| abstract |
High magnesium-content magnesium aluminosilicate glasses are used to form green tape compositions that are fired stepwise, i.e., first to about 500 °C to remove organic materials, then to a temperature 10-30 °C above the glass transition temperature for a time sufficient to nucleate the glass, and finally to a higher temperature near but below the softening temperature to complete crystallization of the glass. The resultant glass-ceramic may include substantial amounts of the forsterite crystalline phase. Multilayer ceramic printed circuit boards are made that are useful for high frequency, microwave applications. The fired high magnesium oxide content glasses have low dielectric constant and low dissipation loss factors, and they have a thermal coefficient of expansion that is compatible with metal or ceramic support substrates that impart mechanical strength to the printed circuit boards and that are thermally conductive. The boards are compatible with gallium arsenide devices. |