| 摘要 |
PROBLEM TO BE SOLVED: To improve surface insulation resistance and to prevent the propagation loss of a signal at a high-frequency band from being generated by forming a ceramic substrate with a non-oxide ceramic substrate and making specific the surface roughness. SOLUTION: A layer 2 made of at least one type of metal out of titanium and chrome is provided on the surface of a ceramic substrate 1, and further a copper layer 3 is laminated on it. A non-oxide ceramic substrate, such as an aluminum nitride substrate, is used as the ceramic substrate. By setting the surface roughness of the ceramic board 1 to less than 1μm at Rmax, surface insulation resistance can be increased and the propagation loss of a signal at a high-frequency band can be prevented. When the surface roughness is 1μm or greater, a propagation loss is generated when a signal at a high-frequency band is propagated and the layer 2 and the copper layer 3 made of at least one type of metal out of titanium and chrome remains on the surface of the ceramic board 1 when performing etching, thus reducing the surface insulation resistance of the ceramic board 1.
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