US Patent 7820233 Method for fabricating a flip chip substrate structure

The present invention relates to a method to fabricate a flip chip substrate structure, which comprises: providing a carrier; forming a patterned resist layer on the surface of the carrier; forming sequentially a first metal layer, an etching-stop layer, and a second metal layer; removing the resist layer, forming a patterned first solder mask, and then forming at least one first circuit build up structure thereon; forming additionally a patterned second solder mask on the circuit build up structure; respectively removing the carrier, the first metal layer, and the etching-stop layer; and forming solder bumps on both sides of the circuit build up structure. The method increases integration and achieves the purpose of miniaturization. The method solves the problem of circuit layer multiplicity and process complexity.