Patent ID: 7031166
Filing Date: 2006-04-18
Classification: C01B,C01P,C04B,H01L,H05K,Y10S,Y10T

Abstract:
1. A circuit board comprising a metal circuit plate bonded to an electrically insulating substrate having bonding areas where electrodes are bonded to the surface of the electrically insulating substrate, wherein said electrically insulating substrate is a silicon nitride substrate constituted by a silicon nitride sintered body comprising Mg and at least one rare earth element selected from the group consisting of La, Y, Gd and Yb, the total oxide-converted content of said elements being 0.6–7 weight %, with Mg converted to MgO and rare earth elements converted to rare earth oxides RE x O y , in which nano-size, fine particles composed of Mg, at least one rare earth element selected from the group consisting of La, Y, Gd and Yb, and O and having an average particle size of 100 nm or less are observed in silicon nitride grains, in said silicon nitride sintered body, in a transmission electron micrograph having a magnitude of 10,000 times or more; an as-sintered surface layer being removed from said electrically insulating substrate in at least the bonding areas of said electrodes to said electrically insulating substrate surface; and an electrically insulating substrate surface, from which said as-sintered surface layer is removed, having a centerline average surface roughness Ra of 0.01–0.6 μm.