Colloidal seed formation for printed circuit board metallization

Abstract

A colloidal metal seed formulation useful for catalytically activating a surface of a non-conductive dielectric substrate in an electroless plating process is provided. The colloidal metal seed formulation includes stannous chloride, palladium chloride, HCl and a surfactant selected from a diphenyloxide disulfonic acid or alkali or alkaline earth metal salt thereof, C 30 H 50 O 10 , an alcohol alkoxylate and mixtures thereof. A method of electroless plating of a conductive metal onto a non-conductive dielectric substrate using the colloidal metal seed formulation is also provided.

1 - 10 . (Cancelled)  
     
     
         11 . A method of electroless plating of a conductive metal onto a surface of a non-conductive dielectric substrate, said method comprising the steps of: 
 laminating a roughened metal sheet to at least one surface of a non-conductive dielectric substrate;    etching away all of the roughened metal sheet;    contacting the etched surface with an acidic solution containing at least two available ionic moieties to provide a conditioned surface;    contacting the conditioned surface with a colloidal metal seed formulation so as to provide an activated surface, said colloidal metal seed formulation comprising stannous chloride, palladium chloride, HCl and a surfactant comprising a diphenyloxide disulfonic acid or an alkali or alkaline metal salt thereof, C 30 H 50 O 10 , an alcohol alkoxylate or mixtures thereof; and    plating a conductive metal onto said activated surface    
     
     
         12 . The method of  claim 11  wherein said non-conductive dielectric substrate comprises vias or plated-through holes that have a diameter of about 300 μm or less.  
     
     
         13 . The method of  claim 11  wherein, following contact, but prior to plating, the activated surface is subjected to the steps of: rinsing the activated surface with deionized water; bringing the rinsed surface into contact with HCl, drying the substrate at a temperature between 60° C. and 100° C.; applying a photoresist layer to the cleaned, activated surface; exposing the photoresist layer to a pattern of radiation; and developing the photoresist layer using a conventional resist developer.  
     
     
         14 . The method of  claim 11  wherein said conductive metal is copper (Cu), tungsten (W), nickel (Ni), cobalt (Co), cobalt tungsten (CoW), or cobalt tungsten phosphorus (CoWP).  
     
     
         15 . The method of  claim 11  wherein said surfactant is a diphenyloxide disulfonic acid or an alkali metal salt thereof.  
     
     
         16 . The method of  claim 15  wherein said diphenyloxide disulfonic acid is a compound having the formula:  
       
         
           
           
               
               
           
         
       
       wherein at least one of R 1 , R 2 , R 3  and R 4  on each phenyl ring is SO 3  and the remaining R groups on each phenyl ring, independently, are hydrogen, a linear or branched alkyl containing from 1 to about 22 C atoms, a linear or branched alkylene containing from 2 to about 22 C atoms, an alkynyl containing 2 to 22 C atoms, hydroxy, or alkoxy containing from 1 to 22 carbon atoms, or two adjacent remaining R groups taken together form an alicyclic ring containing from 5 to 6 carbon atoms which may optionally include a heteroatom such as N, S or P.  
     
     
         17 . The method of  claim 15  wherein said alkali metal salt of said diphenyloxide disulfonic acids includes an alkali metal which provides a net zero charge to the compound.  
     
     
         18 . The method of  claim 11  wherein said surfactant is C 30 H 50 O 10 .  
     
     
         19 . The method of  claim 11  wherein said surfactant is an alcohol alkoxylate.  
     
     
         20 . The method of  claim 19  wherein said alcohol alkoxylate has the formula R—O—(CH 2 CH 2 O) n (CH 2 CHCH 3 O) n CH 2 CH 2 OH wherein R is hydrogen, a linear or branched alkyl containing from 1 to about 22 C atoms, a linear or branched alkylene containing from 2 to about 22 C atoms or an alkynyl containing 2 to 22 C atoms, and n is from 1 to 50.