Study on thermo-mechanical reliability of embedded chip during thermal cycle loading

With the development trend of microelectronic system with small size, high speed, high frequency and high density, passive and active components are directly embedded into a core or high-density-interconnect layers. This System-in-Package (SiP) technology could shorten interconnection between the die and substrate and reduce the inductance and noise interference. However, there are many electrical and mechanical reliability issues including the reliability issue for embedded structure. An embedded structure was chosen in this study. The embedded chip was surrounded by epoxy. An epoxy was selected as the adhesive to embed the chip. The active surface of the chip was face up, to form a planar surface with the substrate. Benzocylobutene (BCB) was chosen as the dielectric polymer for embedding technology because of its low curing temperature. One quarter 3D model of embedded structure was loaded on six thermal cycles according to the temperature cycling standards JESD22-A104C. The thermo-mechanical reliability was investigated and the modified Coffin-Manson equation was employed to predict the fatigue life of copper films. FEA simulation results revealed that the fatigue life of copper film is 35.7 cycles. Stresses in the die always lead to various failures in manufacturing and using process, so equivalent von Mises stress and peel stress were also analyzed in this study.