In recent years, PCB drills with smaller diameters less than 0.1 mm are used and thus there are growing needs for ultra-fine grained cemented carbides. However, ultra-fine WC powder usually causes extraordinary grain growth during sintering which weakens mechanical strength of ultra-fine grained cemented carbides. So we examined several kinds of WC powders to make new ultra-fine grained cemented carbides having superior performance. We found that direct carburized WC powder is very good as a WC raw material. The PCB drills made of the developed ultra-fine grained cemented carbides have higher hardness, toughness and stiffness than conventional ones.

• Okuno
• Takuya
• Hirose
• Kazuhiro
• Moriguchi
• Hideki
• Yamamoto
• Eiji
• Uchino
• Katsuya
• Kitagawa
• Nobuyuki