CBGA to FR4 printed circuit board with no underfill thermal mismatch study

With the turn of the century, EGA-type packages are now widely used in the micro-electronic industry. From a passive component manufacture that uses ceramic (Aluminia) as its main substrate carrier, the reliability of ceramic EGA (CBGA) packages mounted to FR4 printed circuit board is still a noteworthy concern. The reliability concern is for the different thermal expansion rates of the two-substrate materials and how that CTE mismatch creates added stress to the BGA solder joint when thermal cycled. The point of thermal fatigue in a solder joint is an important factor of CBGA packages and knowing at how many thermal cycles can be ran before failure in the solder EGA joint is a must for designing a reliable CBGA package. In this paper, one will describe a reliable, quick, FEA method to accurately predict the number of thermal fatigue cycles to produce a crack failure in the CBGA solder joint.