A comprehensive numerical analysis for preventing cracks in 2.5D glass interposer

Despite its many advantages, the glass interposer in 2.5D package has been largely restricted in use due to the formation of cracks in through-glass-via (TGV) structure. In this study, we systematically demonstrated the cracks in TGVs can be reduced or eliminated by selecting the appropriate glass material, annealing temperature, and Cu via structure. The energy release rate (ERR) of the circumferential and radial crack in the glass was analyzed using numerical simulation. The ERR of five different glasses which are fused silica, aluminosilicate, borosilicate, Gorilla, and ceramic glass was analyzed during annealing process. The ERR values of various glasses are ranked from highest to lowest as follows: fused silica, aluminosilicate, borosilicate, Gorilla, and ceramic glass. The ERR of the ceramic glass is 4.4 times lower than that of the fused silica glass. The overall ERR value of the ceramic glass is very low (less than 2 J/m²), unlikely to crack even when exposed to water. The types of TGV structure and Cu pad also affect crack formation. The hollow TGV with the Cu pad showed the lowest ERR. We also investigated the TGV crack formation when the 2.5D package with the glass interposer was subjected to thermal cycling condition. Even though the absolute ERR value is not large compared to that which occurred during the annealing process, cracks can still occur during thermal cycling. This study will provide a useful guidance to prevent thermomechanical cracks and ensure the reliability of the 2.5D package.