Electroless metallization of dielectrics with alkaline stable pyrimidine derivative containing catalysts

Abstract

Pyrimidine derivatives which contain one or more electron donating groups on the ring are used as catalytic metal complexing agents in aqueous alkaline environments to catalyze electroless metal plating on metal clad and un-clad substrates. The catalysts are monomers and free of tin and antioxidants.

What is claimed is: 
     
         1 . A method comprising:
 a) providing a substrate comprising a dielectric;   b) applying an aqueous alkaline catalyst solution to the substrate comprising the dielectric, the aqueous alkaline catalyst comprises a monomeric complex of metal ions and one or more pyrimidine derivatives having formula:   
       
         
           
           
               
               
           
         
         
           wherein R 1 , R 2 , R 3  and R 4  may be the same or different and are hydrogen, (C 1 -C 3 )alky, —N(R) 2 , hydroxyl, hydroxy(C 1 -C 3 )alkyl, (C 1 -C 3 )alkoxy, carboxy or halogen, and where R may be the same or different and is hydrogen or (C 1 -C 3 )alkyl, and with the proviso that when R 2  and R 4  are hydroxyl, R 1  is also hydroxyl, R 1 , R 2  and R 4  cannot be —N(R) 2  at the same instance and when R 2  is an alkyl, R 1 , R 3  and R 4  cannot all be hydrogen, and R 1 , R 2 , R 3  and R 4  are not hydrogen at the same instance; or salts thereof; 
         
         c) applying a reducing agent to the substrate comprising the dielectric; and 
         d) immersing the substrate comprising the dielectric into an alkaline metal plating bath to electrolessly plate metal on the substrate comprising the dielectric. 
       
     
     
         2 . The method of  claim 1 , wherein the one or more pyrimidine derivatives are chosen from uracil, barbituric acid, orotic acid, thymine, 2-aminopyrimidine, 6-hydroxy-2,4,6-triaminopyrimidine, 6-methyluracil, 2-hydroxypyrimidine, 4,6-dichloropyrimidine, 2,4-dimethoxypyrimidine, 2-amino-4,6-dimethylpyrimidine, 2-hydroxy-4,6-dimethylpyrimidine and 6-methylisocytosine. 
     
     
         3 . The method of  claim 1 , wherein a molar ratio of the one or more pyrimidine derivatives to the metal ions is 1:1 to 4:1. 
     
     
         4 . The method of  claim 1 , wherein the metal ions are chosen from palladium, silver, gold, platinum, copper, nickel and cobalt. 
     
     
         5 . The method of  claim 1 , wherein the metal on the substrate is copper, copper alloy, nickel or nickel alloy. 
     
     
         6 . The method of  claim 1 , wherein the aqueous alkaline catalyst solution has a pH of 8.5 or greater. 
     
     
         7 . The method of  claim 6 , wherein the aqueous alkaline catalyst solution has pH of 9 or greater. 
     
     
         8 . The method of  claim 1 , wherein the substrate comprising the dielectric further comprises a plurality of through-holes. 
     
     
         9 . The method of  claim 8 , wherein the substrate comprising the dielectric further comprises metal cladding.