Thermal compression bonding challenge: Interposer attachment technology for next generation package-on-package structure

According to smart phone application trend, in nowadays, the application processor of the smart phone with higher performance and power efficiency that will be required. Therefore, in this study, it reports the development of alternative current PoP (package-on-package) structure with routable substrate interposer for stacking solution. Interposer will be alternative PoP for wide I/O approach, and the package can be directly connected with high I/O counts memory by interposer as the transmission medium to achieve the product requirement and will be the next generation PoP structure. However, the key challenge of the thin interposer and substrate are how to overcome the large war-page by thermal bonding process effect. Hence, in this research, thermal compressing bond was chosen to decrease the thermal war-page effect. According to the crosssection photo, it shows that the solder joint clearly forms a good joint shape of the interposer and bottom flip chip substrate. And there are without any shift, crack or non-wetting observed. The results clearly indicate successful formation of the solder joints through the adoption of using thermal compress bond processes. Furthermore, thermal compressing bond technology is also proven for ultra fine pitch flip chip thin package process application [1] and well controlled the war-page effect.