Mechanism investigation on die tilt in die attach process based on minimal free energy theory

Die attach process is widely used to realize the connection between the die, the device and the rest of the system in electronic packaging. In die attach process with solder, the reflow is necessary. During this process, the die moves under the action of capillary force induced by the liquid solder. A common phenomenon, die tilt usually occurs and strongly worsens the reliability and performance of devices. In this paper, the mechanism of die tilt in discrete style packages was studied by the numerical model based on minimal free energy theory. Die attach experiments were also conducted to verify the model. The comparison between experimental and simulation results proved that this model is flexible to predict the die tilt in die attach. Based on numerical results, it is found that the interface distortion of the solder layer at sharp die corners is the main reason to induce the die tilt.