Abstract: A metal-ceramic composite substitute is produced by joining a metal plate to a ceramic substrate by using a brazing material in a paste form prepared by adding 10-14 parts by weight of a vehicle to 100 parts by weight of a powder of which the solid centent comprises 90.0˜99.5% of an Ag powder, 0˜9.5% of a Cu powder and 0.5˜4.0% of an active metal powder, and 0.0˜0.9% of a titanium oxide powder if necessary.

Abstract: A metal-ceramic composite substitute is produced by joining a metal plate to a ceramic substrate by using a brazing material in a paste form prepared by adding 10-14 parts by weight of a vehicle to 100 parts by weight of a powder of which the solid centent comprises 90.0˜99.5% of an Ag powder, 0˜9.5% of a Cu powder and 0.5˜4.0% of an active metal powder, and 0.0˜0.9% of a titanium oxide powder if necessary.

Abstract: In the present invention, a metal-ceramic composite substitute is produced by joining a metal plate to a ceramic substrate by using a brazing material in a paste form prepared by adding 10-14 parts by weight of a vehicle to 100 parts by weight of a powder of which the solid centent comprises 90.0˜99.5% of an Ag powder, 0˜9.5% of a Cu powder and 0.5˜4.0% of an active metal powder, and 0.0˜0.9% of a titanium oxide powder if necessary.

Abstract: A metal-ceramic composite circuit substrate having a ceramic substrate and a metal plate joined to at least one main surface of the ceramic substrate, the rate of voids formed on at least a joint surface at a semiconductor mounting portion of the metal plate per unit surface area being not more than 1.49%. The diameter of void formed on at least the joint surface at a semiconductor mounting portion of the metal plate is not larger than 0.7 mm. The surface undulation of the ceramic substrate is not more than 15 .mu.m/20 mm measured by a surface roughness tester in case that the ceramic substrate is joined directly to the metal plate. The metal plate is joined to the ceramic substrate through a brazing material containing at least one active metal selected from a group consisting of Ti, Zr, Hf and Nb. The ceramic substrate is at least one kind of ceramic substrate selected from a group consisting of Al.sub.2 O.sub.3, AlN, BeO, SiC, Si.sub.3 N.sub.4 and ZrO.sub.2.

Abstract: A paste of active metallic brazing material is applied to the entire surface of each side of aluminum nitride or alumina ceramic substrate 1; circuit forming copper plate 3 having a thickness of 0.3 mm is placed in contact with one surface of the substrate and a heat dissipating copper plate 4 having a thickness of 0.25 mm placed in contact with the other surface; the individual members are compressed together and heated at 850.degree. C.

Abstract: A conductor pattern is formed on at least one surface of an AlN- or Si.sub.3 N.sub.4 -based ceramic substrate which is such that the ratio between the principal metal component binding with N to form the ceramic mass and the B in the BN remaining on the surface layer is no more than 50.times.10.sup.-6 as either B/Al or B/Si, wherein B/Al represents the ratio of I.sub.B to I.sub.Al where I.sub.B is the X-ray diffraction intensity of boron present on the surface layer and I.sub.Al is the X-ray diffraction intensity of aluminum, and B/Si represents the ratio of I.sub.B to I.sub.Si where I.sub.B is as defined above and I.sub.Si is the X-ray diffraction intensity of silicon. The thus produced circuit board has both a peel strength of at least 30 kg/mm.sup.2 and a capability of withstanding at least 30 heat cycles and, hence, satisfies the performance requirements of the recent models of power module ceramic circuit boards.