JP4404909B2 - Electric tin and tin alloy plating solution - Google Patents

Description

  The present invention relates to an electrotin plating solution and an electrotin alloy plating solution.

  Conventionally, electrotin plating and electrotin alloy plating, particularly tin zinc alloy plating, have difficulty in solder wettability, and therefore have low reliability after soldering and have not been put to practical use. Also in the plating process, the cathode current efficiency is poor, the plating rate is slow, and the obtained plating film has coarse and matte appearance problems.

  Under such circumstances, the first object of the present invention is to improve the solder wettability of electrotin plating and electrotin alloy plating and to increase the reliability after soldering. Another object is to improve the plating speed and the appearance after plating, which have been regarded as problems in the past.

  As a result of intensive studies on the above problems, the present inventors have used a plating solution in which a compound having both an imidazole group and a hydroxyl group in one molecule is added to a conventional electrotin or tin alloy plating solution. The inventors have found that the above problems can be solved.

That is, the present invention
[1] An electrolytic tin and tin alloy plating solution comprising one or more compounds having an imidazole group and a hydroxyl group in one molecule.

[2] The electrolytic tin and tin alloy plating solution according to [1], wherein the compound having an imidazole group and a hydroxyl group in one molecule is an imidazole alcohol compound represented by the following general formula (1): .
(In the general formula (1), R ¹ , R ² , and R ³ are each hydrogen, a vinyl group, or an alkyl group having 1 to 20 carbon atoms, and R ² and R ³ form an aromatic ring. R ⁴ is hydrogen, vinyl group, alkyl group having 1 to 20 carbon atoms, phenyl group, or — (CH ₂ CH (R ⁵ ) O) _k H, R ⁵ is hydrogen, alkyl having 1 to 20 carbon atoms. Group, X represents hydrogen, an alkyl group having 1 to 6 carbon atoms, or a substituent which may contain N or O, m is an integer of 0 to 20, n and l are integers of 1 to 3, k is Represents an integer of 1 to 20.)

[3] Imidazole alcohol obtained by reacting the compound represented by the general formula (1) with an imidazole compound represented by the following general formula (2) and an epoxy compound represented by the following general formula (3) The electrolytic tin and tin alloy plating solution according to [2] above, which is a compound.
(In the general formulas (2) and (3), R ¹ , R ² and R ³ are each hydrogen, vinyl group, or alkyl group having 1 to 20 carbon atoms, and R ² and R ^{3 form an} aromatic ring. R ⁴ is hydrogen, vinyl group, alkyl group having 1 to 20 carbon atoms, phenyl group, or — (CH ₂ CH (R ⁵ ) O) _k H, R ⁵ is hydrogen, 1 carbon atom. -20 alkyl group, X represents hydrogen, an alkyl group having 1 to 6 carbon atoms, or a substituent which may contain N or O, m is an integer of 0 to 20, n and l are 1 to 3; Integer, k represents an integer of 1 to 20.)

  By using the electrotin plating solution and electrotin alloy plating solution of the present invention, the solder wettability and appearance of the plated product can be improved. In addition, the plating rate can be improved by using the plating solution of the present invention.

  As the electrotin plating solution and the electrotin alloy plating solution of the present invention, basically, an electrotin plating solution and an electrotin alloy plating solution which have been conventionally studied can be used, and the specific imidazole alcohol compound is added thereto. It is to be added.

  Electrotin plating solution and electrotin alloy plating solution are a metal salt or metal salt stabilizer that forms an alloy with tin salt or tin salt as a plating film metal component (the tin should be divalent to tetravalent) Stabilizers), brighteners (smoothing agents, prevention of abnormal precipitation), conductive salts, pH adjusters, and the like.

Specifically, as a tin salt that is a metal component of the plating film and a metal salt that forms an alloy with tin, examples of the tin salt include tin sulfate, tin chloride, tin sulfamate, tin methanesulfonate, etc. I can do it. Moreover, as a metal which forms an alloy with tin, zinc, indium, bismuth, gold | metal | money, silver, copper, nickel etc. can be illustrated, for example, The salt similar to tin can be used as a salt.
In the electrotin plating solution, the concentration of tin salt is preferably 1 to 60 g / L as a metal. In the case of an electrotin alloy plating solution, a tin salt having the above concentration and a metal salt forming an alloy with tin are used. It is preferable to contain 0.01-50 g / L as a metal.

The metal salt stabilizer basically has a function of preventing oxidation of tin, and ascorbic acid, erythorbic acid, polyhydric phenol, hypophosphite and the like can be used.
In the plating solution, the metal salt stabilizer is preferably contained in an amount of 1 to 50 g / L when hypophosphite is used, and 0.05 to 10 g / L in other cases.

As the brightener, polyacrylamide and derivatives thereof, polyethylene glycol, triethanolamine and derivatives thereof, and the like can be used.
The brightening agent is preferably contained in the plating solution in an amount of 0.01 to 10 g / L.

Examples of the conductive salt include methanesulfonic acid and its salt, sulfamic acid and its salt, hydrochloric acid and its salt, sulfuric acid and its salt, and the like.
The plating salt preferably contains 5 to 300 g / L of the conductive salt.

  Examples of the pH adjuster include sodium hydroxide, potassium hydroxide, ammonia, hydrochloric acid, sulfuric acid and the like.

Examples of the complexing agent include malic acid, citric acid, gluconic acid, lactic acid, succinic acid, ethanethiol, thiourea, and ethylenediaminetetraacetic acid.
In the plating solution, the complexing agent is preferably contained in an amount of 0.05 to 100 g / L.

  In the present invention, one or more compounds having an imidazole group and a hydroxyl group in one molecule are added to the electrotin plating basic solution or the electrotin alloy plating basic solution. The complexing agent, a compound having an imidazole group and a hydroxyl group in one molecule may be mixed and added in advance.

  The present invention uses a plating solution in which one or more compounds having an imidazole group and a hydroxyl group in one molecule are added to the above-described conventional electrotin plating solution and electrotin alloy plating solution. is important. This can improve the solder wettability and appearance of the electroplated tin product and the electrotin alloy plated product, and can also improve the plating rate.

The compound having an imidazole group and a hydroxyl group in one molecule used in the present invention is preferably synthesized by a reaction represented by the following reaction formula (4).
(Wherein R ¹ , R ² , R ³ , R ⁴ , X, l, m and n are the same as defined above.)

In the general formulas (1) to (3), R ¹ , R ² , R ³ , and R ⁴ sufficiently exhibit the effects of the present invention as long as they are hydrogen, a vinyl group, or an alkyl group having 1 to 20 carbon atoms. . As an alkyl group, it is C1-C20, However, 1-9 are preferable. Moreover, when forming an aromatic ring with R < ² > and R < ³ >, the aromatic ring to form is preferable a benzene ring. X is hydrogen, an alkyl group having 1 to 6 carbon atoms, or a substituent that may contain N or O, and the alkyl group having 1 to 6 carbon atoms may be an alkyl group having 1 to 4 carbon atoms. Preferably, the substituent containing N and O includes a hydroxyl group, a carboxyl group, an amino group, and the like. In addition to the above, R ⁴ is a phenyl group, — (CH ₂ CH (R ⁵ ) O) _k H (R ⁵ is hydrogen, an alkyl group having 1 to 20 carbon atoms, and k is an integer of 1 to 20). Is also preferable.

Preferred as the imidazole compound represented by the general formula (2) are imidazole, 2-alkylimidazole, 2,4-dialkylimidazole, 4-vinylimidazole and the like. In the case where R ^{1 to} R ³ bonded to the imidazole group are alkyl groups, when the number of carbon atoms is 10 or more, the wettability of the material to be plated may decrease and the characteristics may deteriorate due to the increase in hydrophobicity. A preferable carbon number is 1-9. Of these, imidazole and 2-methylimidazole are particularly preferred.

  Examples of the epoxy compound represented by the general formula (3) include epoxypropanol, epoxybutanol, epoxypentanol, epoxyhexanol, methoxyglycidol, n-butoxyglycidol, tert-butoxyglycidol, phenoxyglycidol such as ethylene of glycidol. Epoxy compounds having an alkylene oxide such as an oxide adduct can be listed.

  The reaction may be performed while dropping 0.1 to 10 moles of an epoxy compound in an imidazole compound heated to a temperature of 80 to 200 ° C., and a reaction time of about 5 minutes to 3 hours is sufficient. This reaction does not particularly require a solvent, but an organic solvent such as chloroform, dioxane, methanol, or ethanol may be used as a reaction solvent. In addition, since this reaction dislikes moisture, it is preferably performed in an atmosphere of a gas not containing moisture such as dry nitrogen or argon so that moisture is not mixed.

The amount of one or more compounds having an imidazole group and a hydroxyl group in one molecule is preferably 0.01 g / L to 10 g / L, more preferably 0.1 g / L to 5 g. / L.
When there is too little addition amount, plating will not become semi-glossy but will become rough plating. In addition, since the cathode current efficiency is not improved, the expected effect cannot be obtained, for example, the plating speed is slow and the improvement effect of the solderability is not seen. In addition, if the amount added is excessive, the plating speed will decrease, and physical properties (oxidation resistance, solderability, soldering strength, etc.) will deteriorate due to the bite of the additive into the film. To do.

Next, the plating conditions of electrotin plating and electrotin alloy plating using the plating solution of the present invention will be described.
The plating temperature is 10 ° C to 50 ° C, preferably 20 ° C to 45 ° C. Further, the pH of the plating solution can be used in a range from strong acidity to neutrality. In particular, tin-zinc plating is used in the range of pH 2 to pH 6.5, but is not particularly limited thereto. As electroplating current density, electroplating can be performed under conditions of 0.1 A / dm ² to 30 A / dm ² , particularly 1 A / dm ² to 15 A / dm ² .
As the plating method, any of barrel plating, rack type plating, hoop type plating and the like can be applied.

Next, the present invention will be described in detail with reference to examples.
Synthesis Example Synthesis of imidazole alcohol compounds 1 to 3 9.2 g of imidazole was heated to 120 ° C., 10 g of 2,3-epoxypropanol was added dropwise, and reacted at 150 ° C. for 3 hours to obtain imidazole alcohol 1.
Imidazole alcohols 2 and 3 shown below were synthesized in the same manner as the above synthesis method so that the molar ratio of imidazole compound to epoxy compound was 1: 1.

An imidazole alcohol compound having the above structure was added to a tin plating basic solution or a tin alloy plating basic solution, and a plating test was performed.

Example 1
The liquid of the following composition was used for the basic solution of the electrotin alloy plating solution.

Plating was performed using a plating solution obtained by adding 1 g / L of the imidazole alcohol compound 1 to the composition, and the plating rate and solderability were confirmed.
For plating, a tin plate with an anode back (150 × 150 × 10 mm in thickness) was used as an anode in a ³ dm ³ beaker, and stirring was performed (rotor 50 mm, 300 rpm). The cathode was a 10 × 25 mm copper plate, and the cathode was rocked at a stroke length of 60 mm and 24 rpm. The plating temperature is 35 ° C.
The plating rate was measured by a weight method and a fluorescent X-ray film thickness measurement method after plating at a cathode current density of ² , ^{3, 5} , 10 A / dm ² .

The evaluation of solderability was performed by plating with a cathode current density of 5 A / dm ² and a constant film thickness of 5 μm.
As pre-processing for soldering test, autoclave at a temperature of 105 ° C. and humidity of 100% (hereinafter PCT) for 4 to 16 hours, or as a reflow process, the total processing time is 3 minutes, preheating is 160 ° C., main heating is 230 ° C. Reflowed. For the soldering test, the meniscograph method was used.
Using NA-200 (made by Tamura Kaken Co., Ltd.) as the flux, measured the zero crossing time at tin-3silver-0.5copper lead free solder, temperature 240 ° C, immersion depth 2mm, immersion speed 2mm / sec. did.
The results are shown in Table 5 for plating speed and Table 7 for solderability.

Example 2

Plating was performed in the same manner as in Example 1 using a plating solution obtained by adding 3 g / L of the imidazole alcohol compound 2 to the composition shown in Table 2 above, and the plating speed, solderability, and reflowability were confirmed. Moreover, the density of the crystal | crystallization of the plating film in an electron microscope was measured.
Evaluation of reflow property put the test piece which carried out tin zinc plating on the aluminum plate (0.3 mm thickness, 1020 material), and performed reflow on the hotplate. The reflow temperature was 230 ° C. ± 5 ° C., and the reflow time was 30 seconds.
The results are shown in Table 5 for the plating rate, Table 7 for solderability, Table 9 for reflowability, and the appearance after plating and after reflowing in FIG.

Example 3

Plating was performed using a plating solution obtained by adding 1 g / L of the imidazole alcohol compound 1 to the composition (pH 4.0) shown in Table 3 above, and the plating speed and solderability were confirmed. For plating, a connector part (made of brass) having a base nickel plating thickness of 1 μm was plated at a cathode current density of ² , ³ , 5, 10 A / dm ² in the same manner as in Example 1, and the plating rate was measured. . Further, solderability was measured and evaluated in the same manner as in Example 1 except that the cathode current density was 10 A / dm ² and the plating film thickness was 2 μm.
The results are shown in Table 5 for plating speed and Table 8 for solderability.

Example 4
Plating was performed using a plating solution obtained by adding 3 g / L of imidazole alcohol compound 1 to the composition (pH 6.0) shown in Table 3 above, and the plating speed and solderability were confirmed. Plating was performed with a barrel (mini-barrel: manufactured by Yamamoto Metal Testing Co., Ltd.), and a copper plate (10 × 25 mm) was used as the material.
The plating conditions were the same as in Example 1 except that the liquid volume was 3 L, the plating temperature was 35 ° C., the plating time was 50 minutes, and the rotation speed was 10 rpm. The plating rate and solderability were measured and evaluated in the same manner as in Example 1.
The results are shown in Table 5 for plating speed and Table 7 for solderability.

Example 5

Plating was performed in the same manner as in Example 3 using a plating solution obtained by adding 1 g / L of imidazole alcohol compound 1 to the composition (pH 4.0) shown in Table 4-1 above, and the plating speed and solderability were confirmed. . Moreover, the density of the crystal | crystallization in an electron microscope was measured.
The results are shown in Table 5 for the plating rate, Table 8 for solderability, and the crystal state of the plating film in FIG.

Example 6
Plating is performed in the same manner as in Example 3 using a plating solution obtained by adding 0.5 g / L of imidazole alcohol compound 2 to the composition (pH 4.0) shown in Table 4-1 above. It was confirmed.
The results are shown in Table 5 for plating speed and Table 8 for solderability.

Example 7
Plating is performed in the same manner as in Example 3 using a plating solution in which 0.5 g / L of imidazole alcohol compound 3 is added to the composition (pH 4.0) shown in Table 4-1 above. confirmed.
The results are shown in Table 5 for plating speed and Table 8 for solderability.

Example 8
Plating was performed in the same manner as in Example 3 using a plating solution obtained by adding 5 g / L of imidazole alcohol compound 2 to the composition (pH 4.0) shown in Table 4-1 above, and the plating speed and solderability were confirmed. .
The results are shown in Table 5 for plating speed and Table 8 for solderability.

Example 9
Using the plating solution in which 0.5 g / L of an equimolar mixture of imidazole alcohol compound 1 and citric acid was added to the composition (pH 4.0) shown in Table 4-1 above, plating was performed in the same manner as in Example 3, The plating speed and solderability were confirmed.
The results are shown in Table 5 for plating speed and Table 8 for solderability.

Example 10
Plating was performed in the same manner as in Example 1 using a plating solution obtained by adding 3 g / L of imidazole alcohol compound 1 to the composition shown in Table 4-1 above, and the plating rate and solderability were confirmed.
The results are shown in Table 5 for plating speed and Table 7 for solderability.

Example 11

Except for using a plating solution obtained by adding 0.5 g / L of imidazole alcohol compound 1 to the composition shown in Table 4-2, plating was performed in the same manner as in Example 1 and Example 3, respectively. The attachment was confirmed.
The results are shown in Table 5 for plating speed and Table 7 for solderability.

Comparative Examples 1-5, 10, 11
Using the plating solutions shown in Tables 1 to 4, that is, except that an imidazole alcohol compound-free plating solution was used, plating was performed in the same manner as in Examples 1 to 5, 10 and 11, and the same. Measurement and evaluation were performed. The results are shown in Table 6 for the plating rate, Tables 7 and 8 for solderability, Table 9 for reflowability, and the crystal state of the plating film obtained in Comparative Examples 2 and 5.
In addition, Comparative Examples 1-5, 10, and 11 correspond to Examples 1-5, 10 and 11, respectively.

The electron micrograph of the plating film obtained in Example 2 and Comparative Example 2. The electron micrograph of the plating film obtained in Example 5 and Comparative Example 5.

Claims (2)

An electrolytic tin and tin alloy plating solution containing one or more compounds having an imidazole group and a hydroxyl group in one molecule, wherein the compound having the imidazole group and the hydroxyl group in one molecule is represented by the following general formula (1) An electrotin and electrotin alloy plating solution, which is an imidazole alcohol compound represented by the formula:
(In the general formula (1), R ¹ , R ² , and R ³ are each hydrogen, a vinyl group, or an alkyl group having 1 to 20 carbon atoms, and R ² and R ³ form an aromatic ring. R ⁴ is hydrogen, vinyl group, alkyl group having 1 to 20 carbon atoms, phenyl group, or — (CH ₂ CH (R ⁵ ) O) _k H, R ⁵ is hydrogen, alkyl having 1 to 20 carbon atoms. Group, X represents hydrogen, an alkyl group having 1 to 6 carbon atoms, or a substituent which may contain N or O, m is an integer of 0 to 20, n and l are integers of 1 to 3, k is Represents an integer of 1 to 20.) The compound represented by the general formula (1) is an imidazole alcohol compound obtained by reacting an imidazole compound represented by the following general formula (2) with an epoxy compound represented by the following general formula (3). The electroplated tin and tin alloy plating solution according to claim 2.
(In the general formulas (2) and (3), R ¹ , R ² and R ³ are each hydrogen, vinyl group, or alkyl group having 1 to 20 carbon atoms, and R ² and R ^{3 form an} aromatic ring. R ⁴ is hydrogen, a vinyl group, an alkyl group having 1 to 20 carbon atoms, a phenyl group, or — (CH ₂ CH (R ⁵ ) O) _k H, R ⁵ is hydrogen, having 1 carbon atom. -20 alkyl group, X represents hydrogen, an alkyl group having 1 to 6 carbon atoms, or a substituent which may contain N or O, m is an integer of 0 to 20, n and l are 1 to 3; Integer, k represents an integer of 1 to 20.)