| 摘要 |
PROBLEM TO BE SOLVED: To provide a ceramic substrate, which is excellent in heat radiation and has a high insulation property for a dielectric breakdown voltage and partial discharge, for a circuit board used for a power module so as to efficiently dissipate heat from a power semiconductor element.SOLUTION: A circuit board is constituted by forming a metal circuit 2 on one surface of a silicon nitride substrate 1 and forming a metal heat dissipation plate 3 on the other surface. In a silicon nitride circuit board including the circuit board, the integral pore volume in a diameter of 1 μm or more and less than 100 μm of the substrate surface, which is obtained by a mercury penetration method, is 0.05 cm/g or less (not including 0). The shortest distance from the end part of the circuit to the end part of the silicon nitride substrate is 0.8 mm or more. The difference between the shortest distance h1 from the end part of the circuit to the end part of the silicon nitride substrate and the shortest distance h2 from the end part of the heat dissipation plate to the end part of the silicon nitride substrate is set to 0-0.3 mm, thereby improving partial discharge start voltage to be 90% or higher of an insulation breakdown voltage. |
