The Temperature Cycling Characteristic of Copper Pillar Solder Joints
Yong Wang, S. Yu, Junhui Li
Abstract
In this paper, the temperature cycling reliability of copper pillar micro-bump joints was investigated. Copper pillar solder joints with different morphologies were obtained by varying the hot-press bonding process. A three-dimensional model was established using Ansys to analyze the stress-strain distribution of the solder joints under temperature cycle loading and to predict the fatigue life of the solder joints. It was found that the most vulnerable solder joints of flip-chip bonding were located at the outermost corners of the device; The thermal fatigue life of copper pillar solder joints was predicted based on the Darveaux model, and it was found that the hourglass-shaped solder joints had a strong resistance to thermal cycling; The orthogonal experiments revealed that the factors affecting the thermal fatigue life of copper pillar solder joints were ranked as follows: solder joint height > solder joint volume > copper pillar diameter. Reliability experiments were also conducted, and it was found that the cracks started from the contact surface between the copper pillar and the solder on the substrate and expanded from the IMC layer to the inside of the solder. The improved Darveaux can predict the thermal fatigue life of copper pillar solder joints more accurately.