2001 Volume 42 Issue 5 Pages 820-824
UBM-coated Si-wafer was fluxlessly soldered with glass substrate in N2 atmosphere using plasma cleaning method. The bulk Sn-37 mass%Pb and Sn–3.5 mass%Ag solders were rolled to the sheet of 100 \\micron thickness in order to achieve bonding to Si-wafer by fluxless 1st reflow process. The oxide layer on the solder surface was analyzed by AES (Auger Electron Spectroscopy). After 1st reflow the Si-wafer with a solder disk was plasma-cleaned, and soldered to glass by 2nd reflow soldering process without flux in N2 atmosphere. The thickness of oxide layer decreased with increasing plasma power and cleaning time. The optimum plasma treatment condition in this study was 500 W for 12 min and at this condition, 100% bonding ratio for Sn–3.5 Ag and over 80% bonding ratio for Sn–37Pb solder were achieved. The intermetallic compound of continuous Cu6Sn5 was observed along the Si-wafer/solder interface but discrete Cu6Sn5 along the glass/solder interface and the different shapes of Cu6Sn5 were caused by different thickness of Cu as a pad. The fracture of the tensile test specimen occurred at not only solder/UBM and solder/TSM interface but also in Si-wafer and glass substrate.