Structure and method for fine pitch flip chip substrate

A method for making a fine pitch flip chip substrate, comprising the steps of:

• providing a substrate, with a first metal layer, the said substrate having a plurality of through holes, a first metal plated layer on the first metal layer and the through holes;
• forming an inner circuit on said substrate;
• forming a black oxide inner circuit by oxidizing said inner circuit;
• forming a dielectric layer and a second metal layer on said substrate;
• forming vias in the dielectric layer by drilling to form a plurality of dielectric layer vias, and a second metal plated layer formed in said vias, which are plated and filled to form the surface of the second metal plated layer;
• forming a circuit layer on said second metal layer;
• forming a plurality of solder resist opening areas on said second metal layer excluding IC bump pad area;
• forming a plurality of black oxide dams on said second metal layer by oxidization;
• packaging flip chip by underfilling said IC bumping area, connecting the through holes of the flip chip substrate and said vias of the dielectric layer.