Warpage in plastic packages: Effects of process conditions, geometry and materials

The effects of several important parameters, including processing conditions, package geometry and materials, are specifically studied on the occurrence of warpage and coplanarity for a plastic package. Special emphasis is placed on the evaluation of moulding compound properties and optimal processing conditions that can effectively minimize warpage. It is found that moulding compounds requiring a low moulding temperature and having a low coefficient of thermal expansion (CTE) can significantly reduce warpage. The elastic modulus was found to be inversely proportional to warpage, indicating the modulus should be kept as high as possible. The post-mould curing is essential to reducing warpage as it increases the glass transition temperature, but lowers the thermal shrinkage. A cross-shaped die paddle against a full square paddle, a thick die attach and a large die size are also favorable to reducing warpage.