Method and composition for direct metallization of non-conductive substrates

Abstract

The present invention relates to a method for the metallization of an electrically non-conductive substrate using a thiosulfate conductor which employs a thiosulfate-containing conductor solution further comprising an alkali metal ion selected from the group consisting of lithium, potassium, rubidium, caesium, and combinations thereof.

1 . A method for metallizing an electrically non-conductive substrate comprising the steps:
 (a) contacting the electrically non-conductive substrate with a metal containing activator solution to yield an activated substrate;   (b) contacting the activated substrate with a conductor solution comprising (i) a source of thiosulfate and (ii) a source of alkali metal ion selected from the group consisting of lithium, potassium, rubidium, caesium, and combinations thereof, to yield an electrically conductive substrate;   (c) contacting the electrically conductive substrate with an electrolytic plating solution comprising a source of deposition metal ions; and   (d) applying an external source of electrons to reduce the deposition metal ions and deposit a metal or metal alloy layer on the electrically conductive substrate.   
     
     
         2 . The method of  claim 1  wherein the alkali metal ion source is added to the conductor solution as a salt comprising an anion selected from the group consisting of fluoride, chloride, bromide, nitrate, sulfate, and combinations thereof. 
     
     
         3 . The method of  claim 1  wherein the source of thiosulfate is selected from the group consisting of sodium thiosulfate, sodium thiosulfate pentahydrate, silver thiosulfate, ammonium thiosulfate, barium thiosulfate, magnesium thiosulfate hexahydrate, potassium thiosulfate, potassium thiosulfate hydrate, palladium(II) potassium thiosulfate monohydrate, and 2-benzyl-2-imidazoline thiosulfate, and combinations thereof. 
     
     
         4 . The method of  claim 1  wherein the source of thiosulfate is selected from the group consisting of sodium thiosulfate, silver thiosulfate, and a combination thereof. 
     
     
         5 . The method of  claim 1  wherein the conductor solution further comprises a completing agent selected from the group consisting of tartaric acid, salts of tartaric acid, ethylenediamine tetraacetic acid (EDTA), salts of ethylenediamine tetraacetic acid, citric acid, salts of citric acid, and combinations thereof. 
     
     
         6 . The method of  claim 1  wherein the deposition metal ions are copper ions or nickel ions. 
     
     
         7 . The method of  claim 1  wherein the alkali metal ion is selected from the group consisting of lithium, potassium, and combinations thereof. 
     
     
         8 . The method of  claim 7  wherein:
 the metal ions are selected from the group consisting of Ni and Cu;   the conductor solution has a pH between about 11.5 and about 13.5 and comprises the source of thiosulfate in a concentration between about 0.001 mol/L and about 0.5 mol/L, and the source of alkali metal ion selected from the group consisting of lithium, potassium, and combinations thereof in a concentration between about 0.01 mol/L and about 5 mol/L.   
     
     
         9 . The method of  claim 8  wherein the conductor solution comprises the source of thiosulfate in a concentration between about 0.01 mol/L and about 0.02 mol/L, and the source of alkali metal ion is selected from the group consisting of lithium, potassium, and combinations thereof in a concentration between about 0.2 mol/L and about 1 mol/L. 
     
     
         10 . The method of  claim 9  wherein the conductor solutions comprises:
 about 0.013 mol/L sodium thiosulfate as the source of thiosulfate;   about 0.6 mol/L lithium chloride as the source of alkali metal ion; and   a complexing agent in a concentration between about 0.01 and about 5 mol/L.   
     
     
         11 . A method for metallizing an electrically non-conductive substrate comprising the steps:
 (a) contacting the electrically non-conductive substrate with a metal-containing activator solution comprising between about 100 and about 300 mg/L Pd, between about 5 and about 20 g/L Sn, and between about 100 and about 350 ml/L concentrated HCl to yield an activated substrate;   (b) contacting the activated substrate with a conductor solution having a pH between about 11.5 and about 13.5 and comprising (i) a source of thiosulfate in a concentration between about 0.001 mol/L and about 0.5 mol/L, and (ii) a source of lithium ion in a concentration between about 0.01 mol/L and about 5 mol/L, to yield an electrically conductive substrate;   (c) contacting the electrically conductive substrate with an electrolytic plating solution comprising a source of deposition metal ions selected from the group consisting of Cu and Ni; and   (d) applying an external source of electrons to reduce the deposition metal ions and deposit a metal or metal alloy layer on the electrically conductive substrate.   
     
     
         12 . A conductor solution for rendering the surface of an electrically non-conductive substrate electrically conductive for the galvanic deposition of a metal layer, a metal alloy layer, or a metal compound layer on the electrically non-conductive substrate, the conductor solution comprising:
 (a) a source of thiosulfate ion; and   (b) an alkali metal ion selected from the group consisting of lithium, potassium, rubidium, caesium, and combinations thereof.   
     
     
         13 . The conductor solution of  claim 12  wherein the alkali metal ion is added to the conductor solution as a salt comprising an anion selected from the group consisting of fluoride, chloride, bromide, nitrate, sulfate, and combinations thereof. 
     
     
         14 . The conductor solution of  claim 12  wherein the alkali metal ion is added at a concentration between about 0.01 mol/L and about 5 mol/L. 
     
     
         15 . The conductor solution of  claim 12  wherein the source of thiosulfate is selected from the group consisting of sodium thiosulfate, sodium thiosulfate pentahydrate, silver thiosulfate, ammonium thiosulfate, barium thiosulfate, magnesium thiosulfate hexahydrate, potassium thiosulfate, potassium thiosulfate hydrate, palladium(II) potassium thiosulfate monohydrate, and 2-benzyl-2-imidazoline thiosulfate, and combinations thereof. 
     
     
         16 . The conductor solution of  claim 12  wherein the source of thiosulfate is selected from the group consisting of sodium thiosulfate, silver thiosulfate, and a combination thereof. 
     
     
         17 . The conductor solution of  claim 12  wherein the source of thiosulfate is added at a concentration between about 0.001 mol/L and about 0.5 mol/L. 
     
     
         18 . The conductor solution of  claim 12  further comprising a complexing agent selected from the group consisting of tartaric acid, salts of tartaric acid, ethylenediamine tetraacetic acid (EDTA), salts of ethylenediamine tetraacetic acid, citric acid, salts of citric acid, and combinations thereof. 
     
     
         19 . The conductor solution of  claim 12  comprising the source of thiosulfate in a concentration between about 0.01 mol/L and about 0.02 mol/L, and the source of alkali metal ion is selected from the group consisting of lithium, potassium, and combinations thereof in a concentration between about 0.2 mol/L and about 1 mol/L. 
     
     
         20 . The conductor solution of  claim 12  comprising:
 about 0.013 mol/L sodium thiosulfate as the source of thiosulfate;   about 0.6 mol/L lithium chloride as the source of alkali metal ion; and   a complexing agent selected from the group consisting of tartaric acid, salts of tartaric acid, ethylenediamine tetraacetic acid (EDTA), salts of ethylenediamine tetraacetic acid, citric acid, salts of citric acid, and combinations thereof in a concentration between about 0.01 and about 5 mol/L.