The role of water in delamination in electronics packages: water evaporation from epoxy

Water can act as an agent to weaken interfaces as well as a driving force to drive interfaces to delaminate. The magnitude of the build-up steam pressure driving delamination in electronics packaging is determined by the steam evaporation rate of the polymer. A thermogravitic methodology to characterize the steam evaporation rate of electronic polymer is developed. Isothermal weight loss experiments were conducted using epoxy to determine the evaporation rate at constant temperature. The experimental results indicated that the conventional estimate of water evaporation overestimated the measured rate by nearly two orders of magnitude. A thermally activated evaporation rate model is developed to model the dependence of the evaporation rate on temperature and water concentration. Analysis of the isothermal data revealed that ΔE_F, the activation energy for the evaporation of water from epoxy is 53.9 kJ/mol. and the constant F_o is 16 700 mm/s. Validity of the evaporation model in fast temperature ramping situation is then experimentally benchmarked and comparison of the data with the evaporation model gave good agreement.