Study on the behavior characteristics of solder balls for FCBGA package

Abstract

Warpage issues are of concern for flip chip Ball Grid Array (FCBGA) package reliability on thin substrates. Despite advantages in electrical performance of thin substrates, FCBGA warpage hampers reliability of the solder balls making up the ball grid array. Warpage and plastic strain of both the FCBGA package and solder balls are calculated under assembly conditions. Temperature dependent material properties were investigated using finite element analysis. FEM calculations of thermal deformation and equivalent plastic strain of solder balls considered to determine overall reliability of the solder balls. Solder ball plastic strain decreased with substrate core thickness. This can explain why solder ball reliability decreases with substrate thickness. Substrate surface warpage fluctuated significantly as core thickness decreased due to reduced stiffness. In addition, it is possible that solder balls and surface mounted components can be affected by surface fluctuations. Although thinner substrates have advantages in terms of electrical performance, high warpage is a critical root cause of package failure. Despite these tradeoffs, developing thinner substrates while avoiding warpage is a forefront issue.