| 摘要 |
PROBLEM TO BE SOLVED: To improve the productivity when a substrate main body is processed by specifying a concentricity and a roundness of the carbon substrate main body before the surface is processed. SOLUTION: After a carbon substrate main body 1A is backed, surface- processing and chamfering are carried out thereby the produce the magnetic disk carbon substrate (GC substrate) 1 of 1.8-inch outer diameter. The concentricity of the substrate main body 1A after the baking and carbonization before the surface-processing is 300μm or smaller and, a roundness thereof is not larger than 300μm. Accordingly, a time required for the chamfering of the substrate main body 1A becomes short, thereby, productivity is improved. Moreover, a flatness of the substrate main body 1A before the surface-processing after the backing and carbonization is not larger than 50μm, and the thickness irregularity in one substrate main body 1A is not larger than 50μm. It is hence eliminated to add an extra grind margin to improve the flatness in a lapping process or grind with a small grinding pressure. The process time is shortened and the productivity is improved. |
