Dielectric properties and crystalline characteristics of borosilicate glasses

Packaging substrates play a significant role in the development of large-scale integrated circuit. Low dielectric constant materials are expected in order to reduce the time delay of signal propaganda. On the other hand, sintering aid is required for low temperature co-firing process. Glass/ceramic composite system is considered one of the most promising candidates because of its both low dielectric constant and low temperature co-firable properties. Borosilicate glass is an important component of the substrate material as a sintering agent. To reduce the firing temperature, some of the alkali metal or bivalent metal oxides must be introduced, often at the expense of dielectric properties as well as crystallization behavior. The paper has designed two groups of glasses doped with different metal oxides. Dielectric constant and loss, crystalline characteristics as well as softening point and thermal expansion coefficient of these glasses have been studied. The glass system is characterized with lower dielectric constant (5-6) and loss (10(-2)-10(-3)), higher electric resistivity (10(12-13) Omega cm). Softening point of the glass is also satisfactory for low temperature co-firing process. Furthermore, the glass shows a severe tendency of phase separation and followed by crystallization, with cristobalite as the main crystal. (c) 2007 Elsevier B.V. All rights reserved.