| 摘要 |
PROBLEM TO BE SOLVED: To provide a silicon nitride board having high strength and toughness, 90 W/mK or higher thermal conductivity, high joining strength to a circuit layer and extremely enhanced heat cycle-resistant characteristics. SOLUTION: The method for manufacturing a silicon nitride sintered compact comprises sintering a planar silicon nitride compact, which is obtained by compacting a powdery mixture obtained by adding a magnesium compound and the oxides of at least one metal selected from the group of yttrium and lanthanide group to silicon nitride powder and has 0.3 μm or smaller surface roughness (Ra value), in pressurized nitrogen atmosphere at 1,750-1,900 deg.C. The silicon nitride sintered compact for a circuit board obtained by this method has 0.6 μm or smaller surface roughness (Ra value). |
