3
In the case of a valent gold salt, it represents the number of grams as Au ³⁺ .

Example 1 A replacement gold plating bath was constructed with the following composition. Sodium chloroaurate (III); 3.0 g / L sodium sulfite; 10.0 g / L sodium thiosulfate; 20.0 g / L disodium malate; 50.0 g / L betaine stearyl dimethylaminoacetate; 0.1 g / L L Ammonium chloride: pH adjusted to 6.0 with 20.0 g / L hydrochloric acid When displacement plating was performed under the conditions described below using the displacement gold plating bath described above, the resulting gold film had a thickness of 0.07 μm. And a uniform appearance with a bright yellow color tone.

Example 2 A replacement gold plating bath was constructed with the following composition. Potassium chloroaurate (III); 2.0 g / L sodium sulfite; 5.0 g / L sodium thiosulfate; 15.0 g / L dithiodianiline; 0.5 g / L EDTA; 15.0 g / L 2-octyl- 1-carboxymethyl-1-carboxyoxyethyl imidazolium betaine; 0.15 g / L ammonium chloride; 15.0 g / L adjusted to pH 5.0 with hydrochloric acid. Upon application, the resulting gold film had a thickness of 0.05 μm and exhibited a uniform appearance with a bright yellow color and a good appearance.

Example 3 A replacement gold plating bath was constructed with the following composition. Potassium chloroaurate (III); 1.0 g / L sodium sulfite; 20.0 g / L sodium thiosulfate; 10.0 g / L trisodium citrate; 50.0 g / L amide laurate betaine; 0.05 g / L L Ammonium chloride: pH adjusted to 6.0 with 10.0 g / L hydrochloric acid When displacement plating was performed under the conditions described below using the displacement gold plating bath, the resulting gold film had a thickness of 0.10 μm. And a uniform appearance with a bright yellow color tone.

Example 4 A replacement gold plating was prepared with the following composition. Potassium chloroaurate (III); 5.0 g / L sodium sulfite; 25.0 g / L sodium thiosulfate; 10.0 g / L trisodium citrate; 60.0 g / L tartaric acid; 5.0 g / L myristyl dimethylamino Betaine acetate; 0.01 g / L ammonium chloride; 10.0 g / L Sulfuric acid, pH 7.0 Using the above-described substitutional gold plating bath, substitution plating was performed under the conditions described below. It had a film thickness of .12 µm and exhibited a uniform and good appearance with a bright yellow color tone.

Example 5 A replacement gold plating bath was constructed with the following composition. Potassium chloroaurate (III); 3.0 g / L sodium sulfite; 30.0 g / L sodium thiosulfate; 20.0 g / L trisodium citrate; 10.0 g / L bipyridyl; 0.1 g / L 2-undecyl -1-Carboxymethyl-1-hydroxyethylimidazolium betaine; 0.05 g / L octylamine polyethoxylate (EO8); 0.01 g / L ammonium chloride; 10.0 g / L Sulfuric acid, pH 6.0 When the displacement plating was performed using a gold plating bath under the conditions described below, the obtained gold film had a thickness of 0.09 μm and exhibited a uniform appearance with a bright yellow color tone and a good appearance.

Example 6 A replacement gold plating bath was constructed with the following composition. Potassium chloroaurate (III); 4.0 g / L sodium sulfite; 20.0 g / L sodium thiosulfate; 10.0 g / L trisodium citrate; 50.0 g / L 1,10-phenanthroline; 0.5 g / L L Lauryl dimethylaminoacetate betaine; 0.1 g / L ammonium chloride; 20.0 g / L Adjust pH to 7.0 with hydrochloric acid Using the above substituted gold plating bath, displacement plating was performed under the conditions described below. The gold film had a thickness of 0.09 μm and exhibited a uniform appearance with a bright yellow color tone.

Example 7 A replacement gold plating bath was constructed with the following composition. Potassium chloroaurate (III); 5.0 g / L sodium sulfite; 30.0 g / L sodium thiosulfate; 15.0 g / L ethylenediamine; 5.0 g / L coconut oil fatty acid amidopropyl betaine; 0.15 g / L chloride Ammonium: pH was adjusted to 6.0 with 15.0 g / L sulfuric acid. Using the above substituted gold plating bath, displacement plating was performed under the conditions described below. As a result, the obtained gold film had a thickness of 0.13 μm. Uniform and good appearance with bright yellow color tone.

Example 8 A replacement gold plating bath was constructed with the following composition. Potassium chloroaurate (III); 1.0 g / L sodium sulfite; 30.0 g / L sodium thiosulfate; 20.0 g / L ethylenediamine; 20.0 g / L coconut oil fatty acid amidopropyl acetate betaine; 0.1 g / L Ammonium chloride: 10.0 g / L Nickel chloride: 0.05 g / L Adjusted to pH 6.0 with hydrochloric acid The displacement gold plating bath was subjected to displacement plating under the conditions described below. It had a thickness of .11 µm and exhibited a uniform and good appearance with a bright yellow color tone.

Comparative Example 1 A replacement gold plating bath was constructed with the following composition. Potassium chloroaurate (III); 1.0 g / L sodium sulfite; 20.0 g / L sodium thiosulfate; 10.0 g / L EDTA; 20.0 g / L polyoxyethylene glycol lauryl ether; 0.1 g / L dodecyl Sodium sulfate; 0.1 g / L boric acid; 5.0 g / L hydrochloric acid to pH 6.0

Comparative Example 2 A replacement gold plating bath was constructed with the following composition. Potassium chloroaurate (III); 1.0 g / L sodium sulfite; 20.0 g / L sodium thiosulfate; 10.0 g / L trisodium citrate; 45.0 g / L polyethylene glycol (PEG4000); 001 g / L boric acid; pH 6.0 with 5.0 g / L hydrochloric acid

Comparative Example 3 A replacement gold plating bath was constructed with the following composition. Potassium chloroaurate (III); 1.0 g / L sodium sulfite; 20.0 g / L sodium thiosulfate; 10.0 g / L trisodium citrate; 45.0 g / L sodium lauryl sulfate; 0.1 g / L chloride Ammonium: pH 6.0 with 8.0 g / L hydrochloric acid

Comparative Example 4 A replacement gold plating bath was constructed with the following composition. Potassium chloroaurate (III); 1.0 g / L sodium sulfite; 20.0 g / L sodium thiosulfate; 10.0 g / L trisodium citrate; 45.0 g / L ammonium chloride; 8.0 g / L hydrochloric acid pH 6.0

Comparative Example 5 A replacement gold plating bath was constructed with the following composition. Potassium chloroaurate (III); 1.0 g / L sodium sulfite; 20.0 g / L sodium thiosulfate; 10.0 g / L betaine lauryl dimethylaminoacetate; 0.05 g / L pH 6.0 with hydrochloric acid

Comparative Example 6 A replacement gold plating bath was constructed with the following composition. Potassium chloroaurate (III); 1.0 g / L sodium sulfite; 20.0 g / L trisodium citrate; 45.0 g / L betaine lauryl dimethylaminoacetate; 0.05 g / L ammonium chloride; 8.0 g / L Adjust pH to 6.0 with hydrochloric acid

<< Appearance Test Example of Gold Plating Film >> First, electroless nickel plating was applied to a patterned BGA (Ball Grid Array) substrate to a thickness of 5 μm, and this test piece was used in Examples 1 to 8 and Comparative Examples. Each of the substituted gold plating baths Nos. 1 to 6 was immersed in a bath, and a gold plating film was formed on the above-mentioned pattern by the replacement method under the processing conditions of 60 ° C. and 10 minutes as described above. Then, the thickness of the gold plating film is measured (each film thickness is described in each of the above examples), and with respect to the obtained gold film, plating spread, abnormal deposition, degree of deposition unevenness, or throwing power is measured. Was visually observed.

The evaluation criteria for each test object are as follows. (1) Spread of plating ○: No bleeding of the gold film spreading in places other than the pattern was observed. ×: A gold film was deposited on the periphery other than the pattern, and bleeding was observed. (2) Abnormal deposition ：: No gold film was deposited at a position away from the pattern. ×: The gold film was abnormally deposited at places other than the pattern as if flying. (3) Deposition unevenness ○: The color tone of the deposited gold film was homogeneous. X: Shading of the color tone of the deposited gold film occurred. (4) Powerfulness 回 り: A gold film was uniformly formed on the entire surface of the pattern. ×: A non-plated portion occurred.

The four columns on the left side of FIG. 1 show the test results. The gold coatings obtained from the displacement plating baths of Examples 1 to 8 did not cause plating spread, abnormal deposition or deposition unevenness, and had good throwing power. On the other hand, in the gold film obtained from Comparative Example 4 in which no surfactant was added, plating spread, uneven deposition occurred, poor throwing power, and a comparative example in which both nonionic and anionic surfactants were used in combination. The gold coating obtained from Comparative Example 1 or Comparative Example 2 in which only a nonionic surfactant was used alone caused plating spreading, abnormal deposition, and deposition unevenness. Comparative Example 6 lacking thiosulfate as a complexing agent
In the gold film obtained from the above, uneven deposition occurred. Therefore,
A gold film obtained from the substituted gold plating bath of the present invention using an amphoteric surfactant alone, or using an amphoteric surfactant and a nonionic surfactant in combination and using a sulfite and a thiosulfate as complexing agents. As compared with Comparative Examples 1 to 6, clear superiority was confirmed in terms of overall plating appearance such as plating spread, uneven deposition, and throwing power.

<< Characteristic Test Example of Gold Plated Film >> With respect to each of the gold plated films of Examples 1 to 8 and Comparative Examples 1 to 6 obtained in the above test examples, the pattern diameter of the gold-plated film was 0.5.
A 0.74 mm diameter 6/4 eutectic solder ball is mounted on each BGA substrate with a thickness of 0.8 mm, and a shear strength tester (PTR-0)
1; manufactured by Resca Corporation), and a ball shear test was performed by applying a lateral impact, and the breaking mode of each substrate was visually evaluated. The evaluation criteria for this test are as follows. A: 100% of eutectic solder remained on the substrate. B: The residual ratio of solder was 50% or more and less than 100%. C: The residual ratio of solder was less than 50%. D: No solder was left on the substrate side.

The second column from the right in FIG. 1 shows the test results. In the gold films obtained from the displacement plating baths of Examples 1 to 8, 100% of the eutectic solder remained on the substrate side, and it was observed that the solder was firmly bonded on the gold plating film. A. In contrast, Comparative Example 2,
In 3 and 5, the failure mode was both B, and it was observed that the solder was not necessarily firmly bonded on the gold coating. Therefore, the gold film obtained from the displacement plating bath of the present invention is also strong in terms of mechanical strength, and when the displacement gold plating bath of the present invention is applied to mounting of electronic components such as a printed circuit board, the reliability of the electronic component is reduced. Can be effectively improved.

<< Example of bath life test in displacement gold plating bath >>
The replacement gold plating was repeated using each of the plating baths of Examples 1 to 8 and Comparative Examples 1 to 6, and the number of turns (replenishment times) of the plating solution for returning to the initial concentration of the bath was measured. Normal,
As the displacement plating is repeated, the impurities in the bath increase and the plating ability decreases, so if the bath deteriorates or decomposes below a predetermined level, the plating ability recovers even if a new replenisher is added. Can no longer hope. Therefore, a large number of turns before reaching this level (that is, until the bath is decomposed) is an indicator of the stability of the plating bath. Therefore, the evaluation of the bath life was represented by the specific number of turns (Metal TurnOver) of the plating solution.

The rightmost column in FIG. 1 shows the test results. In the displacement plating baths of Examples 1 to 8, the number of turns was 5-1.
It showed 0 times, the progress of deterioration was slow, and the bath had a long life.
In particular, in Example 8 in which a very small amount of nickel metal salt was blended, the number of turns was 10 times. In contrast, in Comparative Example 5 in which the concealing complexing agent was not added, or in Comparative Example 6 in which thiosulfate was omitted as the complexing agent, the number of turns was 0.2 to 0.5 times, It was observed that the bath deteriorated and the bath life was particularly short-lived. In Comparative Example 4 in which no surfactant was added or in Comparative Examples 1 to 3 in which a surfactant different from the present invention was used, the number of turns was 3 to 5 times. Therefore, it was clarified that the substitutional gold plating bath of the present invention was superior to Comparative Examples 1 to 6 in terms of bath life.

[Brief description of the drawings]

FIG. 1 shows the life of each substituted gold plating bath of Examples 1 to 8 and Comparative Examples 1 to 6, and plating spread, abnormal deposition, deposition unevenness, throwing power, and gold plating of a gold film obtained from each plating bath. It is a chart showing each test result of destruction mode.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kaoru Tanaka F-term (reference) in Ishihara Pharmaceutical Co., Ltd. 5-26, Nishiyanagihara-cho, Hyogo-ku, Kobe-shi, Hyogo 4K022 AA02 BA03 DA03 DB01 DB02 DB04 DB07 DB08

Claims (5)

[Claims] 1. A complexing agent comprising (A) a soluble gold salt, (B) a sulfite and a thiosulfate, (C) an oxycarboxylic acid such as tartaric acid, citric acid and malic acid, aminoacetic acid, ethylenediamine and ethanolamine. At least one of an amine compound such as ethylenediaminetetraacetic acid and benzylamine, a nitrogen-containing heterocyclic compound such as pyridine, bipyridyl and phenanthroline, an ammonium compound such as ammonium chloride, and a masking complexing agent comprising ammonia; (D) pH adjustment (E) a substituted gold plating bath containing an amphoteric surfactant or a mixture of an amphoteric surfactant and a nonionic surfactant. 2. The substituted gold plating bath according to claim 1, wherein at least one of a sulfide compound and a sulfinic acid is contained in place of the complexing agent (B). 3. The displacement gold plating bath according to claim 1, further comprising a buffer. 4. A substituted gold plating bath, characterized in that the plating bath according to claim 1 further contains a trace amount of at least one of a copper salt and a nickel salt. 5. A gold plating method, wherein gold plating is performed on a copper, nickel or palladium metal surface forming a substrate by the replacement gold plating bath according to any one of claims 1 to 4.