Advanced Metrology Suite to Link Residual Stress and Fundamental Properties in Semiconductor Packaging Polymers

Multicomponent thermosetting polymer composites are frequently used in semiconductor packaging. In these materials, residual stresses begin to develop during the manufacturing process as the material cures, shrinks, and solidifies. These stresses continue to evolve throughout the life of the package as hygrothermal conditions change. Residual stress is closely linked to the material’s reaction kinetics, liquid-to-solid transition, cure shrinkage, and hygrothermal interaction with surrounding components. Characterizing these behaviors requires specialized measurements, which can be difficult to perform on the complicated, proprietary formulations popular in industry. Here, we present a suite of advanced measurement approaches to evaluate the fundamental material properties of a commercial liquid encapsulant. Differential scanning calorimetry measurements reveal complex cure kinetics. Digital image correlation experiments confirm that the material shrinks during curing. Rheological measurements identify the liquid-to-solid transition. Thin film curvature measurements demonstrate that the liquid-to-solid transition predicts the development of residual stress during curing. Additional curvature measurements reveal that fluctuations in hygrothermal conditions can change the residual stress experienced by the fully cured material. When taken together, these experiments combine fundamental and part-scale measurements for a holistic understanding of residual stress in semiconductor packaging polymers.