Study On High Thermal Expansion LTCC Substrate

Low temperature co-fired ceramics was used to package the system with high thermal expansion such as steel, that is required that materials possess high coefficients of thermal expansion.In this paper, there are two approaches to obtain ceramic composites. The one approach is glass-ceramics, the other approach is glass/ceramics composite. Firstly, the developed glasses were characterized through measurement of different properties, thermal property, coefficient of thermal expansion, crystallization behavior, dielectric constant etc. In addition, ZrO2, P5O2, TiO2 were doped in BaO-CaO-SiO2 (BCS) glass-ceramics as nucleating additives to study crystallization dynamics. Secondly, BaO-Al2O3-B2O3-SiO2 (BABS) glasses were prepared to study the thermal properties by thermal expansion testing and differential thermal analysis. The glass was further incorporated with silica to prepare glass/ceramics composites. The shrinkage behavior, crystalline phases, coefficient of thermal expansion and dielectric constant of the composites were investigated by sintering, XRD and so on.The results show:(1) BCS glass-ceramics has low crystallization temperature, sintering temperature and high coefficient of thermal expansion. After sintering process at 900℃/10min., BaSi2O5 phase was formed in the glass-ceramics with 41%BaO-6%CaO-53%SiO2 (mol%). The density, coefficient of thermal expansion and the dielectric constant of the sample are 3.54,12x10-6/K and 6.6 respectively, which is desirable for LTCC application.(2) The BABS system glass possesses low glass transition temperature and high coefficient of thermal expansion. The 50%BaO-7.5%Al2O3-30%B2O3-12.5%SiO2 (mol%) glass/tridymite composites have low dielectric constant. The composite at the ratio of 1:1 could result in high quality samples at 850℃/10min. The porosity, coefficient of thermal expansion and dielectric constant of the sample are 3.4%,5.3 and 12.18×10-6/K respectively.