Research on the Reliability of Interconnected Solder Joints of Copper Pillars under Random Vibration

In this paper, the reliability of copper pillar micro-bump under random vibration is investigated. Three kinds of copper pillar solder joints with different morphologies were obtained by changing the hot press bonding process, and the random vibration fatigue simulation of flip-flop interconnect solder joints was carried out by using Ansys to obtain the stress–strain distribution law of the solder joints and predict the vibration fatigue life of the solder joints. It is found that the outermost solder joints of flip-flop bonding are most likely to fail; the fatigue life of copper pillar solder joints is predicted based on the three interval method, the Miner linear cumulative damage criterion and the high cycle fatigue formula; reliability experiments are conducted, and it is found that the drum solder joints are most prone to cracking, followed by hourglass and columnar shapes and that all cracks are caused by the substrate side of copper pillar. Cracks are sprouted from the contact surface between the copper pillar and solder on the substrate side and expand internally in the intermetallic compound (IMC) layer, while the presence of voids aggravates the generation of cracks.