MULLITE-ALUMINOSILICATE GLASSY MATRIX SUBSTRATES OBTAINED BY REACTIVECOATING

Layered kaolinite-alumina composites have been obtained by a sequentia l slip casting technique. The interfacial reaction as well as the micr ostructure of different layers have been studied in laminates fired at 1650 degrees C. The results are discussed on the basis of the SiO2-Al 2O3-K2O equilibrium diagram. Taking into account these results, a new low-cost ceramic substrate for electronic applications - reinforced by mullite whiskers and with controlled closed porosity, low permittivit y value (epsilon approximate to 4 at 1 MHz) and thermal expansion coef ficient close to that of silicon (3.8 x 10(-6) degrees C-1) - has been developed starting from conventional kaolinite powder.