JPH11269692A - Tin-silver alloy acidic electroplating bath - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the plating bath stable at a high temp. for a long period and to obtain a plating film having high gloss, soldering property and whisker resistance by incorporating aminothiophenol compds. or the like into a tin-silver alloy plating liquid containing no cyanide compd. SOLUTION: This tin-silver alloy acid plating bath contains aminothiophenol compds. expressed by the formula, and reaction products of unsatd. aliphatic aldehydes and/or unsatd. aliphatic aldehydes and amine compds. The plating bath does not contain cyanide compds. In the formula, R<1> , R<2> , R<4> and R<5> are each H or NH2 groups, R<3> is H, NH2 , OH, COOH, Cl, Br, NO2 , CH3 or OCH3 groups, and at least one of R<1> to R<5> has a NH2 group and R<4> , R<5> are each preferably hydrogen. The aminothiophenol compds. can be used in a single compd. or together, however, even a single aminothiophenol compd. gives an enough effect to maintain stability of the bath and plating performance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an acidic tin-silver alloy plating bath containing substantially no cyanide.

2. Description of the Related Art An alkaline cyanide bath containing a cyanide compound has been known as a tin-silver alloy plating bath used for forming a tin-silver alloy plating film on a metal substrate or the like. However, this bath is extremely toxic because it contains a toxic cyanide, so that special care must be taken in handling it, and it is necessary to perform special wastewater treatment and the working environment is deteriorated. there were. On the other hand, examples of the acidic bath containing no cyanide compound include mercaptoalkanecarboxylic acid and / or mercaptoalkanesulfonic acid bath described in JP-A-7-252684, JP-A-8-13185 and JP-A-8-185.
No. 41676 discloses an alkanesulfonic acid or alkanolsulfonic acid bath.

However, in these acidic baths, silver, which is an essential component for forming a tin-silver alloy, cannot be stably dissolved together with tin, and immediately after the preparation of the plating bath or within 24 hours, a black or brown precipitate is formed. As a result, silver was insoluble and it was difficult to maintain the bath component concentration. On the other hand, as a result of diligent research, the present applicant has developed an acid bath which is an alkanesulfonic acid and / or sulfamic acid bath containing a thioamide compound and a thiol compound as silver complexing agents,
Japanese Patent Application No. 7-330437 (Japanese Unexamined Patent Application Publication No.
No.). Here, as the thiol compound, a compound having 4 to 8 carbon atoms such as mercaptosuccinic acid and mercaptolactic acid is used.
Are preferred. Although this plating bath does not precipitate and insolubilize silver immediately after production or within 24 hours, when this plating bath is left or used for a long time,
There has been a problem that thioamide compounds and thiol compounds such as mercaptosuccinic acid and mercaptolactic acid adversely affect plating performance, particularly the smoothness and throwing power of plating films.

[0003] When left at a higher temperature, silver becomes insoluble as a black or brown precipitate within 24 hours, as in the acidic bath disclosed in the above-mentioned JP-A-7-252684 and JP-A-8-13185. It was difficult to maintain bath component concentrations. Further, in the acidic bath which is an alkanesulfonic acid or alkanolsulfonic acid bath described in JP-A-9-143786, the above-mentioned applicant's JP-A-9-170 is disclosed.
Thiourea-based, thiazole-based, sulfenamide-based, thiuram-based, dithiocarbamate-based compounds similar to or other than the silver complexing agent disclosed in JP-A-0994
Bisphenol, benzimidazole, and organic thioacid compounds are shown as silver complexing agents, but among these sulfur-containing compounds, compounds that are stably dissolved in the acidic region such as alkanesulfonic acid and alkanolsulfonic acid are limited. ing. Further, in order to prevent silver from being replaced in the plating object and to keep the plating bath stable without turbidity, a plurality of sulfur-containing compounds, mainly thiourea-based compounds, must be used. For industrial use, bath management becomes complicated, and it is difficult to maintain a constant plating performance for a long period of time.

[0004] On the other hand, Sn alloy plating with a metal other than Pb including Sn-Ag alloy is considered to be more advantageous than conventional tin-lead alloy plating in terms of safety and prevention of environmental pollution, but whiskers are generated. There is fear. JP-A-2-41
No. 794, Sn-3.5Ag, S
Generation of whiskers has been confirmed in an n-5Ag solder alloy at 50 ° C. for 7000 hours. As a whisker prevention measure, a method of adding a small amount of Pb or Sb to form a ternary alloy is disclosed. As a method for preventing whiskers of tin plating, Japanese Patent Application Laid-Open No. 2-270986 discloses that gloss and whisker resistance are excellent by strictly controlling the carbon content in the plating layer at the material interface and in the plating layer on the plating surface. A method for obtaining a tinned metal plate has been proposed.

[0005]

The present invention can stably dissolve tin, silver and other metal ions in a bath for a long period of time even at a high temperature without containing a cyanide compound. Another object of the present invention is to provide an acidic tin-silver alloy plating bath having excellent gloss, solderability and whisker resistance.

According to the present invention, an aminothiophenol compound has an action of stably dissolving all of tin, silver and other metal ions in an acid bath containing no cyanide compound. Finding that when used in combination with a saturated aliphatic aldehyde or unsaturated aliphatic aldehyde and an amine-based compound, it has the effect of depositing a tin-silver-based alloy plating film having excellent gloss, solderability and whisker resistance. It was made based on. That is, the present invention provides an aminothiophenol-based compound represented by the following general formula (I), an unsaturated aliphatic aldehyde and / or
Another object of the present invention is to provide a tin-silver alloy acidic plating bath containing a reaction product of an unsaturated aliphatic aldehyde and an amine compound and containing no cyanide compound.

[0006]

Embedded image

(Where R¹, R^Two, R^FourAnd R^FiveIs H
Or NH_TwoGroup, R^ThreeIs H, NH _Two, OH, COO
H, Cl, Br, NO_Two, CH_ThreeOr OCH_ThreeIs the base
Is R ¹~ R^FiveAt least one is NH_TwoHaving a group.
R^FourAnd R^FiveIs preferably hydrogen. )

BEST MODE FOR CARRYING OUT THE INVENTION The tin compound used in the present invention may be any compound capable of releasing tin ions into an acidic bath, such as stannous oxide, stannous sulfate, tin chloride, sulfide, and the like. One or a mixture of two or more of tin, tin iodide, tin citrate, tin oxalate, stannous acetate and the like can be mentioned. The tin ion concentration in the plating bath can be arbitrarily set, but it is preferable that the tin concentration be 1 to 100 g / l, more preferably 10 to 60 g / l.

The silver compound used in the present invention may be any compound capable of releasing silver ions into an acidic bath. For example, one or more of silver oxide, silver sulfate, silver chloride and silver nitrate may be used. Mixtures. The silver ion concentration in the plating bath can be arbitrarily set, but is preferably 0.01 to 100 g / l as silver, more preferably 0.01 to 80 g / l, and still more preferably 0.1 to 80 g / l. It is good to be 1 to 50 g / l.
Examples of the aminothiophenol-based compound represented by the general formula (I) used in the present invention include, for example, 2-aminothiophenol, 4-aminothiophenol, 4-hydroxy-2-aminothiophenol, 4-chloro- 2-
Aminothiophenol compounds such as aminothiophenol, 4-carboxy-2-aminothiophenol, 4-methyl-2-aminothiophenol, 4-methoxy-2-aminothiophenol, and 4-bromo-2-aminothiophenol It is preferred to use Further, these aminothiophenol compounds more preferably have a structure having an NH ₂ group at the ortho position.

In the present invention, the aminothiophenol-based compound may be used alone or in combination of two or more, or may be used as a mixture of two or more. However, even when used alone, it is necessary to maintain bath stability and plating performance. Effective enough. Also,
These also act as brighteners. The amount of the aminothiophenol-based compound in the plating bath can be any amount as long as tin, silver and all other metal elements in the bath can be stably dissolved, but the amount is 0.1 to 200 g / l. And more preferably 0.2 to 50 g / l. In the present invention, only tin and silver can be used as metal elements, but other metal elements can be used in combination. Preferred are Bi, Zn,
One or a mixture of two or more of In, Cu, Sb, Ti, Fe, Ni, and Co can be mentioned. As a compound of these metal elements, any compound that can release these metal ions in an acidic bath may be used.For example, each element is an oxide, chloride, sulfate, nitrate, carbonate, sulfide,
One or a mixture of two or more of iodide, citrate, oxalate, acetate, tartrate and the like can be mentioned. The concentration of the added metal element ion other than tin and silver in the plating bath can be arbitrarily determined.
g / l, more preferably 0.01 to 10 g / l.

The unsaturated aliphatic aldehyde used in the present invention includes one or more unsaturated aliphatic aldehydes having 3 to 12 carbon atoms such as acrolein, methacrolein, crotonaldehyde, sorbinaldehyde, heptenal and dodecenal. Mixtures. The concentration of the unsaturated aliphatic aldehyde in the plating bath can be arbitrarily set, but is preferably 0.001 to 10 g / l, more preferably 0.01 to 1 g / l. Is good. As the reactant of the unsaturated aliphatic aldehyde and the amine compound used in the present invention, acrolein,
For 1 mole of unsaturated aliphatic aldehyde such as crotonaldehyde, sorbinaldehyde, 2-ethylcrotonaldehyde and 3-methyl-2-butenal, ethylenediamine, diethylenetriamine, triethylenetetramineamine, 1,3-propyldiamine and dipropylenetriamine Aliphatic amines having 2 to 10 carbon atoms, such as
0.001 mol is added, and a compound which is easily soluble in a plating bath condensed by heating at 25 to 150 ° C. for 30 minutes or more is exemplified. The concentration of the reactant of the unsaturated aliphatic aldehyde and the amine compound in the plating bath can be arbitrarily set, but is preferably 0.001 to 10 g / l as the reactant of the unsaturated aliphatic aldehyde and the amine compound. And more preferably 0.01 to 1 g / l.

In the present invention, an unsaturated aliphatic aldehyde and a reaction product of an unsaturated aliphatic aldehyde and an amine compound can be used in combination. In the present invention, any acidic substance can be contained in order to make the pH of the tin-silver-based alloy plating bath acidic. Among them, alkanesulfonic acids such as methanesulfonic acid, ethanesulfonic acid and hydroxy Alkanesulfonic acids having 1 to 3 carbon atoms, such as propanesulfonic acid, and benzenesulfonic acids and phenolsulfonic acids, for example, those having 6 to 7 carbon atoms such as sulfosalicylic acid and cresolsulfonic acid, and alkanolsulfonic acids, for example, Isopropanol sulfonic acid,
It is preferable to use sulfamic acid or the like. These acids can be used as one kind or as a mixture of two or more kinds. The acid concentration of the plating bath can be arbitrary as long as tin and silver and all other metal elements can be dissolved.
Preferably from 10 to 500 g / l, more preferably from 50 to 500 g / l.
It is good to be 400 g / l. Especially the pH of the bath
Is preferably 2 or less, more preferably 1 or less. In the present invention, a tin-silver-based alloy acidic plating bath containing the above components as essential components and the remainder as water, and substantially free of a cyanide compound.

In the present invention, additives such as a brightener and a smoothing agent may be further contained. For example, the brightener may be any of those used as brighteners for plating of tin and silver or their alloys, for example, nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants, synthetic Polymers (PVA, PEG, PVP), amines (hexamethylenetetramine, triethanolamine, etc.), ketones (benzalacetone, acetophenone, etc.), aliphatic aldehydes (formalin, valeraldehyde, etc.), aromatic aldehydes ( Salicylaldehyde, vanillin, etc.). The brightener is 0.0
The amount is preferably 5 to 50 g / l, more preferably 0.1 to 30 g / l. Further, as an antioxidant for tin, hydroxyphenyl compounds such as phenol, catechol, pyrogallol and hydroquinone, L-ascorbic acid, sorbitol and the like may be used.

Using the acidic tin-silver alloy plating bath of the present invention, tin-silver alloy plating can be applied to various metal substrates, for example, iron, copper and their alloys, in a conventional manner. Specifically, a metal substrate is used as a cathode, and a single plate of tin or silver, a tin-silver alloy plate, or a plate of another metal element or an insoluble electrode is used as an anode and immersed in a tin-silver alloy plating bath. Then, a current of about 0.1 to 100 A is applied for 0.5 to 10
By flowing for about 10 minutes, the thickness of the tin-silver alloy of 10 to 99.9% by weight of tin and 90 to 0.1% by weight of silver (or silver and other metals) is 1 to 50 μm, preferably 1 to 30 μm. Can be formed on a metal substrate.

[0014]

The tin-silver alloy plating bath of the present invention has the advantage of low toxicity and high safety because it is a cyanide-free type. Further, silver easily forms insoluble salts with various silver, but in the tin-silver alloy plating bath of the present invention, silver is stably present for a long period of time, and there is no change in plating performance. In addition, there is an advantage that a tin-silver-based alloy plating film excellent in gloss, solderability and whisker resistance can be obtained in a tin-based alloy plating film in which whiskers may be generated. Furthermore, since no special wastewater treatment is required, there is an advantage that the wastewater treatment cost is reduced. Next, the present invention will be described with reference to examples.

[0015]

EXAMPLE 1 An acidic tin-silver alloy plating bath was prepared which was composed of the following components and the balance was water. SnO 50 g / l Ag ₂ SO ₄ 4 g / l 4-hydroxy-2-aminothiophenol 7 g / l hydroxypropanesulfonic acid 150 g / l PEG 11000 4 g / l Anionic surfactant (Rapidol B-80 manufactured by NOF Corporation) 10 g / l l Acrolein 1.5g / l

Example 2 An acidic tin-silver alloy plating bath comprising the following components and the balance being water was prepared. _{SnO 50g / l Ag 2 SO 4} 5g / l Ag 2 O 4g / l hydroxypropane sulfonic acid _{150g / l In 2 (SO 4} ) 3 · 9H 2 O 5g / l 4- hydroxy-2-aminothiophenol 7 g / l Polyvinylpyrrolidone K-15 10 g / l Crotonaldehyde 10 g / l Triethylenetetramine 2 g / l

Example 3 An acid tin-silver alloy plating bath having the following components and the balance being water was prepared. SnO 50 g / l Ag ₂ SO ₄ 4 g / l 4-chloro-2-aminothiophenol 7 g / l Unsaturated aldehyde condensate 0.5 g / l hydroxypropanesulfonic acid 150 g / l Condensation of unsaturated aliphatic aldehyde As a product, a reaction product of crotonaldehyde and triethylenetetramine was used (the same applies hereinafter).

Example 4 An acid tin-silver alloy plating bath comprising the following components and the balance being water was prepared. _{SnO 30g / l Ag 2 O 4g} / l 2- aminothiophenol _{4g / l NiSO 4 · 7H 2} O 10g / l unsaturated aliphatic aldehyde condensation product 1 g / l hydroxypropane sulfonic acid 250 g / l

Example 5 An acidic tin-silver alloy plating bath comprising the following components and the balance being water was prepared. _{SnSO 4 50g / l Ag 2 SO} 4 1g / l 4- hydroxy-2-aminothiophenol _{6g / l ZnSO 4 · 7H 2} O 9g / l condensate 0.1 g / l of methanesulfonic acid unsaturated aliphatic aldehydes 320g / L PEG 20000 6g / l

Example 6 An acidic tin-silver alloy plating bath having the following components and the balance being water was prepared. _{SnSO 4 40g / l Ag 2 O} 1.5g / l 4- hydroxy-2-aminothiophenol 5g / l CoSO ₄ 10g / l condensate 0.05 g / l hydroxypropane sulfonic acid 350 g / l of unsaturated aliphatic aldehydes Anionic surfactant (Sanlex BNS manufactured by Nikka Chemical Co., Ltd.) 6 g / l Piperonal 0.1 g / l Hexamethylenetetramine 4 g / l

COMPARATIVE EXAMPLE 1 An acidic tin-silver alloy plating bath having the following components and the balance being water was prepared. SnO 30 g / l Ag ₂ O 2 g / l thiourea 5 g / l methanesulfonic acid 150 g / l Sn-222 (manufactured by Dipsol, tin plating brightener) 30 g / l Comparative Example 2 Consists of the following components, with the balance being water An acid tin-silver alloy plating bath was prepared. _{SnSO 4 30g / l Ag 2 SO} 4 2g / l 2- aminothiophenol 5 g / l methanesulfonic acid 150g / l Sn-222 (manufactured by Dipsol tinned brightener) 30 g / l

Comparative Example 3 An acidic tin-silver alloy plating bath having the following components and the balance being water was prepared. SnO 50 g / l Ag ₂ SO ₄ 5 g / l 4-hydroxy-2-aminothiophenol 5 g / l hydroxypropanesulfonic acid 200 g / l Nonionic surfactant (Nichika Chemical Sunmol BN-13D) 4 g / l hexamethylene Tetramine 4 g / l Benzal acetone 1.5 g / l Comparative Example 4 An acidic tin-silver alloy plating bath comprising the following components and the balance being water was prepared. SnSO ₄ 50 g / l Ag ₂ O 5 g / l 4-aminothiophenol 5 g / l methanesulfonic acid 200 g / l Anionic surfactant (S-010S, manufactured by Nikka Kagaku) 6 g / l

Comparative Example 5 An acidic tin-silver alloy plating bath having the following components and the balance being water was prepared. SnSO ₄ 50 g / l Ag ₂ O 5 g / l 4-aminothiophenol 5 g / l methanesulfonic acid 200 g / l polyvinylpyrrolidone K-30 5 g / l 35% formalin 10 g / l Comparative Example 6 An acidic tin plating bath, which was water, was prepared. SnSO ₄ 35 g / l 98% H ₂ SO ₄ 140 g / l Sn-222 (dip sole tin-plated brightener) 30 g / l

Comparative Example 7 An acidic tin plating bath comprising the following components and the balance being water was prepared. 45 g / l SnO 2 g / l PbO 2 g / l methanesulfonic acid 150 g / l TL-290S (tin-lead alloy plating brightener manufactured by Dipsol) 20 ml / l Using the plating baths of Examples 1 to 6 and Comparative Examples 1 to 5 described above. After the plating bath was prepared, it was left at 60 ° C. for 4 hours.
After 10 days, 30 days, and 120 days, visual observation of the presence or absence of precipitation in the plating bath and analysis of silver concentration by atomic absorption spectrometry were performed. The results are shown in Table 1.

[0025]

[Table 1] Table-1 Silver concentration in the presence or absence bath precipitate (g / l) a b c d a b c d Example 1 ○ ○ ○ ○ 2.77 2.77 2.77 2.77 Example 2 ○ ○ ○ ○ 7.18 7.16 7.17 7.17 Example 3 ○ ○ ○ ○ 2.75 2.76 2.76 2.76 Example 4 ○ ○ ○ ○ 3.70 3.72 3.70 3.72 Example 5 ○ ○ ○ ○ 0.70 0.70 0.70 0.69 Example 6 ○ ○ ○ ○ 1.40 1.40 1.40 1.39 Comparative example 1 × × × × 1.01 0.00 0.00 0.00 Comparative example 2 ○ ○ ○ ○ 1.37 1.38 1.37 1.38 Comparative Example 3 ○ ○ ○ ○ 3.44 3.44 3.44 3.45 Comparative Example 4 ○ ○ ○ ○ 4.65 4.65 4.66 4.65 Comparative Example 5 ○ ○ ○ ○ 4.65 4.66 4.66 4.66

：: No precipitation a: 4 hours after plating bath preparation ×: Precipitation b: 10 days after plating bath preparation c: 30 days after plating bath preparation d: 120 days after plating bath preparation Progress In addition, using the plating baths of Examples 1 to 6 and Comparative Examples 1 to 7, after preparing the plating bath, 50 × 10 mm
Was plated on a copper plate. A rosin-based flux applied to this plated copper plate was used as a sample, and a solder bath temperature of 2
A solderability test was performed using a solder checker (manufactured by Resca Co., Ltd., SAT-2000) under the conditions of 30 ° C. and an immersion time of 10 seconds, and a zero cross time was measured.
Table 2 shows the evaluation results. (Plating conditions) Cathode current density: 10 A / dm2 Bath temperature: 30 ° C. Plating film thickness: 10 μm

[0027]

[Table 2] Table-2 (Evaluation results) Example 1 ◎ Comparative Example 1 × Example 2 ◎ Comparative Example 2 ○ Example 3 ◎ Comparative Example 3 ○ Example 4 ◎ Comparative Example 4 ○ Example 5 ◎ Comparative Example 5 ○ Example 6 ◎

A: Zero cross time is comparative example 7 (tin-lead alloy plating)
Length equivalent to. ：: Zero-cross time is the same length as Comparative Example 6 (tin plating). ×: The length of the zero cross time is longer than Comparative Example 6 (tin plating). Further, using the plating baths of Examples 1 to 6 and Comparative Examples 2 to 7, after preparing the plating bath, a Hull cell test was performed under the following conditions. After the appearance of the Hull cell was evaluated, the surface was left at 45 ° C., and the surface was observed with a scanning electron microscope after elapse of 7, 30, 100, and 300 days.

(Test conditions) Bath temperature: 25 ° C. Anode plate: Tin plate Negative plate: Polished steel plate Current: 3A Plating time: 10 minutes Plating baths of Examples 1 to 6 and Comparative examples 2 to 7 In each of the treatments described above, a uniform film was deposited. Among them, those treated in the plating baths of Examples 1 to 6 deposited a particularly uniform glossy film. No whiskers were observed after 300 days in each of the plating baths of Examples 1 to 6 and Comparative Example 7. In all of the samples treated in the plating baths of Comparative Examples 2 to 5, generation of whiskers was confirmed after 300 days, particularly in a thin portion of the plating film in the low electric part of Hull cell. In the case where the treatment was performed in the plating bath of Comparative Example 6, generation of whiskers was confirmed on the entire surface of the Hull cell after 7 days. The results are shown in Table-3.

[0030]

[Table 3] Table-3 Presence EXAMPLE 1 ◎ ○ ○ ○ ○ Example 2 ◎ ○ ○ ○ ○ Example 3 ◎ ○ ○ ○ ○ Example 4 ◎ ○ ○ ○ ○ Example 5 ◎ ○ ○ ○ ○ exemplary coating appearance whiskers a b c d Example 6 ◎ ○ ○ ○ ○ Comparative Example 2 ○ ○ ○ △ △ Comparative Example 3 ○ ○ ○ △ △ Comparative Example 4 ○ ○ ○ △ △ Comparative Example 5 ○ ○ ○ △ △ Comparative Example 6 ○ × × × × Comparative Example 7 ○ ○ ○ ○ ○

◎: Uniform gloss appearance a: 7 days after the Hull cell test ○: Uniform appearance b: 30 days after the Hull cell test c: 100 days after the Hull cell test d: 300 days after the Hull cell test ：: No whisker was generated. Δ: Whisker was generated in a part of Hull cell. X: Whisker generation was confirmed on the entire Hull cell.

Claims (3)

[Claims] An aminothiocyanate represented by the following general formula (I):
Ophenolic compounds, unsaturated aliphatic aldehydes and / or
Or the reaction with unsaturated aliphatic aldehydes and amine compounds
Reaction products and no cyanide compounds.
And a tin-silver alloy acid plating bath. Embedded image(Where R¹, R^Two, R^FourAnd R^FiveIs H or NH
_TwoGroup, R^ThreeIs H, NH _Two, OH, COOH, Cl, B
r, NO_Two, CH_ThreeOr OCH_ThreeIs a group, ¹~ R
^FiveAt least one is NH_TwoHaving a group. ) 2. Bi, Zn, In, Cu, Sb, Tl,
The acid plating bath according to claim 1, wherein the bath contains at least one metal ion selected from the group consisting of Fe, Ni, and Co. 3. The acidic plating bath according to claim 1, which contains at least one selected from the group consisting of alkanesulfonic acid, alkanolsulfonic acid and sulfamic acid.