JP2003027277A - Tinning bath, tinning method and electronic parts subjected to tinning using plating bath used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve film appearance and solder wettability in an electrodeposition film obtained from a neutral tinning bath. SOLUTION: The neutral tinning bath of pH 2 to 9 contains (A) a soluble stannous salt, and (B) a complexing agent such as gluconic acid, citric acid and glucoheptonic acid, and (C) a specified quaternary ammonium salt such as an alkylpyridinium salt, N,N-dialkylmorpholinium salt, arylated alkylammonium salt or aralkylammonium salt, trialkylsulfoalkylene ammonium betaine, pyridium sulfobetaine and an alkylisoquinolinium salt. By the incorporation of the specified quanternary ammonium salt, the appearance and solder wettability of the tin film obtained from the bath are more excellent, compared with the case of a neutral bath containing a betaine type amphoteric surfactant or a trimethylalkylammonium salt.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a neutral tin plating bath having a pH range of 2 to 9, a tin plating method, and an electronic component electroplated using the plating bath, which is excellent in plating appearance and solder wettability. A tin film can be formed.

[0002]

BACKGROUND OF THE INVENTION Tin plating is widely used as a coating for improving solderability, a coating for etching resist, etc. in the weak electric industry and electronic parts. In conventional tin plating, borofluoride baths, sulfuric acid baths, organic sulfonic acid baths, etc. have been commonly used, but since these are strongly acidic baths with a pH of 1.0 or less, for example, ceramics, lead glass, plastics, etc. When these strong acid tin plating baths are applied to an electronic component in which the insulating component is integrated with the electroplated product, there is a problem that the insulating component is adversely affected by erosion, deformation, deterioration and the like. In order to overcome this problem, tin plating baths with a pH value close to neutral have been developed, but tin ions are stable under acidic conditions, but neutral tin tends to cause white precipitates. It is necessary to contain a complexing agent such as gluconic acid, citric acid, tartaric acid in the bath to prevent the occurrence of such a white precipitate of stannate.

[0003]

2. Description of the Related Art The following are examples of neutral tin plating baths. (1) Japanese Unexamined Patent Publication No. 10-298793 (Prior Art 1) Glycine is used for the purpose of improving the dissolution efficiency of a metal from a tin anode and maintaining the metal concentration of a plating bath during plating operation substantially constant. , Alanine, aminocarboxylic acids such as aspartic acid, or a complexing agent combining citric acid, oxalic acid, malonic acid, succinic acid, and the like, and a betaine-type amphoteric surfactant (chemical formula b in the publication),
A neutral tin plating bath containing a surfactant such as polyoxyethylene alkylamine (the same chemical formula a) and having a pH of 4 to 8 is disclosed. Further, in addition to the specific surfactant, the neutral tin plating bath contains a monoalkylamine salt, a dialkylamine salt, a trialkylamine salt,
It is disclosed that cationic surfactants such as alkyl trimethyl ammonium halides and dialkyl dimethyl ammonium halides, anionic surfactants, nonionic surfactants and the like may be blended (paragraph 23 of the publication). .

(2) Japanese Patent Application Laid-Open No. 9-272995 (Prior Art 2) No corrosion of the ceramic portion of the object to be plated,
In addition, for the purpose of performing tin plating only on the portion to be originally plated, a complexing agent such as polyoxymonocarboxylic acid, polycarboxylic acid, aminocarboxylic acid or lactone compound and (CH ₂ CH (OH) CH ₂ -N ⁺ -(CH ₃ ) ₂
· Cl ^-) _{n (n} is a specific quaternized amine polymer represented by the general formula, such as an integer) of 30 to 50, or, (CH ₂ CH
(OH) CH ₂ -A ⁺ · Cl ⁻ ) _n (A is an imidazoline ring, n
Is an integer of 2 to 10) and a specific quaternized imidazole derivative represented by the general formula, and a non-acidic tin plating bath having a pH of 7-14 is disclosed.

(3) Japanese Unexamined Patent Publication No. 10-245694 (Prior Art 3) Citric acid, gluconic acid, and pyrroline for the purpose of not corroding electronic parts and preventing metal deposition on the insulator part. A complexing agent such as an acid and an aliphatic alkyl type such as stearyl trimethyl ammonium bromide or cetyl triethanol ammonium bromide (chemical formula A in the publication) or a carboxy betaine type such as lauryl dimethyl betaine or cetyl dimethyl betaine (chemical formula B) and a specific quaternary ammonium salt, and p
A tin plating bath having H of 3 to 10 is disclosed.

[0006]

In the neutral tin plating baths of the prior arts 1 to 3 described above, the inclusion of the complexing agent can improve the stabilization of tin ions in the bath and the prevention of corrosion of the object to be plated. On the other hand, the electrodeposition coating obtained from the bath is not easy to obtain a uniform silver-white to white coating appearance, and the solder wettability is not satisfactory, and the reliability of mounting electronic components is insufficient. Is. An object of the present invention is to simultaneously improve the film appearance and the solder wettability of an electrodeposition film obtained from a neutral tin plating bath.

[0007]

DISCLOSURE OF THE INVENTION The inventors of the present invention have disclosed 4 types of aliphatic alkyl type (the chemical formula A) and carboxybetaine type (the chemical formula B and the chemical formula b) disclosed in the prior art 1 and the prior art 3. As a result of intensive studies on a neutral tin plating bath containing various kinds of quaternary ammonium salts starting from a quaternary ammonium salt or polyoxyethylene alkylamine (the above chemical formula a), the quaternary ammonium salt was alkylated. The present invention has been completed by finding out that when specified to a pyridinium salt, a dialkylmorpholinium salt, a pyridinium sulfobetaine, an aralkylammonium salt, etc., the appearance and solder wettability of an electrodeposition coating obtained from a tin plating bath can be significantly improved. .

That is, the present invention 1 comprises (A) a soluble stannous salt, (B) an oxycarboxylic acid, a polycarboxylic acid, a monocarboxylic acid, or at least one complexing agent selected from these salts, (C) An alkylpyridinium salt represented by the general formula (a) containing at least one quaternary ammonium salt selected from the group consisting of the following compounds (a) to (h):

[Chemical 9] (In the above formula (a), R ₁ is C ₁ -C ₂₄ alkyl and R ₂ is C
₁ -C ₂₄ alkyl, aryl, and aralkyl; X is C ₁ -C ₅ alkyl sulfonate, halogen, acetate, sulphate, perchlorate, hydro diene sulfate, hydroxide, aromatic sulfonate, phosphate, tetrafluoroborate. ) (b) 1,2-dialkyl-1-hydroxyethylimidazolinium salt represented by the general formula (b)

[Chemical 10] (In the above formula (b), R ₁ is C ₁ -C ₂₄ alkyl, aryl, aralkyl, R ₂ is C ₁ -C ₂₄ alkyl; X is C ₁ -C ₅ alkyl sulfonate, halogen, acetate, (Sulfate, perchlorate, hydrogensulfate, hydroxide, aromatic sulfonate, phosphate, tetrafluoroborate.) (C) N, N-dialkylmorpholinium salt represented by general formula (c)

[Chemical 11] (In the formula (c), R ₁ and R ₂ are C ₁ -C ₂₄ alkyl; X
Are C ₁ -C ₅ alkyl sulfonates, halogens, acetates, sulphates, perchlorates, hydrogen sulphates, hydroxides, aromatic sulphonates, phosphates, tetrafluoroborate. ) (d) N, N, N-trialkyl-N represented by general formula (d)
-Sulfoalkylene ammonium betaine

[Chemical 12] (In the above formula (d), R ₁ , R ₂ , and R ₃ are C _{1 to} C ₂₄ alkyl; n is an integer of 1 to 6; X is a C _{1 to} C ₅ alkyl sulfonate, halogen, acetate, Sulfate, perchlorate, hydrogensulfate, hydroxide, aromatic sulfonate, phosphate, tetrafluoroborate.) (E) Arylalkyl ammonium salt or aralkyl ammonium salt represented by the general formula (e).

[Chemical 13] (In the above formula (e), at least one of R _{1 to} R ₄ is a substituted or unsubstituted aryl or aralkyl, and R _{1 to} R ₄
At least one of C ₁ -C ₂₄ alkyl; X is C ₁
~ C ₅ alkyl sulfonate, halogen, acetate,
These are sulphates, perchlorates, hydrogen sulphates, hydroxides, aromatic sulphonates, phosphates and tetrafluoroborate. ) (f) Pyridinium sulfobetaine represented by the general formula (f)

[Chemical 14] (In the above formula (f), R ₁ is C _{1 to} C ₂₄ alkyl, aryl, aralkyl; n is an integer of ₁ to 6; X is C ₁ to
These are C ₅ alkyl sulfonates, halogens, acetates, sulphates, perchlorates, hydrogen sulphates, hydroxides, aromatic sulphonates, phosphates, tetrafluoroborate. ) (g) Alkylisoquinolinium salt represented by the general formula (g)

[Chemical 15] (In the above formula (g), R ₁ is C ₁ -C ₂₄ alkyl; X is C ₁
~ C ₅ alkyl sulfonate, halogen, acetate,
These are sulphates, perchlorates, hydrogen sulphates, hydroxides, aromatic sulphonates, phosphates and tetrafluoroborate. ) (h) Polyoxyethylene alkyl ammonium salt represented by general formula (h)

[Chemical 16] (In the above formula (h), R ₁ and R ₂ are C ₁ -C ₂₄ alkyl; A
O is oxyethylene or oxypropylene, and the chain may be constituted by only one of oxyethylene and oxypropylene, or both may be mixed and the two AO chains may be the same or different from each other; m and n are 1 to 18 respectively
X is a C ₁ -C ₅ alkyl sulfonate, halogen, acetate, sulfate, perchlorate,
They are hydrogen sulphate, hydroxide, aromatic sulphonate, phosphate and tetrafluoroborate. ) A tin plating bath having a pH of 2-9.

The second aspect of the present invention is the above-mentioned first aspect, wherein the oxycarboxylic acid, the polycarboxylic acid or the monocarboxylic acid is
Gluconic acid, citric acid, glucoheptonic acid, gluconolactone, glucoheptolactone, formic acid, acetic acid, propionic acid, butyric acid, ascorbic acid, oxalic acid, malonic acid, succinic acid, glycolic acid, malic acid, tartaric acid, diglycolic acid The tin plating bath is characterized by

The third aspect of the present invention is the tin plating bath according to the first or second aspect of the present invention, wherein the quaternary ammonium salt (C) is a C _{1 to} C ₅ alkyl sulfonate salt.

[0012] A tin plating method, which comprises subjecting the object to be plated to electroplating by immersing the object to be plated in the tin plating bath according to the present invention 4 or any one of the above inventions 1 to 3.

A fifth aspect of the present invention is a printed circuit board, a semiconductor integrated circuit, a resistor, a variable resistor, a capacitor, a filter, an inductor, which has a tin electrodeposition film formed by using the plating bath according to any one of the first to third aspects. Thermistor, crystal unit,
Electronic components such as switches and lead wires.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is firstly a neutral tin plating bath having a pH of 2 to 9 containing a soluble stannous salt, a complexing agent and a specific quaternary ammonium salt, and secondly, A tin plating method in which an object to be plated is immersed in the plating bath and electroplated on the object to be plated. Thirdly, a printed circuit board, a semiconductor integrated circuit, etc., on which an electrodeposition film of tin is formed using the plating bath. It is an electronic component.

The above-mentioned soluble stannous salt is basically S in water.
An organic or inorganic tin salt capable of generating n ²⁺ , specifically, a first organic sulfonic acid such as methanesulfonic acid, ethanesulfonic acid, 2-propanolsulfonic acid, sulfosuccinic acid, and p-phenolsulfonic acid. Starting with tin salt,
Examples include stannous borofluoride, stannous sulfate, stannous oxide, stannous chloride and the like. The above soluble stannous salts can be used alone or in combination, and the content thereof in the plating bath is 0.5 to 300 g / L in terms of metal, preferably 10 to 120.
It is g / L.

Since the tin plating bath of the present invention is a neutral bath having a pH of 2 to 9, the above complexing agent stabilizes Sn ^{2+ in} this pH range, so that a white precipitate is generated or the bath is decomposed. It is used for the purpose of preventing. The complexing agent is oxycarboxylic acid, polycarboxylic acid, monocarboxylic acid, or the like, and specifically, gluconic acid, citric acid, glucoheptonic acid, gluconolactone, glucoheptolactone, formic acid, acetic acid, propionic acid. , Butyric acid, ascorbic acid, oxalic acid, malonic acid, succinic acid, glycolic acid, malic acid,
Examples thereof include tartaric acid, diglycolic acid, and salts thereof. Preferred are gluconic acid, citric acid, glucoheptonic acid, gluconolactone, glucoheptolactone, and salts thereof. Also, ethylenediamine, ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), nitrilotriacetic acid (NTA), iminodiacetic acid (IDA), iminodipropionic acid (IDP), hydroxyethylethylenediaminetriacetic acid (HEDTA), triethylene Tetramine hexaacetic acid (TTHA), ethylenedioxybis (ethylamine) -N, N, N ', N'-tetraacetic acid, glycines, nitrilotrimethylphosphonic acid, or salts thereof are also effective as complexing agents. The above complexing agents can be used alone or in combination, and the content thereof in the plating bath is 0.05 to 5 mol / L, preferably 0.1 to 2 mol / L.
It is L.

The tin plating bath of the present invention is basically an organic acid bath, an inorganic acid bath, or a bath based on its alkali metal salt, alkaline earth metal salt, ammonium salt, amine salt or the like. Examples thereof include organic sulfonic acid and aliphatic carboxylic acid, and examples of inorganic acid include sulfuric acid, hydrochloric acid, borofluoric acid, silicofluoric acid, sulfamic acid and the like. Of these, organic sulfonic acids or salts thereof are preferable from the viewpoints of tin solubility, ease of wastewater treatment, and the like. As the organic sulfonic acid salt, sodium, potassium, magnesium, calcium, ammonium, monoethanolamine, diethanolamine, triethanolamine, ethylenediamine of organic sulfonic acid,
Diethylenetriamine, triethylenepentamine, pentaethylenetetramine salt and the like can be used. However, since the present invention is a neutral plating bath, when the above-mentioned organic acid or inorganic acid is used as a bath base, various bases are added to the bath as a pH adjusting agent to adjust the pH to 2 as described later. Needless to say, it is properly adjusted to the range of 9. The above acids or salts thereof can be used alone or in combination, and the content thereof is 0.1 to 10 m.
ol / L, preferably 0.5-5 mol / L.

The above-mentioned organic sulfonic acid is alkane sulfonic acid, alkanol sulfonic acid, sulfosuccinic acid, aromatic sulfonic acid, and the like, and as the alkane sulfonic acid,
Those represented by the chemical formula C _n H _{2n + 1} SO ₃ H (for example, n = 1 to 11) can be used. Specifically, methanesulfonic acid,
Examples thereof include ethanesulfonic acid, 1-propanesulfonic acid, 2-propanesulfonic acid, 1-butanesulfonic acid, 2-butanesulfonic acid and pentanesulfonic acid.

The above alkanol sulfonic acid has the chemical formula C _m H _{2m + 1} -CH (OH) -C _p H _2p -SO ₃ H (for example, m = 0.
~ 6, p = 1 to 5), specifically, 2-hydroxyethane-1-sulfonic acid, 2-hydroxypropane-
1-sulfonic acid (2-propanolsulfonic acid), 2-hydroxybutane-1-sulfonic acid, 2-hydroxypentane-1-sulfonic acid, etc., 1-hydroxypropane-2-sulfonic acid, 3-hydroxypropane- 1-sulfonic acid, 4-hydroxybutane-1-sulfonic acid, 2
-Hydroxyhexane-1-sulfonic acid and the like can be mentioned.

The above-mentioned aromatic sulfonic acid is basically benzenesulfonic acid, alkylbenzenesulfonic acid, phenolsulfonic acid, naphthalenesulfonic acid, alkylnaphthalenesulfonic acid, naphtholsulfonic acid and the like, and specifically, 1-naphthalenesulfone. Acid, 2-naphthalenesulfonic acid, toluenesulfonic acid, xylenesulfonic acid, p-phenolsulfonic acid, cresolsulfonic acid, sulfosalicylic acid, nitrobenzenesulfonic acid, sulfobenzoic acid, diphenylamine-4-sulfonic acid and the like can be mentioned. Of the above organic sulfonic acids, methanesulfonic acid, ethanesulfonic acid, 2-propanolsulfonic acid, isethionic acid and the like are preferable.

The present invention is characterized in that the neutral tin bath contains the specific quaternary ammonium salt of the above (a) to (h) for the purpose of improving the appearance and solder wettability of the electrodeposition coating. . Among these quaternary ammonium salts, alkylpyridinium salts (a), 1,2-dialkyl-1-hydroxyethylimidazolinium salts (b), N, N-dialkylmorpholinium salts (c), N, N , N-trialkyl-N-sulfoalkylene ammonium betaine (d), pyridinium sulfobetaine (f), alkylisoquinolinium salt
In (g) or the polyoxyethylene alkylammonium salt (h), the substituent bonded to the N atom is C ₁ -C ₂₄ alkyl, aryl or aralkyl, and bonded to the other aromatic ring. substituents are C ₁ -C ₂₄ alkyl.
When the substituent is an alkyl group, regardless of the bonding position,
C ₁ -C ₁₈ alkyl is preferred. In the arylalkyl ammonium salt or aralkyl ammonium salt of (e), at least one of R _{1 to} R ₄ is a substituted or unsubstituted aryl or aralkyl, and at least one is C _{1 to} C ₁₈ alkyl. Is. Examples of the substituent bonded to the aromatic ring include C ₁ -C ₃ alkyl, halogen, CF ₃ ,
, Etc. C ₁ -C ₆ alkoxy. As the alkylpyridinium salt (a), laurylpyridinium chloride, octylpyridinium chloride, cetylpyridinium methanesulfonate, oleylpyridinium sulfate and the like are preferable. 1,2-dialkyl-1-
The hydroxyethyl imidazolinium salt (b) includes 2
-Nonyl-1-methyl-1-hydroxyethylimidazolinium chloride, 2-lauryl-1-methyl-1-
Hydroxyethylimidazolinium chloride, 2-oleyl-1-ethyl-1-hydroxyethylimidazolinium methanesulfonate and the like are preferable. Above N, N
As the dialkylmorpholinium salt (c), N, N-
Dimethylmorpholinium chloride and N, N-diethylmorpholinium acetate are preferred. Above N, N,
As N-trialkyl-N-sulfoalkylene ammonium betaine (d), N, N-dimethyl-N-stearyl-N- (3-sulfopropyl) ammonium betaine, N, N-dimethyl-N-myristyl-N- (3-Sulfopropyl) ammonium betaine, N, N-dibutyl-
N-lauryl-N- (4-sulfobutyl) ammonium betaine and the like are preferable. As the arylalkylammonium salt (e), phenyltrimethylammonium chloride, phenyltri-n-butylammonium-p-toluenesulfonate and the like are preferable. Similarly, the aralkyl ammonium salt of the above (e) includes R _{1 to} R ₄
Is a substituted or unsubstituted benzyl group, and the remaining three are C ₁ -C ₁₈ alkyl, preferably a trialkylbenzylammonium salt, and specifically, benzyldimethyllaurylammonium chloride, benzylcetyldimethylammonium methylsulfonate, Benzyl dimethyl decyl ammonium salt, benzyl dimethyl tetradecyl ammonium salt, benzyl dimethyl octadecyl ammonium salt, benzyl diethyl octyl ammonium salt, (trifluoromethyl) phenylmethyl dimethyl dodecyl ammonium salt, benzyl ethyl methyl octadecyl ammonium salt, monochlorophenylmethyl dimethyl hexadecyl Examples thereof include ammonium salt and benzyl diethyldecyl ammonium salt. Examples of the pyridinium sulfobetaine (f) include 1- (3-sulfopropyl)
-Pyridinium betaine, 4-benzyl-1- (3-sulfopropyl) -pyridinium betaine, 2-methyl-
1- (2-hydroxy-3-sulfopropyl) -pyridinium betaine and the like are preferable. As the alkylisoquinolinium salt (g), laurylisoquinolinium chloride, methylisoquinolinium chloride, butylisoquinolinium perchlorate and the like are preferable. Examples of the polyoxyethylene alkylammonium salt (h) include oleylmethyldi (polyethoxylate) ammonium chloride and laurylmethyldi (polyethoxylate).
Ammonium chloride, dilauryl di (polyethoxylate) ammonium methanesulfonate and the like are preferable.

The anion portion X of each of the quaternary ammonium salts of (a) to (h) is a C _{1 to} C ₅ alkyl sulfonate, halogen, acetate, sulfate, perchlorate, hydrogen sulphate, hydroxide,
Examples of aromatic sulfonates, phosphates, tetrafluoroborate, etc., as shown in the present invention 2, C ₁ -C ₅ alkyl sulfonates are preferable from the viewpoint of effectively suppressing metal corrosion of equipment.

On the other hand, in the neutral tin plating bath of the present invention, in addition to the above components, known surfactants, brighteners, and
It goes without saying that various additives such as a semi-brightening agent, a pH adjusting agent, a conductive salt, a preservative, an antioxidant, and an antifoaming agent can be mixed. Examples of the above-mentioned surfactants include various nonionic, anionic, amphoteric, or cationic surfactants, such as the appearance, denseness, smoothness, adhesion, and uniform electrodeposition of the plating film. Further contribute to improvement. Examples of the anionic surfactants include alkyl sulfates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkylphenyl ether sulfates, alkylbenzene sulfonates, and alkylnaphthalene sulfonates. Examples of the cationic surfactant include mono-trialkylamine salts, dimethyldialkylammonium salts, trimethylalkylammonium salts and the like. Nonionic surfactants include C _{1 to} C ₂₀ alkanols, phenols, naphthols, bisphenols,
C ₁ -C ₂₅ alkylphenols, arylalkylphenols, C ₁ -C ₂₅ alkylnaphthols, C ₁ -C ₂₅ alkoxyl phosphoric acids (salts), sorbitan esters, polyalkylene glycols, C ₁ -C ₂₂ aliphatic amides, ethylene oxide (EO), etc. ) And / or propylene oxide (PO)
2 to 300 mol of these compounds are added and condensed. Examples of the amphoteric surfactant include carboxybetaine, imidazoline betaine, aminocarboxylic acid and the like.

Examples of the brightener or semi-brightener include benzaldehyde, o-chlorobenzaldehyde, 2,4,6.
-Trichlorobenzaldehyde, m-chlorobenzaldehyde, p-nitrobenzaldehyde, p-hydroxybenzaldehyde, furfural, 1-naphthaldehyde, 2-naphthaldehyde, 2-hydroxy-1-naphthaldehyde, 3-acenaphthaldehyde, benzylideneacetone, pyri Various aldehydes such as didenacetone, furfurylideneacetone, cinnamaldehyde, anisaldehyde, salicylaldehyde, crotonaldehyde, acrolein, glutaraldehyde, paraaldehyde, vanillin, triazine, imidazole, indole, quinoline, 2-vinylpyridine, aniline, phenanthroline , Neocuproine, picolinic acid, thioureas, N- (3-hydroxybutylidene) -p-sulfanilic acid, N-butylidene Rufaniru acid, N- cinnamoethyl ylidene sulfonyl acid, 2,4-diamino-6- (2'
Methylimidazolyl (1 ')) ethyl-1,3,5-triazine, 2,4-diamino-6- (2'-ethyl-4-methylimidazolyl (1')) ethyl-1,3,5-triazine, 2,4-Diamino-6- (2'-undecylimidazolyl (1 ')) ethyl-1,3,5-triazine, phenyl salicylate, or benzothiazole, 2-methylbenzothiazole, 2-aminobenzothiazole 2-amino-6-methoxybenzothiazole, 2-methyl-5-
Chlorobenzothiazole, 2-hydroxybenzothiazole, 2-amino-6-methylbenzothiazole, 2-
Examples include benzothiazoles such as chlorobenzothiazole, 2,5-dimethylbenzothiazole and 5-hydroxy-2-methylbenzothiazole.

The pH of the tin plating bath of the present invention must be adjusted to 2-9, preferably 4-6.
Modifiers are added for this purpose as required. Specific examples thereof include hydrochloric acid, various acids such as sulfuric acid, ammonia water, potassium hydroxide, various bases such as sodium hydroxide, but formic acid, acetic acid, monocarboxylic acids such as propionic acid, boric acid, Also effective are phosphoric acids, dicarboxylic acids such as oxalic acid and succinic acid, oxycarboxylic acids such as lactic acid and tartaric acid, amines such as mono-, di- or trialkylamines, mono-, di- or triacylamines. As mentioned above, when an acid is used as the base of the plating bath of the present invention, the above base is used as a pH adjuster. Examples of the conductive salt include sodium salts such as sulfuric acid, hydrochloric acid, phosphoric acid, sulfamic acid, and sulfonic acid, potassium salts, magnesium salts, ammonium salts, amine salts, and the like. is there. The above-mentioned antioxidant is contained for the purpose of preventing the oxidation of Sn ^{2+ in} the bath, and ascorbic acid or a salt thereof,
Examples thereof include hydroquinone, catechol, resorcin, phloroglucin, cresolsulfonic acid or a salt thereof, phenolsulfonic acid or a salt thereof, catecholsulfonic acid or a salt thereof, hydroquinonesulfonic acid or a salt thereof, and hydrazine. However, ascorbic acid or a salt thereof is preferable from the viewpoint of effectively acting even in a neutral bath. As the above preservative, boric acid, 5-chloro-2-methyl-
4-isothiazolin-3-one, benzalkonium chloride, phenol, phenol polyethoxylate, thymol, resorcin, isopropylamine, guaiacol and the like can be mentioned. Examples of the defoaming agent include pluronic surfactants, higher aliphatic alcohols, acetylene alcohols and polyalkoxylates thereof.

The content concentration of each of the above additives in the neutral tin plating bath of the present invention can be arbitrarily adjusted and selected in accordance with barrel plating, rack plating, high speed continuous plating, rackless plating and the like. The conditions for electroplating using the neutral tin bath of the present invention include a bath temperature of 0 ° C. or higher, preferably 10 to
It is about 50 ° C and the cathode current density is 0.001 to 30A.
/ Dm ² , preferably 0.01 to 10 A / dm ² .

The present invention 3 is a tin plating method in which the object to be plated is immersed in the neutral tin plating bath of the present invention 1 or 2 to electroplate the object to be plated. The present invention 4
Is an article on which an electrodeposition film of tin is formed by using the neutral plating bath of the present invention 1 or 2, specifically, a printed circuit board, a semiconductor integrated circuit (TAB film carrier, BGA substrate, etc.). , Resistors, variable resistors, capacitors, filters, inductors, thermistors, crystal oscillators, switches, connectors, lead wires, hoop materials, etc. The electronic components of are suitable.

[0027]

INDUSTRIAL APPLICABILITY Since the present invention is a neutral tin plating bath containing a specific quaternary ammonium salt together with a complexing agent, both the appearance and solder wettability of the electrodeposition coating obtained from the bath can be improved satisfactorily. Quaternary ammonium salts such as alkylpyridinium salts, pyridinium sulfobetaines, aryl or aralkylammonium salts, alkylisoquinolinium salts show more pronounced efficacy. Incidentally, the aliphatic alkyl type quaternary ammonium salt, trialkylcarboxybetaine, or polyoxyethylene alkylamine disclosed in the prior art 1 or 3 is relatively similar in chemical structure to the quaternary ammonium salt of the present invention. However, as can be seen from the test examples described below, the specific quaternary ammonium salt of the present invention is a tin film obtained from the bath when these similar compounds are contained in the neutral plating bath. It has a remarkable advantage in that the appearance and solder wettability can be improved.

[0028]

EXAMPLES Examples of the neutral tin plating bath of the present invention will be described below.
Test examples of the appearance and solder wettability of the electrodeposition coating of tin obtained from each of the neutral plating baths of the examples will be sequentially described. The present invention is not limited to the following examples and test examples, and it goes without saying that any modifications can be made within the scope of the technical idea of the present invention.

Of the following Examples 1 to 16, Examples 1 and 6 are examples of using the quaternary ammonium salt (a), and Examples 3 and 10
Are examples of use of the quaternary ammonium salt (b), Examples 7 and 14 are examples of use of the quaternary ammonium salt (c), Examples 4 and 9
Is a use example of quaternary ammonium salt (d), Examples 11 and 15
And 16 are examples of use of quaternary ammonium salt (e), Examples 5 and 12 are examples of use of quaternary ammonium salt (f), Examples 2 and 1
3 is a use example of a quaternary ammonium salt (g), Examples 8 and 16
Is an example of using the quaternary ammonium salt (h). Example 16
Are examples of combined use of the quaternary ammonium salt of the present invention, and the other examples are single-use examples. Moreover, among Comparative Examples 1 to 4,
Comparative Example 1 is a blank example containing no quaternary ammonium salt of the present invention, and Comparative Example 2 is an aliphatic alkyl type quaternary ammonium salt described in Chemical Formula A of Prior Art 3 in place of the quaternary ammonium salt of the present invention. Similarly, Comparative Example 3 includes the trialkylcarboxybetaine described in Chemical Formula b of Prior Art 1 or Chemical Formula B of Prior Art 3, and Comparative Example 4 similarly corresponds to Chemical Formula a of Prior Art 1. This is an example containing the described polyoxyethylene alkylamine.

Example 1 A neutral tin plating bath was constructed with the following composition. Stannous methanesulfonate (as Sn ²⁺ ) 20 g / L Methanesulfonic acid 40 g / L Sodium gluconate 200 g / L Laurylpyridinium chloride 1 g / L pH adjusted to 5.5 with aqueous ammonia

Example 2 A neutral tin plating bath was constructed with the following composition. Stannous sulfate (as Sn ²⁺ ) 15 g / L 2-propanol sulfonic acid 30 g / L potassium gluconate 120 g / L succinic acid 10 g / L bisphenol F-4,4′-polyethoxylate (EO 10 mol) 1 g / L Lauryl isoquinolinium chloride 1g / L Adjusted to pH 4.0 with potassium hydroxide

Example 3 A neutral tin plating bath having the following composition was constructed. Stannous methanesulfonate (as Sn ²⁺ ) 60 g / L Methanesulfonic acid 80 g / L Sodium citrate 250 g / L Ammonium oxalate 10 g / L 2-nonyl-1-methyl-1-hydroxyethyl-imidazolinium chloride Adjust to pH 2.0 with 3g / L potassium hydroxide

Example 4 A neutral tin plating bath was constructed with the following composition. Stannous sulfate (as Sn ²⁺ ) 45 g / L Sulfuric acid 80 g / L Gluconolactone 250 g / L Ammonium acetate 5 g / L N, N-dimethyl-N-stearyl-N- (3-sulfopropyl) -ammonium betaine 6 g / L Adjust to pH 5.4 with sodium hydroxide

Example 5 A neutral tin plating bath was constructed with the following composition. Stannous sulfate (as Sn ²⁺ ) 25 g / L Sulfuric acid 50 g / L Sodium glucoheptonate 180 g / L Glycolic acid 20 g / L 1- (3-Sulfopropyl) -pyridinium betaine 4 g / L Sodium hydroxide to pH 4.4 Adjustment

Example 6 A neutral tin plating bath having the following composition was constructed. Stannous sulfate (as Sn ²⁺ ) 10 g / L 2-propanolsulfonic acid 40 g / L Sodium gluconate 100 g / L Sodium citrate 100 g / L Octylpyridinium chloride 0.1 g / L Adjusted to pH 6.5 with sodium hydroxide

Example 7 A neutral tin plating bath was constructed with the following composition. Stannous 2-propanol sulfonate (as Sn ²⁺ ) 15 g / L Methanesulfonic acid 40 g / L Sodium gluconate 190 g / L Oxalic acid 10 g / L N, N-Dimethylmorpholinium chloride 10 g / L Naphthol polyethoxylate (EO20 mol) 1g / L Adjusted to pH 4.0 with ammonia water.

Example 8 A neutral tin plating bath having the following composition was constructed. Stannous isethionate (as Sn ²⁺ ) 25 g / L Isethionic acid 70 g / L Potassium gluconate 180 g / L Potassium acetate 10 g / L 1-Hydroxy-8-naphthalene sulfonate potassium 0.4 g / L Oleylmethyldi (polyethoxy) Rate) -Ammonium chloride (2 mol EO in total) 0.01 g / L Adjusted to pH 7.5 with potassium hydroxide

Example 9 A neutral tin plating bath having the following composition was constructed. Stannous methanesulfonate (as Sn ²⁺ ) 35 g / L Methanesulfonic acid 80 g / L Ammonium gluconate 250 g / L N, N-dimethyl-N-myristyl-N- (3-sulfopropyl) -ammonium betaine 8 g / Adjusted to pH 4.8 with L ammonia water

Example 10 A neutral tin plating bath having the following composition was constructed. Stannous sulfate (as Sn ²⁺ ) 15 g / L Sulfuric acid 60 g / L Sodium gluconate 180 g / L 2-pentyl-1-butyl-1-hydroxyethyl-imidazolinium chloride 1.5 g / L pH 5 with sodium hydroxide Adjust to 0.0

Example 11 A neutral tin plating bath having the following composition was constructed. Stannous methanesulfonate (as Sn ²⁺ ) 15 g / L Methanesulfonic acid 40 g / L Sodium gluconate 200 g / L Benzyldimethyllauryl ammonium chloride 1.0 g / L Adjusted to pH 4.5 with ammonia water.

Example 12 A neutral tin plating bath having the following composition was constructed. Stannous 2-propanol sulfonate (as Sn ²⁺ ) 25 g / L Methanesulfonic acid 60 g / L Ammonium citrate 220 g / L Ammonium formate 6 g / L 4-Benzyl-1- (3-sulfopropyl) -pyridinium betaine 0 0.03 g / L polyoxypropylene glycol-monobutyl ether (25 mol PO) 0.01 g / L pH adjusted to 8.0 with aqueous ammonia.

Example 13 A neutral tin plating bath having the following composition was constructed. Stannous 2-propanol sulfonate (as Sn ²⁺ ) 25 g / L 2-Propanol sulfonic acid 60 g / L Ammonium gluconate 220 g / L Malonic acid 10 g / L Sodium acetate 20 g / L Methylisoquinolinium chloride 0.01 g / L Adjust to pH 7.5 with ammonia water

Example 14 A neutral tin plating bath having the following composition was constructed. Stannous sulfate (as Sn ²⁺ ) 25 g / L Methanesulfonic acid 40 g / L Citric acid 250 g / L Sodium potassium tartrate 60 g / L N, N-diethylmorpholinium acetate 5 g / L Potassium hydroxide to pH 9.0 Adjustment

Example 15 A neutral tin plating bath having the following composition was constructed. Stannous methanesulfonate (as Sn ²⁺ ) 15 g / L Methanesulfonic acid 40 g / L Sodium gluconate 200 g / L Benzylcetyldimethylammonium-methylsulfonate 0.5 g / L Adjusted to pH 4.5 with potassium hydroxide

Example 16 A neutral tin plating bath having the following composition was constructed. Stannous sulphate (as Sn ²⁺ ) 1 g / L 2-propanolic acid 30 g / L ammonium gluconate 120 g / L succinic acid 10 g / L laurylmethyldi (polyethoxylate) -ammonium chloride (total EO 15 mol) 1 g / L Phenyltrimethylammonium chloride 1g / L Adjusted to pH 4.0 with ammonia water

Comparative Example 1 A neutral tin plating bath having the following composition was constructed. Stannous sulfate (as Sn ²⁺ ) 15 g / L Sulfuric acid 60 g / L Gluconic acid 160 g / L Ammonia water adjusted to pH 5.0

Comparative Example 2 A neutral tin plating bath having the following composition was constructed. Stannous sulfate (as Sn ²⁺ ) 15 g / L Sulfuric acid 60 g / L Gluconic acid 120 g / L Stearyltrimethylammonium bromide 1 g / L Ammonia water adjusted to pH 5.0

Comparative Example 3 A neutral tin plating bath having the following composition was constructed. Stannous sulfate (as Sn ²⁺ ) 15 g / L Sulfuric acid 40 g / L Tripotassium citrate 220 g / L Lauryl dimethyl betaine 1 g / L Adjusted to pH 6.0 with potassium hydroxide

Comparative Example 4 A neutral tin plating bath having the following composition was constructed. Stannous sulfate (as Sn ²⁺ ) 15 g / L Sulfuric acid 40 g / L 3 potassium citrate 220 g / L Dipolyoxide decylamine (EO total 5 mol) 1 g / L Adjust pH to 6 with potassium hydroxide

<< Appearance evaluation test example of tin plating film >> Then, this test plate was immersed in each neutral tin plating bath of the above Examples 1 to 16 and Comparative Examples 1 to 4 using a 25 mm × 25 mm copper plate as a test plate, Electroplating was performed under the following conditions, and the appearance of the obtained tin film was visually evaluated mainly based on the color tone. The electroplating conditions are as follows. (1) Bath temperature 25 ° C. (2) cathode current density and 12 minutes plating time 0.1 A / dm ² at 120 minutes 0.5A / dm ² at 60 minutes 1.0A / dm ² The evaluation of the coating appearance The criteria are as follows. ⊚: The color tone was uniform silver white. ◯: The color tone was uniform white. Δ: The color tone was gray. X: The whole was blackish, or black unevenness was scattered in the gray tone. The second column from the right in each of FIGS. 1 and 2 shows the test results.

<< Example of solder wettability test of tin plating film >>
The test plate on which a tin plating film was formed using each of the neutral tin plating baths of Examples 1 to 16 and Comparative Examples 1 to 4
It was immersed in a tin-lead eutectic solder bath at 5 ° C. under the conditions of a depth of 10 mm and 3 seconds, and the wet area on the plating film was visually observed. The solder wettability evaluation criteria are as follows. A: Wetting of 95% or more was shown. ◯: Wetting of 90 to 95% was shown. Δ: Wetting of 60 to 90% was exhibited. X: Wetting was less than 60%. The rightmost columns in FIGS. 1 and 2 show the test results.

<< Comprehensive Evaluation of Film Appearance and Solder Wettability >> As shown in FIGS. 1 and 2, in Comparative Example 1 containing no quaternary ammonium salt of the present invention, the film appearance and solder wettability were evaluated as x. On the other hand, in each of the tin coatings obtained from Examples 1 to 16, both the coating appearance and the solder wettability were greatly improved to ◯ or higher regardless of the three plating conditions. In particular, Examples 1-2, Examples 5-8, and Example 10
In all of Examples 13 to 13 and Example 15, regardless of the magnitude of the current density, the evaluation was ⊚. Therefore, among the quaternary ammonium salts of the present invention, (a), (e), (f) or ( It has been found that quaternary salts such as g) are more effective in improving the appearance and solder wettability of the film obtained from the neutral tin bath. On the other hand, the aliphatic alkyl type quaternary ammonium salt, trialkylcarboxybetaine, or polyoxyethylene alkylamine of the above-mentioned prior art 1 or 3 is relatively similar in chemical structure to the quaternary ammonium salt of the present invention. However, in Comparative Examples 2 to 4 containing these similar compounds, the film appearance and the solder wettability were evaluated to be Δ or less,
It was revealed that the specific quaternary ammonium salt of the present invention has a remarkable superiority in improving the appearance and solder wettability of the tin film obtained from the neutral plating bath.

[Brief description of drawings]

FIG. 1 shows current density and plating time when electroplating was performed using each neutral tin plating bath of Examples 1 to 10, and a tin film appearance obtained from the plating bath and a test result of solder wettability. It is a chart shown.

FIG. 2 is a diagram corresponding to FIG. 1 showing numerical values and results regarding each neutral tin plating bath of Examples 11 to 16 and Comparative Examples 1 to 4.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4K023 AA17 BA06 BA29 CA01 CB03                       CB05 CB08 CB19 CB28 CB29                       CB33 DA02                 4K024 AA07 AB01 BB09 BB11 BB12                       CA02 GA02 GA14

Claims (5)

[Claims] 1. (A) a soluble stannous salt, (B) an oxycarboxylic acid, a polycarboxylic acid, a monocarboxylic acid, or at least one complexing agent selected from these salts, and (C) the following: (a) to (h) containing at least one quaternary ammonium salt selected from the group consisting of compounds, (a) an alkylpyridinium salt represented by the general formula (a): (In the above formula (a), R ₁ is C ₁ -C ₂₄ alkyl and R ₂ is C
₁ -C ₂₄ alkyl, aryl, and aralkyl; X is C ₁ -C ₅ alkyl sulfonate, halogen, acetate, sulphate, perchlorate, hydro diene sulfate, hydroxide, aromatic sulfonate, phosphate, tetrafluoroborate. ) (b) 1,2-dialkyl-1-hydroxyethylimidazolinium salt represented by the general formula (b): (In the above formula (b), R ₁ is C ₁ -C ₂₄ alkyl, aryl, aralkyl, R ₂ is C ₁ -C ₂₄ alkyl; X is C ₁ -C ₅ alkyl sulfonate, halogen, acetate, Sulfate, perchlorate, hydrogensulfate, hydroxide, aromatic sulfonate, phosphate, tetrafluoroborate.) (C) N, N-dialkylmorpholinium salt represented by the general formula (c): (In the formula (c), R ₁ and R ₂ are C ₁ -C ₂₄ alkyl; X
Are C ₁ -C ₅ alkyl sulfonates, halogens, acetates, sulphates, perchlorates, hydrogen sulphates, hydroxides, aromatic sulphonates, phosphates, tetrafluoroborate. ) (d) N, N, N-trialkyl-N represented by general formula (d)
-Sulfoalkylene ammonium betaine (In the formula (d), R ₁ , R ₂ and R ₃ are C _{1 to} C ₂₄ alkyl; n is an integer of 1 to 6; X is a C _{1 to} C ₅ alkyl sulfonate, halogen, acetate, Sulfate, perchlorate, hydrogen sulfate, hydroxide, aromatic sulfonate, phosphate, tetrafluoroborate.) (E) Arylalkylammonium salt or aralkylammonium salt represented by the general formula (e). (In the above formula (e), at least one of R _{1 to} R ₄ is a substituted or unsubstituted aryl or aralkyl, and R _{1 to} R ₄
At least one of C ₁ -C ₂₄ alkyl; X is C ₁
~ C ₅ alkyl sulfonate, halogen, acetate,
These are sulphates, perchlorates, hydrogen sulphates, hydroxides, aromatic sulphonates, phosphates and tetrafluoroborate. ) (f) Pyridinium sulfobetaine represented by the general formula (f): (In the above formula (f), R ₁ is C _{1 to} C ₂₄ alkyl, aryl, aralkyl; n is an integer of ₁ to 6; X is C ₁ to
These are C ₅ alkyl sulfonates, halogens, acetates, sulphates, perchlorates, hydrogen sulphates, hydroxides, aromatic sulphonates, phosphates, tetrafluoroborate. ) (g) Alkylisoquinolinium salt represented by the general formula (g): (In the above formula (g), R ₁ is C ₁ -C ₂₄ alkyl; X is C ₁
~ C ₅ alkyl sulfonate, halogen, acetate,
These are sulphates, perchlorates, hydrogen sulphates, hydroxides, aromatic sulphonates, phosphates and tetrafluoroborate. ) (h) Polyoxyethylene alkyl ammonium salt represented by the general formula (h): (In the above formula (h), R ₁ and R ₂ are C ₁ -C ₂₄ alkyl; A
O is oxyethylene or oxypropylene, and the chain may be constituted by only one of oxyethylene and oxypropylene, or both may be mixed and the two AO chains may be the same or different from each other; m and n are 1 to 18 respectively
X is a C ₁ -C ₅ alkyl sulfonate, halogen, acetate, sulfate, perchlorate,
They are hydrogen sulphate, hydroxide, aromatic sulphonate, phosphate and tetrafluoroborate. ) A tin plating bath having a pH of 2-9. 2. An oxycarboxylic acid, a polycarboxylic acid or a monocarboxylic acid is gluconic acid, citric acid, glucoheptonic acid, gluconolactone, glucoheptolactone, formic acid, acetic acid, propionic acid, butyric acid, ascorbic acid, oxalic acid. , Malonic acid, succinic acid, glycolic acid, malic acid,
The tin plating bath according to claim 1, wherein the tin plating bath is tartaric acid or diglycolic acid. 3. The quaternary ammonium salt (C) is a C ₁ -C ₅ alkyl sulfonate salt.
Or the tin plating bath according to 2. 4. A tin plating method, wherein the object to be plated is immersed in the tin plating bath according to any one of claims 1 to 3 to electroplate the object to be plated. 5. A printed circuit board, a semiconductor integrated circuit, a resistor, a variable resistor, a capacitor, a filter, an inductor, on which an electrodeposition film of tin is formed by using the plating bath according to claim 1. Electronic components such as thermistors, crystal units, switches, and lead wires.