| 摘要 |
PROBLEM TO BE SOLVED: To provide a lapping plate having high stiffness, surface roughness small of which can be made fine allowing little surface roughening in an acid cleaning process. SOLUTION: This lapping plate has a sintered structure, where a density of air holes observed in a mirror surface by an optical microscope, is less than 1000 per 1 mm<2> , and an average of crystal size is 3-100 μm when the mirror is formed out, and the plate is formed of a sintered alumina body with the purity >=99.9%. The manufacture of the lapping plate comprises a process preforming alumina powder with the purity >=99.9% together with binder, a process humidifying the preformed body, a process of pressure-forming the humidified preformed body, and of a process sintering the preformed body. In the sintering process, the maximum temperature is >=1550 deg.C, the lapping plate is held at 1000 to 1200 deg.C until the temperature reaches the maximum temperature, and furthermore, a heating rate is 5 deg.C/hour to 30 deg.C/hour in a temperature range of 1000 deg.C to 1500 deg.C. |
