CN110770371A - Noble metal salt preparation, method for producing same and use thereof for electroplating - Google Patents

Noble metal salt preparation, method for producing same and use thereof for electroplating Download PDF

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CN110770371A
CN110770371A CN201780091162.2A CN201780091162A CN110770371A CN 110770371 A CN110770371 A CN 110770371A CN 201780091162 A CN201780091162 A CN 201780091162A CN 110770371 A CN110770371 A CN 110770371A
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noble metal
metal salt
salt formulation
formulation according
solution
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赖科·埃纳特
弗兰克·科斯特
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Saxony Edmetar Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/28—Per-compounds
    • 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
    • C25D3/48—Electroplating: Baths therefor from solutions of gold
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/31—Coating with metals
    • C23C18/42—Coating with noble metals
    • C23C18/44—Coating with noble metals using reducing agents
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B13/00—Diaphragms; Spacing elements
    • C25B13/04—Diaphragms; Spacing elements characterised by the material
    • C25B13/08—Diaphragms; Spacing elements characterised by the material based on organic materials
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B3/00—Electrolytic production of organic compounds
    • C25B3/01—Products
    • C25B3/13—Organo-metallic compounds
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B3/00—Electrolytic production of organic compounds
    • C25B3/20—Processes
    • C25B3/23—Oxidation
    • 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
    • C25D3/50—Electroplating: Baths therefor from solutions of platinum group metals
    • C25D3/52—Electroplating: Baths therefor from solutions of platinum group metals characterised by the organic bath constituents used
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/18—Electroplating using modulated, pulsed or reversing current
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/54—Contact plating, i.e. electroless electrochemical plating

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  • Inorganic Chemistry (AREA)
  • Electroplating And Plating Baths Therefor (AREA)
  • Chemically Coating (AREA)

Abstract

The invention relates to a method for producing a noble metal salt preparation comprising at least one noble metal sulfonate and thiourea, and to the use thereof for surface coating by electroplating or electroless plating of noble metals or metal alloys.

Description

Noble metal salt preparation, method for producing same and use thereof for electroplating
The invention relates to a method for producing a noble metal salt preparation comprising at least one noble metal sulfonate and thiourea, and to the use thereof for surface coating by electroplating or electroless plating of noble metals or metal alloys.
In the field of electronic and electrical engineering, coatings using noble metals, in particular gold, are widely used because of their high conductivity, high corrosion resistance, low contact resistance and good solderability.
In general, coatings using noble metals are produced from noble metal cyanide complexes by electroplating or electroless plating. The alkaline, acidic or neutral plating solution includes a source of precious metals, such as potassium dicyanoaurate, potassium tetracyanoaurate or alkaline sulfite.
The disadvantage of conventional baths is the use of toxic cyanide and therefore high requirements for plant safety, occupational protection and storage.
WO 2014/054429 a1 or US 2015/0137356 a1 respectively disclose a non-cyanide metal plating bath comprising alkaline gold sulfite or gold ammonium sulfite and a conductive salt comprising sulfite and sulfate. The main disadvantage of the disclosed plating solution is poor stability.
EP 0611840 a1 discloses a cyanide-free electroplating solution for the deposition of monovalent copper, silver, gold and other metals complexed with thiosulfate ions, and stabilizers of organic sulfinate compounds which stabilize the thiosulfate ions in sufficient amounts when the solution is operated at an acidic pH of less than 7. The main drawbacks of the disclosed bath are the limitation of the current density and the formation of toxic sulphur dioxide in the presence of sulphites.
JP 3365866B2 discloses a non-cyanide noble metal plating bath comprising a water-soluble noble metal salt and a nonionic surfactant. The acidic noble metal plating bath includes alkanesulfonic acid having a noble metal selected from gold or silver, and the like. The nonionic surfactant is preferably Pururafakku LF401 (manufactured by BASF), Tetronic TR-702 (manufactured by Asahi Denka Kogyo Co., Ltd.), Nymeen L-207 (manufactured by NOF Corporation), or Liponox NC-100 (manufactured by Lion Corporation).
US 6,251,249B 1 discloses an iodide-free formulation comprising an organic sulfur compound and/or a carboxylic acid and a source of soluble noble metal ions, and a procedure for depositing noble metals onto a solid substrate the source of soluble noble metal ions is selected from the group consisting of noble metal alkane sulfonates, noble metal alkane sulfonamides or noble metal alkane sulfonamides, preferably silver methylsulfonate, silver methylsulfonamide or silver dimethylsulfonimide the organic sulfur compound is selected from the group consisting of alkyl thiols, aryl thiols, heterocyclic thiols, dialkyl sulfides, diaryl sulfides, arylalkyl sulfides, organic disulfides, organic polysulfides, organic xanthates, organic thiocyanates or thioureas, and the carboxylic acid is selected from the group consisting of alkane carboxylic acids, aromatic carboxylic acids, α -amino acids, dicarboxylic acids or polycarboxylic acids the substrate for electroplating is selected from the group consisting of brass, bronze, silver, gold, palladium, copper alloys, nickel alloys, iron alloys, tin alloys, zinc alloys, aluminum or organic based plastics the noble metal is selected from the group consisting of silver, gold, platinum, palladium, rhodium, osmium and ruthenium, preferably silver, palladium and gold.
DE 102009024396 a1 discloses cyanide-free neutral or alkaline aqueous electrolytes comprising anionic gold mercaptide complexes for electroplating gold or gold alloys. Furthermore, DE 102009024396 a1 describes the addition of complexing agents, brighteners, surfactants and/or conducting salts.
DE 102103215476B 3 discloses cyanide-free acidic and aqueous electrolytes for electroplating silver-palladium alloys comprising a silver compound, a palladium compound, tellurium or selenium compound, urea and/or at least one amino acid and a sulfonic acid. Furthermore, DE 102103215476B 3 discloses a method for electroplating.
CN 105316718A discloses a plating solution with good dispersibility and covering power, and a method for plating cyanide-free gold with sulfite. The electroplating solution comprises gold chloride, sulfite serving as a coordination agent and alkali metal mercaptopropionate serving as an auxiliary coordination agent.
US 2016/0230287 a1 discloses a reductive electroless gold plating bath comprising a water-soluble gold compound, citric acid or citrate, ethylenediaminetetraacetic acid (EDTA) or ethylenediaminetetraacetate, hexamethylenetetramine and a chain polyamine having an alkyl group having 3 or more carbon atoms and 3 or more amino groups; and a method for electroless gold plating using the plating solution.
A disadvantage of these disclosed baths and methods for electroplating is the use of toxic or persistent substances. Therefore, a problem occurs in degradation of the plating solution after the plating.
Alternatively, DE 19928047 a1 discloses low to contaminant-free and therefore environmentally compatible aqueous solutions for electroplating noble metals and noble metal alloys. The plating solution comprises gold and/or silver complexes with amino acid derivatives and/or at least one water-soluble sulfonic acid and/or at least one water-soluble nitro compound. Disadvantageously, the plating solution includes gold (III). The main disadvantage of using a plating solution comprising gold (III) is that the current requirements are much higher compared to gold (I).
It is an object of the present invention to provide an alternative to cyanide-based noble metal baths, and to provide noble metal baths that are biodegradable after metal plating.
This object is solved by a process for the production of a noble metal salt formulation by electromembrane electrolysis, comprising the steps of:
a) providing an electrolytic cell comprising an anode and a cathode, the anode comprising a noble metal, wherein an anode region and a cathode region are separated by a membrane,
b) at least one sulfonate solution is provided in the anode region,
c) anodising the noble metal by passing an electric current through the electrolytic cell and forming a noble metal salt formulation comprising a noble metal sulphonate,
wherein thiourea is added in the anode region after step b) or after step c),
wherein the concentration of thiourea is from 0.005g/l to 200g/l, preferably from 10g/l to 100g/l, more preferably from 35g/l to 55 g/l.
According to the invention, the term "noble metal" means a metal that is resistant to corrosion and oxidation in humid air. Preferably, the term "noble metal" relates to elements of groups 8 to 10 other than iron metals (Fe, Co and Ni) according to the IUPAC nomenclature of inorganic chemistry in 1989. However, In embodiments of the present invention, the term "noble metal" includes indium (In).
Preferably, the at least one noble metal is selected from gold (Au), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru) or indium (In). More preferably, the at least one noble metal is gold (Au).
Preferably, the membrane is a cation exchange membrane or an anion exchange membrane, more preferably, the membrane is a cation exchange membrane, preferably with a sulfonated tetrafluoroethylene based fluoropolymer-copolymer (e.g., Nafion @)TM)。
The sulfonates according to the invention are alkylsulfonates or alkali metal or alkaline earth metal salts thereof, sulfonamides or sulfonimides. In an embodiment, the sulfonate is an alkyl sulfonate, preferably a C1-to C10-alkyl sulfonate. As used herein, the term "alkyl sulfonate" refers to a linear, cyclic, or aromatic organic sulfonate. The term C1-to C10-alkyl refers to alkyl groups having 1 to 10 carbon atoms.
In a preferred embodiment, the sulfonate is a methanesulfonate, an ethanesulfonate, a propylsulfonate, a phenylsulfonate or an alkali or alkaline earth metal salt thereof.
Preferably, the concentration of the at least one sulfonate solution is from 0.1% (w/w) to 20% (w/w). In an embodiment, the sulfonate salt solution is an aqueous solution.
An effective molar ratio of noble metal to thiourea is between 10,000:1 and 1:10, preferably 100:1 to 1:5, more preferably 10:1 to 1: 2.
The pH of the at least one sulfonate solution is in the range between pH 1 and pH 8, preferably between pH3 and pH 8.
In an embodiment, the anodization according to step c) is carried out with a current between 0.1A and 500A, preferably with a current between 0.5A and 50A.
In an embodiment, the anodization according to step c) is carried out with a voltage between 0.1V and 10V.
In another embodiment, the at least one sulfonate salt solution further comprises at least one additional complexing agent, preferably selected from chelating agents or organic sulfur compounds, more preferably selected from methylglycinediacetic acid or ethylenediamine-N, N' -disuccinic acid (EDDS) or alkali metal or alkaline earth metal salts of these acids (e.g. Trilon @)TMM), methionine or cysteine. The term complexing agent refers to compounds that form complexes with metal ions. The term chelating agent refers to a compound that forms a chelate with a metal ion. The term chelate refers to a complex in which there are two or more independent coordination bonds between a multidentate (multiply-bonded) ligand and a single metal ion.
Advantageously, the at least one chelating agent or organosulfur compound stabilizes the noble metal salt formulation. Further advantageously, the at least one additional complexing agent is biodegradable. As used herein, the term "biodegradable" refers to a compound that is broken down by bacteria, fungi, or other biological means under composting conditions.
In another embodiment, the method for producing a noble metal salt formulation comprises at least one additional step selected from precipitation, flocculation, complexation, oxidation and/or reduction.
In another embodiment, the method for producing a noble metal salt formulation further comprises a step after step c), wherein the further step is mixing at least two noble metal salt formulations.
In another embodiment, the method for producing a noble metal salt formulation further comprises a step after step c), wherein the further step is dissolving or diluting the noble metal salt formulation in an aqueous, organic or ionic solution.
The invention also includes a noble metal salt formulation comprising at least one noble metal sulfonate and thiourea, wherein the molar ratio of noble metal to thiourea is from 10,000:1 to 1:10, preferably from 100:1 to 1:5, more preferably from 10:1 to 1: 2.
The at least one noble metal sulfonate is preferably selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru) or indium (In) sulfonates. Preferably, the at least one noble metal salt is a gold (Au) salt, more preferably a gold (I) (Au (I)) salt.
The at least one noble metal sulfonate is preferably an alkyl sulfonate, more preferably a C1-to C10-alkyl sulfonate. In a preferred embodiment, the at least one noble metal sulfonate is a methanesulfonate, an ethanesulfonate, a propylsulfonate, a phenylsulfonate or an alkali or alkaline earth metal salt thereof.
In an embodiment, the noble metal salt formulation is an aqueous, organic or ionic solution, wherein the concentration of the noble metal is from 0.001mol to 5mol, preferably from 0.01mol to 0.5 mol.
The concentration of the noble metal sulfonate in the formulation is 0.1% (w/w) to 20% (w/w).
In another embodiment, the noble metal salt formulation is an aqueous solution having a pH value between pH 1 and pH 8, preferably between pH3 and pH 8.
In another embodiment, the noble metal salt formulation comprises at least one additional complexing agent, preferably selected from chelating agents or organic sulphur compounds, more preferably selected from methylglycinediacetic acid or ethylenediamine-N, N' -disuccinic acid (EDDS) or alkali metal or alkaline earth metal salts of these acids (e.g. Trilon)TMM), methionine or cysteine.
In an embodiment, the stability of the aqueous solution of the noble metal salt formulation is at least several months, preferably at least several years.
Advantageously, the noble metal salt formulation according to the invention does not comprise cyanide. Further advantageously, the noble metal salt formulation according to the invention does not comprise halide ions and/or resistance complexing agents. As used herein, the term "resistant" refers to compounds that are not biodegradable.
In an embodiment, the noble metal salt formulation according to the invention further comprises a carboxylic acid. As used herein, the term "carboxylic acid" refers to an organic compound having at least one carboxyl group and 1 to 20 carbon atoms. Advantageously, the carboxylic acid is a complexing agent and adjusts the pH.
In an embodiment, the carboxylic acid is selected from formic acid, acetic acid, succinic acid, citric acid or salts thereof. In another embodiment, the salt of a carboxylic acid is selected from sodium acetate, sodium succinate or sodium citrate.
In another embodiment, the noble metal salt formulation according to the invention further comprises aldehydes, alcohols, ketones, ethers and/or esters. Advantageously, the aldehydes, alcohols, ketones, ethers and/or esters are complexing agents and surfactants (surfactants). As used herein, the term "surface active material" refers to a compound that reduces the surface tension (or interfacial tension) between two liquids or between a liquid and a solid.
In another embodiment, the noble metal salt formulation according to the invention further comprises a surfactant. In another embodiment, the surfactant is selected from the group consisting of cationic, anionic, nonionic and betaine type surfactants, preferably the surfactant is Sodium Dodecyl Sulfate (SDS).
In another embodiment, the noble metal salt formulation according to the invention further comprises an amine, preferably a primary amine. Advantageously, the amine is a complexing agent and a buffering agent. In an embodiment, the amine is selected from the group consisting of amino acids, ethylenediamine, and ethylamine.
Advantageously, the noble metal salt formulation according to the invention is stable at temperatures between 0 ℃ and 100 ℃.
The invention also includes a plating solution comprising a noble metal salt formulation according to the invention.
Another object of the invention is the use of the noble metal salt formulation according to the invention for surface coating by electroplating or electroless plating of noble metals or metal alloys. The term electroplating refers to a process that uses an electric current to reduce dissolved metal cations so that they form a thin coherent metal coating on an electrode.
Advantageously, the noble metal of the surface coating using the noble metal salt formulation according to the invention is a metal that is resistant to corrosion and oxidation in humid air.
Further advantageously, the noble metal salt formulation according to the invention is biodegradable after surface coating of the noble metal according to the OECD standard (OECD 1992).
The invention also includes a method for electroplating a noble metal or metal alloy, the method comprising the steps of:
a) providing an electroplating bath comprising an anode, a cathode and a solution of at least one noble metal salt formulation according to the invention,
b) applying an electric current to the electroplating bath to form at least one noble metal on the cathode, and
c) the cathode is removed from the electroplating bath.
In an embodiment, the anode is an inert or soluble anode, preferably a mixed oxide anode or a noble metal anode.
In an embodiment, the anode is selected from ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), osmium (Os), iridium (Ir), platinum (Pt), gold (Au), or indium (In).
In another embodiment, the solution of the at least one noble metal salt formulation has a metal content of 0.001mol to 0.25mol, preferably 0.01mol to 0.1 mol.
In another embodiment, the method for electroplating a noble metal or metal alloy is performed at a pH value between pH 1 and pH 8, preferably between pH 2 and pH 6.
In another embodiment, the method for electroplating a noble metal or metal alloy is performed at a temperature between 0 ℃ and 100 ℃.
In an embodiment, the method for electroplating a noble metal or metal alloy uses 0.1A/dm2To 20A/dm2Current density in between.
In another embodiment, the method for electroplating is performed by pulse electroplating.
In an embodiment, the method for electroplating a metal alloy is carried out with a solution of at least one noble metal salt formulation according to the invention, which solution also comprises at least one noble metal or other metal. The at least one noble metal is selected from ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), osmium (Os), iridium (Ir), platinum (Pt), or gold (Au). In embodiments, the at least one other metal is selected from nickel (Ni), cobalt (Co), iron (Fe), copper (Cu), cadmium (Cd), or indium (In).
The invention also includes a method for electroless plating of noble metals, comprising the steps of:
a) providing a plating bath comprising a solution of a noble metal salt formulation according to the invention,
b) contacting the solid substrate with a plating bath to form a noble metal on the solid substrate, an
c) The solid substrate is removed from the plating bath.
In another embodiment, the solution of the noble metal salt formulation has a metal content of 0.001 to 0.25mol, preferably 0.01 to 0.1 mol.
In another embodiment, the process for electroless plating of noble metals is carried out at a pH value between pH 1 and pH 8, preferably between pH 2 and pH 6.
In another embodiment, the process for electroless plating of noble metals is carried out at a temperature between 0 ℃ and 100 ℃, preferably between 60 ℃ and 80 ℃.
In an embodiment, the thickness of the layer of at least one noble metal is from 10nm to 100 μm, preferably from 100nm to 10 μm.
Advantageously, the layer of at least one noble metal is used as a flux or as an anti-corrosive coating.
In another embodiment, the most recently described embodiments may be combined.
The invention will now be further explained by means of the following non-limiting figures and examples.
Figure 1 shows a schematic of an electrolytic cell comprising an anode and a cathode, the anode comprising a noble metal, wherein the anode region and the cathode region are separated by a membrane.
Production of gold (I) salt solutions
For the production of the au (i) salt solution, the cell of fig. 1 was used. The cell comprises an anode comprising gold with a high surface (specific surface) and a cathode, which is produced according to known methods, in particular by the wohlville process (Gmelin1974), wherein the anode region and the cathode region are separated by a membrane. In the anodic region, the electrolytes are alkylsulfonic acids and thiourea. In the cathode region, the electrolyte is an alkyl sulfonic acid.
The anodization was carried out with a direct current of 0.5A, 1A or 10A. The membrane electrolysis was carried out at 25 ℃. Alternatively, the membrane electrolysis may be carried out at a temperature between 20 ℃ and 80 ℃.
In the anode region, a gold (I) salt solution is contained and filtered.
Example 1: preparation of gold (I) methanesulfonate
The catholyte was a solution of 70% methanesulfonic acid and distilled water mixed to 5% methanesulfonic acid. The anolyte comprises an aqueous solution of methanesulfonic acid (5%) and 20g/l thiourea. Titanium platinate was used as the cathode and the anode was pure gold from the walwell process. The membrane between the cathode and anode is a cation selective membrane (Nafion) from DuPont.
The anodization was carried out with a direct current of 1.0A for two hours. Thereafter, the anolyte contained 13.9g of gold in the form of gold (I).
Example 2: preparation of gold (I) methanesulfonate
The catholyte mixed 70% methanesulfonic acid and distilled water to a 20% solution of methanesulfonic acid. The anolyte comprised an aqueous solution of methanesulfonic acid (20%) and 40g/l thiourea. Titanium platinate was used as the cathode and the anode was pure gold from the walwell process. The membrane between the cathode and anode is a cation selective membrane (Nafion) from DuPont.
The anodization was carried out with a direct current of 1.0A for five hours. Thereafter, the anolyte contained 33.1g of gold in the form of gold (I).
Example 3: preparation of gold (I) methanesulfonate
Both the catholyte and anolyte were 100% methanesulfonic acid. Titanium platinate was used as the cathode and the anode was pure gold from the walwell process. The membrane between the cathode and anode is a cation selective membrane (Nafion) from DuPont.
The anodization was carried out with a direct current of 0.5A for four hours. Thereafter, the anolyte contained 13.4g of gold in the form of gold (I) and was diluted with distilled water with thiourea dissolved at a concentration of 20 g/l.
Example 4: electroplating of
The solution of methanesulfonic acid Au (I) from example 1 was used in a conventional Hull CellA nickel plated brass (messing) plate was plated. The Au (I) plating solution comprises 2g/l Au (I), 5g/l thiourea, 5g/l sodium methanesulfonate and 5ml of 0.005% sodium dodecyl sulfate solution. In use at 0.5A/dm2After 5min of plating, the nickel/brass plate of the cathode was yellow due to gold plating.
Example 5: chemical plating
The methanesulfonic acid au (i) solution of example 2 was used for electroless plating of nickel-plated printed circuit boards in a conventional beaker. The Au (I) plating solution comprises 2g/l Au (I), 5g/l thiourea, 2g/l Trilon M and 5ml of 0.005% sodium dodecyl sulfate solution. After heating to 62 ℃ and plating for 5min, the printed circuit board was yellow due to gold plating.
Cited non-patent documents
OECD(1992)OECD Guideline for testing of chemicals,Section 3-Degradation and Accumulation,Test No.301:Ready Biodegradability,DOI:10.1787/9789264070349-en.
Gmelin L(1974)Gmelin Handbuch der anorganischen Chemie:Gold.Lieferung2,Springer-Verlag Berlin Heidelberg GmbH,8thEdition,ISBN 3-540-93265-8.
Reference numerals
1 cathode
2 anode
3 film
4 catholyte solution
5 anolyte solution

Claims (15)

1. Method for producing a noble metal salt formulation by electromembrane electrolysis, comprising the following steps
a) Providing an electrolytic cell comprising an anode and a cathode, the anode comprising a noble metal, wherein an anode region and a cathode region are separated by a membrane,
b) providing at least one sulfonate solution in the anode region,
c) anodising the noble metal by passing an electric current through the electrolytic cell and forming a noble metal salt formulation comprising a noble metal sulphonate,
wherein thiourea is added in the anode region after step b) or after step c),
wherein the concentration of the thiourea is 0.005g/l to 200 g/l.
2. The method for producing a noble metal salt formulation according to claim 1, wherein at least one noble metal is selected from gold (Au), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru), or indium (In).
3. The method for producing a noble metal salt formulation according to claim 1 or 2, wherein the membrane is a cation exchange membrane or an anion exchange membrane.
4. The method for producing a noble metal salt formulation according to any one of claims 1 to 3, wherein the sulfonate is an alkyl sulfonate, preferably a C1-to C10-alkyl sulfonate.
5. The method for producing a noble metal salt formulation according to any one of claims 1 to 4, wherein the concentration of the at least one sulfonate salt solution is 0.1% (w/w) to 20% (w/w).
6. The process for producing a noble metal salt formulation according to any one of claims 1 to 5, wherein the process comprises at least one further step selected from precipitation, flocculation, complexation, oxidation and/or reduction.
7. A noble metal salt formulation comprising at least one noble metal sulfonate and thiourea, wherein the molar ratio of noble metal to thiourea is from 10,000:1 to 1: 10.
8. The noble metal salt formulation according to claim 7, wherein the noble metal salt formulation is an aqueous, organic or ionic solution having a noble metal concentration of 0.001 to 5mol, preferably 0.01 to 0.5 mol.
9. The noble metal salt formulation according to claim 7 or 8, wherein the noble metal sulfonate is selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru) or indium (In) sulfonates.
10. The noble metal salt formulation of any one of claims 7 to 9, wherein the pH value is from pH 1 to pH 8.
11. A precious-metal salt formulation according to any one of claims 7 to 10, comprising at least one further complexing agent, preferably selected from chelating agents or organic sulphur compounds, more preferably selected from methylglycinediacetic acid or ethylenediamine-N, N' -disuccinic acid (EDDS) or alkali or alkaline earth metal salts of these acids, methionine or cysteine.
12. The noble metal salt formulation of any one of claims 7 to 11, wherein the aqueous solution of the noble metal salt formulation has a stability of at least several months.
13. Use of the noble metal salt formulation according to any one of claims 7 to 12 for surface coating by electroplating or electroless plating of noble metals or metal alloys.
14. Method for electroplating a noble metal or metal alloy, said method comprising the following steps
a) Providing an electroplating bath comprising an anode, a cathode and a solution of at least one noble metal salt formulation according to any one of claims 7 to 12,
b) applying an electric current to the electroplating bath, thereby forming at least one noble metal on the cathode, and
c) removing the cathode from the electroplating bath.
15. Method for electroless plating of noble metals, comprising the following steps
a) Providing a plating bath comprising a solution of a noble metal salt formulation according to any one of claims 7 to 12,
b) contacting a solid substrate with the plating bath to form a noble metal on the solid substrate, an
c) Removing the solid substrate from the plating bath.
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