Patent ID: 6443351
Filing Date: 2002-09-03
Classification: B23K,H01L,H05K,Y02P

Abstract:
A method of achieving solder ball coplanarity on an integrated circuit package, comprising the steps of:(1) determining in advance the relation of solder ball height against pad size; (2) measuring the warpage degree of the integrated circuit package; (3) preparing a substrate having a front surface for die attachment and a bottom surface for solder ball implantation; (4) forming a plurality of solder-ball pads over the bottom surface of the substrate, each solder-ball pad having a specified size predetermined in accordance with the measured package warpage from said step (2) and the relation of solder ball height against pad size from said step (1); (5) forming a solder mask having a plurality of fixed-size openings over the bottom surface of the substrate, each solder mask opening behind aligned with one of the solder-ball pads on the substrate, wherein each solder mask opening is larger than the solder-ball pad retained therein; and (6) performing a solder-ball implantation process to implant a plurality of solder balls through the solder mask openings onto the solder-ball pads on the substrate, the implanted solder balls substantially having coplanarity after reflow over the solder-ball pads.