JP4675626B2 - Bronze electrodeposition method and electrolyte - Google Patents

Description

  The present invention relates to a bronze electrodeposition method for plating a support to be coated in an acidic electrolyte containing at least tin ions and copper ions, an alkylsulfonic acid, and a wetting agent, and to the production of the electrolyte.

  Methods for electrodepositing tin and tin alloys based on various types of electrolytes are known from the prior art and are already widely used. A method of precipitating tin and / or a tin alloy from a cyanide electrolyte is often used. However, since such electrolytes are extremely toxic and their use is also problematic from an environmental point of view, for several years on the basis of electrolytes that do not contain cyanide, for example pyrophosphates or oxalates. The development of electrolytes that operate in the pH range of 5-9 is being pushed forward. However, such methods have economic and technical disadvantages and some mention that the deposition rate is relatively slow.

  For these reasons, development is currently proceeding primarily to create available methods for depositing tin and / or tin alloys from acidic electrolytes. For one thing, divalent tin can be reduced very easily to metallic tin in acidic electrolytes, so that a homogeneous coating can be obtained with a better deposition rate, This prevents the adverse effect of the alkaline electrolyte on the support, for example a ceramic structural element.

  As described above, an acidic electrolyte and a method for depositing high-grade tin or tin alloy at a high deposition rate are known from Patent Documents 1 and 2, for example. These are electrolytes containing at least a divalent metal salt of an organic sulfonic acid, and corrosion resistant solder that can be used as a coating instead of a lead-containing solder coating of an electronic circuit for producing a circuit board or the like from the electrolyte. A coating is deposited.

  However, such methods are limited in depositing tin-copper alloys having a high copper content, for example so-called “true” bronzes with a copper content of at least 10%. For example, due to the large potential difference between tin and copper, divalent tin oxidizes faster, and as a result, divalent tin is oxidized very easily in an acidic electrolyte to tetravalent tin. However, in this form, tin can no longer be electrodeposited in acid, so it is excluded from the precipitation process, resulting in uneven deposition of the two metals, and the deposition rate decreases. Furthermore, when oxidized to tetravalent tin, sludge formation increases, which can inhibit the stable action and long-term service life of acidic electrolytes. Also, due to such quality degradation, coatings with high adhesion and no pores are no longer guaranteed.

Due to such technical processing disadvantages, the field of application of electrodeposition bronze coatings is not wide at present. Bronze coatings are sometimes used in the jewelry industry in place of expensive silver or allergenic nickel. Similarly, bronze electrodeposition is also gaining importance in several technical fields such as electronic component coating electronics or mechanical engineering and / or bearing overlay and friction layer coating processing techniques. In this case, however, white bronzes, i.e. so-called "false bronzes", in which the copper content can be kept very low due to the processing conditions, are deposited as nickel substitutes.
European Patent Application Publication No. 1111097 US Pat. No. 6,176,996 B1

  The present invention is therefore largely different from the methods known from the prior art and is based on the problem of providing a bronze deposition method that can deposit at least tin and copper from an acidic electrolyte uniformly at a fairly fast deposition rate. Furthermore, this method is believed to deposit a bronze coating with high copper content and various decorative and mechanical properties, high adhesion, and no pores.

  Furthermore, an acidic electrolyte that can have a high divalent copper ion content, is stable with respect to sludge formation by oxidation, and is economical and eco-friendly when used over a long period of time is provided.

This problem is solved according to the present invention by a method of the kind mentioned at the outset, characterized in that an aromatic nonionic wetting agent is added to the electrolyte.
According to the present invention, a bronze electrodeposition method is provided, in which a coating is formed by joining a copper-tin alloy anode and cathode to a support to be coated with an electrolyte and passing a direct current through them. Arise. Furthermore, the invention provides electrolytes that can be used in particular in this process and the coatings obtained by this process.

The method of the present invention improves the disadvantages known in the prior art by providing a novel electrolyte composition, and achieves fairly good deposition results by the method. Furthermore, this method can be implemented simply and economically. This is also mainly based on the advantageous composition of the electrolyte. For example, the method of the present invention is carried out at room temperature, i.e. 17-25 [deg.] C., and the support to be coated is plated in a highly acidic environment with a pH <1. The electrolyte of the present invention is particularly stable in this temperature range. In addition, the cost of heating the electrolyte is not required, and it is not necessary to highly cool the plating support with much time and cost. In particular, a deposition rate of 0.25 μm / min is achieved at a current density of 1 A / dm ² , thanks to the pH value and the advantage of adding at least one aromatic nonionic wetting agent. By increasing the metal content, it can be increased up to 7 A / dm ² during rack operation and up to 120 A / dm ^{2 in} the case of a continuous plant. A current density suitable for use in the range of 0.1 to 120 A / dm ² is thus achieved in any case according to the type of plant.

  Surprisingly, in particular, the addition of at least one aromatic nonionic wetting agent to the electrolyte significantly improves the wetting of the surface to be plated, especially the more complex support surfaces. Advantageously, this improvement in wetting not only provides a significant increase in the deposition rate achieved by using the method of the present invention, but the coating obtained by the method of the present invention is uniform and of high quality, The result is good adhesion and generally no pores.

  Another advantage of the aromatic non-ionic wetting agent used is that thanks to the advantageous wettability, only a little agitation of the electrolyte and / or the support in the electrolyte is required to achieve the desired deposition result. Or it is not even necessary to stir at all, so that an additional electrolyte stirrer can be omitted. In addition, the use of an advantageous aromatic non-ionic wetting agent reduces the entrainment loss when the plating support is removed from the electrolyte, so that the electrolyte residue is better drained from the support, thereby reducing its entrainment loss (Verschlungpunsverlusten). As a result, the processing cost is reduced.

It is particularly advantageous to add 2 to 40 g / L of one or more aromatic nonionic wetting agents, β
It is particularly preferred to use naphthol ethoxylate and / or nonylphenol ethoxylate.

Thus, advantageously, the proposed method is more economical and environmentally friendly than the cyanide method.
In some cases, one or more anionic wetting agents and / or aliphatic nonionic wetting agents known from the prior art can also be used provided that they support or enhance the beneficial effects of the aromatic nonionic wetting agents. It is. In this regard, it is preferred to add polyethylene glycol and / or anionic surfactant to the electrolyte as an anionic wetting agent and / or an aliphatic nonionic wetting agent.

  As mentioned earlier, the method of the invention is particularly characterized by a special composition of the electrolyte. The electrolyte of the present invention essentially contains tin and copper ions, an alkyl sulfonic acid, and an aromatic non-ionic wetting agent. In addition, the electrolyte may optionally include stabilizers and / or complexing agents, anionic wetting agents and / or aliphatic nonionic wetting agents, antioxidants, brighteners, and other metal salts.

  The metals (tin and copper) initially added to the electrolyte for depositing bronze according to the present invention are first of all a salt of an alkyl sulfonic acid, preferably a methane sulfonic acid salt, otherwise a mineral acid salt. , Preferably in the form of sulfate. Tin methanesulfonate is particularly preferably used as a tin salt in the electrolyte in an amount of 5 to 195 g per liter of electrolyte, preferably 11 to 175 g per liter of electrolyte. This corresponds to the use of divalent tin ions of 2 to 75 g / L, preferably 4 to 57 g / L. Copper methanesulfonate is particularly preferably used as a copper salt in the electrolyte and is advantageously added to the electrolyte in an amount of 8 to 280 g per liter of electrolyte, preferably 16 to 260 g per liter of electrolyte. This corresponds to the use of 2-70 g / L, preferably 4-65 g / L of divalent copper ions.

  Since precipitation is clearly increased in an acidic environment, an acid, preferably mineral acid and / or alkyl sulfonic acid, is added to the electrolyte in an amount of 140-382 g per liter of electrolyte, preferably 175-245 g per liter of electrolyte. It has proven particularly advantageous to use methanesulfonic acid. For one thing, methanesulfonic acid is advantageous for dissolving metal salts, and furthermore, due to its acid strength, it provides the pH required for the precipitation process or is easy to adjust the pH. Because it makes it. In addition, methanesulfonic acid has the advantageous property of greatly contributing to bath stability.

  According to a further feature of the present invention, at least one additional metal and / or chlorine compound is added to the electrolyte. The metal is advantageously in the form of a soluble salt. In particular, the addition of zinc and / or bismuth greatly affects the properties of the deposited coating. The metal, zinc and / or bismuth added to the electrolyte may specifically be in the form of a salt of an alkyl sulfonic acid, preferably a methane sulfonate, or a salt of a mineral acid, preferably a sulfate. Particularly preferred for use as a zinc salt in the electrolyte is zinc sulfate, which is advantageously added in an amount of 0 to 25 g per liter of electrolyte, preferably 15 to 20 g per liter of electrolyte. Particularly preferred for use as a bismuth salt in the electrolyte is bismuth methanesulfonate, which is advantageously added to the electrolyte in an amount of 0-5 g per liter of electrolyte, preferably 0.05-0.2 g per liter of electrolyte. It is.

  In addition, various additives may be added to the electrolyte, such as stabilizers and / or complexing agents, antioxidants and brighteners that are typically used in acidic electrolytes to precipitate tin alloys.

  Specifically, the use of a compound suitable for stabilizing the electrolyte is an important condition for depositing bronze at high speed and high quality. It is advantageous to add gluconate as a stabilizer and / or complexing agent to the electrolyte. In the case of the process according to the invention, it has proven particularly advantageous to use sodium gluconate. The concentration of the stabilizer and / or complexing agent is 0-50 g per liter of electrolyte, preferably 20-30 g per liter of electrolyte. As antioxidants it is preferred to use compounds of the class of dihydroxybenzenes, for example mono- or polyhydroxyphenyl compounds such as pyrocatechol or phenolsulfonic acid. The concentration of the antioxidant is 0 to 5 g per liter of the electrolyte. It is advantageous if the electrolyte contains hydroquinone as an antioxidant.

  By carrying out the method of the present invention, bronze can be deposited on various supports. For example, any ordinary electronic component manufacturing method may be used. Similarly, the method of the present invention allows a particularly hard and wear resistant bronze coating to be deposited on a device such as a bearing. The method of the present invention is also advantageously used in the field of cosmetic coatings such as, for example, equipment and jewelry, where plating of multi-component alloys containing tin, copper, zinc and bismuth is particularly advantageous. is there.

  A very special advantage is that the process according to the invention makes it possible to deposit so-called “true” bronzes with a copper content> 60%, the copper content in any case depending on the desired properties. Up to 95% by weight can be reached. Moreover, the ratio of the amount of copper and the amount of tin in the electrolyte has a great influence on properties such as the hardness and color of the bronze coating. For example, a tin / copper ratio of 40/60 deposits a relatively soft silver coating, so-called white bronze. If the tin / copper ratio is 20/80, a yellow gold coating, so-called yellow bronze, is formed. If the tin / copper ratio is 10/90, a red gold coating, so-called red bronze, is formed. The

Furthermore, high tin white bronze with a copper content of ≧ 10% can be deposited.
In either case, depending on the desired appearance of the bronze coating, in addition to the electrolyte having various copper contents, additives such as brighteners are added to the electrolyte. The electrolyte advantageously contains brighteners of the class of aromatic carbonyl compounds and / or α, β-unsaturated carbonyl compounds. The concentration of brightener is 0-5 g per liter of electrolyte.

Several embodiments are presented below to describe the present invention in more detail, but the present invention is not limited to these embodiments.
Electrolyte composition:
The electrolyte base of the highly acidic electrolyte of the present invention is basically (per 1 L of electrolyte).
2 to 75 g divalent tin 2 to 70 g divalent copper 2 to 40 g aromatic non-ionic wetting agent, and 140 to 382 g mineral acid and / or alkyl sulfonic acid.

In some cases, other components (per liter of electrolyte) are added to the electrolyte.
0-10 g of an anionic wetting agent and / or an aliphatic nonionic wetting agent;
0-50 g of stabilizer and / or complexing agent,
0-5 g of antioxidant,
0-5 g of brightener,
0-5 g of trivalent bismuth,
0-25 g of divalent zinc can be added.

  In order to achieve the inherent color of the deposited bronze coating, the electrolyte is prepared by varying the individual components, for example as shown in the examples below. Additional information regarding the corresponding processing conditions and other properties of the individual coatings can be found in Table 1.

(Example 1: Red bronze)
4 g / L Sn ²⁺
18 g / L Cu ²⁺
286 g / L methanesulfonic acid 3 g / L aromatic nonionic wetting agent 0.4 g / L aliphatic nonionic wetting agent 2 g / L antioxidant 20 mg / L complexing agent (Example 2a: Yellow bronze) )
4 g / L Sn ²⁺
18 g / L Cu ²⁺
240 g / L methanesulfonic acid 32.2 g / L aromatic non-ionic wetting agent 2 g / L antioxidant 25 mg / L stabilizer / complexing agent (Example 2b: Yellow bronze)
4 g / L Sn ²⁺
18 g / L Cu ²⁺
286 g / L methanesulfonic acid 32.2 g / L aromatic non-ionic wetting agent 6 mg / L brightener 2 g / L antioxidant 50 mg / L stabilizer / complexing agent (Example 3: White Bronze)
5 g / L Sn ²⁺
10 g / L Cu ²⁺
240 g / L methanesulfonic acid 32.2 g / L aromatic non-ionic wetting agent 6 mg / L brightener 2 g / L antioxidant 25 mg / L stabilizer / complexing agent (Example 4: Matt White Bronze) )
18 g / L Sn ²⁺
2 g / L Cu ²⁺
258 g / L methane sulfonic acid 9 g / L aromatic non-ionic wetting agent To improve the hardness and / or ductility of the deposited bronze coating, the electrolytes are used with the contents of zinc and / or bismuth shown below as examples Added. Additional data regarding the corresponding processing conditions and other properties of individual coatings can be found in Table 1.

(Example 5: High ductility)
4 g / L Sn ²⁺
18 g / L Cu ²⁺
238 g / L methanesulfonic acid 32.2 g / L aromatic non-ionic wetting agent 3 mg / L brightener 2 g / L antioxidant 25 mg / L stabilizer / complexing agent 20 g / L ZnSO ₄
(Example 6: Hardness)
4 g / L Sn ²⁺
18 g / L Cu ²⁺
238 g / L methanesulfonic acid 32.2 g / L aromatic non-ionic wetting agent 2 g / L antioxidant 25 mg / L stabilizer / complexing agent 0.1 g / L Bi ³⁺
(Example 7: Yellow bronze)
14.5 g / L Sn ²⁺
65.5 g / L of Cu ²⁺
382 g / L methanesulfonic acid 32.2 g / L aromatic non-ionic wetting agent 4 g / L antioxidant 25 mg / L stabilizer / complexing agent 20 g / L ZnSO ₄
These typical electrolyte compositions were used to deposit coatings with unique properties under the processing conditions listed in the table below.

Claims (27)

A bronze electrodeposition method having a copper content of at least 10%,
The acidic electrolyte to which the substrate to be coated is exposed is
At least 2 g / L to 75 g / L of divalent tin ions and 10 g / L to 70 g / L of copper ions;
An aromatic non-ionic wetting agent;
238 g / L to 382 g / L of free methanesulfonic acid,
Including at least one of bismuth and zinc ,
Wherein the precipitating at a current density range of ^{0.1A / dm 2 ~120A / dm 2} .   The method of claim 1, wherein the copper content is at least 60%.   The method according to claim 1 or 2, characterized in that 2 to 40 g / L of aromatic nonionic wetting agent is added to the electrolyte. characterized in that it added to the electrolyte at least one aromatic nonionic wetting agents of β- naphthol ethoxylate and nonylphenol ethoxylate method according to claim 1 or 2. Divalent tin ions or copper ions, characterized in that added to the electrolyte in the form of soluble salts, the method according to claim 1 or 2.   The process according to claim 5, characterized in that the soluble salt is a salt of an alkyl sulfonic acid.   The process according to claim 6, characterized in that the salt of the alkyl sulfonic acid is methane sulfonate. Characterized in that the addition of methanesulfonic acid tin 5~195g / L in the electrolyte, the method according to claim 1 or 2. Characterized in that the addition of copper methane sulfonate for 8~180g / L in the electrolyte, the method according to claim 1 or 2. Wherein the precipitating at a temperature of 17 to 25 ° C., The method according to claim 1 or 2 wherein. 3. A process according to claim 1 or 2 , characterized in that the precipitation is carried out in a pH range <1. An electrolyte used for electrodeposition of bronze having a copper content of at least 10% ,
At least 2 g / L to 75 g / L of divalent tin ions and 10 g / L to 70 g / L of copper ions;
An aromatic nonionic wetting agent,
238 g / L to 382 g / L of free methanesulfonic acid,
Electrolyte, characterized in including that the at least any of the bismuth and zinc. The electrolyte of claim 12 , wherein the bronze has a copper content of at least 60%. 14. Electrolyte according to claim 12 or 13 , characterized in that it contains 2-40 g / L of aromatic non-ionic wetting agent. The electrolyte according to claim 12 or 13 , wherein at least one of β-naphthol ethoxylate and nonylphenol ethoxylate is used as an aromatic nonionic wetting agent. The electrolyte according to claim 12 or 13 , characterized in that it contains divalent tin ions and copper ions in the form of a soluble salt. The electrolyte according to claim 16 , wherein the soluble salt is a salt of an alkyl sulfonic acid. The electrolyte according to claim 17 , wherein the salt of alkylsulfonic acid is methanesulfonate. The electrolyte according to claim 12 or 13 , characterized by containing 5 to 195 g / L of tin methanesulfonate. The electrolyte according to claim 12 or 13 , comprising 8 to 280 g / L of copper methanesulfonate. The electrolyte according to claim 12 or 13 , comprising at least one of polyethylene glycol and an anionic surfactant as a wetting agent. The electrolyte according to claim 12 or 13 , wherein the electrolyte contains a chlorine compound. 14. Electrolyte according to claim 12 or 13 , characterized in that it contains gluconate as a complexing agent. 14. Electrolyte according to claim 12 or 13 , characterized in that it contains a class of dihydroxybenzene antioxidants. 14. The electrolyte according to claim 12 , comprising at least one class of brighteners among aromatic carbonyl compounds and α, β-unsaturated carbonyl compounds. 14. Electrolyte according to claim 12 or 13 , characterized in that it has a pH value <1. An electrolyte,
10 to 70 g / L of divalent copper,
2 to 4 0 g / L aromatic nonionic wetting agent,
0-50 g / L of at least one of stabilizer and complexing agent,
At least one of 0-10 g / L anionic wetting agent and aliphatic nonionic wetting agent;
0-5 g / L antioxidant,
0-5 g / L brightener,
0-5 g / L trivalent bismuth,
0-25 g / L of divalent zinc,
The including, electrolyte according to claim 12 or 13.