Dynamic Resistance Monitoring of Nano Silver Paste during Sintering and Thermoelectric Aging Process

Abstract

：Due to the excellent thermal and electrical conductivity of nano-silver solder paste, it has attracted great attention in the packaging of third-generation semiconductors. Research on long-term service reliability of solder joints has always been a hot spot in the electronic packaging field. An in-situ dynamic resistance monitoring method is presented by a self-built corresponding real-time monitoring system. The resistivity (calculated from resistance) of silver paste joints are in situ monitored during the sintering process and the thermoelectric aging process. Moreover, by analyzing the corresponding microstructure and morphology evolution process of solder joints, a resistivity change model is established. The results show that the resistivity of the solder joint gradually decreases during the sintering process, and the change can be divided into three stages. In the first stage, the holding time is so short that no effective interconnection is formed in the solder joint, and the resistivity is extremely high. In the second stage, sintered necks are formed between the silver nanoparticles, and the resistivity decreases dramatically. In the third stage, the sintering necks grow, and the organics in the solder joints are completely volatilized, resulting in the gradually decrease of resistivity. In the thermoelectric aging process, the resistivity change can be divided into four stages. In the first stage, the resistivity rises with temperature. In the second stage, the densification behavior of the solder joint at high temperature causes the decrease of resistivity. In the third stage, the densification process is nearly completed and the resistivity remains stable. In the fourth stage, under the influence of the electromigration effect, silver atoms migrate from the cathode to the anode, resulting in cracks near the cathode, and the resistivity increases significantly until the solder joint fails.