Advanced through-glass via (TGV) electro-filling and solder bumping for miniaturized 3D MEMS packaging

In this study, we have fabricated a glass interposer containing through-glass via (TGV) using laser-modified chemical etching (LMCE). Further, the conductive filling of TGVs was achieved by the electroplating method using an acidic bath. The bottom-up Cu-filling in TGVs was obtained by applying pulse periodic reverse (PPR) current electroplating. Further, lead-free Sn-57Bi-0.3Ag solder bumps were also deposited on Cu-filled TGV using an acidic sulphate bath. The eutectic Sn-Bi-Ag solder was obtained at a current density of −55 mA/cm². The Sn-Bi-Ag solder bumps were bonded to Cu-filled TGV at 170 °C for 30 s. Subsequently, the shear strength of the Sn-Bi-Ag/Cu/TGV joint was studied. The findings show that a smooth and defect-free interface without any brittle Bi and Ag₃Sn intermetallic compounds (IMCs) was formed across the joint. With an increase in shear speeds from 0.5 to 10 mm/s, the shear strength initially increased to 96 MPa, and then dropped when the shear speed exceeded 10–500 mm/s. It was shown that the ductile fracture mode gradually vanished beyond the shear speed of 10 mm/s and turned to brittle fracture completely at 500 mm/s. It is concluded that with further in-depth research, TGV technology holds enough potential to serve as a viable alternative to Through-Silicon Via (TSV) technology for miniaturized electronic devices.