TWI641729B - Copper-tin alloy plating bath - Google Patents

Abstract

An object of the present invention is to provide a copper-tin alloy plating bath which can be thickened even without using cyanide ions, and can also cope with barrel plating. The present invention relates to a copper-tin alloy plating bath which is composed of an aqueous solution containing a water-soluble copper compound, a water-soluble divalent tin compound, a sulfur-containing compound represented by the formula (1), and an aromatic compound having a hydroxyl group. Composition; R-(CH ₂ ) _l -S-(CH ₂ ) _m -S-(CH ₂ ) _n -R (1) (wherein R is H, OH or SO ₃ Na; each of l, m and n Independent and an integer from 0 to 3).

Description

Copper-tin alloy plating bath Technical field

This invention relates to a copper-tin alloy plating bath.

Background technique

In the field of electroplating, nickel plating has been widely used since the past. However, in the case of nickel plating, it is often pointed out that there is a problem of nickel allergy, which is caused by a metal element (nickel) contained in the plating film, which causes rash or inflammation of the skin, so it is necessary to seek an alternative technology that can replace this. .

On the other hand, a copper-tin alloy is known as an alloy having the same white appearance and film properties as nickel. Thus, as an alternative to nickel plating, copper-tin alloys have attracted attention.

In the past, in a plating bath for performing copper-tin alloy plating, a plating bath containing cyanide ions (cyanide bath) was used, but there was a problem from the standpoint of the working environment and the drainage treatment control. In recent years, as a copper-tin alloy bath which does not mix cyanide ions (hereinafter referred to as "cyanogen-free"), there are proposed pyrophosphoric acid baths (for example, Patent Documents 1 to 3) and acidic baths (for example, Patent Document 4~) 5) Wait. However, compared with the cyanide bath, the internal stress of the plating film formed by the pyrophosphoric acid bath is high, and cracks are generated during plating, so that it is difficult to form a thick film on the plating film. In addition, the acid bath does not adjust the precipitation potential of copper and tin at the current In the case of barrel plating having a large density variation, there is a problem that copper is preferentially precipitated and the alloy composition is seriously misaligned.

Because of the above, it is desirable to have a plating bath which, like the cyanide bath, can thicken the plating film and also cope with barrel plating.

Prior technical literature Patent literature

Patent Document 1: Japanese Patent Laid-Open No. Hei 10-102278

Patent Document 2: Japanese Patent Laid-Open Publication No. 2001-295092

Patent Document 3: Japanese Patent Laid-Open Publication No. 2004-035980

Patent Document 4: Japanese Patent Laid-Open Publication No. 2009-161804

Patent Document 5: Japanese Patent Laid-Open Publication No. 2010-189753

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and its main object is to provide a copper-tin alloy plating bath which can be thickened without using cyanide ions and which can cope with barrel plating.

The inventors of the present case and others have devoted themselves to research in order to achieve the above objectives. As a result, it has been found that by using a specific sulfur-containing compound and an aromatic compound having a hydroxyl group, the obtained copper-tin alloy plating bath can be thickened without using cyanide ions, and can also cope with barrel plating. The present invention is based on this finding and is further completed by the results of the repeated review.

That is, the present invention provides the following copper-tin alloy plating bath and the like.

Item 1. The copper-tin alloy plating bath is composed of an aqueous solution containing a water-soluble copper compound, a water-soluble divalent tin compound, a sulfur-containing compound represented by the formula (1), and an aromatic compound having a hydroxyl group; R-(CH ₂ ) _l -S-(CH ₂ ) _m -S-(CH ₂ ) _n -R (1)

(wherein R is H, OH or SO ₃ Na; and l, m and n are each independently and are an integer of 0 to 3).

The copper-tin alloy plating bath according to the above item 1, which contains the water-soluble copper compound in an amount of 1 to 60 g/L in terms of copper ions, and 5 to 40 g in terms of divalent tin ions. /L of the water-soluble divalent tin compound, 5 to 500 g/L of the sulfur-containing compound, and 1 to 50 g/L of the aromatic compound having a hydroxyl group.

The copper-tin alloy plating bath according to the above item 1, wherein the sulfur-containing compound is selected from the group consisting of methyldithiol, 1,2-ethanedithiol, and 1,3-. At least one of the group consisting of propylene dithiol, 3,6-dithia-1,8-octanediol, and 3,3'-dithiobis(sodium 1-propanesulfonate).

The copper-tin alloy plating bath according to any one of the items 1 to 3, wherein the aromatic compound having a hydroxyl group is selected from the group consisting of phenol, catechol, and hydroquinone. At least one of the group consisting of resorcinol, pyrogallol, p-cresolsulfonic acid, sodium ascorbate, and sodium erythorbate.

The copper-tin alloy plating bath according to any one of the items 1 to 4, wherein the aqueous solution further contains: a nonionic surfactant; and an aromatic ketone or an aromatic aldehyde.

Item 6. A copper-tin alloy plating method, wherein the object to be plated is used as a cathode for electrolysis in the copper-tin alloy plating bath according to any one of the above items 1 to 5.

Item 7. An article in which a copper-tin alloy plating film is formed by the copper-tin alloy plating method according to the above item 6.

In the copper-tin alloy plating bath of the present invention, an alloy containing copper and tin in an arbitrary ratio can be obtained by using a specific sulfur-containing compound together with a specific aromatic compound having a hydroxyl group. Further, the copper-tin alloy plating bath of the present invention is less likely to cause cracks than a conventional pyrophosphoric acid bath by using a specific sulfur-containing compound as a binder, even if a cyanide bath is not used. The film is thickened. Further, the copper-tin alloy plating bath of the present invention has a smaller influence on the alloy ratio than the conventional acid bath, and therefore can cope with barrel plating having a large variation in current density. Further, in the copper-tin alloy plating bath, a nonionic surfactant and an aromatic ketone or an aromatic aldehyde are further added, whereby a plating film having an excellent gloss appearance can be obtained.

Figure 1 shows the relationship between the current density of the copper-tin alloy plating bath and the copper content of the plating film.

Form for implementing the invention

Hereinafter, the copper-tin alloy plating bath according to the present invention will be specifically described.

The copper-tin alloy plating bath of the present invention is composed of an aqueous solution containing a water-soluble copper compound as a metal source and a water-soluble divalent tin compound as a crosslinking agent and represented by the formula (1). a sulfur-containing compound, and an aromatic compound having a hydroxyl group; R-(CH ₂ ) _l -S-(CH ₂ ) _m -S-(CH ₂ ) _n -R (1) (wherein R is H, OH or SO ₃ Na; l, m and n are each independently and are an integer of 0 to 3).

The water-soluble copper compound which is a copper ion source can be used as long as it is a water-soluble compound containing divalent copper as a copper component, and is not particularly limited. Specific examples of the water-soluble copper compound include copper (II) chloride, copper (II) sulfate, copper (II) nitrate, copper (II) carbonate, copper (II) oxide, copper (II) acetate, and methane. Copper (II) sulfonate, copper (II) amine sulfonate, copper (II) fluoride, copper (II) 2-hydroxyethanesulfonate, copper (II) 2-hydroxypropane sulfonate, copper pyrophosphate ( II) and so on. Among these copper compounds, copper (II) sulfate is preferred. These water-soluble copper compounds can be used alone or in combination of two or more. The concentration of the water-soluble copper compound is, for example, about 1 to 60 g/L as the copper ion concentration, and preferably about 10 to 40 g/L.

The water-soluble divalent tin compound which is a source of tin ions can be used as long as it is a water-soluble compound containing divalent tin as a tin component, and is not particularly limited. Specific examples of the water-soluble divalent tin compound include, for example, stannous chloride, stannous sulfate, stannous acetate, stannous pyrophosphate, tin methanesulfonate, stannous amine sulfonate, stannous gluconate, and tartaric acid. Stannous, stannous oxide, stannous fluoroborate, tin 2-hydroxyethane sulfonate, tin 2-hydroxypropane sulfonate, and the like. Among these tin compounds, stannous sulfate is preferred. The water soluble 2 price The tin compound can be used alone or in combination of two or more. The concentration of the water-soluble divalent tin compound is, for example, about 5 to 40 g/L as the divalent tin ion concentration, and preferably about 5 to 25 g/L.

The ratio of the water-soluble copper compound and the water-soluble divalent tin compound, copper: tin (mole ratio of the metal portion) should be set to 1:0.1 to 0.6. Copper: Tin (the molar ratio of the metal portion) is particularly preferably set to 1:0.1 to 0.3.

In the present invention, the use of the sulfur-containing compound represented by the formula (1) as a crosslinking agent is a major feature; R-(CH ₂ ) _l -S-(CH ₂ ) _m -S-(CH ₂ ) _n -R (1)

(wherein R is H, OH or SO ₃ Na; and l, m and n are each independently and are an integer of 0 to 3). Specific examples of the sulfur-containing compound represented by the formula (1) include methyldithiol, 1,2-ethanedithiol, 1,3-propanedithiol, and 3,6-dithia-1,8. - Octanediol, 3,3'-dithiobis(sodium 1-propanesulfonate), and the like. Among these compounds, 3,6-dithia-1,8-octanediol and 3,3'-dithiobis(sodium 1-propanesulfonate) are less odorous from the viewpoint of the working environment. And so on, and 3,6-dithia-1,8-octanediol is preferred. These sulfur-containing compounds may be used alone or in combination of two or more. The concentration of the complexing agent is, for example, about 5 to 500 g/L, preferably about 80 to 320 g/L.

In the present invention, an aromatic compound having a hydroxyl group is used. The aromatic compound having a hydroxyl group may, for example, be a compound substituted with one or more hydroxyl groups on a benzene ring or a furan ring, and a compound having a benzene ring is used from the viewpoint of work environment and liquid stability. good. Specific examples of the aromatic compound having a hydroxyl group include phenol, catechol, hydroquinone, resorcin, pyrogallol, p-cresolsulfonic acid, ascorbic acid, isoascorbic acid, and the like. Salt and so on. The alkali metal may, for example, be sodium, potassium or the like. The aromatic compound having a hydroxyl group is preferably: phenol, catechol, hydroquinone, resorcin, pyrogallol, p-cresolsulfonic acid, sodium ascorbate, and sodium erythorbate. The aromatic compound having a hydroxyl group has a function of reducing a divalent copper ion (Cu ²⁺ ) to a monovalent copper ion (Cu ¹⁺ ), and is considered to assist the copper ion to form a complex with the above-mentioned complexing agent. These aromatic compounds having a hydroxyl group may be used alone or in combination of two or more. The concentration of the aromatic compound having a hydroxyl group is, for example, about 1 to 50 g/L, preferably about 5 to 30 g/L.

The amount of the complexing agent and the aromatic compound having a hydroxyl group is preferably 2 mol/L or more with respect to 1 mol/L of copper, and the aromatic compound having a hydroxyl group is preferably 1 mol/L or more.

As the acid constituting the substrate of the copper-tin alloy plating bath, known organic acids and inorganic acids can be widely used. Specific examples of the organic acid include methanesulfonic acid, ethanesulfonic acid, 2-propanolsulfonic acid, 2-sulfoacetic acid, 2-sulfopropionic acid, 3-sulfopropionic acid, and sulfosuccinic acid. ), sulfomethyl succinic acid, sulfo-fumarate, sulfo-maleic acid, 2-sulfobenzoic acid, 3-sulfobenzoic acid, 4-sulfobenzoic acid, 5-sulfuric acid, 4-sulfoyl Phthalic acid, 5-sulfoisophthalic acid, 2-sulfo terephthalic acid, phenolsulfonic acid, and the like. Specific examples of the inorganic acid include sulfuric acid, hydrochloric acid, and aminosulfonic acid. Among these, sulfuric acid, methanesulfonic acid, and sulfosuccinic acid are preferred. The above-mentioned acid can be used alone or in combination of two or more. The concentration of the acid is about 10 to 400 g/L, preferably about 150 to 200 g/L.

The pH range of the copper-tin alloy plating bath is usually weakly acidic to strong The range of the acidity, specifically, the pH of the plating bath is adjusted to 4.5 or less. If the pH is too high, a plating film lacking smoothness is formed, which is not preferable. Further, as the pH adjuster, various acids such as hydrochloric acid and sulfuric acid, and various bases such as ammonium hydroxide, sodium hydroxide, and potassium hydroxide can be used. Further, in order to reduce the fluctuation of the pH of the plating bath, a pH buffer may be added. As the pH buffer, a known buffer can be used. The pH buffering agent may, for example, be sodium acetate or potassium acetate; sodium borate, potassium borate or ammonium borate; sodium formate or potassium formate; sodium tartrate or potassium tartrate; sodium dihydrogen phosphate, potassium dihydrogen phosphate or ammonium dihydrogen phosphate. These pH adjusters and pH buffers can be used alone or in combination of two or more.

In the plating bath, an additive such as a polymer compound, a surfactant, or a leveler may be added as needed.

The polymer compound may, for example, be polyethylene glycol or the like.

As the surfactant, any of a known nonionic surfactant, a cationic surfactant, an anionic surfactant, and an amphoteric surfactant may be used. These surfactants may be used alone or in combination of two or more, and it is preferred to contain at least one nonionic surfactant.

The nonionic surfactant may, for example, be a polyoxyalkylene alkyl ether, a polyoxyalkylene alkylphenyl ether, a polyoxyalkylene naphthyl ether, a polyoxyalkylene alkyl ester, or a polyoxyalkylene. Alkyl sorbitan fatty acid ester, polyoxyalkylene sorbitan fatty acid ester, polyethylene glycol fatty acid ester, polyoxyalkylene glycerol fatty acid ester, polyoxyalkylene alkylamine, etc. . Among these, a polyoxyalkylalkylamine is preferred, and a polyoxyethylene alkylamine is preferred. Cation system The surfactant may, for example, be a tetra-lower alkylammonium halide, an alkyltrimethylammonium halide, an alkylamine hydrochloride, an alkylamine oleate or an alkylaminoethylglycine. Examples of the anionic surfactant include alkyl-β-naphthalenesulfonic acid, fatty acid soap surfactant, alkylsulfonate, alkylsulfate, polyoxyethylene alkylphenol ether sulfate, and the like. . The amphoteric surfactant may, for example, be 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolium betaine, dimethyl alkyl betaine or sulfobetaine ( Sulfobetaine), N-alkyl-β-aminopropionic acid, and the like.

When a polymer compound or a surfactant is added to the plating bath, the concentration of the polymer compound or the surfactant may be used in the range of about 0.01 to 100 g/L, preferably about 0.1 to 40 g/L.

A leveling agent is an additive used to improve smoothness and gloss. As such a leveling agent, a ketone compound or an aldehyde compound can be used. As the ketone compound, known aromatic ketones and aliphatic ketones can be widely used. Examples of the aromatic ketone include acetophenone, diphenyl ketone, and benzalacetone; and the aliphatic ketone may, for example, be acetone or diethyl ketone. As the aldehyde compound, a known aromatic aldehyde and an aliphatic aldehyde can be widely used. Examples of the aromatic aldehyde include cinnamaldehyde, α-methylcinnamaldehyde, α-pentylcinnamaldehyde, α-hexylcinnamaldehyde, cuminaldehyde, benzaldehyde, anisaldehyde, and the like; The aldehyde may, for example, be formaldehyde, acetaldehyde or propionaldehyde. Among these, aromatic ketones and aromatic aldehydes are preferred. These leveling agents may be used alone or in combination of two or more.

When the leveling agent is added to the plating bath, the concentration of the leveling agent can be It should be used in the range of 0.01~30g/L, preferably about 0.01~10g/L.

It is advisable to use a surfactant and a leveling agent as an additive. By using a surfactant and a leveling agent together, the current density range for obtaining gloss plating can be expanded. Thereby, the plating film obtained from the plating bath can be made smoother and higher in gloss. The combination of the surfactant and the leveling agent is preferably a combination of a nonionic surfactant and an aromatic ketone or an aromatic aldehyde. The nonionic surfactant is preferably a polyoxyethylene alkylamine. In the plating bath, a non-ionic surfactant and an aromatic ketone are further added, or a nonionic surfactant and an aromatic aldehyde are added to obtain a plating film having an excellent gloss appearance.

When using a surfactant and a leveling agent together, the concentration of the surfactant should be set to about 0.1 to 40 g/L, the concentration of the leveling agent should be set to about 0.01 to 10 g/L, and the surfactant: The ratio of the flat agent is set to be about 1:1 to 100:1.

An additive other than the above may be appropriately selected depending on the demand, for example, a stress reducing agent, a conductive auxiliary agent, an antifoaming agent, a glossing agent, or the like, and added to the plating bath.

Examples of the stress reducing agent include naphtholsulfonic acid, saccharin, and sodium 1,5-naphthalene disulfonate. These stress reducing agents may be used alone or in combination of two or more. Examples of the conductive auxiliary agent include acids such as hydrochloric acid, sulfuric acid, acetic acid, nitric acid, aminosulfonic acid, pyrophosphoric acid, and boric acid, and such ammonium salts, sodium salts, potassium salts, and organic amine salts. These conductive auxiliary agents may be used alone or in combination of two or more. Defoamer and brightener, suitable for copper plating and plating Tin, copper-tin alloy and commercially available pharmaceuticals for general plating.

The bathing method of the plating bath of the present invention is not particularly limited. For example, a water-soluble copper compound and a water-soluble divalent tin compound are dissolved in an aqueous solution in which an acid such as sulfuric acid or the like is dissolved, and then a mixed agent and a reducing agent are mixed, and other additives are mixed as needed, and finally adjusted to a predetermined pH. In order to obtain the target plating solution.

The plating bath of the present invention is not limited to a specific plating method, and can be used in a known plating method, and can also cope with barrel plating having a large variation in current density.

Regarding the bath temperature during the plating operation, when the bath temperature is low, the plating power is increased, but the film forming speed is lowered. On the contrary, when the bath temperature is high, the film forming speed is increased but low. The ability to plate thickness in the current density range tends to decrease, so this can be taken into account to determine the appropriate bath temperature. A suitable bath temperature is in the range of about 5 to 40 °C.

The cathode current density can be appropriately determined depending on the plating solution to be used and the type of the object to be plated, and is preferably about 0.1 to 3 A/dm ² .

The anode can be used as an anode for copper-tin alloy plating and is known to be usable, such as a soluble anode (eg, tin anode, phosphorus-containing copper anode, oxygen-free copper anode, copper-tin alloy anode, etc.), insoluble anode (eg : stainless steel anode, carbon anode, lead anode, lead-tin alloy anode, lead-bismuth alloy anode, platinum anode, titanium anode, titanium-platinum anode, oxide coated anode such as tantalum oxide coated titanium electrode, etc.) . The cathode is a material to be plated which will be described later. Therefore, the copper-tin alloy plating method of the present invention can be said to be a kind In the above copper-tin alloy plating bath, a method of performing electrolysis using the object to be plated as a cathode.

The copper-tin plating film is formed on the surface of the article to be coated by the above plating method. The alloy composition of the obtained film is 95:5 to 5:95 in terms of a weight ratio of Cu:Sn, and the alloy composition can be easily changed by changing the Cu concentration or the Sn concentration in the plating solution. As the object to be plated, the surface thereof is electrically conductive, and as long as it is a smooth object, the object to be used is not particularly limited. For example, various items such as home electric appliances, faucets, miscellaneous goods, decorations, and furnishings can be mentioned.

The copper-tin alloy plating bath of the present invention can be suitably used for plating for plating, electronic or electric parts such as articles for clothing or decorations, but there is no limitation on the application to other uses.

[Examples]

Hereinafter, the examples and comparative examples will be given to explain the present invention in more detail.

The plating bath of each composition shown in the following Tables 1 to 6 was used, and plating treatment was performed under the following conditions to form a plating film on the object to be plated.

Plated: iron plate (5cm × 5cm)

Plating method: anode pure tin plate (10cm × 5cm 2)

Liquid volume 1.5L (14cm × 8cm × 18cm using plastic container)

Stirring by the cathode rocker

Plating conditions: temperature 18~20°C

Current density 1A/dm ²

Electrolysis time 25 minutes

The characteristics of the plating solution and the characteristics of the plating film formed by the above method are shown in Tables 1 to 6. The evaluation method of each characteristic is as follows.

Liquid status: visual confirmation

Stability of the liquid: visually confirm the plating solution after 24 hours of standing

Plating appearance and crack occurrence: observation by digital electron microscope

Cu:Sn ratio: evaluation by X-ray fluorescence thickness gauge

Further, in the plating baths of Example 3 and Comparative Examples 11 and 12, plating treatment was performed by setting current densities to 0.01, 0.1, 0.5, ^{1, 2} , and 3 A/dm ^{2 ,} and plating was formed. The copper content of the coating. The result is shown in Figure 1.

From the results of Tables 1 to 5, it was found that the plating baths of Examples 1 to 50 did not precipitate, particularly the plating baths of Examples 1 to 5, 10 to 31, 34 to 42 and 45 to 50. For stability, a crack-free plating film can be obtained by performing plating. From the results of Examples 1 to 5 of Table 1, it was found that copper-tin alloy plating of an arbitrary ratio can be obtained by adjusting the metal concentration in the plating solution. As can be seen from the results of Tables 3 to 5, the addition of a surfactant or a leveling agent can enhance the gloss of the plating appearance in the plating solution, and both of them can obtain a plating appearance with excellent gloss when added. Further, as is clear from Fig. 1, the current density of the plating bath of the present invention has less influence on the alloy ratio than the conventional acid bath (Comparative Example 12).

Claims (5)

A copper-tin alloy plating bath comprising a water-soluble copper compound, a water-soluble divalent tin compound, a sulfur-containing compound represented by the formula (1), an aromatic compound having a hydroxyl group, a surfactant, and a leveling agent Composition of an aqueous solution; R-(CH ₂ ) _l -S-(CH ₂ ) _m -S-(CH ₂ ) _n -R (1) (wherein R is H, OH or SO ₃ Na; l, m And n are each independently and an integer of 0 to 3); the surfactant is selected from the group consisting of polyoxyethylene alkylamine, polyoxyalkylene alkylphenyl ether, and polyoxyalkylene naphthyl ether At least one nonionic surfactant in the group; the leveling agent is selected from the group consisting of benzylideneacetone, cinnamaldehyde, α-methylcinnamaldehyde, α-hexylcinnamaldehyde, α-amylcinnamaldehyde, and cumin At least one aromatic ketone or aromatic aldehyde in the group consisting of aldehyde, benzaldehyde and anisaldehyde; and containing the water-soluble copper compound in an amount of from 1 to 60 g/L in terms of copper ion, and converted into a divalent tin ion 5 to 40 g/L of the water-soluble divalent tin compound, 5 to 500 g/L of the sulfur-containing compound, 1 to 50 g/L of the aromatic compound having a hydroxyl group, and 0.1 to 40 g/L of the surfactant, And 0 .01~10g/L of the above leveling agent; and the aforementioned surfactant: the ratio of the aforementioned leveling agent is 1:1 to 100:1. The copper-tin alloy plating bath of claim 1, wherein the sulfur-containing compound is selected from the group consisting of methyldithiol, 1,2-ethanedithiol, 1,3-propanedithiol, 3,6- At least one of the group consisting of dithia-1,8-octanediol and 3,3'-dithiobis(sodium 1-propanesulfonate). The copper-tin alloy plating bath according to claim 1 or 2, wherein the aromatic compound having a hydroxyl group is selected from the group consisting of phenol, catechol, hydroquinone, resorcinol, pyrogallol, and At least one of the group consisting of cresylic acid, sodium ascorbate and sodium erythorbate. A copper-tin alloy plating method for electrolysis of a substrate to be plated as a cathode in a copper-tin alloy plating bath according to any one of claims 1 to 3. An article in which a copper-tin alloy plating film is formed by a copper-tin alloy plating method as claimed in claim 4.