Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/56—Electroplating: Baths therefor from solutions of alloys
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/56—Electroplating: Baths therefor from solutions of alloys
  • C25D3/58—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of copper
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/56—Electroplating: Baths therefor from solutions of alloys
  • C25D3/60—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of tin

Definitions

• This invention concerns a method for electrodeposition of bronzes, with which the substrate to be coated is plated in an acid electrolyte that contains at least tin and copper ions, an alkylsulfonic acid and a wetting agent, and the preparation of such an electrolyte.
• acid electrolytes and methods for deposition of qualitatively high grade tin or tin alloys with a higher deposition rate are known from EP 1 111 097 A2 and US 6,176,996 B1. These are electrolytes that contain at least two divalent metal salts of an organic sulfonic acid and from which are deposited solderable and corrosion resistant coatings that can be used, for example, as substitutes for lead-containing solderable coatings in electronics for manufacture of circuit boards, etc.
• bronze coatings are used in the jewelry industry as a substitute for expensive silver or allergy-triggering nickel.
• methods for electrodeposition of bronzes are also gaining importance in some technical fields, for example in electronics for coating electronic components or in mechanical engineering and/or in process technology for coating bearing overlays and friction layers.
• chiefly white bronzes or the so-called "false bronzes,” whose copper content can be kept quite low due to process conditions, are deposited as nickel substitutes.
• the invention is based on the task of providing a method for deposition of bronzes that, in contrast to the methods known from the prior art, enables uniform deposition of at least tin and copper side by side from an acid electrolyte at considerably higher deposition rates. Moreover, with this method firmly bonding and pore-free bronze coatings with high copper contents as well as various decorative and mechanical properties are said to be deposited.
• an acid electrolyte that can have a high content of divalent copper ions, is stable with respect to oxidation-caused sludge formation, and is both economical and environmentally friendly when used over a long period of time, is to be made available.
• the task is solved in accordance with the invention by a method of the kind mentioned at the start, which is characterized by the fact that an aromatic, nonionic wetting agent is added to the electrolyte.
• a method for electrodeposition of bronzes is made available, where an anode of a copper-tin alloy and a cathode are connected to the substrate that is to be coated by means of an electrolyte, and coating takes place by passing a direct current through them.
• an electrolyte that is usable in particular for this method and the coatings that are obtainable by this method are made available.
• the disadvantages known in the prior art are remedied with the offering of a new electrolyte composition and in this way considerably better deposition results are achieved.
• the conduct of the method is made to be simpler and more economical.
• This, too, is chiefly based on the advantageous composition of the electrolyte.
• the method is carried out at room temperature, or between 17 and 25 C, and the substrate to be coated is plated in a highly acid environment at a pH ⁇ 1.
• the electrolyte is particularly stable in this temperature range.
• there are no longer any costs for heating the electrolyte and the plated substrates also do not have to be cooled very much, with large expenditures of time and money.
• deposition rates of 0.25 ⁇ m/min at a current density of 1 A/dm 2 are achieved due to, among other things, the pH value and the advantageous addition of at least one aromatic non-ionic wetting agent.
• this rate can be raised up to 7 A/dm 2 in rack operation and even up to 120 A/dm 2 for continuous plants.
• usable current densities in a range from 0.1-120 A/dm 2 are reached in each case according to plant type.
• the wetting of the surfaces to be plated is considerably improved in particular through the addition of at least one nonionic wetting agent to the electrolyte.
• nonionic wetting agent that is used is that because of the advantageous wetting properties the electrolyte and/or the substrate in the electrolyte need to be agitated only a little or even not at all, in order to achieve the desired deposition results, so that additional devices for agitation of the electrolyte can be omitted.
• aromatic nonionic wetting agent because of the advantageous use of the aromatic nonionic wetting agent, electrolyte residues drain from the plated substrate better when it is removed from the electrolyte, which leads to reduced entrainment losses and thus to lower process costs.
• the proposed method is therefore advantageously economical and environmentally friendly compared to the cyanide processes.
• anionic and/or aliphatic nonionic wetting agent that is known from the prior art is also optionally possible, provided these wetting agents support or even enhance the advantageous effects of the aromatic nonionic wetting agent.
• polyethylene glycols and/or anionic surfactants are preferably added to the electrolyte as anionic and/or aliphatic nonionic wetting agents.
• Additional exemplary aliphatic nonionic wetting agents include aliphatic fatty alcohol ethoxylates.
• substituted dithioglycols act advantageously as wetting agents and brighteners. Therefore, certain embodiments of the invention include substituted dithioglycols, such as, for example, those selected from the group consisting of: (1) Thiobis(diethyleneglycol) represented by H-(OCH 2 CH 2 ) 2 -S-(CH 2 CH 2 O) 2 -H, (2) Thiobis(hexaethylene glycol), (3) Thiobis(pentadecaglycelol) represented by H-(OCH 2 CH(OH)CH 2 ) 15 -S-(CH 2 CH(OH)CH 2 O) 15 -H, (4) Thiobis(icosaethyleneglycol) represented by H-(OCH 2 CH 2 ) 20 -S-(CH 2 CH 2 O) 20 -H, (5) Thiobis(pentacontaethyleneglycol), (6) 4,10-dioxa-7-thiatridecane-2,12-diol represented by:
• the method in accordance with the invention is characterized in particular by the special composition of the electrolyte. It contains essentially tin and copper ions, an alkylsulfonic acid and an aromatic nonionic wetting agent.
• stabilizers and/or complexing agents, anionic and/or nonionic, aliphatic and/or substituted dithioglycol wetting agents, oxidation inhibitors, brighteners, and other metal salts can optionally be contained in the electrolyte.
• the metals that are primarily added to the electrolyte for deposition of bronzes in accordance with the invention – tin and copper – can first and foremost be in the form of salts of alkylsulfonic acids, preferably as methanesulfonates, or as salts of mineral acids, preferably as sulfates.
• Tin methanesulfonate is especially preferably used as tin salt in the electrolyte preferably in an amount of 5-195 g/L of electrolyte, preferably 11-175 g/L of electrolyte. This corresponds to a use of 2-75 g/L, preferably 4-57 g/L divalent tin ions.
• Copper methanesulfonate is especially preferably used in the electrolyte as the copper salt, which is advantageously added to the electrolyte in an amount of 8-280 g/L of electrolyte, preferably 16-260 g/L of electrolyte. This corresponds to the use of 2-70 g/L, preferably 4-65 g/L divalent copper ions.
• an acid preferably a mineral and/or an alkylsulfonic acid
• an acid is added to the electrolyte in amounts of 140-382 g/L of electrolyte, preferably 175-245 g/L of electrolyte.
• methanesulfonic acid turned out to be especially advantageous, since for one thing this produces advantageous solubility of metal salts and for another, because of its acid strength, it produces or facilitates the adjustment of the pH needed for the process.
• methanesulfonic acid has the advantageous property of contributing considerably to the stability of the bath.
• At least one additional metal and/or chloride is added to the electrolyte.
• the metals are in the form of their soluble salts.
• the addition of zinc and/or bismuth has a considerable effect on the properties of the deposited coatings.
• the metals zinc and/or bismuth added to the electrolyte can namely be in the form of salts of alkylsulfonic acids, preferably as methanesulfonates or as salts of mineral acids, preferably as sulfates.
• Zinc sulfate is especially preferably uses in the electrolytes as zinc salt, and is advantageously added in an amount of 0-25 g/L of electrolyte, preferably 15-20 g/L of electrolyte.
• Bismuth methane sulfate is especially preferably used in the electrolyte as bismuth salt and is advantageously added to the electrolyte in an amount of 0-5 g/L of electrolyte, preferably 0.05-0.2 g/L of electrolyte.
• additives for example stabilizers and/or complexing agents, oxidation inhibitors and brighteners, that are usually used in acid electrolytes for deposition of tin alloys can be added to the electrolyte.
• Gluconates are advantageously added to the electrolyte and stabilizers and/or complexing agents.
• the concentration of the stabilizers and/or complexing agents is 0-50 g/L of electrolyte, preferably 20-30 g/L of electrolyte.
• Compounds from the class of the dihydroxybenzenes, for example mono- or polyhydroxyphenyl compounds like pyrocatechol or phenolsulfonic acid are preferably used as oxidation inhibitors.
• the concentration of oxidation inhibitors is 0-5 g/L of electrolyte.
• the electrolyte contains hydroquinone as oxidation inhibitor.
• the conduct of the method in accordance with the invention enables the deposition of bronzes onto various substrates.
• all of the usual methods for making electronic components can be used.
• especially hard and wear-resistant bronze coatings can be deposited on materials like bearings, etc., to the method in accordance with the invention.
• the method in accordance with the invention is advantageously also used in the fields of decorative coating of, for example, fixtures and jewelry, etc., where the deposition of multi-component alloys that contain tin, copper, zinc and bismuth is particularly advantageous in these areas.
• a really special advantage is that the so-called "true" bronzes that have a copper content >60% can be deposited with the method in accordance with the invention, where the copper content can be up to 95 wt% in each according to the desired properties.
• the ratio of the amount of copper to the amount of tin in the electrolyte has a considerable effect of properties like hardness and color of the bronze coatings. For instance, at a tin/copper ratio of 40/60 silver-colored coatings, the so-called white bronzes, which are relatively soft, are deposited. At a tin/copper ratio of 20/80 yellow gold colored coatings result, the so-called yellow bronzes, and at a tin/copper ratio of 10/90 red gold colored coatings are formed, the so-called red bronzes.
• the electrolyte contains brighteners from the class of the aromatic carbonyl compounds and/or á,â-unsaturated carbonyl compounds.
• the concentration of brighteners is 0-5 g/L of electrolyte.
• Electrolyte composition :
• the base electrolyte of the highly acid electrolyte in accordance with the invention contains essentially (per liter of electrolyte) 2-75 g divalent tin, 2-70 g divalent copper, 2-40 g of an aromatic nonionic wetting agent, and 140-382 g of a mineral and/or alkylsulfonic acid.
• electrolyte per liter of electrolyte: 0-10 g of an anionic and/or aliphatic nonionic wetting agent, 0-50 g of a stabilizer and/or complexing agent, 0-5 g of an oxidation inhibitor, 0-5 g of a brightener 0-5 trivalent bismuth 0-25 g divalent zinc.
• the electrolyte is prepared by varying the individual components, as given below as a matter of example. Additional information about the corresponding process conditions as well as other properties of the individual coatings can be seen 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 oxidation inhibitor 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 nonionic wetting agent 2 g/L oxidation inhibitor 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 nonionic wetting agent 6 mg/L brightener 2 g/L oxidation inhibitor 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 nonionic wetting agent 6 mg/L brightener 2 g/L oxidation inhibitor 25 mg/L stabilizer/complexing agent
• Example 4 (matte white bronze) 18 g/L Sn 2+ 2 g/L Cu 2+ 258 g/L methanesulfonic acid 9 g/L aromatic nonionic wetting agent
• Example 5 (high ductility) 4 g/L Sn 2+ 18 g/L Cu 2+ 238 g/L methanesulfonic acid 32.2 g/L aromatic nonionic wetting agent 3 mg/L brightener 2 g/L oxidation inhibitor 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 nonionic wetting agent 2 g/L oxidation inhibitor 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 Cu 2+ 382 g/L methanesulfonic acid 32.2 g/L aromatic nonionic wetting agent 4 g/L oxidation inhibitor 25 mg/L stabilizer/complexing agent 20 g/L ZnSO 4
• Example 8 (yellow bronze) 2 g/L Sn 2+ 8 g/L Cu 2+ 400 g/L methanesulfonic acid 2.5 g/L aromatic nonionic wetting agent 1 g/L fatty alcohol ethoxylate 4 g/L oxidation inhibitor
• Example 9 (white bronze) 4 g/L Sn 2+ 8 g/L Cu 2+ 400 g/L methanesulfonic acid 1 g/L aromatic nonionic wetting agent 40 mg/L substituted dithioglycol 4 g/L oxidation inhibitor

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• Electroplating And Plating Baths Therefor (AREA)
• Electroplating Methods And Accessories (AREA)

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• 2005
  • 2005-04-14 US US11/105,947 patent/US20060260948A2/en not_active Abandoned
• 2006
  • 2006-04-14 EP EP06750231.0A patent/EP1874982B1/fr not_active Expired - Lifetime
  • 2006-04-14 WO PCT/US2006/014141 patent/WO2006113473A1/fr not_active Ceased
  • 2006-04-14 KR KR1020077026291A patent/KR101361431B1/ko not_active Expired - Lifetime
  • 2006-04-14 TW TW095113445A patent/TWI391534B/zh active
  • 2006-04-14 JP JP2008506756A patent/JP2008537017A/ja active Pending
  • 2006-04-14 CN CN2006800208357A patent/CN101194049B/zh not_active Expired - Lifetime

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