Wiring Board and Production Method Thereof

Abstract

It is an object of the present invention to provide a wiring board having high-density wiring with a controlled shape without masking by a resist film and a production method thereof. In the present invention, the production method of a wiring board having copper wiring on an insulating substrate includes the steps of forming a metal seed layer on the insulating substrate, the metal seed layer having a roughened shape in a portion on which the copper wiring or a bump is to be formed, and forming an electroplated film of copper or an alloy of copper through electroplating on the portion of the metal seed layer having the roughened shape. A substance for suppressing the plating reaction is added to a plating bath to provide an angle of 90 degrees or smaller between a surface of the insulating substrate and a side of the electroplated film.

1 . A method of producing a wiring board having copper wiring on an insulating substrate, comprising the steps of:
 forming a metal seed layer on the insulating substrate, the metal seed layer having a roughened shape in a portion on which the copper wiring is to be formed; and   forming an electroplated copper film on the portion of the metal seed layer having the roughened shape through electroplating using a plating bath containing a substance for suppressing plating reaction,   wherein the electroplated copper film is formed at an angle of 90 degrees or smaller between a surface of the insulating substrate and a side of the electroplated copper film.   
     
     
         2 . The method of producing a wiring board according to  claim 1 , wherein the angle between the surface of the insulating substrate and the side of the electroplated copper film is adjusted by controlling a current density in performing the electroplating. 
     
     
         3 . The method of producing a wiring board according to  claim 1 , wherein the metal seed layer is formed on the insulating substrate and then the roughened shape is formed thereon, and the electroplated copper film is formed on the metal seed layer through the electroplating and then the metal seed layer and the electroplated copper film are removed except their portions having the roughened shape thereon. 
     
     
         4 . The method of producing a wiring board according to  claim 1 , wherein the metal seed layer having the roughened shape formed thereon is formed on the insulating substrate, the roughened shape is planarized except its portion on which the copper wiring or bumps are to be formed, the electroplated copper film is formed through the electroplating on the metal seed layer, and then the metal seed layer and the electroplated copper film are removed except their portions having the roughened shape thereon. 
     
     
         5 . The method of producing a wiring board according to  claim 1 , wherein the metal seed layer serving as a power supply layer for the electroplating is formed, and then an insulating film serving as the insulating substrate is formed on the metal seed layer with a casting method, the roughened shape is formed in a portion of the metal seed layer on which wiring or bumps are to be formed, the electroplated copper film is formed on the metal seed layer through the electroplating, and the metal seed layer and the electroplated copper film are removed except their portions having the roughened shape thereon. 
     
     
         6 . The method of producing a wiring board according to  claim 1 , wherein an arithmetic average roughness Ra, defined in JIS B0601, of the portion having the roughened shape of the insulating substrate or the metal seed layer is larger than an arithmetic average roughness Ra of the remaining portion. 
     
     
         7 . The method of producing a wiring board according to  claim 1 , wherein an average length of a roughness curve element RSm, defined in JIS B0601, of the portion having the roughened shape of the insulating substrate or the metal seed layer is smaller than an average length RSm of the remaining portion. 
     
     
         8 . The method of producing a wiring board according to  claim 1 , wherein the surface roughness of the portion having the roughened shape has an arithmetic average roughness Ra, defined in JIS B0601, of 0.01 to 4 μm, and an average length of a roughness curve element RSm of 0.005 to 8 μm. 
     
     
         9 . The method of producing a wiring board according to  claim 1 , wherein the substance added to the plating bath increases the overpotential of the metal deposition through the electroplating when the velocity of the plating bath containing the substrate to increases. 
     
     
         10 . The method of producing a wiring board according to  claim 1 , wherein at least one of cyanine dyes is added to the plating bath. 
     
     
         11 . The method of producing a wiring board according to  claim 10 , wherein the cyanine dye is a compound shown in the following formula (where X represents an anion and n represents one of the numbers 0, 1, 2, and 3): 
       
         
           
           
               
               
           
         
       
     
     
         12 . The method of producing a wiring board according to  claim 10 , wherein the cyanine dye has a concentration of 3 to 15 mg/dm 3 . 
     
     
         13 . The method of producing a wiring board according to  claim 10 , wherein the electroplating is performed with a constant current at a current density of 0.1 to 2.0 A/dm 2 . 
     
     
         14 . The method of producing a wiring board according to  claim 1 , wherein at least one substance selected from a polyether, an organic sulfur compound, and a halide ion is added to the plating bath.