Method of achieving solder ball coplanarity on ball grid array integrated circuit package

摘要

A BGA (Ball Grid Array) package fabrication method is proposed for the purpose of achieving solder ball coplanarity on a warped BGA package, such as a concavely-warped BGA package or a convexly-warped BGA package. The proposed method is characterized in the provision of a plurality of variably-sized solder-ball pads over the bottom surface of the substrate, each solder-ball pad having a specified size predetermined in accordance with pre-measured package warpage and predetermined relation of solder ball height against pad size. This provision allows the use of a solder mask having fixed-size openings, as contrary to the prior art that uses a solder mask having variably-sized openings, to allow the implanted solder balls to achieve coplanarity and have strengthened shear for robust solder joint.