Electricity: measuring and testing – Magnetic – Magnetic information storage element testing
Reexamination Certificate
2001-05-23
2003-05-20
Lefkowitz, Edward (Department: 2862)
Electricity: measuring and testing
Magnetic
Magnetic information storage element testing
C324S262000, C360S099120
Reexamination Certificate
active
06566870
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related to disc drive testing. More specifically, the present invention is related to a disc stabilizer for use in a spin-stand tester.
BACKGROUND OF THE INVENTION
In a computer disc drive, data is stored on a computer disc in concentric tracks. In many drives, the data is stored using a write head that changes a physical property of the disc. The data is read from the disc by positioning a read head over a desired track and sensing the physical properties of the disc along the track. For example, in a magnetic disc drive, the read head senses magnetic moment boundaries along the disc.
The process for producing a read head or a write head varies depending upon the type of read head or write head being produced. Nonetheless, all head manufacturing methods share common characteristics, such as high degree of manufacturing complexity, small feature sizes, and a susceptibility to manufacturing errors. Because of this, each production method generates some heads that do not meet specifications. In order to detect faulty heads accurately, the transducing heads must be tested over a disc surface. In particular, each transducing head must be flown over a disc surface while it performs writing and/or reading operations. Early in the disc drive manufacturing art, this type of testing was performed after the head was assembled in a complete disc drive. However, this in-drive testing proved to be unacceptable because the disc drive had to be rebuilt if the head was found to be faulty.
To overcome the ineffectiveness of in-drive testing, the art developed a “spin-stand” which allowed the head to be tested before it was placed in a disc drive. In general, a spin-stand includes a spinning computer disc and a mounting support that supports the head and moves the transducing head to a desired position over the spinning disc. The spin-stand allows a series of tests to be performed on the transducing head including, for example, error-rate testing, pulse width—fifty testing, track average amplitude testing and track scan testing.
Tester to tester variation and variation within a tester should be small so that properly functioning heads are not classified as “failed” and defective heads are not classified as “good”. One component of tester variation is the stability of the head position over the data tracks on the disc. Several tests such as track scan and bit error rate rely on the head being at a known location with respect to a given track centerline. Test integrity is degraded if there is undesired cross-track head movement during the test.
A head-gimbal assembly (HGA) which includes a head, a suspension assembly for positioning the head, and a flexible circuit that carries electrical signals between the head and drive electronics is the first subassembly where the head can be tested under conditions similar to those in a hard disc drive. Electrical tests on HGAs, performed using conventional spin-stand testers in which the disc is clamped to a shaft of a spindle motor, have shown that heads that pass measurement at inner diameter (ID) tracks on the disc can fail when tested at outer diameter (OD) tracks. This is because the disc is only supported by the shaft at the ID. Other measurements have shown that positional relationship between a read/write head and a written data track is less stable at OD tracks on the same type tester. Because OD testing has become important for many HGA products, it is possible that good HGA assemblies will be failed because of instabilities in the tester, resulting from inadequate support at OD tracks of the disc, and not because of head performance characteristics.
The present invention addresses these problems, and offers other advantages over the prior art.
SUMMARY OF THE INVENTION
The present invention relates to a disc stabilizer for use in a spin stand tester with the disc stabilizer including a vacuum plate that supports the disc, thereby addressing the above-identified problems.
A disc stabilizer for use in a spin-stand tester having a spindle motor for rotating a disc is provided. The spin-stand tester is capable of positioning a transducing head adjacent a first surface of the disc. The disc stabilizer includes a vacuum plate coupled to a spindle of the spindle motor. The vacuum plate has a top surface and a bottom surface opposite the top surface. At least one of the top and the bottom surfaces is a grooved surface including multiple vacuum channels. The grooved surface is substantially in contact with a second surface of the disc. Vacuum distributed through the multiple vacuum channels of the grooved surface is applied directly to the second surface of the disc, thereby holding the disc in place.
These and various other features as well as advantages which characterize the present invention will be apparent upon reading of the following detailed description and review of the associated drawings.
REFERENCES:
patent: 3980810 (1976-09-01), Tinet
patent: 4071854 (1978-01-01), Bijon et al.
patent: 4334302 (1982-06-01), Peppers
patent: 4734809 (1988-03-01), Inuma et al.
patent: 5589771 (1996-12-01), Chur
patent: RE35670 (1997-11-01), Immamura et al.
patent: 5872451 (1999-02-01), Guzik
Schmitt Thomas J.
Sorenson Gary D.
Lefkowitz Edward
Seagate Technology LLC
Westman Champlin & Kelly
Zaveri Subhash
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