Glass-ceramic on metal substrates for high performance packaging

Abstract

Several glass-ceramic on metal coatings have been evaluated to address the need for a high thermal conductivity substrate. The substrate materials have been chosen and processed to given them thermal expansion coefficients which are similar to that of silicon, thus avoiding the creation of stresses in the device during thermal cycling. The thermal expansion matching of the glass-ceramic to the metal is achieved by the controlled crystallization of phases of known thermal expansion coefficients. This has been confirmed by X-ray and microstructural examination of a lithium aluminosilicate type glass-ceramic on copper/Invar/copper and of a magnesium aluminosilicate type glass-ceramic on molybdenum and on tungsten give values for the relative permittivity of the glass-ceramic layer of 5.9 and 5.8 respectively and values for tan delta between 10/sup -3/ and 10/sup -2/.<>