Circuit substrate having a circuit pattern and method for making the same

Abstract

A circuit substrate includes: an insulative substrate formed with a pattern of a recess, the recess being defined by a recess-defining wall that has a bottom wall surface and a surrounding wall surface extending upwardly from the bottom wall surface; a patterned metallic layer structure including at least a patterned active metal layer disposed within the recess, formed on the bottom wall surface of the recess-defining wall, and spaced apart from the surrounding wall surface of the recess-defining wall, the patterned active metal layer containing an active metal capable of initiating electroless plating; and a primary metal layer plated on the patterned metallic layer structure.

1 . A circuit substrate comprising:
 an insulative substrate having a top surface and formed with a pattern of a recess that is indented from said top surface, said recess being defined by a recess-defining wall that has a bottom wall surface and a surrounding wall surface extending upwardly from said bottom wall surface;   a patterned metallic layer structure including at least a patterned active metal layer that is disposed within said recess, that is formed on said bottom wall surface of said recess-defining wall, and that is spaced apart from said surrounding wall surface of said recess-defining wall, said patterned active metal layer containing an active metal capable of initiating electroless plating, a pattern of said patterned active metal layer corresponding in shape to the pattern of said recess; and   a primary metal layer plated on said patterned metallic layer structure.   
     
     
         2 . The circuit substrate of  claim 1 , wherein said active metal is selected from the group consisting of palladium, rhodium, platinum, iridium, osmium, gold, nickel, iron, and combinations thereof. 
     
     
         3 . The circuit substrate of  claim 1 , wherein said primary metal layer is made from a metal selected from the group consisting of copper, nickel, silver, and gold. 
     
     
         4 . The circuit substrate of  claim 1 , wherein said insulative substrate is made from a material selected from the group consisting of polycarbonate, a combination of acryl resin and acrylonitrile butadiene styrene (ABS) resin, and a combination of polycarbonate and ABS resin. 
     
     
         5 . The circuit substrate of  claim 1 , wherein said active metal is reduced. 
     
     
         6 . The circuit substrate of  claim 1 , wherein said active metal is non-reduced, said patterned metallic layer structure further including an intermediate metal layer electroless plated on said patterned active metal layer, said primary metal layer being electroplated on said intermediate metal layer. 
     
     
         7 . A method for making a circuit substrate having a circuit pattern, the method comprising:
 (a) providing an insulative substrate having a top surface;   (b) forming a pattern of a recess in the insulative substrate such that the recess is indented from the top surface, the recess being defined by a recess-defining wall having a bottom wall surface and a surrounding wall surface extending upwardly from the bottom wall surface;   (c) forming a metallic layer structure on the recess-defining wall of the recess and the top surface of the insulative substrate, the metallic layer structure including at least one active metal layer containing an active metal capable of initiating electroless plating;   (d) removing a portion of the metallic layer structure that is disposed along a peripheral edge of the bottom wall surface of the recess-defining wall so as to form the metallic layer structure into a first region which is disposed on the bottom wall surface, and a second region which is physically separated from the first region; and   (e) plating a primary metal layer on the first region of the metallic layer structure.   
     
     
         8 . The method of  claim 7 , wherein, in step (c), the active metal of the active metal layer is a reduced active metal, and the metallic layer structure is formed on the recess-defining wall of the recess and the top surface of the insulative substrate by immersing the insulative substrate into an active metal solution containing a non-reduced active metal so as to form a non-reduced metal layer containing the non-reduced active metal on the recess-defining wall of the recess and the top surface of the insulative substrate and then reducing the non-reduced active metal of the non-reduced metal layer so as to form the active metal layer containing the reduced active metal. 
     
     
         9 . The method of  claim 8 , wherein, in step (e), the primary metal layer is formed on the first region of the metallic layer structure by electroplating. 
     
     
         10 . The method of  claim 7 , wherein, in step (c), the active metal of the active metal layer is a non-reduced active metal, and the metallic layer structure is formed on the recess-defining wall of the recess and the top surface of the insulative substrate by immersing the insulative substrate into an active metal solution containing the non-reduced active metal so as to form the active metal layer containing the non-reduced active metal on the recess-defining wall of the recess and the top surface of the insulative substrate and then electroless plating an intermediate metal layer on the active metal layer. 
     
     
         11 . The method of  claim 10 , wherein, in step (e), the primary metal layer is formed on the intermediate metal layer of the first region of the metallic layer structure by electroplating. 
     
     
         12 . The method of  claim 7 , wherein, in step (c), the active metal of the active metal layer is a non-reduced active metal, and the metallic layer structure is formed on the recess-defining wall of the recess and the top surface of the insulative substrate by immersing the insulative substrate into an active metal solution containing the non-reduced active metal so as to form the active metal layer containing the non-reduced active metal on the recess-defining wall of the recess and the top surface of the insulative substrate. 
     
     
         13 . The method of  claim 12 , wherein, in step (e), the primary metal layer is formed on the active metal layer of the first region of the metallic layer structure by electroless plating. 
     
     
         14 . The method of  claim 13 , further comprising, after step (e), electroplating a top metal layer on the primary metal layer. 
     
     
         15 . The method of  claim 7 , wherein, in step (b), the recess in the insulative substrate is formed by laser or plasma ablation. 
     
     
         16 . The method of  claim 7 , wherein, in step (d), the portion of the metallic layer structure is removed by laser ablation. 
     
     
         17 . The method of  claim 7 , further comprising, after step (e), removing the second region of the metallic layer structure from the insulative substrate. 
     
     
         18 . The method of  claim 17 , wherein the second region of the metallic layer structure is removed from the insulative substrate by electrolysis.