Structure and sintering behavior of BaO–SrO–B2O3–SiO2 sealing glass for Al2O3 ceramic substrates

Abstract

BaO–SrO–B2O3–SiO2 sealing glass for Al2O3 ceramic substrates was prepared and the effect of B2O3 on its structure, sintering behavior, and properties was studied. Owing to the fluxing action of B2O3, the glass transition temperature, sintering temperature, and crystallization temperature of the sealing glass were decreased with increasing B2O3. With an increase in the B2O3/SiO2 ratio, the average bridge oxygen number of the glass network first increased and then decreased, and the boron abnormality phenomenon was detected at a B2O3/SiO2 ratio of 0.55, at which the polymerization degree of the glass network was maximized. Furthermore, the precipitation of BaAl2Si2O8 crystals was promoted and the crystallinity of the sealing glass was increased, inhibiting sintering densification and weakening the material. The sealing glass with a B2O3/SiO2 ratio of 0.55 sintered at 800 °C for 10 min showed the best properties: a thermal expansion coefficient of 7.89 × 10−6 K−1, flexural strength of 114.28 MPa, Vickers hardness of 622.98 HV, dielectric constant of 12.14, and a dielectric loss value of 4.11 × 10−3. After the sealing glass was co-sintered with the Al2O3 ceramic substrate, the interface was tightly bonded. This indicates the great potential applicability of BaO–SrO–B2O3–SiO2 sealing glass for Al2O3 ceramic substrate packaging.