Thermal Stability and Viscoelasticity Behavior of Underfill Encapsulants in Sustained High Temperature Environment up to 1-year

The Underfill encapsulants are widely used in FCBGA packages to improve the reliability. There is insufficient information on plastic encapsulated electronic components capable of surviving high temperatures for long periods (>100,000 hours). In this paper, the aging effects of a number of underfill encapsulants subjected to sustained high temperature long term aging have been studied. Four developmental UFs are cure and aged under two aging temperatures: 100C, below glass transition temperature, 150°C, above glass transition temperature. Results for uniaxial tensile tests are reported and analysis. The dynamic mechanical analyzer (DMA) and thermomechanical Analysis (TMA) are conducted to study the evolution of viscoelasticity, glass transition region and coefficient of thermal expansion as the function of aging time and temperature from pristine to 1 year. TGA tests are conducted to study thermal stability and weight loss change as the function of aging temperature and aging time. Both weight loss and derivative of weight loss as function of temperature are reported and analysis for samples under different aging time. SEM and optical microscope are applied to study the microstructure evolution of UFs.