KR100684818B1 - Electrolytic Precipitation Method of Bronze - Google Patents

Abstract

The present invention relates to a bronze galvanic coating which comprises metallising by immersing a substrate to be coated in an acidic electrolyte comprising at least tin and copper ions, alkylsulfonic acid and a wetting agent. It is an object of the present invention to essentially increase the deposition rate and to perform a non-porous bronze coating process with good adhesion, high copper content, various mechanical properties and decorative properties. To this end, aromatic nonionic wetting agents are added to the electrolyte. In addition, the present invention discloses a novel electrolyte for bronze coating.

Bronze Coating, Aromatic Nonionic Wetting Agent

Description

Electrolytic Precipitation Method of Bronze {METHOD FOR BRONZE GALVANIC COATING}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for electrolytic precipitation of bronze, and to a method of plating a substrate to be coated in an acidic electrolyte containing at least tin, copper ions, alkylsulfonic acid, and a humectant, and a method for producing such an electrolyte.

Precipitation methods of tin and tin alloys based on various kinds of electrolytes are known in the art and are actually used. The method of depositing tin and / or tin alloy from a cyan compound-based electrolyte is conventional. However, these electrolytes are very toxic and their use is problematic in the environment, and for many years, there have been attempts to develop an electrolyte free of cyanide compounds. As an example, an electrolyte based on pyrophosphate or oxalate acting in the pH region 5-9 may be mentioned. However, these methods suffer from economic and technical disadvantages, such as relatively low precipitation rates.

Therefore, the development in the direction which makes it possible to use the method of depositing tin and / or tin alloy from an acidic electrolyte is currently made | formed. This can be very easily reduced to metallic tin in acidic electrolytes in the case of divalent tin to form a qualitatively uniform coating at a faster deposition rate, while alkalinizing to substrates such as, for example, ceramic structures. This is because the bad effects of the electrolyte can be prevented.

Accordingly, acidic electrolytes and methods for the precipitation of high quality tin or tin alloys at higher deposition rates are disclosed in EP 1 111 097 A2 and US Pat. No. 6,176,996B1. These are electrolytes containing a divalent or higher metal salt of organic sulfonic acid, from which a solderable corrosion resistant coating is obtained, these coatings being used, for example, in the manufacture of circuit boards and the like in the electronics industry. Can be used as a substitute for a braze-containing coating.

However, the method has limitations in the precipitation of tin-copper alloys having a high copper content, such as so-called true bronze having a copper content of 10% or more. For example, due to the high potential difference between tin and copper, the oxidation rate of divalent tin becomes higher, and as a result, it is easily oxidized to tetravalent tin in the acidic electrolyte. However, this type of tin can no longer be electrolytically precipitated in an acidic medium and exits from the process, resulting in non-uniform precipitation between the two metals and a reduction in the precipitation rate. Furthermore, the increase in sludge formation due to oxidation to tetravalent tin is an obstacle in achieving stable operation and long life of the electrolyte. In addition, due to such contamination, it is not possible to ensure a strong bond and a pore-free coating.

Due to this technical process disadvantage, the use of electrolytically deposited bronze coatings is currently not varied. Bronze coatings are sometimes used in the jewelry industry as substitutes for expensive silver metals or allergenic nickel. In the same way, in some technical fields, for example in the electronics industry or in the mechanical and / or processing arts, for the coating of electronic components or for the coating of bearing outlays and friction layers, Electrolytic deposition of bronze has attracted attention. In this case, however, mainly white bronze or so-called "imitation bronze", which can keep the copper content low by the process conditions, is used as the nickel substitute.

Accordingly, the present invention is based on a problem to provide a method for depositing bronze from an acidic electrolyte, which can precipitate at least tin and copper side by side at a significantly higher deposition rate than in the prior art. When using the process according to the invention, it is possible to precipitate bronze coatings which have a high copper content as well as various decorative and mechanical properties, which are firmly fixed and free from pores.

In addition, according to the present invention, an acid electrolyte which may contain a high content of divalent copper ions, is not only stable to sludge formation due to oxidation, but also economical and environmentally friendly even in long-term use is provided.

According to this invention, the said subject is solved by the method of the kind mentioned above characterized by adding aromatic nonionic humectant to electrolyte.

According to the present invention, there is provided a bronze electrolytic deposition method, in which an anode of a copper-tin alloy and a cathode are connected to a substrate to be coated by an electrolyte and a coating is performed by direct current flow through them. In addition, according to the present invention there is provided in particular an electrolyte which can be used in the process and a coating obtainable by the process.

The problems in the prior art are solved by providing a novel electrolyte composition through the method according to the present invention, which results in better precipitation results. Furthermore, the implementation of the present invention is simpler and more economical. This is based on the composition of the electrolyte according to the invention. For example, the method is carried out at room temperature or at a temperature of 17 to 25 ° C., and the substrate to be coated is plated in a highly acid atmosphere of pH <1. The electrolyte is particularly stable in the above temperature range. In addition, there is no cost for heating the electrolyte and there is no need to cool the plated substrate for a long time and a high cost. Furthermore, in the case of the present invention, a precipitation rate of 0.25 μm / min can be achieved at a current density of 1 A / dm ² , thanks to the pH value and the addition of one or more aromatic nonionic wetting agents. When increasing the metal content, the speed can be raised to 7 A / dm ^{2 in} rack operation, and even to 120 A / dm ^{2 in} continuous plant. Thus, depending on the plant type, in each case a current density in the range of 0.1-120 A / dm ² can be used.

Surprisingly, in particular, the addition of one or more aromatic nonionic wetting agents to the electrolyte greatly improves the wetting properties of the substrate to be plated, especially of complex substrates. As a result, a fairly high precipitation rate can be obtained by using the process according to the invention, and furthermore, the coatings produced by the process of the invention have uniform, qualitatively high grades and have very good adhesion properties and are generally fine There is no

Another advantage of using aromatic nonionic wetting agents is that, because of their excellent wetting properties, there is very little or even little need to stir the electrolyte and / or the substrate in the electrolyte to achieve the desired precipitation result. In addition, because the aromatic nonionic wetting agent is advantageously used, when removing the substrate from the electrolyte, the electrolyte residue is better escaped from the plated substrate, thereby reducing entrainment loss and lowering the process cost. have.

Particularly advantageous is the addition of at least one aromatic nonionic wetting agent in an amount of 2-40 g / L, with β-naphthol ethoxylate and / or nonylphenol ethoxylate being particularly preferably used.

Therefore, the invention proposed according to the present invention is economically advantageous and environmentally friendly compared to a process using a cyanide compound.

Further use of one or more anionic and / or aliphatic nonionic wetting agents, known in the art, is optionally possible only if they support or enhance the beneficial effects of the aromatic nonionic wetting agents. Preferably, as anionic and / or aliphatic nonionic wetting agent, polyethylene glycol and / or anionic surfactant are added into the electrolyte.

As mentioned above, the process according to the invention is characterized in particular by the special composition of the electrolyte. The electrolyte essentially comprises tin and copper ions, alkylsulfonic acids and aromatic nonionic wetting agents. In addition, stabilizers and / or complexing agents, anionic and / or nonionic, aliphatic wetting agents, oxidation inhibitors, brighteners and other metal salts may optionally be included in the electrolyte.

The main metals (tin and copper) added to the bronze precipitation electrolyte according to the invention are firstly in the form of salts of alkyl sulfonic acids, preferably methanesulfonate salts, or salts of mineral acids, preferably sulfate salts. Can be. As tin salt in the electrolyte, in particular, tin methane sulfonate is preferably used in an amount of 5-195 g, preferably in an amount of 11-175 g, per electrolyte L. This corresponds to the use of divalent tin ions of 2-75 g / L, preferably 4-57 g / L. Copper methanesulfonate is particularly preferably used in the electrolyte as the copper salt, and is added in an amount of 8-280 g per L of electrolyte, preferably in an amount of 16-260 g. This corresponds to the use of 2-70 g / L, preferably 4-65 g / L, divalent copper ions.

Since the precipitation is clearly high under acidic conditions, an acid, preferably an inorganic acid and / or an alkyl sulfonic acid, is added to the electrolyte in an amount of 140 -382 g, preferably 175-245 g per L of electrolyte. The use of methanesulfonic acid is particularly useful because the solubility of the metal salts is improved by this use, and its acid strength facilitates or facilitates the adjustment of the required pH during the process. In addition, methane sulfonic acid is characterized by a significant contribution to the stability of the bath.

According to a further feature of the invention, one or more additional metals and / or chlorides are added to the electrolyte. Advantageously, the metal may be in the form of its soluble salts. In particular, the addition of zinc and / or bismuth has a significant effect on the characteristics of the deposited coating. The metal zinc and / or bismuth added to the electrolyte may, in other words, be in the form of a salt of alkylsulfonic acid, preferably in the form of a salt of methanesulfonate, or a mineral acid, preferably sulfate. Zinc sulphate is particularly preferably used as a lead salt in the electrolyte, and is advantageously added in an amount of 0-25 g per electrolyte L, preferably in an amount of 15-20 g. Particularly preferably, bismuth methane sulfate is used as bismuth salt in the electrolyte, advantageously in an amount of 0-5 g, preferably 0.05-0.2 g per L of electrolyte.

In addition, various additives commonly used in acidic electrolytes for the precipitation of tin alloys, such as stabilizers and / or coordination agents, antioxidants and brighteners, may be added to the electrolyte.

In particular, the use of a suitable compound for the stabilization of the electrolyte is an important condition for the rapid precipitation of high quality bronze. Advantageously, gluconate is added to the electrolyte and stabilizer and / or coordinating agent. Here, the preferred use of sodium gluconate in the process according to the invention is particularly advantageous. The concentration of stabilizer and / or coordinating agent is 0-50 g, preferably 20-30 g per L electrolyte. Dihydroxybenzene-based compounds such as mono- or polyhydroxyphenyl compounds, such as pyrocatechol or phenol sulfonic acid, can be preferably used as oxidation inhibitors. The concentration of the antioxidant is 0-5 g per L electrolyte. Advantageously, the electrolyte contains hydroquinone as an oxidation inhibitor.

By carrying out the process according to the invention, it is possible to deposit bronze on various substrates. For example, all the usual methods of manufacturing electronic components can be used. In the same way, by the method according to the invention, a particularly hard and wear resistant bronze coating can be deposited on materials such as bearings. The method according to the invention can advantageously be used in the field of decorative coatings, in which, for example, multicomponent precipitations, including tin, copper, zinc and bismuth, are particularly useful, such as furniture and jewelry.

A particularly advantageous advantage of the invention is that the process according to the invention makes it possible to produce so-called "bronze bronzes" with a copper content of more than 60%, in which case the copper content is each 95 wt%, depending on the desired properties. It can be up to%. On the other hand, the ratio of the amount of copper to the amount of tin in the electrolyte significantly affects properties such as hardness and color of the bronze coating. For example, when the tin / copper ratio is 40/60, a relatively soft silver-colored coating, so-called white bronze, is deposited. When the tin / copper ratio is 20/80, the so-called sulfur bronze, which is a golden-colored coating, and the so-called red bronze, which is a red gold-colored coating, is precipitated when the tin / copper ratio is 10/90.

Furthermore, precipitation of high-tin white bronzes of 10% or more copper is also possible.

Depending on the desired appearance of the bronze coating, in each case, additives such as brighteners can be added to the electrolyte with various copper contents. Advantageously, the electrolyte may comprise a brightener selected from aromatic carbonyl compounds and α, β-unsaturated carbonyl compounds. The concentration of the brightener is 0-5 g, per liter of electrolyte.

Preferred embodiments are provided in more detail below for illustration of the invention, but the invention is not limited to these examples.

Electrolyte Composition:

Basic electrolyte of strongly acidic electrolyte according to the present invention: (per L electrolyte)

2-75 g divalent tin

2-70 g of divalent copper

2-40 g of aromatic nonionic wetting agent, and

Inorganic and / or alkylsulfonic acid 140-382 g.

Optionally, other components may be added to the electrolyte (per L electrolyte):

0-10 g of anionic and / or aliphatic nonionic wetting agents

Stabilizer and / or coordination agent 0-50 g

Antioxidant inhibitor 0-5g

Polishing 0-5 g

Trivalent Bismuth 0-5g

Divalent zinc 0-25 g.

In order for the precipitated bronze coating to have a particular color, each component of the electrolyte is changed as shown in the following examples. Further information on the corresponding process and other properties of the individual coatings are shown in Table 1:

Example 1 (Red Bronze)

Sn ²⁺ 4g / L

Cu ²⁺ 18g / L

Methanesulfonic acid 286 g / L

Aromatic Nonionic Wetting Agent 3g / L

Aliphatic nonionic wetting agent 0.4 g / L

Antioxidant inhibitor 2g / L

Coordinating agent 20mg / L

Example 2a (sulfur bronze)

Sn ²⁺ 4g / L

Cu ²⁺ 18g / L

Methanesulfonic Acid 240g / L

Aromatic Nonionic Wetting Agent 32.2g / L

Antioxidant inhibitor 2g / L

Stabilizer / Coordinator 25mg / L

Example 2b (sulfur bronze)

Sn ²⁺ 4g / L

Cu ²⁺ 18g / L

Methanesulfonic acid 286 g / L

Aromatic Nonionic Wetting Agent 32.2g / L

Polish 6mg / L

Antioxidant inhibitor 2g / L

Stabilizer / Coordinator 50mg / L

Example 3 (white bronze)

Sn ²⁺ 5g / L

Cu ²⁺ 10g / L

Methanesulfonic Acid 240g / L

Aromatic Nonionic Wetting Agent 32.2g / L

Polish 6mg / L

Antioxidant inhibitor 2g / L

Stabilizer / Coordinator 25mg / L

Example 4 [matte white bronze]

Sn ²⁺ 18g / L

Cu ²⁺ 2g / L

Methanesulfonic acid 258g / L

9 g / L aromatic nonionic wetting agent.

In order to improve the hardness and / or ductility of the precipitated bronze coating, zinc and / or bismuth may be added to the electrolyte as in the examples given below. Additional data on the corresponding process conditions and other properties of the individual coatings are shown in Table 1.

Example 5 (high ductility)

Sn ²⁺ 4g / L

Cu ²⁺ 18g / L

Methanesulfonic acid 238g / L

Aromatic Nonionic Wetting Agent 32.2g / L

Polish 3mg / L

Antioxidant inhibitor 2g / L

Stabilizer / Coordinator 25mg / L

ZnSO ₄ 20g / L

Example 6 (hardness)

Sn ²⁺ 4g / L

Cu ²⁺ 18g / L

Methanesulfonic acid 238g / L

Aromatic Nonionic Wetting Agent 32.2g / L

Antioxidant inhibitor 2g / L

Stabilizer / Coordinator 25mg / L

Bi ³⁺ 0.1g / L

Example 7 (sulfur bronze)

Sn ²⁺ 14.5g / L

Cu ²⁺ 65.5 g / L

Methanesulfonic acid 382 g / L

Aromatic Nonionic Wetting Agent 32.2g / L

Antioxidant inhibitor 4g / L

Stabilizer / Coordinator 25mg / L

ZnSO ₄ 20g / L

From these exemplary electrolyte compositions, coatings having specific properties were deposited under the process conditions shown in the following table:

Claims (35)

A bronze electrolytic deposition method for plating a substrate to be coated in an acidic electrolyte containing at least tin ions, copper ions, alkyl sulfonic acids and wetting agents, An aromatic nonionic wetting agent is added to an electrolyte having a concentration of free methanesulfonic acid of 290 g / L or more, and a layer having a copper content of 10% or more is precipitated from the electrolyte. The electrolytic precipitation method according to claim 1, wherein the aromatic nonionic wetting agent is added to the electrolyte in an amount of 2 to 40 g / L. The electroprecipitation method according to claim 1 or 2, wherein β-naphthol ethoxylate, nonylphenol ethoxylate, or a mixture thereof is added as the aromatic nonionic wetting agent. The electrolytic precipitation method according to claim 1 or 2, wherein the tin or copper ions are added to the electrolyte in the form of soluble salts. The electrolytic precipitation method according to claim 1 or 2, wherein the tin ions are added to the electrolyte in a content of 2-75 g / L. The electrolytic precipitation method according to claim 1 or 2, wherein 5-195 g / L tin methanesulfonate is added to the electrolyte. The electrolytic precipitation method according to claim 1 or 2, wherein the copper ions are added to the electrolyte at a content of 2-70 g / L. The electroprecipitation method according to claim 1 or 2, wherein 8-280 g / L of copper methanesulfonate is added to the electrolyte. The electrolytic precipitation method according to claim 1 or 2, wherein the precipitation is performed at a temperature of 17 to 25 ° C. The electrolytic precipitation method according to claim 1 or 2, wherein the precipitation is performed at a current density of 0.1 to 120 A / dm ² . The electrolytic precipitation method according to claim 1 or 2, wherein the precipitation is performed in a highly acid medium. The method of claim 1 or 2, wherein the precipitation is carried out in the range of pH <1. An electrolyte for bronze electrolytic precipitation, containing at least tin ions and copper ions, alkylsulfonic acids and wetting agents, Wherein the electrolyte comprises an aromatic nonionic wetting agent, and a layer having a concentration of free methanesulfonic acid of 290 g / L or more and a copper content of 10% or more is precipitated from the electrolyte. The electrolyte of claim 13, wherein the electrolyte comprises 2-40 g / L of aromatic nonionic surfactant. The electrolyte according to claim 13 or 14, wherein β-naphthol ethoxylate, nonylphenol ethoxylate, or a mixture thereof is used as the aromatic nonionic surfactant. The electrolyte according to claim 13 or 14, wherein the electrolyte includes the tin ions and the copper ions in the form of soluble salts. 15. The electrolyte according to claim 13 or 14, wherein the electrolyte contains 2 to 75 g / L of tin ions. 15. The electrolyte of claim 13 or 14 comprising from 5 to 195 g / L tin methanesulfonate. The electrolyte according to claim 13 or 14, which contains 2 to 70 g / L of copper ions. 15. The electrolyte of claim 13 or 14 comprising from 8 to 280 g / L copper methanesulfonate. The electrolyte according to claim 13 or 14, wherein the wetting agent comprises polyethylene glycol, anionic surfactant, or a mixture thereof. 15. The electrolyte of claim 13 or 14, wherein the electrolyte comprises bismuth, zinc, or a mixture thereof. 15. The electrolyte of claim 13 or 14, wherein said electrolyte comprises chloride. 15. The electrolyte of claim 13 or 14, wherein the electrolyte comprises gluconate as a complexing agent. The electrolyte according to claim 13 or 14, wherein the electrolyte includes a dihydroxy benzene-based oxidation inhibitor. 15. The electrolyte according to claim 13 or 14, wherein the electrolyte comprises a aromatic carbonyl compound-based brightener, an α, β-unsaturated carbonyl compound-based brightener, or a mixture thereof. 15. The electrolyte of claim 13 or 14, wherein said electrolyte has a pH value of less than one. The method according to claim 13 or 14, Divalent Tin 2-75g / L Divalent Copper 2-70g / L Aromatic nonionic wetting agent 2-40 g / L, 0-50 g / L stabilizer, coordinating agent or mixtures thereof, Anionic wetting agents, nonionic aliphatic wetting agents, or mixtures thereof 0-10 g / L, Oxidation inhibitor 0-5 g / L, Polisher 0-5g / L, Trivalent bismuth 0-5 g / L, Divalent zinc 0-25 g / L, and 140 g / L or more alkylsulfonic acid Electrolyte comprising a. delete The method of claim 1, Electrolytic precipitation method characterized in that to deposit a layer containing 60% or more copper from the electrolyte. The method of claim 4, wherein The tin or copper ions are added to the electrolyte as a salt of alkylsulfonic acid. The method of claim 31, wherein The tin or copper ions are added to the electrolyte as methanesulfonate. The method of claim 13, Electrolyte, characterized in that for depositing a layer containing more than 60% copper from the electrolyte. The method of claim 16, And said electrolyte comprises said tin ions and copper ions as salts of alkylsulfonic acids. The method of claim 34, wherein The electrolyte comprises the tin ions and the copper ions as methanesulfonate.