Preparation of lower alkyl polysilsesquioxane and formation of

Abstract

A lower alkyl polysilsesquioxane having a general formula ##STR1## wherein R is CH.sub.3 or C.sub.2 H.sub.5, and n is an integer equal to about 50 to about 10,000, prepared by (a) dissolving a lower alkyl trifunctional silane in an organic solvent at a temperature of -20.degree. C. to -50.degree. C. to form an organic solution thereof; (b) hydrolyzing the lower alkyl trifunctional silane by dropping water into the organic solution at a temperature of -20.degree. C. to -50.degree. C. under an inert gas pressurized at 1,000 to 3,000 Pa; and (c) gradually heating the organic solution together with a water phase lying therebeneath up to a temperature of 60.degree. C. to 100.degree. C. under an inert gas pressurized at 1,000 to 3,000 Pa. Also, a flat surfaced insulating layer of a silylated organopolysilsesquioxane having a general formula ##STR2## wherein R is an alkyl or phenyl group, and n is an integer equal to about 50 to about 2,000, preferably about 50 to about 500, formed on a circuit board having stepwise differences in height thereon, by applying an organic solution of the polymer; evaporating the solvent; and melting the polymer to flatten the surface of the polymer and curing the polymer.