SILICON NITRIDE SUBSTRATE, CIRCUIT BOARD INCLUDING THE SAME, AND ELECTRONIC DEVICE

摘要

PROBLEM TO BE SOLVED: To provide: a silicon nitride substrate with improved strength of connection with metal while having excellent mechanical strength; a circuit board including the silicon nitride substrate; and an electronic device.SOLUTION: A silicon nitride substrate is made of a sintered body that is composed mainly of silicon nitride and has a surface serving as a surface connected with metal. Rhombohedral boron nitride exists in the surface. A content of the rhombohedral boron nitride is not less than 5 mass% and not more than 20 mass% with respect to 100 mass% of all ingredients in the surface. The silicon nitride substrate makes it possible to improve strength of connection with metal while having excellent mechanical strength.