Board for mounting BGA semiconductor chip thereon, semiconductor device, and methods of fabricating such board and semiconductor device

Abstract

To fabricate a semiconductor device, a pattern of recesses and lands is formed on a copper sheet as a matrix sheet, and BGA pads are formed on the lands on the copper sheet. An insulating layer is formed on the copper sheet to transfer the pattern of recesses and lands from the copper sheet to the insulating layer for thereby forming recesses in the insulating layer and placing BGA pads in the recesses in the insulating layer. Vias are formed through the insulating layer, and a conductive layer serving as circuits and interconnections is formed, the conductive layer being connected to the BGA pads by the vias. When the copper sheet is removed, the BGA pads are positioned within the recesses in the insulating layer. The BGA pads have surfaces positioned higher than the bottom of the recesses and lower than the surface of the insulating layer. A semiconductor chip is mounted on the conductive layer, and solder balls are joined to the BGA pads. Both the productivity of a process of mounting the solder balls and the bonding strength of the solder balls are increased.

What is claimed is:  
     
         1 . A board for mounting a semiconductor chip thereon, comprising: 
 an insulating layer;    a recess defined in one surface of said insulating layer;    an electrode pad disposed in said recess and having a surface positioned higher than the bottom of said recess and lower than said one surface of said insulating layer;    a conductive layer disposed on an opposite surface of said insulating layer; and    a via extending through said insulating layer and connecting said electrode pad and said conductive layer to each other.    
     
     
         2 . A board according to  claim 1 , wherein said recess is formed in said insulating layer by transferring a pattern of recesses and lands of a matrix sheet to said insulating layer.  
     
     
         3 . A board according to  claim 2 , wherein said matrix sheet comprises a metal sheet.  
     
     
         4 . A board according to  claim 1 , wherein said electrode pad has a portion embedded in said insulating layer.  
     
     
         5 . A semiconductor device comprising: 
 a board for mounting a semiconductor chip thereon comprising an insulating layer, a recess defined in one surface of said insulating layer, an electrode pad disposed in said recess and having a surface positioned higher than the bottom of said recess and lower than said one surface of said insulating layer, a conductive layer disposed on an opposite surface of said insulating layer, and a via extending through said insulating layer and connecting said electrode pad and said conductive layer to each other;    a semiconductor chip connected to said conductive layer; and    a solder ball joined to said electrode pad.    
     
     
         6 . A semiconductor device according to  claim 5 , wherein said solder ball is disposed in said recess in said insulating layer.  
     
     
         7 . A semiconductor device according to  claim 5 , wherein said recess is formed in said insulating layer by transferring a pattern of recesses and lands of a matrix sheet to said insulating layer.  
     
     
         8 . A semiconductor device according to  claim 7 , wherein said matrix sheet comprises a metal sheet.  
     
     
         9 . A semiconductor device according to  claim 5 , wherein said electrode pad has a portion embedded in said insulating layer.  
     
     
         10 . A method of fabricating a board for mounting a semiconductor chip thereon, said method comprising the steps of: 
 forming a pattern of recesses and lands on a surface of a matrix sheet;    forming an electrode pad on said surface of said matrix sheet;    forming an insulating layer in covering relation to said surface of said matrix sheet to transfer said pattern of recesses and lands from said matrix sheet to a surface of said insulating layer for thereby forming a recess in said insulating layer and placing said electrode pad in said recess, said electrode pad having a surface positioned higher than the bottom of said recess and lower than said surface of said insulating layer;    forming a via through said insulating layer;    forming a conductive layer on a surface of said insulating layer remote from said matrix sheet, said conductive layer being connected to said electrode pad through said via; and    removing said matrix sheet.    
     
     
         11 . A method according to  claim 10 , wherein said electrode pad is formed on the land of said matrix sheet when said electrode pad is formed on said surface of said matrix sheet.  
     
     
         12 . A method according to  claim 10 , wherein said matrix sheet comprises a metal sheet.  
     
     
         13 . A method according to  claim 10 , wherein said electrode pad has a portion embedded in said insulating layer when said electrode pad is placed in said recess in said insulating layer.  
     
     
         14 . A method of fabricating a semiconductor device comprising the steps of: 
 forming a pattern of recesses and lands on a surface of a matrix sheet;    forming an electrode pad on said surface of said matrix sheet;    forming an insulating layer in covering relation to said surface of said matrix sheet to transfer said pattern of recesses and lands from said matrix sheet to a surface of said insulating layer for thereby forming a recess in said insulating layer and placing said electrode pad in said recess, said electrode pad having a surface positioned higher than the bottom of said recess and lower than said surface of said insulating layer;    forming a via through said insulating layer;    forming a conductive layer on a surface of said insulating layer remote from said matrix sheet, said conductive layer being connected to said electrode pad through said via;    removing said matrix sheet;    mounting a semiconductor chip on said conductive layer; and    joining a solder ball to said electrode pad after said matrix sheet is removed.    
     
     
         15 . A method according to  claim 14 , wherein said solder ball is disposed in said recess in said insulating layer.  
     
     
         16 . A method according to  claim 14 , wherein said electrode pad is formed on the land of said matrix sheet when said electrode pad is formed on said surface of said matrix sheet.  
     
     
         17 . A method according to  claim 14 , wherein said matrix sheet comprises a metal sheet.  
     
     
         18 . A method according to  claim 14 , wherein said electrode pad has a portion embedded in said insulating layer when said electrode pad is placed in said recess in said insulating layer.