Method for fabricating high-density IC board by selectively electroplating without electrical conductive route

Abstract

A method for fabricating the high-density IC substrate by selectively electroplating without the electrically conductive route is provided. In this method, the specific resin layer with thickness of 1-5 μm is coated on the matte side of the copper clad, and then the compound layer of the copper clad and the resin is attached to the build up material layer, such as glass-fiber reinforced resin layer by hot pressing technique. The specific resin layer has good adhesion to the electrically conductive layer so that the subsequent process can be performed well. In such a way, a very thin electrically conductive plating layer can be applied on the IC substrate to form high density lines, and another selectively plating can be performed on the IC substrate without the electrically conductive route by applying another electrically conductive layer on the IC substrate.

1 . A method for fabricating the high-density IC substrate by selectively electroplating without the electrically conductive route comprising: 
 forming an electrically conductive layer on a resin layer, the resin layer having good adhesion to the electrically conductive plating layer;    flash etching a conductive layer to form high-density circuit layers; forming an electroless copper on the resin between the circuit layers and the circuit layers;    forming a pattern to be selectively electroplated on the circuit layers using a photoresist ; and    selectively electroplating a metal layer on an selected circuit by introducing an electric current from an outside of an substrate to an inside of an substrate via the electrically conductive layer, wherein the selected circuit is enclosed by the selectively electroplated metal layer.    
   
   
       2 . The method as claimed in  claim 1 , wherein a method for fabricating the high density circuit layers of the IC substrate, comprising: 
 providing a substrate formed with a resin layer coated on a copper clad, an inner circuit layer being covered by a glass-fiber reinforced resin covered by the resin layer;    removing the copper clad to expose the resin layer;    forming a micro-via connected to the inner circuit in the resin layer and the glass-fiber reinforced resin layer, forming an electroless metal layer on an wall of the micro-via, the inner circuit layer under the micro-via, and the resin layer,    wherein the micro-via is formed by mechanically drilling or laser drilling a predetermined region on the resin layer and the glass-fiber reinforced resin layer until portions of the inner circuit layer are exposed;    forming a patterned dry film on the electroless metal layer; and    performing an electroplating process on the electroless metal layer uncovered by the patterned dry film, removing the dry film, and removing the electroless metal covered by the dry film by flash etching to form high density circuit layers.    
   
   
       3 . The method as claimed in  claim 1 , wherein the electrically conductive layer is made of an electroless meta,  1  or a sputtered metal.  
   
   
       4 . The method as claimed in  claim 1 , wherein the metal layer on the selected circuit is made of a material selected from the group consisting of electroplated nickel, electroplated gold, electroplated tin, electroplated silver, electroplated silver, and any combination thereof.