Abstract
Warpage determination and minimization in molded plastic packages is critical to package reliability, especially for large plastic packages. Power modules with exposed heat sinks fall in this category. Seamless contact of these power modules with the external heat sink, or cold plate, is also required for effective thermal dissipation. Hence, accurate prediction of warpage is very important for reducing the design cycle time for this class of packages.
Conventional modeling methodologies maintain the assumption that the package is stress-free and undeformed at the molding temperature. Warpage prediction is typically based solely on the differential thermal expansion of the package materials during cool down from the mold temperature. These assumptions, however, result in a large discrepancy between the predicted warpage and the actual measured warpage. This study resolves this disparity by proposing a methodology which accounts for the impact of polymerization of the mold compound on package warpage after the package is removed from the mold.
A hybrid FEM and experimental methodology has been developed which determines the impact on package warpage prediction due to polymerization, in addition to the differential thermal contractions of the various materials in the package during the cool down process after mold release.
