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Micro defect entry method in defect mapping at hard disk drive test

IP.com Disclosure Number: IPCOM000014735D
Original Publication Date: 2001-Feb-01
Included in the Prior Art Database: 2003-Jun-20
Document File: 1 page(s) / 38K

Publishing Venue

IBM

Abstract

Disclosed is a defect sector mapping method for hard disk drive to skip the

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This is the abbreviated version, containing approximately 77% of the total text.

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Micro defect entry method in defect mapping at hard disk drive test

Disclosed is a defect sector mapping method for hard disk drive to skip the

particular defect sites described in below at manufacturing test.

Contemporary hard disk drive has the function to alternate defect sectors. The defects are identified by referring to the bit error length and the depth. However, the data at the sites with a very small defect (called micro defect) can be easily recovered by error correction code (ECC) algorism so that they have not been alternated so far. But micro defects lead to uncorrectable read errors on modern disks with very smooth surface.

The micro defects have the following characteristics.

1. The defect length is too short to capture by surface analysis test (SAT)

function in channel module.

2. The defect has dent or dimple.

3. The read signal has repeatable bit errors at the defect.

The mechanism of the uncorrectable hard error is, very small contaminations condensate after the defect like driftsnow. The defect itself does not grow, but read error happens after the condensation gets long.

This particular defect is hard to distinguish from conventional soft errors since both errors are correctable. But the following test can finely detect the micro defects. 1. Set minimum values for ECC correctable data length and number of retry.

The values can be determined concerning soft error rate.

If the soft error rate is larger, set the values a little bigger.

2. Read ma...