Abstract: A phenolic resin obtained by reacting a phenol with an aromatic aldehyde and a xylylene compound represented by the formulaROH.sub.2 C(C.sub.6 H.sub.4)CH.sub.2 ORwhere R is hydrogen, an alkyl group having a carbon atom number of 1-4, or an acyl group having a carbon atom number of 2-4 in the presence of acid catalyst, with the sum of aromatic aldehydes and xylylene compounds to phenols molar ratio being 0.1-0.95, and the xylylene compounds to aromatic aldehydes molar ratio being 0.1-1.4.The phenolic resin thus obtained is useful as an industrial material by virtue of its excellent moisture resisting property, alkali resistance and fair thermosetting property. Having low moisture absorption ratio and high glass transition temperature, this phenolic resin is also suitable used as hardener for semiconductor encapsulating epoxy resin which has excellent package crack resistance after solder dipping and high reliability.

Abstract: A process for the preparation of a silicon carbide sintered body of high purity which has a content of 1 ppm or less of each atom harmful to the manufacture of semiconductor equipment including the step of shaping a silicon carbide powder, calcining the shaped body in a non-oxidizing atmosphere to form a porous body, and subjecting the porous body to reaction sintering while being impregnated with molten metallic silicon. The starting silicon carbide powder also has a content of 1 ppm or less of each harmful atom and it has a free carbon content of not greater than 20% by weight and an average particle diameter of 0.5-20 .mu.m.

Abstract: A heat-resistant, electrical insulating layer which is suitable for use as an insulating substrate in printed circuit boards and as an insulating film for semiconductor devices and which surpasses a polyimide-based insulating layer with respect to heat resisting properties, dielectric properties, and water absorption. The insulating layer comprises a polycondensed fused polycyclic, polynuclear aromatic resin prepared by a polycondensation reaction of a starting material with a crosslinking agent in the presence of an acid catalyst. The starting material is selected from the group consisting of fused polycyclic aromatic hydrocarbons which may have a hydroxyl group as a ring substituent and mixtures of a fused polycyclic aromatic hydrocarbon and a monocyclic aromatic hydrocarbon both of which may have a hydroxyl group as a ring substituent. The crosslinking agent is an aromatic compound having at least two hydroxymethyl or halomethyl groups as ring substituents.

Abstract: A process for the preparation of a beta-silicon carbide powder of high purity which is suitable for use in the manufacture of semiconductor equipment and which has a content of 1 ppm or less of each atom harmful to the manufacture of semiconductor devices. The process comprises preparing a carbon- and silicon-containing starting mixture comprising (a) at least one siliceous material selected from liquid silicon compounds and solid siliceous substances derived from a hydrolyzable silicon compound, and (b) at least one carbonaceous material selected from polymerizable or cross-linkable organic compounds prepared in the presence of a catalyst which is substantially free from atoms harmful to the manufacture of semiconductor devices. The starting mixture comprises at least one liquid substance used as component (a) or (b). The starting mixture is then solidified by heating and/or by use of a catalyst or a curing agent.

Abstract: A condensed polycyclic, polynuclear aromatic thermosetting resin with improved moldability which is prevented from forming a cloud on a mold during molding is disclosed. The resin is a prepolymer derived by condensation polymerization of a condensed polycyclic aromatic compound or a mixture thereof with a monocyclic aromatic compounds and an aromatic compound having at least two hydroxymethyl groups as a crosslinking agent in the presence of an acid catalyst. The resin has a flow temperature of not higher than 150.degree. C. The acid catalyst is water-insoluble or when it is water-soluble the resin has an insolubilized acid ratio of at least 50%. The resin is useful in the manufacture of thermoset molded articles having good heat resistance and good mechanical and electrical properties. It can be blended with a filler and/or reinforcing agent to form a molding compound.