Finite Element Simulation Of Reliability And Life Prediction On Solder Joint Of MCM

In order to adapt the development of the integrated circuit, electronic productions must satisfy the requests of big power, high speed, high density, high precision, high reliability etc. Electronic packages develop in the direction of high density with ensuring the high reliability. Packaging technologies are changing at an ever more rapid pace. IC packages are becoming smaller in size, faster in speed, higher in power, stronger in elimination of the heat and lower cost. In addition to these, the numbers of electrical interconnection (I/O) in IC packages have been maximized. The multi-chip module (MCM) is one of new electronic packages and gets attention from the people in electronic industries. However, the reliability of the solder joint is one of the key factors during the development of MCM.The problems about the reliability of the solder joint are important and urging to solve in the electronic package. The reliability of the solder joint decides the quality and development of electronic production. In fact, heat is the main reason for the failure of electronic package. So the reliability study of the solder joint is very important under the condition of thermal recycle.In this paper, the lead-free solder Sn3.5Ag0.75Cu was chose in the simulation of MCM. A 3-D slice model of MCM was built using the soft ANSYS. Based on the Amand's constitutive model, the process of thermal cycle was simulated on the temperature condition from -55℃to 125℃. The position of the most danger solder joint and the region of the danger solder joint were decided. The variety rule of the stress and strain was acquired. The thermal fatigue life of the solder joint was predicted using the Darveaux's equation. The thermal fatigue life of the lead-free solder joint Sn3.5Ag0.75Cu contrasted with the Sn37Pb solder's thermal fatigue life.The reliability of the lead-free solder joint was assessed. The research finds: During the thermal cycle, the little chips around the big chip are the most danger; the edges of the chip are most danger in the same little chip. The equivalent deformation, equivalent stress and equivalent strain of solder joints under the same chip increase from centre to edges. The dangerous solder joint is in the edge far from the centre of the little chip. Stress and strain are biggest is in the region where the danger solder ball joints with pad. The most dangerous spot is in the edge of the top surface of the dangerous solder joint and the crack comes into being on this spot and expends from there. The accumulation of inelastic strain is obvious during the fluctuation of temperature, but not obvious under constant temperature. The reason is that both temperature and stress combine to affect the accumulation of inelastic strain. So the fluctuation of temperature is the main factor that affects the life of the solder joint. The Darveaux's equation was used to predict the thermal fatigue life of the Sn3.5Ag0.75Cu solder joint. The Sn3.5Ag0.75Cu solder joint's life is longer than the 63Sn37Pb solder joint's by contrasting with each other.