Ceramic circuit board and production method therefor

A ceramic circuit substrate comprising:

• a circuit pattern provided on a ceramic substrate having two main surfaces,
• a braze material layer interposed between the circuit pattern and the ceramic substrate, and
• a protruding portion formed by the braze material layer protruding from an outer edge of the circuit pattern, wherein:
• the braze material layer comprises:
• 85.0 to 95.0 parts by mass of Ag;
• 5.0 to 13.0 parts by mass of Cu;
• 0.4 to 2.0 parts by mass of Sn or In;
• and
• 1.5 to 5.0 parts by mass of Ti,
• relative to 100 parts by mass, in total, of the Ag, Cu, and Sn or In, and
• Ag-rich phases are formed continuously for 300 μm or more, towards an inside of the circuit pattern, from an outer edge of the protruding portion along a bonding interface between the ceramic substrate and the circuit pattern, and the bonding void ratio is 1.0% or less.