JP3180918B2 - Electroless tin and electroless tin-lead alloy plating bath - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

This invention relates to electroless tin or tin-tin alloys used to apply tin or tin-lead alloy layers on copper or copper alloys.
It relates to a lead alloy plating bath.

[0002]

2. Description of the Related Art Tin and tin-lead alloy plating on copper and copper alloys has been used for electronic parts, semiconductor device packages and the like because of their good solderability and bonding property. Also, with the recent miniaturization, complexity, and increase in the number of pins of electronic components, the performance required for electroless tin-lead alloy plating has become increasingly higher. However, conventional electroless tin and tin-lead alloy plating baths have a short service life of the bath and low stability of appearance, so they are not suitable for complicated shapes and have many restrictions in pretreatment. Also,
In the case of a tape carrier with a copper foil circuit on an insulating resin sheet such as polyimide, peeling due to the permeation of the plating solution into the joint between the resin and copper, and remaining ions in the bath on the insulating resin sheet Has raised the problem of insulation failure, which has become a problem in technological reform in this field.

JP-A-63-230883 and JP-A-Hei-1
No. 184279 describes an electroless tin and tin-lead alloy plating bath based on an organic sulfonic acid, a metal salt, sodium hypophosphite and thiourea. But,
In these plating baths, the deposition rate of metal is slow and the bath temperature needs to be set as high as 80 ° C., so oxidation of tin proceeds, the bath life is short, and it is economically disadvantageous. Further, in these plating baths, components such as a chelating agent such as EDTA and a pH adjuster such as citric acid increase the residual ions on the resin, and there is a possibility that problems such as poor insulation may occur.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems and aims to improve the uniformity and adhesion of a coating film and a particle size so as to correspond to a complicated shape. It is an object of the present invention to provide an electroless tin and tin-lead alloy plating bath which enables densification of a plating solution, and further reduces the penetration of a plating solution into a joint portion and avoids the adverse effects of residual ions in an insulating portion.

[0005]

The present invention provides (A) a soluble metal salt comprising a stannous salt or a mixture of a stannous salt and a lead salt, (B) an alkanesulfonic acid, an alkanolsulfonic acid, and an aromatic metal salt. At least one acid selected from the group consisting of sulfonic acids, mineral acids and aliphatic carboxylic acids, at least one selected from the group consisting of (C) thiourea, (D) hypophosphorous acid and hypophosphite At least one selected from the group consisting of one reducing agent, (E) imidazoline betaine, dimethylalkyl betaine and alkylamine oxide;
The present invention relates to an electroless tin or tin-lead alloy plating bath characterized by containing various kinds of nitrogen-containing compounds.

[0006]

DETAILED DESCRIPTION OF THE INVENTION As mentioned above, the present invention relates to an acid selected from the group consisting of alkanesulfonic acids, alkanolsulfonic acids, aromatic sulfonic acids, mineral acids and aliphatic carboxylic acids, A plating bath containing a tin salt and / or a lead salt, a thiourea as a complexing agent and a reducing agent as a basic composition has the following formula (I)

Embedded image (Where R represents a C ₅ -C ₂₅ alkyl group, R ₁ represents H, Na or CH ₂ COOM, and R ₂ represents COO
M, CH ₂ COOM or CHOHCH ₂ SO ₃ M, M represents Na, K or H, and R ₃ represents OH) imidazoline betaine of the following formula (II)

Embedded image (Where R represents a C ₅ -C ₂₅ alkyl group;
Represents a group RCONHR'-, R 'is C ₁ -C ₃ Al
Dimethyl alkyl betaine of the Killen group to Table Wa), and the following equation (III)

Embedded image (Where R represents a C ₅ -C ₂₅ alkyl group;
Electroless tin represents a group RCONHR'-, R 'is characterized in that the addition of C ₁ -C ₃ at least one nitrogen-containing compound selected from the group consisting of alkyl amine oxides represents an alkylene group) Or a tin-lead alloy plating bath.

The imidazoline betaines of the formula (I) include: 2-undecyl-1-carboxymethyl-1-hydroxyethylimidazolium hydroxydobetaine 2-octyl-1-carboxymethyl-1-carboxymethyloxyethylimidazolium such as hydroxide solid <br/> in-2-oleyl-1-carboxymethyl-1-hydroxyethyl imidazolium hydroxide betaine. The dimethylalkylbetaines of the formula (II) include: N-stearyl-N, N-dimethyl-N-carboxymethylbetaine N-oleyl-N, N-dimethyl-N-carboxymethylbetaine N-lauryl-N, N-dimethyl-N-carboxymethylbetaine N-dodecyl-N, N-dimethyl-N-carboxymethylbetaine and the like can be mentioned. The alkyl amine oxides of the formula (III), - lauryl dimethylamine oxide, coconut oil fatty acid amidopropyl dimethylamine oxy de
Do etc., and the like. The nitrogen-containing compound is generally 0.01 to
It is contained in an amount of 60 g / l, preferably 0.1-20 g / l.

Examples of the acid used include hydrochloric acid, hydrofluoric acid, sulfuric acid, hydrofluoric acid, perchloric acid and the like. Alkanesulfonic acids include those of the formula C _n H _{2n + 1} SO ₃
H (where n is 1-5, preferably 1-3)
Can be used. For example, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, 2-propanesulfonic acid, butanesulfonic acid, 2-butanesulfonic acid, pentanesulfonic acid and the like can be mentioned. The alkanol sulfonic acid, the formula _{C m H 2m + 1 -CH (} OH) -C p H 2p + 1 -SO 3 H ( wherein, m is 0 to 2, p is 1 to 3) Can be used. For example, 2-hydroxyethane-1-sulfonic acid, 2-hydroxypropane-1-sulfonic acid, 2-hydroxybutane-1-sulfonic acid, 2
-Hydroxypentane-1-sulfonic acid; As the aromatic sulfonic acid, the following formulas (IV) and (V)

Embedded image

Embedded image A part of the hydrogen atom of which is a hydroxyl group, a halogen atom, an alkyl group, a carboxyl group,
Those substituted with a mercapto group, an amino group, a sulfonic acid group or the like can be used. For example, benzenesulfonic acid, toluenesulfonic acid, xylenesulfonic acid, p-phenolsulfonic acid, cresolsulfonic acid, sulfosalcylic acid, nitrobenzenesulfonic acid, sulfobenzoic acid, diphenylamine-4-sulfonic acid, F acid, NW acid, 1- Naphthol-8-sulfonic acid, 2-naphthalenesulfonic acid, 1,5-naphthalenedisulfonic acid, diphenylamine-4-naphthalenesulfonic acid, 2-naphthol-6-
Sulfonic acid, crosanoic acid, 1-chloro-3-sulfonic acid and the like can be mentioned. Aliphatic carboxylic acids include those of the formula C
(Here, n is the 1~5) _n H _2n + 1 COOH can be used those represented by. For example, acetic acid, propionic acid,
Butyric acid and the like. The acids shown above are generally 0.1
It is added in an amount of ~ 200 g / l.

As the stannous salt and a mixture of the stannous salt and the lead salt, any soluble salts can be used, preferably salts with the above-mentioned acids, and metals or metal oxides as the above-mentioned acids. Can also be used. The amount added in terms of a metal salt is generally 0.1 to 200 g / l.

Examples of the reducing agent include hypophosphorous acid, sodium hypophosphite, potassium hypophosphite, calcium hypophosphite, lithium hypophosphite, ammonium hypophosphite and the like. Hypophosphorous compounds are generally 5-200
g / l are added.

In the plating bath of the present invention, the stability of precipitation, the improvement of appearance, the improvement of adhesion and the densification of surface particles, and the penetration of plating solution into the joint between copper and resin are improved by the combination of each component. A remarkable effect of suppression and reduction of residual ions in the insulating portion can be obtained. Further, by adding the hypophosphorous acid compound, effects of improving and stabilizing the deposition rate and extending the life of the plating solution can be obtained.

The conditions of the plating bath are as follows: pH 2 or less;
Preferably it is 1 or less, and the bath temperature is 45 to 90 ° C, but 50 to 70 ° C is suitable because the deposition rate is high. The plating bath of the present invention may contain known additives such as a plating surface smoothing agent and a brightening agent.

[0013]

Example 1 The following components: Tin methanesulfonate: 0.13 mol / l Lead methanesulfonate: 0.025 mol / l Methanesulfonic acid: 0.4 mol / l Thiourea: 1 An electroless plating bath containing 0.5 mol / l, hypophosphorous acid: 0.8 mol / l, and N-lauryl-N, N-dimethyl-N-carboxymethylbetaine: 20 g / l. 55 ° C of the resulting bath
And a test piece of a rolled copper plate of 25 × 25 mm was immersed for 3 minutes. The obtained film had a thickness of 0.9 μm and a thickness of 7 μm.
% Lead content and exhibited a matte, uniform, good appearance, excellent adhesion and dense particle appearance. By increasing the bath temperature, the lead content could be changed (up to 40%), and good film properties could be maintained at that time. Also,
There was almost no deterioration of the solution during plating by repetition, and good performance was maintained.

Example 2 The following components: tin phenolsulfonate: 0.13 mol / l, lead borofluoride: 0.08 mol / l, borofluoric acid: 0.4 mol / l, phenolsulfonic acid: 0 0.4 mol / l Thiourea: 1.2 mol / l Ammonium hypophosphite: 0.8 mol / l 2-octyl-1-carboxymethyl-1-carboxyoxyethyl imidazolium betaine: 10 g / l An electroless plating bath containing was prepared. 55 ° C of the resulting bath
And a test piece of a rolled copper plate of 25 × 25 mm was immersed for 3 minutes. The resulting film had a thickness of 0.8 μm and a thickness of 7.
It had a lead content of 5% and exhibited a matte, uniform and good appearance, excellent adhesion and dense particle appearance. There was almost no deterioration of the solution during plating by repetition, and good performance was maintained.

Example 3 The following components: tin 2-propanolsulfonate: 0.14 mol / l, lead acetate: 0.08 mol / l, phenolsulfonic acid: 0.5 mol / l, 2-naphthalenesulfonic acid : 0.1 mol / l ・ Thiourea: 1.5 mol / l ・ Sodium hypophosphite: 1.0 mol / l ・ Electroless plating bath containing coconut oil fatty acid amidopropyldimethylamine oxide: 15 g / l I took a bath. 60 ° C.
And a test piece of a rolled copper plate of 25 × 25 mm was immersed for 3 minutes. The resulting film has a thickness of 0.9 μm and 8%
, And exhibited a matte, uniform and good appearance, excellent adhesion and dense particle appearance. There was almost no deterioration of the solution during plating by repetition, and good performance was maintained. In addition, when the tape carrier was plated under the same conditions, it had a matte, uniform, good appearance and excellent adhesion, no attack on the resin part was observed, and the film and material remained after extraction with distilled water. The ion amount was 97 μS / cm (electric conductivity), which was a good value.

Example 4 The following components: tin sulfate: 0.25 mol / l, phenolsulfonic acid: 0.8 mol / l, hydrochloric acid: 0.1 mol / l, sodium hypophosphite: 0.5 mol / L. Thiourea: 1.4 mol / l. N-dodecyl-N, N-dimethyl-N-carboxymethylbetaine: 5 g / l. The obtained plating bath was kept at 70 ° C., and a test piece of a 25 × 25 mm rolled copper plate was immersed for 3 minutes. The obtained film has a thickness of 0.6 μm.
The resulting tin plating was dull, uniform, and had good appearance with good adhesion. When the tape carrier was plated under the same conditions, the same appearance and film characteristics as described above could be obtained, and the amount of residual ions after extraction with distilled water was 1%.
It showed a good value of 40 μS / cm (electric conductivity).

Comparative Example 1 A known borofluoride bath for electroless solder plating containing the following components was prepared. Stannous fluoride: 0.1 mol / l Lead borofluoride: 0.025 mol / l Hydrofluoric acid: 0.1 mol / l Thiourea: 1.3 mol / l Sodium hypophosphite: 0.3 mol / l Nonionic surfactant: 15 g / l The obtained plating bath is kept at 65 ° C., and 25 × 25 mm
Was immersed for 3 minutes. The obtained film had many irregularities, lacked uniformity, had a low deposition rate, and had a film thickness of only 0.4 μm. The lead content was 10%.

Comparative Example 2 A known electroless solder plating bath containing the following components was prepared. Stannous chloride: 0.1 mol / l Lead chloride: 0.025 mol / l Thiourea: 1.0 mol / l Hydrazine hydrochloride: 0.5 mol / l Hydrochloric acid: 1.0 mol / l l The obtained plating bath is maintained at 65 ° C.
Was immersed for 3 minutes. The resulting film is dull, lacks smoothness and uniformity, and has a lead content of 9
%, And the film thickness was 0.5 μm.

Comparative Example 3 A known electroless solder plating bath containing the following components was prepared. Methanesulfonic acid: 50 g / l Tin methanesulfonate: 20 g / l Lead methanesulfonate: 13 g / l Thiourea: 75 g / l Sodium hypophosphite: 80 g / l Citric acid: 15 g / l・ Laurylpyridinium chloride: 5 g / l ・ EDTA: 3 g / l The obtained plating bath was kept at 80 ° C., and 25 × 25 mm
Was immersed for 10 minutes. The obtained film had a thickness of 1.0 μm, a low deposition rate, and a lead content of 38%. Regarding the stability of the bath, oxidation of Sn ²⁺ was recognized, and the amount of lead deposited was extremely increased by repeated plating. Although the plating of the tape carrier was also attempted, the resin portion was discolored, and the amount of residual ions after extraction with distilled water was high, and was 250 μS / cm.

Comparative Example 4 A known electroless solder plating bath containing the following components was prepared. -Tin methanesulfonate: 0.13 mol / l-Lead methanesulfonate: 0.025 mol / l-Methanesulfonic acid: 0.4 mol / l-Thiourea: 1.5 mol / l-Hypophosphorous acid : 0.8 mol / l The obtained plating bath was kept at 55 ° C and 25 × 25 mm
Was immersed for 3 minutes. The obtained film had a film thickness of 0.9 μm and a lead content of 9%, was dull, lacked uniformity, and caused uneven appearance. The particle surface was rough and many pinholes were observed.

Comparative Example 5 A known electroless tin plating bath containing the following components was prepared. Stannous fluoride: 0.25 mol / l Hydrofluoric acid: 0.25 mol / l Phenolsulfonic acid: 0.55 mol / l Potassium hypophosphite: 0.5 mol / l l. Thiourea: 1.5 mol / l. Polyoxyethylene nonylphenol ether: 10 g / l. The obtained plating bath was kept at 70 ° C. and 25 × 25 mm
Was immersed for 3 minutes. The obtained tin film was dull and uniform, but partially uneven in appearance. When the plated material was observed over time for several days, yellowing was observed.

Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited to these embodiments, and many modifications can be made without departing from the spirit of the invention. Of course.

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Michihide Miyazaki 5-26 Nishiyanagihara-cho, Hyogo-ku, Kobe City, Hyogo Prefecture Inside Ishihara Pharmaceutical Co., Ltd. (56) References JP-A-2-197580 (JP, A) 1-184279 (JP, A)

Claims (1)

(57) [Claims] 1. A soluble metal salt comprising (A) a stannous salt or a mixture of a stannous salt and a lead salt, (B) an alkanesulfonic acid, an alkanolsulfonic acid,
At least one acid selected from the group consisting of aromatic sulfonic acids, mineral acids and aliphatic carboxylic acids; (C) thiourea; and (D) selected from the group consisting of hypophosphorous acid and hypophosphite The electroless tin or tin-lead alloy plating bath having at least one reducing agent as a basic composition is provided with (E) the following formula (I): (Wherein, R represents a C ₅ -C ₂₅ alkyl group, R ₁ is
H, Na or CH ₂ COOM, R ₂ is COO
M, CH ₂ COOM or CHOHCH ₂ SO ₃ M
M represents Na, K or H, and R ₃ represents OH.
Imidazoline betaine of the following formula (II) : (Where R represents a C ₅ -C ₂₅ alkyl group;
Represents a group RCONHR'-, R 'is C ₁ -C ₃ Al
A dimethylalkyl betaine of the formula
The following formula (III) (Where R represents a C ₅ -C ₂₅ alkyl group;
Represents a group RCONHR'-, R 'is C ₁ -C ₃ Al
Alkylene oxide)
Add at least one nitrogen-containing compound selected from the group
Electroless tin or tin, characterized in that the - lead alloy plating bath.