Development of sealing glass and fiber type sealant for laser sealing

Abstract

The sealing method using a laser has been widely used since laser beams supplied locally the necessary energy to allow the formation of a hermetic bonding. The most common sealing techniques using a glass frit and a screen printer have some problems such as pores, non-uniform height, imperfect hermetic sealing. To reach high quality of laser sealing, the difference of coefficient thermal expansion (CTE) between the laser sealing glass and glass substrate should be lower than 1.0×10^-6/K. In order to prove the feasibility of novel laser sealing glass as a fiber type sealant, PbO-SiO₂-Al₂O₃-B₂O₃ based glass system was drawn with fiber types ranging from 180 μm to 1000 μm in diameter. CuO and Na₂CO₃ were added into PbO-SiO₂-Al₂O₃-B₂O₃ glass system in order to tuning the CTE. The thermo mechanical and thermal properties were investigated for correlations the CuO and Na₂CO₃ concentrations with PbO-SiO₂-Al₂O₃-B₂O₃ glass system. The 1wt% CuO and 1wt% Na₂CO₃ co-doped PbO-SiO₂-Al₂O₃-B₂O₃ glass system shows the CTE of 9.53×10^-6/K. In this study, the FTO-coated glass substrate with a CTE of 10.23×10^-6/K was sealed with fiber type sealant made of the CuO and Na₂CO₃ co-doped PbO-SiO₂-Al₂O₃-B₂O₃ glass system. These results indicate that the fiber type sealant is feasible as laser sealing material in the packaging industry.