Reliability evaluation of CSP soldered joints based on FEM and Taguchi method

Finite element method and Taguchi method were combined and related to evaluate the reliability of CSP soldered joints with various sets of parameters under temperature cycling. Garofalo–Arrheninus model was implemented to simulate the creep behaviour of soldered joints. It is found that the maximum creep strain is located at the upper surface of the soldered joint which is under the outermost of CSP chip. Subsequently, the L9(34) orthogonal array was applied for Taguchi experiment to investigate the effects of solder alloy, height of the soldered ball, chip thickness and substrate thickness on the reliability of soldered joints, results indicate that substrate thickness and height of soldered ball possess an important effect on the reliability. Furthermore, the above parameters were selected optimally towards the improvement of reliability, and result shows that the optimal parameter settings are that the solder is Sn3.8Ag0.7Cu, the ball height is 0.18 mm, the chip thickness is 0.1 mm and the substrate thickness is 0.42 mm, which could reduce the creep strain energy density by 78.4% compared with the original parameters.