Vicky Wang, Henkel Loctite (China) Co. Ltd. and Dan Maslyk, Henkel Corp. show how underfill type and strategy will be key to enabling highly reliable PoP devices. Though many studies have investigated the board-level reliability of package-on-package (PoP) devices in relation to drop test and thermal cycling performance, packages manufactured with and without underfill and the impact of different underfill dispensing patterns (i.e., full underfill, cornerbond and edgebond), few studies have evaluated the effects of the underfilling strategy — such as underfilling the bottom component only or underfilling both top and bottom components — or the effects of solder alloy choice on the reliability of PoPs. This article presents findings from a recent study on the drop test reliability of PoP devices as a function of underfill dispensing type and PoP ball alloy type.
