JPH05186878A - Electroless tin and electroless tin-lead alloy plating bath - Google Patents

Abstract

PURPOSE:To provide an electroless tin or electroless tin-lead alloy plating bath adaptable to a body of a complex shape. CONSTITUTION:This plating bath contains a soluble tin salt or a mixture of the tin salt with a soluble lead salt, at least one kind of acid selected among alkanesulfonic acid, alkanolsulfonic acid, arom. sulfonic acid, mineral acids and aliphatic carboxylic acids, at least one kind of reducing agent selected among thiourea, hypophosphorous acid and hypophosphites and at least one kind of nitrogen-contg. compd. selected among imidazolinebetaine, dimethylalkylbetaines and alkylamineoxides.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to electroless tin or tin-based alloys used to deposit tin or tin-lead alloy layers on copper or copper alloys.
Regarding a lead alloy plating bath.

[0002]

2. Description of the Related Art Tin and tin-lead alloy plating on copper and copper alloys have been used for electronic parts, semiconductor device packages, etc. because of their good solderability and bondability. In addition, 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 higher and higher. However, the conventional electroless tin and tin-lead alloy plating baths are not suitable for complicated shapes because the bath life is short and the appearance stability is low, and there are many restrictions in pretreatment. Also,
For tape carriers with copper foil circuits on insulating resin sheets such as polyimide, peeling due to penetration of plating solution into the joint between resin and copper, and ion remaining in the bath on the insulating resin sheet The problem of insulation failure has been raised by the company and has become a problem in technological reform in this field.

JP-A-63-230883 and JP-A-1
No. 184279 describes electroless tin and tin-lead alloy plating baths having a basic composition of organic sulfonic acids, metal salts, sodium hypophosphite and thiourea. But,
In these plating baths, the metal deposition rate is slow, and the bath temperature must be set as high as 80 ° C., which promotes the oxidation of tin, shortens the bath life, and is economically disadvantageous. Further, in these plating baths, a chelating agent such as EDTA, a pH adjusting agent such as citric acid, and the like are compounded with components that increase residual ions on the resin, and problems such as poor insulation may occur.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the problems as described above, and its purpose is to improve the uniformity and adhesion of the coating and to improve the adhesion of particles in order to deal with complicated shapes. It is an object of the present invention to provide an electroless tin and tin-lead alloy plating bath, which enables the densification of the plating solution and reduces the permeation of the plating solution into the joint and avoids the adverse effects of residual ions in the insulating part.

[0005]

The present invention is directed to (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, an aromatic At least one acid selected from the group consisting of sulfonic acids, mineral acids and aliphatic carboxylic acids, at least 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, dimethyl alkyl betaine and alkyl amine oxide;
The present invention relates to an electroless tin or tin-lead alloy plating bath containing a certain nitrogen-containing compound.

[0006]

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

[Chemical 1] (Wherein, R represents a C ₅ -C ₂₅ alkyl group, R ₁ represents H, a 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), an imidazoline betaine of the following formula (II)

[Chemical 2] (Wherein R represents a C ₅ -C ₂₅ alkyl group, or R
Represents a group RCONHR'-, and R'represents a C ₁ -C ₃ alkylene group), and dimethylalkyl betaine of the following formula (III)

[Chemical 3] (Wherein R represents a C ₅ -C ₂₅ alkyl group, or R
Is a group RCONHR'-) and is provided with at least one nitrogen-containing compound selected from the group consisting of alkylamine oxides.

The imidazoline betaines of the formula (I) include: 2-undecyl-1-carboxymethyl-1-hydroxyethylimidazolium betaine 2-octyl-1-carboxymethyl-1-carboxyoxyethylimidazolium betaine -Oleyl-1-carboxymethyl-1-hydroxyethyl imidazolium betaine and the like. Examples of the dimethylalkyl betaine 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-carboxymethyl betaine * N-dodecyl-N, N-dimethyl-N-carboxymethyl betaine etc. are mentioned. Examples of the alkylamine oxide of the formula (III) include lauryldimethylamine oxide, coconut oil fatty acid amide propyldimethylamine oxide, and lauryldi (hydroxyethyl) amine oxide. The nitrogen-containing compound is generally 0.01 to
It is added 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. The alkanesulfonic acid has the formula C _n H _{2n + 1} SO ₃
H (where n is 1 to 5, preferably 1 to 3)
The one shown in 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 has the following formula C _m H _{2m + 1} —CH (OH) —C _p H _{2p + 1} —SO ₃ H (where m is 0 to 2 and p is 1 to 3). The one shown in 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 and the like can be mentioned. As the aromatic sulfonic acid, the following formula (IV) and formula (V)

[Chemical 4]

[Chemical 5] In the sulfonic acid represented by, a part of the hydrogen atoms 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, sulfosalicylic 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-
Examples thereof include sulfonic acid, crosenoic acid and 1-chloro-3-sulfonic acid. As the aliphatic carboxylic acid, a compound of formula C
Those represented by _n H _{2n + 1} COOH (where n is 1 to 5) can be used. For example, acetic acid, propionic acid,
Examples include butyric acid. The acids shown above are generally 0.1
~ 200 g / l added.

As the stannous salt and the mixture of the stannous salt and the lead salt, any soluble salt can be used, preferably the salt with the above-mentioned acid, and a metal or metal oxide in the above-mentioned acid. A complex salt (water-soluble) obtained by dissolving a can also be used. When added as a metal salt, the added amount is generally 0.1 to 200 g / l.

Examples of the reducing agent include hypophosphorous acid, sodium hypophosphite, potassium hypophosphite, calcium hypophosphite, lithium hypophosphite and ammonium hypophosphite. The hypophosphite compound is generally 5 to 200.
It is added in an amount of g / l.

In the plating bath of the present invention, the combination of each component can stabilize the precipitation, improve the appearance, improve the adhesion, densify the surface particles, and permeate the plating solution into the joint between the copper and the resin. A remarkable effect of suppressing and reducing residual ions in the insulating portion can be obtained. Further, the addition of the hypophosphorous acid compound also has effects of improving and stabilizing the deposition rate and extending the life of the plating solution.

The conditions for the plating bath include pH of 2 or less,
It is preferably 1 or less, and the bath temperature is 45 to 90 ° C., but 50 to 70 ° C. is preferable because the deposition rate is high. Well-known additives such as a smoothing agent for the plating surface and a brightening agent can be added to the plating bath of the present invention.

[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 0.5 mol / l-hypophosphorous acid: 0.8 mol / l-N-lauryl-N, N-dimethyl-N-carboxymethylbetaine: An electroless plating bath containing 20 g / l was constructed. The resulting bath is 55 ° C
The test piece of a rolled copper plate having a size of 25 × 25 mm was immersed in the sample for 3 minutes. The film obtained has a thickness of 0.9 μm and a thickness of 7
It had a lead content of 0.1% and had a matte, uniform and good appearance with excellent adhesion and a dense particle appearance. The lead content could be changed by increasing the bath temperature (up to 40%), and good film characteristics could be maintained at that time. Also,
Even after repeated plating, there was almost no deterioration of the solution, and good performance was maintained.

Example 2 The following components: tin phenol sulfonate: 0.13 mol / l lead borofluoride: 0.08 mol / l borofluoric acid: 0.4 mol / l phenol sulfonic acid: 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. The resulting bath is 55 ° C
The test piece of a rolled copper plate having a size of 25 × 25 mm was immersed in the sample for 3 minutes. The obtained film had a film thickness of 0.8 μm and 7.
It had a lead content of 5% and exhibited a matte, uniform and good appearance, excellent adhesion and a dense particle appearance. Even after repeated plating, there was almost no deterioration of the solution, and good performance was maintained.

Example 3 The following components: 2-Propanol tin sulfonate: 0.14 mol / l Lead acetate: 0.08 mol / l Phenol sulfonic acid: 0.5 mol / l 2-naphthalene sulfonic acid : 0.1 mol / l-Thiourea: 1.5 mol / l-Sodium hypophosphite: 1.0 mol / l-Patent oil fatty acid amide propyldimethylamine oxide: 15 g / l Electroless plating bath containing I took a bath. The resulting bath is 60 ° C
The test piece of a rolled copper plate having a size of 25 × 25 mm was immersed in the sample for 3 minutes. The film obtained is 0.9 μm thick and 8%
It had a lead content of 10% and had a matte, uniform and good appearance, excellent adhesion, and a dense particle appearance. Even after repeated plating, there was almost no deterioration of the solution, and good performance was maintained. When the tape carrier was plated under the same conditions, it had a dull, 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 (electrical conductivity), which was a good value.

Example 4 Ingredients: 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: An electroless plating bath containing 5 g / l was constructed. The obtained plating bath was maintained at 70 ° C., and a test piece of a 25 × 25 mm rolled copper plate was immersed for 3 minutes. The film obtained has a thickness of 0.6 μm.
Thus, tin plating having a good appearance, which was dull, uniform, and had good adhesion was obtained. Further, when the tape carrier was plated under the same conditions, the same appearance and film characteristics as described above could be obtained, and the residual ion amount after extraction with distilled water was 1
It showed a good value of 40 μS / cm (electrical conductivity).

Comparative Example 1 A known borofluoride bath for electroless solder plating containing the following components was prepared. Stannous borofluoride: 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 was kept at 65 ° C., and 25 × 25 mm
The test piece of the rolled copper plate of 3 was soaked 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 Hold the obtained plating bath at 65 ° C. to obtain 25 × 25 mm
The test piece of the rolled copper plate of 3 was soaked for 3 minutes. The obtained film was dull, lacked smoothness and uniformity, and had 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. to obtain 25 × 25 mm
The test piece of the rolled copper plate of 10 was soaked for 10 minutes. The obtained film had a film thickness of 1.0 μm, a low deposition rate, and a lead content of 38%. Regarding the stability of the bath, Sn ²⁺ oxidation was observed, and the amount of lead deposited was extremely high after repeated plating. An attempt was made to plate the tape carrier, but the resin part was discolored, and the amount of residual ions after extraction with distilled water was also high, which 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 25 × 25 mm by keeping the obtained plating bath at 55 ° C.
The test piece of the rolled copper plate of 3 was soaked for 3 minutes. The obtained film had a film thickness of 0.9 μm and a lead content of 9%, was non-glossy and lacked in uniformity, and caused uneven appearance. The grain surface was rough and many pinholes were observed.

Comparative Example 5 A known electroless tin plating bath containing the following components was prepared. Stannous borofluoride: 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
The test piece of the rolled copper plate of 3 was soaked for 3 minutes. The tin film obtained was dull and uniform, but some uneven appearance occurred. When the plated product was observed with time for several days, yellowing was observed.

The present invention has been described with reference to the preferred embodiments, but 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.

Claims (1)

[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, (D) selected from the group consisting of hypophosphorous acid and hypophosphite An electroless tin or tin-lead containing (E) at least one nitrogen-containing compound selected from the group consisting of (E) imidazoline betaine, dimethylalkyl betaine and alkylamine oxide. Alloy plating bath.