Curing behavior and residual stresses in polymeric resins used for encapsulanting electronic packages

Abstract

ABSTRACT:Polymeric encapsulants are applied in electronic packages to improve the mechanical/thermal performance and the reliability of packaged devices. During the curing process of encapsulating resin, large residual stresses are generated due to the shrinkage of polymer and the mismatches in the coefficient of thermal expansion (CTE) between various package components. In addition, the rheological properties and curing kinetics of the resin also affect the nature and distribution of residual stresses. In this work, the rheological and curing behavior of encapsulating resins are characterized using an oscillatory rheometer. The resin viscosity is closely monitored against curing temperature excursion, which is correlated to exothermic reaction and weight loss as measured from the DSC and TGA analyses.The evolution of residual stresses in encapsulating resin is evaluated in a bimaterial strip bending experiment (BMSB) in situ within a DMA chamber. The CTE values are then calculated based on the thermomechanical analysis, which are well compared with those determined from other sources. A transition temperature, apart from the glass transition temperature, is identified from the study of the changes in resin flexural modulus and residual stress profiles.

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