EP1408141A1 - Process for galvanic deposition of bronze - Google Patents

Abstract

Galvanic deposition of bronze on a substrate comprises using an acidic electrolyte containing tin and copper ions, an alkylsulfonic acid and an aromatic non-ionic wetting agent. An Independent claim is also included for an electrolyte used in the deposition process.

Description

The present invention relates to a process for the electrodeposition of Bronzes, with which the substrate to be coated in an acidic electrolyte, at least tin and copper ions, an alkyl sulfonic acid and a wetting agent has, is metallized and the representation of such an electrolyte.

Process for the deposition of tin as well as tin alloys are from State of the art known and are in practice based on a variety of Electrolyte types already widely used. Widely used is the use of Process for the deposition of tin and / or tin alloys from cyanidic Electrolyte. However, such electrolytes are disadvantageously highly toxic, which makes their use from an environmental point of view problematic, so that since a few years ago the development of cyanide-free electrolytes such as Electrolytes based on pyrophosphate or oxalate, which are in a pH range from 5 to 9 working, being driven forward. However, such methods also have economic and technical disadvantages, of which the proportionate slow deposition rates are mentioned.

For these reasons, development is currently moving in the direction of process for the deposition of tin and / or tin alloys from acidic electrolytes because on the one hand bivalent tin in acidic electrolytes very can be easily reduced to metallic tin, resulting in better deposition rates on qualitatively equivalent coatings, and on the other is thereby the adverse influence of alkaline electrolytes on the substrates, such as ceramic components of assemblies prevented.

For example, EP 1 111 097 A2 and US Pat. No. 6,176,996 B1 disclose acidic electrolytes and Process for the separation of high quality tin or tin alloys known at a higher deposition rate. These are to electrolytes containing at least two divalent metal salts of an organic Have sulfonic acid and from which solderable and corrosion resistant Coatings are deposited, which, for example, as a substitute for leaded, solderable coatings, in electrical engineering for the production of printed circuit boards etc. be used.

However, such processes have their limits in the deposition of tin-copper alloys with high copper contents, such as the so-called "real" Bronzes with a copper content of at least 10%. So can for example, by the large potential difference between tin and copper higher oxidation rates of bivalent tin arise, causing this is very easily oxidized to tetravalent tin in acidic electrolytes. In In this form, however, tin is no longer electrolytically separable in the acidic state and thus deprived of the process, resulting in uneven deposition Both metals and the lowering of the deposition rate leads. In addition, the oxidation to tetravalent tin with a strong sludge formation connected, the stable operation and long life of the acidic Electrolytes can prevent. In addition, by such impurities the Formation of an adherent and non-porous coating no longer guaranteed.

Due to such procedural disadvantages, there is no great Field of application for electrolytically deposited bronze coatings. Occasionally are bronze coatings in the jewelry industry as a substitute for expensive silver or Allergies triggering nickel used. Likewise win procedure to the electrolytic deposition of bronzes also in some technical fields, For example, in electrical engineering for the coating of electronic components or in the field of mechanical engineering and / or process engineering for the coating of running and Friction layers, in importance. As a nickel substitute here, however predominantly white bronze or so-called "fake bronzes" deposited, whose Copper content can be kept very low due to the process.

The invention is therefore based on the object of specifying a method for the deposition of bronzes, which allows a uniform deposition of at least tin and copper next to each other from an acidic electrolyte at much higher deposition rates over the methods known in the art. In addition, with the help of this method, adherent and non-porous bronze coatings with high copper contents and different decorative and mechanical properties should be deposited.

Furthermore, an acidic electrolyte for the deposition of such bronze coatings be provided, which have a high content of bivalent copper ions can be stable to oxidation-induced sludge formation over a extended period of time, and is economically and environmentally sound.

The object is inventively achieved by a method of the type mentioned, which is characterized in that the electrolyte is an aromatic, nonionic wetting agent is added.

With the present invention, a method for electrodeposition provided by bronzes, wherein using an electrolyte, an anode made of a copper-tin alloy and a cathode connected to the coating substrate, the coating while passing through DC he follows. Furthermore, with the invention, in particular for this method usable electrolyte and the coatings obtainable by this method provided.

By the method according to the invention the disadvantages known in the prior art are eliminated with the provision of a novel composition of the electrolyte and achieved in this way significantly better deposition results. In addition, the implementation is simplified and made more economical. This too is mainly due to the advantageous composition of the electrolyte. Thus, for example, the process is carried out at room temperature or between 17 to 25 ° C and the substrate to be coated in a strongly acidic medium at a pH of <1 metallized. In this temperature range, the electrolyte is particularly stable. In addition, there are no costs for heating the electrolyte and also the metallized substrates need not be cooled down in a time and cost intensive manner. In addition, deposition rates of 0.25 μm / min are achieved at a current density of 1 A / dm ² , inter alia due to the pH value and the advantageous addition of at least one aromatic, nonionic wetting agent. This can be increased by the increase of the metal content up to 7 A / dm ² in the rack application and for pass-through systems even up to 120 A / dm ² . Thus, applicable current densities in a range of 0.1 to 120 A / dm ^{2 are} achieved depending on the type of system.

In particular, by the addition of at least one aromatic, nonionic Wetting agent to the electrolyte, surprisingly, the wetting of the metallizing surfaces especially of more complex substrates considerably improved. This advantageously has the consequence that through the use of not only significantly higher deposition rates be achieved, but that also by the method achieved coatings are uniform and high quality, a very good Have adhesive strength and are completely free of pores.

Another advantage of the aromatic, nonionic wetting agent used is that by the advantageous wetting properties during the process of Electrolyte and / or the substrate in the electrolyte little to no movement must be in order to achieve the desired deposition results, so that to the use of additional devices for moving the electrolyte can be waived. In addition, run due to the advantageous use of the aromatic, nonionic wetting agent when removing the metallized substrates from the electrolyte the electrolyte residues better of the substrates, resulting in reduced carry-over losses and thus to lower process costs leads.

Particularly advantageous is the addition of 2 to 40 g / l of one or more aromatic, nonionic wetting agent, with particular preference β-naphtholethoxylate and / or Nonylphenolethoxylat be used.

The proposed method is thus advantageously and economically environmentally friendly to the cyanidic processes.

Optionally, the additional use of one or more in the state of Technique known anionic and / or aliphatic, nonionic wetting agents possible, provided that the advantageous mode of action of the aromatic, support or even reinforce nonionic wetting agent. Preferably In this regard, polyethylene glycols and / or anionic surfactants as anionic and / or aliphatic, nonionic wetting agents to the electrolyte added.

As already shown above, the method according to the invention in particular by the special composition of the electrolyte characterized. This contains essentially tin and copper ions, a Alkyl sulfonic acid and an aromatic, nonionic wetting agent. Optionally additionally stabilizers and / or complexing agents, anionic and / or nonionic, aliphatic wetting agents, antioxidants, brighteners as well be included in the electrolyte further metal salts.

The mainly for the inventive deposition of bronze in the Electrolytes introduced metals - tin and copper - can primarily as Salts of alkylsulfonic acids, preferably as methanesulfonates or as salts of Mineral acids, preferably present as sulfates. As tin salt becomes special preferably the Zinnmethansulfonat used in the electrolyte, which advantageously in an amount of 5 to 195 g / l of electrolyte, preferably 11 to 175 g / l electrolyte is added to the electrolyte. This corresponds to a mission from 2 to 75 g / l, preferably 4 to 67 g / l of divalent tin ions. When Copper salt is particularly preferably the Kupfermethansulfonat in the electrolyte used, which is advantageously in an amount of 8 to 280 g / l electrolyte, preferably 16 to 260 g / l electrolyte is added to the electrolyte. This corresponds to an input of 2 to 70 g / l, preferably 4 to 65 g / l of bivalent Copper ions.

Since the deposition rate in the acidic environment is much higher, the Electrolytes an acid, preferably a mineral and / or an alkylsulfonic acid in Amounts of 140 to 382 g / l electrolyte, preferably 175 to 245 g / l electrolyte, added. The use of methanesulfonic acid turned out to be particularly advantageous out, as these on the one hand, an advantageous solubility of the metal salts conditional and on the other hand, due to their acidity, the setting of the for the Required process pH or facilitates. In addition has the methanesulfonic acid the advantageous property, essential to the stability of Bades contribute.

According to a further feature of the invention, the electrolyte is at least added an additional metal and / or chloride. Advantageously, lie the Metals in the form of their soluble salts. In particular, the addition of zinc and / or bismuth affects the properties of the deposited coatings in the special size. The zinc and / or bismuth introduced into the electrolyte Metals can be used primarily as salts of alkylsulfonic acids, preferably as Methanesulfonates or as salts of mineral acids, preferably as sulfates available. The preferred zinc salt is the zinc sulfate in the electrolyte used, which is advantageously in an amount of 0 to 25 g / l electrolyte, preferably 15 to 20 g / l electrolyte is added to the electrolyte. When Bismuth salt is most preferably bismuth methanesulfonate in the electrolyte used, which is advantageously in an amount of 0 to 5 g / l electrolyte, preferably 0.05 to 0.2 g / l of electrolyte is added to the electrolyte.

Furthermore, the electrolyte various additives, such as Stabilizers and / or complexing agents, antioxidants and brighteners, which usually in acidic electrolytes for the deposition of tin alloys can be added.

In particular, the use of suitable compounds for the stabilization of the electrolyte is an important requirement for fast and high quality Deposition of bronzes. Advantageously, the electrolyte as Stabilizers and / or complexing agents added gluconates. This is in the Process according to the invention, the preferred use of sodium gluconate as particularly advantageous. The concentration of stabilizers and / or Complexing agent is 0 to 50 g / l electrolyte, preferably 20 to 30 g / l electrolyte. As the antioxidant compounds are preferred from the class of Dihydroxybenzenes for example mono- or polyhydroxyphenyl such Catechol or phenolsulfonic acid used. The concentration of Antioxidant is 0 to 5 g / l electrolyte. Advantageously, the Electrolyte Hydroquinone as antioxidant.

The implementation of the method according to the invention enables the deposition of bronzes on different substrates. For example, everyone can conventional materials are used for the production of electronic components. Likewise, by the inventive method in particular hard and Wear-resistant bronze coatings on materials such as plain bearings etc. deposited. Also in the areas of decorative coating, for example of fittings and jewelery, etc., the method according to the invention is advantageously used, which is particularly advantageous in these areas, the deposition of Multi-alloy containing tin, copper, zinc and bismuth, affects.

A very particular advantage is that with the method according to the invention so-called "real" bronzes can be deposited, which have a copper content > 60%, the copper content depending on the desired property up to May be 95 wt .-%. In addition, the ratio of copper content to Tin content in the electrolyte has a significant influence on the properties Hardness and color of bronze coatings. So be at a ratio Tin / copper of 40/60 silver-colored coatings, so-called white bronzes deposited, which are relatively soft. At a tin / copper ratio from 20/80 arise yellow gold colored coatings, so-called yellow bronzes, and at a tin / copper ratio of 10/90 produces red gold-colored coatings, so-called red bronzes.

In addition, the deposition of tin-rich white bronzes with a Copper content ≥ 10% possible.

Depending on the desired appearance of the bronze coatings are the Electrolytes in addition to a different copper content, in addition to additives such as For example, brighteners added. Advantageously, the electrolyte contains Brighteners from the class of aromatic carbonyl compounds and / or α, β-unsaturated carbonyl compounds. The concentration of brighteners is 0 to 5 g / l electrolyte.

For a more detailed explanation of the invention are some preferred Embodiments illustrated, to which the invention, however, not restrict.

Electrolyte composition:

The base electrolyte of the strongly acidic electrolyte according to the invention essentially comprises (per liter of the electrolyte) 2 - 75 g divalent tin, 2 - 70 g divalent copper, 2 - 40 g an aromatic, nonionic wetting agent and 140 - 382 g a mineral and / or alkylsulfonic acid

Optionally, further constituents (per liter of the electrolyte) can be added to the electrolyte: 0-10 g an anionic and / or aliphatic, nonionic wetting agent, 0 - 50 g a stabilizer and / or complexing agent, 0 - 5 g an antioxidant, 0 - 5 g a shine agent 0 - 5 g trivalent bismuth 0 - 25 g divalent zinc

In order to achieve a certain color of the deposited bronze coatings, the electrolyte is prepared by variation of the individual components as exemplified below. Additional information on the corresponding process 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 methane 3 g / l aromatic, nonionic wetting agent 0.4 g / l aliphatic, nonionic wetting agent 2 g / l Antioxidant 20 mg / l complexing Example 2a (yellow bronze) 4 g / l Sn ²⁺ 18 g / l Cu ²⁺ 240 g / l methane 32.2 g / l aromatic, nonionic wetting agent 2 g / l Antioxidant 25 g / l Stabilizer / complexing agent Example 2b (yellow bronze) 4 g / l Sn ²⁺ 18 g / l Cu ²⁺ 286 g / l methane 32.2 g / l aromatic, nonionic wetting agent 6 mg / l brightener 2 g / l Antioxidant 50 g / l Stabilizer / complexing agent Example 3 (white bronze) 5 g / l Sn ²⁺ 10 g / l Cu ²⁺ 240 g / l methane 32.2 g / l aromatic, nonionic wetting agent 6 mg / l brightener 2 g / l Antioxidant 25 g / l Stabilizer / complexing agent Example 4 (Matt white bronze) 18 g / l Sn ²⁺ 2 g / l Cu ²⁺ 258 g / l methane 9 g / l aromatic, nonionic wetting agent

To improve the hardness and / or ductility of the deposited bronze coatings, different contents of zinc and / or bismuth are added to the electrolyte as exemplified below. Additional information on the corresponding process conditions and other properties of the 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 methane 32.2 g / l aromatic, nonionic wetting agent 3 mg / l brightener 2 g / l Antioxidant 25 g / 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 methane 32.2 g / l aromatic, nonionic wetting agent 2 g / l Antioxidant 25 g / l Stabilizer / complexing agent 0.1 g / l Bi ³⁺ Example 7 (yellow bronze) 14.5 g / l Sn ²⁺ 65.5 g / l Cu ²⁺ 382 g / l methane 32.2 g / l aromatic, nonionic wetting agent 4 g / l Antioxidant 25 g / l Stabilizer / complexing agent 20 g / l ZnSO ₄

With the above exemplary electrolyte compositions, coatings having certain properties were deposited under the process conditions listed in the table below. Example no. Coating /
Proportions in% by weight Properties of the coating sn Cu Zn Bi hardness ductility shine colour 1 10 90 - - 180 HV ₅₀ ++ Yes red 2a 20 80 - - 283 HV ₅₀ ± Yes yellow 2 B 20 80 - - 317 HV ₅₀ ± Yes yellow 3 40 60 - - 360 HV ₅₀ ± Yes White 4 90 10 - - - - No White 5 20 80 <1 - - +++ Yes yellow 6 20 80 - <1 345 HV ₅₀ - Yes yellow 7 20 80 <1 - - ++ Yes yellow

Claims (29)

A process for the electrodeposition of bronzes, with which the substrate to be coated is metallized in an acidic electrolyte comprising at least tin and copper ions, an alkylsulfonic acid and a wetting agent,
characterized in that an aromatic nonionic wetting agent is added to the electrolyte. Process according to Claim 1, characterized in that 2 to 40 g / l of the aromatic, nonionic wetting agent are added to the electrolyte. Process according to Claim 1 or 2, characterized in that β-naphthol ethoxylate and / or nonylphenol ethoxylate are added to the electrolyte as an aromatic nonionic wetting agent. Process according to one of Claims 1 to 3, characterized in that tin and copper ions in the form of a soluble salt, preferably as the salt of an alkylsulfonic acid, more preferably as methanesulfonate, are added to the electrolyte. Process according to one of Claims 1 to 4, characterized in that 2 to 75 g / l tin ions are added to the electrolyte. Process according to one of Claims 1 to 5, characterized in that 5 to 195 g / l of tin methanesulphonate are added to the electrolyte. Process according to one of Claims 1 to 6, characterized in that 2 to 70 g / l of copper ions are added to the electrolyte. Process according to one of Claims 1 to 7, characterized in that 8 to 280 g / l of copper methanesulphonate are added to the electrolyte. Method according to one of claims 1 to 8, characterized in that the deposition takes place at a temperature of 17 to 25 ° C. Method according to one of claims 1 to 9, characterized in that the deposition takes place in a current density range of 0.1 to 120 A / dm ² . Method according to one of claims 1 to 10, characterized in that the deposition takes place in strongly acidic medium. Method according to one of claims 1 to 11, characterized in that the deposition takes place in a pH range of <1. An electrolyte for the electrodeposition of bronzes, containing at least tin and copper ions, an alkyl sulfonic acid and a wetting agent,
characterized in that the electrolyte comprises an aromatic, nonionic surfactant. An electrolyte according to claim 13, characterized in that it contains from 2 to 40 g / l of the aromatic, nonionic wetting agent. An electrolyte according to any one of claims 13 to 14, characterized in that β-naphthol ethoxylate and / or nonylphenol ethoxylate are used as the aromatic, nonionic wetting agent. An electrolyte according to any one of claims 13 to 15, characterized in that it contains tin and copper ions in the form of a soluble salt, preferably as the salt of an alkylsulfonic acid, more preferably as methanesulfonate. Electrolyte according to either of Claims 13 and 16, characterized in that it contains from 2 to 75 g / l of tin ions. Electrolyte according to either of Claims 13 and 17, characterized in that it contains 5 to 195 g / l of tin methanesulfonate. Electrolyte according to either of Claims 13 and 18, characterized in that it contains from 2 to 70 g / l of copper ions. An electrolyte according to any one of claims 13 and 19, characterized in that it contains 8 to 280 g / l of copper methanesulfonate. Electrolyte according to one of Claims 13 to 20, characterized in that it contains polyethylene glycol and / or anionic surfactants as wetting agent. An electrolyte according to any one of claims 13 to 21, characterized in that it contains bismuth and / or zinc. An electrolyte according to any one of claims 13 to 22, characterized in that it contains chloride. Electrolyte according to one of Claims 13 to 23, characterized in that it contains gluconate as complexing agent. An electrolyte according to any one of claims 13 to 24, characterized in that it contains an antioxidant of the class of dihydroxybenzenes. An electrolyte according to any one of claims 13 to 25, characterized in that this brightener from the class of aromatic carbonyl compounds and / or α, β-unsaturated carbonyl compounds. Electrolyte according to one of claims 13 to 26, characterized in that it has a pH of <1. An electrolyte according to any one of claims 13 to 27, including 2 - 75 g / l divalent tin, 2 - 70 g / l divalent copper, 2 - 40 g / l an aromatic, nonionic wetting agent, 0 - 50 g / l a stabilizer and / or complexing agent 0-10 g / l an anionic and / or nonionic, aliphatic wetting agent 0 - 5 g / l an antioxidant 0 - 5 g / l a shine agent 0 - 5 g / l trivalent bismuth, 0 - 25 g / l divalent zinc, divalent zinc, at least 140 g / l of an alkyl sulfonic acid. Bronze coating produced by a process for electrodeposition, in particular by a process according to one of claims 1 to 10, characterized in that it has a copper content> 10%.