Magnetic hard disc substrate and process for manufacturing the s

Details Magnetic hard disc substrate and process for manufacturing the s Magnetic hard disc substrate and process for manufacturing the s

1998-06-12

2000-09-26

Scherbel, David A.

Abrading

Abrading process

Utilizing fluent abradant

451 28, 451 41, 451 57, 438692, 216 89, B24B 100

Patent

active

061236039

ABSTRACT:
A magnetic hard disc substrate made of an aluminum alloy for memory devices such as a computer must correspond to an improved structure in which the interval between a head and a medium is made narrower to attain high density recording. In order to prevent head crash, it is required that the magnetic hard disc substrate have a smooth surface and decreased defects. The present invention provides a process for manufacturing a magnetic hard disc substrate made of an aluminum alloy which satisfies the above requirements and also provides a disc substrate which has a surface roughness Ra.ltoreq.0.5 nm and is free from abrasive flaws with a depth of 5 nm or more and from micro-waviness or provides a disc substrate which has a surface roughness Ra.ltoreq.5 angstroms and a surface roughness Rmax.ltoreq.80 angstroms and in which the number of scratches with a depth of 50 angstroms or more is 5 or less and the number of pits with a depth of 50 angstroms or less is 5 or less in the surface.

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