Noble metal salt preparation, a method for production thereof and use for electroplating

Abstract

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

1 . A method for production of a noble metal salt preparation by membrane electrolysis comprising the steps:
 a) providing an electrolytic cell comprising an anode comprising a noble metal and a cathode, wherein an anodic region and cathodic region are separated by a membrane;   b) providing of at least one sulfonate solution in the anodic region; and   c) anodic oxidation of the noble metal and formation of a noble metal salt preparation comprising a noble metal sulfonate by passing a current through the electrolytic cell,
 wherein thiourea is added in the anodic region after step b) or after step c), and wherein the concentration of thiourea is 0.005 g/l to 200 g/l. 
   
     
     
         2 . The method for production of a noble metal salt preparation of  claim 1 , wherein the noble metal is selected from gold (Au), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru) and indium (In). 
     
     
         3 . The method for production of a noble metal salt preparation of  claim 1 , wherein the membrane is a cation-exchange membrane or an anion-exchange membrane. 
     
     
         4 . The method for production of a noble metal salt preparation of  claim 1 , wherein the sulfonate is an alkyl sulfonate. 
     
     
         5 . The method for production of a noble metal salt preparation of  claim 1 , wherein the concentration of the at least one sulfonate solution is 0.1% (w/w) to 20% (w/w). 
     
     
         6 . The method for production of a noble metal salt preparation of  claim 1 , wherein the method comprises at least one further step selected from precipitation, flocculation, complexation, oxidation and/or reduction. 
     
     
         7 . A noble metal salt preparation comprising at least one noble metal sulfonate and thiourea,
 wherein the molar ratio of noble metal to thiourea is 10.000:1 to 1:10.   
     
     
         8 . The noble metal salt preparation of  claim 7 , wherein the noble metal salt preparation is an aqueous, organic or ionic solution with a concentration of the noble metal of 0.001 mol/l to 5 mol/l. 
     
     
         9 . The noble metal salt preparation of  claim 7 , wherein the noble metal sulfonate is selected from gold (Au), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru) and indium (In) sulfonates. 
     
     
         10 . The noble metal salt preparation of  claim 7 , wherein the pH value is pH 1 to pH 8. 
     
     
         11 . The noble metal salt preparation of  claim 7 , comprising at least one further complexing agent. 
     
     
         12 . The noble metal salt preparation of  claim 7 , wherein the stability of an aqueous solution of the noble metal salt preparation is at least one or more months. 
     
     
         13 . The noble metal salt preparation according to  claim 12  wherein the stability of an aqueous solution of the noble metal salt preparation is at least one year. 
     
     
         14 . A method for electroplating of a noble metal or metal alloy comprising the steps:
 a) providing an electroplating bath comprising an anode, a cathode and a solution of at least one noble metal salt preparation according to  claim 7 ;   b) applying a current to the electroplating bath, whereby the at least one noble metal forms on the cathode; and   c) removing the cathode from the electroplating bath.   
     
     
         15 . A method for electroless plating of a noble metal comprising the steps:
 a) providing a plating bath comprising a solution of a noble metal salt preparation according to  claim 7 ;   b) contacting a solid substrate with the plating bath, whereby the noble metal forms on the solid substrate; and   c) removing the solid substrate from the plating bath.   
     
     
         16 . The method for production of a noble metal salt preparation of  claim 4 , wherein the sulfonate is a C1- to C10-alkyl sulfonate. 
     
     
         17 . The noble metal salt preparation of  claim 8 , wherein the noble metal salt preparation has a concentration of the noble metal of 0.01 mol/l to 0.5 mol/l. 
     
     
         18 . The noble metal salt preparation of  claim 11 , wherein the at least one further complexing agent is selected from chelating agents and organosulfur compounds. 
     
     
         19 . The noble metal salt preparation of  claim 11 , wherein the at least one further complexing agent is selected from methylglycinediacetic acid or ethylenediamine-N,N′-disuccinic acid (EDDS) or an alkali or alkaline earth salt of these acids, methionine or cysteine. 
     
     
         20 . The method for production of a noble metal salt preparation of  claim 1 , wherein:
 the noble metal is selected from gold (Au), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru) and indium (In);   the membrane is a cation-exchange membrane or an anion-exchange membrane;   the sulfonate is an alkyl sulfonate; and   the concentration of the at least one sulfonate solution is 0.1% (w/w) to 20% (w/w).