Effects of viscosity and wettability of Pb-B-Si-O glass in silver paste on the co-firing densification of LTCC

Low temperature co-fired ceramic (LTCC) technology is gradually becoming the mainstream integration technology for electronic devices due to its high density, multi-function, and high-reliability packaging. Ag is widely used in the surface wiring and interconnection of LTCC modules. Due to the difference between Ag and LTCC densification behaviors during sintering, co-firing defects may occur, such as delamination, warping, and low density of electrode film. In this work, we selected the lead borosilicate glass/Al2O3 system as the ceramic matrix (America, Dupont 951PT). To reduce sintering mismatch, Pb-B-Si-O glass frits was employed as an additive to prepare the silver electrode. And the effects of glass viscosity, wettability between glass and silver, the microstructures of silver electrodes were studied. The results showed that the suitable viscosity of glass used in silver paste is critical to the sintering densification process. When high-temperature viscosity of glass decreased sharply, the dense structure of the film was formed too early, the gas produced by sintering of green tape can’t be discharged, forming closed pores. Pores partially break through the silver electrode film, with the glass phase overflowing, damaging the dense structure. The properties of silver electrode in LTCC could be improved by simply changing the composition of glass used in silver paste.