Failure life prediction and factorial design of lead‐free flip chip package

Abstract

Abstract As is well known, the design parameters of the packaging material and structure greatly influence the reliability of the packaging. When it comes to flip chip packages, the package reliability design becomes more complicated. In addition, the interactions between these different design parameters remain unclear, especially for lead‐free solder applications. Based on the above, FEM factorial analysis was employed in this study to investigate the interrelationship of the design parameters. A factorial analysis with two levels and five factors was chosen. The factors included pre‐solder thickness, thickness of the BT core in the laminate substrate, bumping height, substrate side pad opening, and the climbing height of the underfill. The factorial design method was repeated twice with two kinds of solder bump materials (63Sn/37Pb and 96.5Sn/3.5Ag). The findings show that the structures with the larger BT core thickness, thicker pre‐solder layer and higher bump height have the better solder bump reliability. In terms of the factorial analysis, the BT core thickness was the factor having the most influence on reliability. The interactions between the factors were observed in this study.