The study of thermal mechanical reliability of different copper stud bump solder joints

With electronic production tending to be large scale integration, digital, lightweight, small-lot and diversification, the traditional bumping fabrication technologies aren´t compatible with the electronic production such as the personalized, medical implants, military and new product development micro-assembly electronic product for cost problem. And then the single chip bumping technology is introduced, among which the stud bumping technology becomes one the most important technologies due to compatible with wire bonding machine, no UBM, flexible and fine pitch fabrication advantages. And especially copper stud bump solder joint technology can be an effective way for low-cost flip-chip assembles. According to the assembly process, the two different solder joint interconnections, the bottom contact type and completely embedded type, are determined. By considering the two different interconnections and whether adding the under-fill to the gap between silicon and substrate, the four kinds FCOB are obtained, but only one-fourth model is used to reduce the computer work. The solder alloy, SAC305, is modeled as rate-dependant visco-plastic material using ANAND model. According the JEDEC JESD22-A104, the temperature cycle test is simulated in order to study the distribution of equivalent stress and plastic strain for solder joints array and to located the maximum stress and strain solder joint, then based on the energy solder joint life predication method Darveaux, the thermal cycle life of the four kinds FCOB are obtained and compared.