Interface toughness characterization in microelectronic packages based on four point bending test and simulation

Microelectronic packaging devices consist of various kinds of materials, such as: die, molding compound, adhesives, copper etc. Due to the mismatch of the materials coefficient of thermal expansion (CTE), thermal stress can accumulate in the device, which would cause the interface delamination of microelectronic packaging devices when ambient temperature changes, and eventually lead to the failure of microelectronic packaging devices. In order to predict delamination, interface properties should be obtained. According to the research, temperature has large effects on the interface toughness. Therefore, interface toughness as function of temperature was studied by experiment and simulation in this paper. The results show that the critical crack energy was affected by temperature largely, the higher the temperature is, the smaller the critical crack energy is. The load speed has no effects on the four-point bending test. Experiments show that the delamination propagation load is stable and the crack propagation load is almost constant after the delamination start. According to the crack propagation load, the interface fracture toughness value (Gc) is obtained from four point bending tests combined with simulation of fitted the crack propagation load. The result of Gc values of formula and simulation can be compared. The critical displacement (Vc) can be estimated by fitting the deformation of the glue between the copper and molding compound with simulations.