Abstract: A ceramic substrate, suitable for use as a circuit substrate on which integrated circuit chips are bonded, which consists essentially of, based on the weight of the substrate, 0.5.about.5.0% by weight of MgO, and 95.0.about.99.5% by weight of the total of Al.sub.2 O.sub.3 and SiO.sub.2, the proportion of the Al.sub.2 O.sub.3 to the SiO.sub.2 being in the range from 50:50 to 80:20 by weight.

Abstract: A method of forming a ceramic circuit substrate allowing mounting of high integration density semiconductor elements. The method provides a multilayered ceramic circuit substrate having via holes formed with high accuracy and high integration density wiring patterns by forming metallic conductive balls to connect the conductive wiring patterns of upper and lower layers; a ball arranging plate having many holes placing on a green sheet uniformly in close contact; filling the holes of the plate with the embedding the conductive balls by pressure into the green sheet; and thereafter baking the green sheet individually or in a stacked layered arrangement.

Abstract: A multilayer circuit board (10) for putting semiconductor devices thereon consists of conductor layers (6, 60, 61, 62, 63) made of a metal selected from the group consisting of Au, Ag, Cu and an alloy thereof, insulating material (2, 7) made of glass-ceramic and an alumina sintered plate (1). The glass-ceramic is comprised of borosilicate glass and alumina and has a low dielectric constant and a thermal expansion coefficient approaching that of the semiconductor devices. The alumina sintered plate (1) is placed between the ground and supply voltage conductor layers (62, 63) and the signal conductor layers (60).

Abstract: In a method of manufacture of a multilayer ceramic board, a conductor land is formed and baked on a first substrate. A second substrate on which the wiring pattern is formed is then electrically connected to the first substrate via the land. An error in the substrate due to shrinkage at the time of sintering is thereby compensated by the conductor land. This assures the formation of a highly accurate wiring pattern on the sintered substrate surface, despite shrinkage of the ceramic during sintering of the raw sheets of ceramic.

Abstract: Disclosed is an alumina substrate having a high density, a high degree of surface smoothness and excellent dielectric properties and a process for its manufacture. The process comprises prefiring a green sheet prepared from alumina powder at an elevated temperature, for example between 1200.degree. and 1350.degree. C., to remove combustible substances from the sheet, treating the resultant prefired substrate with an acid aqueous solution to eliminate acid-soluble and decomposable substances from the substrate, and firing the acid-treated substrate at an elevated temperature, for example between 1500.degree. and 1650.degree. C.

Abstract: An improved alumina substrate comprising alumina and magnesium oxide has a surface finish of no more than 0.05 .mu.m CLA and a density of at least 3.90 g/cm.sup.3 in an as-fired condition and is composed of alumina grains which are sufficiently grown to have straight grain boundaries and flat surfaces to form a surface of the substrate. The improved substrate is produced by firing a green sheet having a high content of raw material powder and a density of more than 2.60 g/cm.sup.3 at a temperature of 1525.degree. to 1650.degree. C. The green sheet with high density is formed by the process of aggregating an organic agent and a high purity alumina powder by dry milling and casting the resultant slip.