Investigation of Copper and Glass Interaction in Through Glass Via (TGV) During Thermal Cycling

Glass interposers have attracted much interest from academia and industry because of the outstanding material properties of glass. However, the thermal mismatch between a copper via and glass causes reliability issues, such as glass and TGV cracking, copper via protrusion, and copper via sliding and delamination. This study investigated the copper and glass (Corning® HPFS® Fused Silica) interaction in TGV during thermal cycling. Optical profilometry was used to measure the copper via protrusion during thermal cycling. The TGV was heated up from room temperature (RT) 23°C to 400°C and then cooled to RT. An irreversible copper protrusion height was recorded at different temperatures. Furthermore, in-plane deformation of the glass caused by thermal mismatch is another reliability concern. Thus, two-dimensional digital image correlation (2D DIC) was applied to measure the in-plane deformation of the HPFS glass near the TGV during thermal cycling. The TGV sample was heated to 400°C from RT by a hotplate, and then the sample was cooled to RT using liquid nitrogen. The in-plane displacement of HPFS glass reached its maximum around 250°C, then it started to decrease because of the copper protrusion and copper material change at elevated temperatures.