Fast-Cure Lid Adhesive Development for Microprocessors

A lid or heat spreader is used for packaging microprocessor chips. There are two primary functions for the lid: dissipate heat efficiently from the microprocessor and provide physical protection to the fragile silicon die. To achieve these two functions, lid material, thermal interface material, lid adhesive and assembly process are key areas of development. Lid adhesive has a critical role in ensuring the whole microprocessor package meets thermal and thermo-mechanical reliability requirements for the microprocessor. Lid adhesive has to provide a good and consistent bonding strength to secure the lid to the organic substrate under various application conditions. At the same time, it also needs to absorb the stresses in the microprocessor package due to thermal mismatch of various materials: silicon, underfill, organic substrate, and lid. Another less known function of lid and adhesive is package warpage reduction. This paper discusses a low-stress lid adhesive material development that features a wide material processing window and fast-cure capability for assembly throughput improvement.