Shinichi Tachizono

Lead-Free Low-Melting and Semiconductive Vanadate Glass Applicable to Low-Temperature Sealing

We optimized the fundamental composition and additives in a semiconducting V2O5–P2O5–TeO2 glass system to develop lead-free low-melting glass suitable for low-temperature sealing below 400 °C. Glass with a composition of 55.7V2O5–19.8P2O5–23.5TeO2 (mol %) has a low glass transformation temperature (Tg < 300 °C) as well as hard crystallization, and it is desired as a low-temperature sealing material. The effects of adding BaO, Sb2O3, MnO2, or Fe2O3 to the fundamental composition of 55.7V2O5–19.8P2O5–23.5TeO2 (mol %) on the thermal properties and water-vapor resistance were then characterized. Adding 11.7 mol % Fe2O3 improved the water-vapor resistance drastically and decreased the thermal expansion coefficient without increasing Tg. Sealing at 360 °C with our lead-free Fe2O3-added vanadate glass enabled practical airtight packaging on an electronic device.