The Role of Glasses on Alumina-Glass Composites

Abstract

Recently, alumina-borosilicate glass composites have been applied as a substrate material for hybrid IC and LSI multi-chip packaging. In this paper, the effects of the composition of borosilicate glasses on the properties and the microstructure of alumina-borosilicate glass composites were studied. These composites were divided into the three groups by composition of borosilicate glasses. In the first group, no crystallization is found. In the second group, crystallization of SiO2 is found. And in the third group, compound by the reaction between alumina and glass is precipitated. It was found that the composites become gradually difficult to densify in the above mentioned order. In the first group, the sintering temperature of the composites has relation to the softening temperature of the glasses. In the composites belonging to the third group, many pores were formed when crystallization occurred. Dielectric constant of the composites depends on the glass compositions, leading to a conclusion that the glass systems with low dielectric constant are desired. On the contrary, thermal expansion coefficient of the composites depends on the crystalline phases, so we need to choose low thermal expansion glasses which do not crystallize or glasses in which crystalline phases of low thermal expansion is precipitated during sintering. It is also important to control the ratio of glass in the composites and the firing conditions.