To shallow the depth of a pit without deteriorating productivity so much by using a second abrasive grain liquid containing abrasive grains smaller than abrasive grains of this liquid after performing work by using a first abrasive grain liquid.
As the first stage, lapping of 50 μm is performed by a first abrasive grain liquid (the maximum particle size is not more than 23 μm, the particle size of a 3% point of an accumulation height is not more than 20 μm, the particle size of a 50% point of the accumulation height is 7.1±0.7 μm and the particle size of a 94% point of the accumulation height is not less than 4.0 μm). Afterwards, lapping of 30 μm is also performed by a second abrasive grain liquid (the maximum particle size is not more than 19 μm, the particle size of a 3% point of a cumulative height is not more than 17 μm, the particle size of a 50% point of the cumulative height is 5.5 μm and the particle size of a 94% point of the cumulative height is not less than 3.0 μm). Thus, a work can be efficiently flattened in the first place by the abrasive grain liquid containing abrasive grains having the comparatively large particle size, and the depth of a pit can be reduced in the next place by the abrasive grain liquid containing abrasive grains having the small particle size.
MIYAZAKI SEIICHI
YOSHIDA MASAHIKO
HAYASHI NOBUYUKI
KASUGA MASAHITO
NAGANO ELECTRONICS IND