Electroless nickel or cobalt plating solution

Abstract

An electroless nickel or cobalt plating solution, comprising nickel ions or cobalt ions, Ti 3+ ions as reducing agent for reducing said nickel ions and cobalt ions, at least one accelerator selected from the group consisting of sulfites, dithionites, thiosulfates, tetrathionates, polythionates, disulfites, sulfides, disulfide, polysulfide, elemental sulfur and mixtures thereof; and one or more than one complexing agent, wherein the pH value of the plating solution is from 5 to 10.5.

1 . An electroless nickel or cobalt plating solution, comprising
 nickel ions or cobalt ions,   Ti 3+  ions as reducing agent for reducing said nickel ions and cobalt ions,   at least one accelerator selected from the group consisting of sulfites, dithionites, thiosulfates, tetrathionates, polythionates, disulfites, sulfides, disulfide, polysulfide, elemental sulfur and mixtures thereof; and   one or more than one complexing agent,   
       wherein the pH value of the plating solution is from 5 to 10.5. 
     
     
         2 . The plating solution according to  claim 1 , wherein the accelerator(s) is/are selected from the group consisting of alkaline metal sulfites, alkaline metal hydrogen sulfites, alkaline earth metal sulfites, alkaline earth metal hydrogen sulfites, ammonium sulfite, ammonium hydrogen sulfite, alkaline metal dithionites, alkaline metal hydrogen dithionites, alkaline earth metal dithionites, alkaline earth metal hydrogen dithionites, alkaline metal thiosulfates, alkaline metal hydrogen thiosulfates, alkaline earth metal thiosulfates, alkaline earth metal hydrogen thiosulfates, ammonium thiosulfate, ammonium hydrogen thiosulfate, alkaline metal tetrathionates, alkaline metal hydrogen tetrathionates, alkaline earth metal tetrathionates, alkaline earth metal hydrogen tetrathionates, ammonium tetrathionates, ammonium hydrogen tetrathionate, alkaline metal polythionates, alkaline metal hydrogen polythionates, alkaline earth metal polythionates, alkaline earth metal hydrogen polythionates, ammonium polythionates, ammonium hydrogen polythionate, alkaline metal disulfites, alkaline metal hydrogen disulfites, alkaline earth metal disulfites, alkaline earth metal hydrogen disulfites, ammonium disulfites, ammonium hydrogen disulfite, alkaline metal sulfide, alkaline metal disulfide, alkaline metal polysulfide, ammonium sulfide, and cyclo-octasulfur (S 8 ). 
     
     
         3 . The plating solution according to  claim 1 , wherein the total amount by weight of the accelerator(s) in the plating solution ranges from 0.01 to 300 ppm. 
     
     
         4 . The plating solution of  claim 1 , wherein the one or more than one complexing agent is/are independently selected from the group consisting of
 an organic phosphonic acid compound, its salts and esters,   an organic polyphosphoric acid compound, its salts and esters,   an inorganic polyphosphoric acid compound, its salts and esters, and   an organic carboxylic acid compound, its salts and esters.   
     
     
         5 . The plating solution of  claim 1 , wherein the one or more than one complexing agent is independently selected from the group consisting of an organic phosphonic acid compound, its salts and esters. 
     
     
         6 . The plating solution of  claim 1 , wherein the organic and/or inorganic polyphosphoric acid compound, its salts and esters, comprise 2 to 10 phospho-building units linked together. 
     
     
         7 . The plating solution of  claim 1 , with the proviso that the plating solution does not comprise pyrophosphate. 
     
     
         8 . The plating solution of  claim 1 , wherein a molar ratio of the complexing agent to the Ti 3+  ions is 1.5:1 or higher. 
     
     
         9 . The plating solution of  claim 1 , wherein a concentration of the Ti 3+  ions is in a range from 0.03-0.2 mol/L. 
     
     
         10 . The plating solution of  claim 1 , wherein a concentration of the one or more than one complexing agent is in a range from 0.03-2.0 mol/L. 
     
     
         11 . The plating solution of  claim 1 , having a pH in a range from 4.0-9.5. 
     
     
         12 . A method for electroless plating of a nickel or a cobalt deposit ( 4 ) on a substrate ( 2 ,  3 ), the method comprising contacting the substrate with the electroless plating solution according to  claim 1  such that the nickel or cobalt deposit ( 4 ) is electrolessly plated on the substrate ( 2 ,  3 ). 
     
     
         13 . The method of  claim 12 , wherein the electroless plating solution has a temperature in a range from 30-80° C. 
     
     
         14 . The method of  claim 12 , wherein the substrate ( 2 ,  3 ) comprises a copper layer ( 3 ), wherein the nickel or cobalt deposit ( 4 ) is plated on the copper layer ( 3 ). 
     
     
         15 . (canceled) 
     
     
         16 . The plating solution according to  claim 1  wherein the one or more than one complexing agent is independently selected from the group consisting of an organic phosphonic acid compound, its salts and esters and the organic phosphonic acid compound, its salts and esters is the only complexing agent in the plating solution.