Adhesion characterization of no flow underfill baselined with fast flow snap cure

Adhesion of underfill is critical to the reliability of a flip chip assembly. This paper focuses on characterization of underfill adhesion between underfill and Si/sub 3/N/sub 4/ passivated chip based on shear testing. A new die shear test vehicle is developed. The adhesion of a no flow underfill before and after post baking is investigated. It was found that post baking enhances the adhesion of the no flow underfill studied significantly. After post baking, the no flow underfill has similar adhesion to the passivated chip compared to a fast flow snap cure underfill used as baselines. In addition, the failure mode in the shear tests shifts from combined adhesive and cohesive failure in non-post-baked samples with no flow underfill, to underfill/substrate interface fracture in post baked samples.