Measuring and testing – Surface and cutting edge testing – Roughness
Reexamination Certificate
2001-04-12
2003-09-16
Larkin, Daniel S. (Department: 2856)
Measuring and testing
Surface and cutting edge testing
Roughness
Reexamination Certificate
active
06619105
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a glide head for quality control testing. In particular, the present invention relates to a glide head for quality control testing for discs of data storage devices.
BACKGROUND OF THE INVENTION
Disc drives are used for storing information, typically as magnetically encoded data and more recently as optically encoded data on a disc surface. Recording heads read data from or write data to the discs. Glide tests are used to test a disc surface for defects. During a glide test, a glide head flies over a disc surface at a predetermined clearance known as a glide height or fly height.
Contacts between the glide head and the disc surface are detected during the glide tests via a glide transducer on the glide head. The transducer detects or measures vibration of the glide head upon contact with the disc surface. The vibration can be measured with a piezoelectric transducer (PZT) which generates a varying potential difference between the electrodes of the PZT due to forces imparted to the transducer. Specifically, when the glide head interacts with a defect on the spinning disc, simultaneously excited vibration modes of the PZT and the glide head result in voltage fluctuations at corresponding frequencies. If the magnitude of the measured voltages exceeds predetermined threshold values, the disc may be rejected. Other types of glide transducers can be used for measurement, such as thermal asperity detectors or capacitance detectors.
As areal storage densities on disc recording media become higher, fly heights of data or read-write heads becomes smaller. Lower fly heights for the read-write heads impose narrower restrictions on acceptable heights of asperities or defects on the disc surface, since larger asperities or defects increase propensity for head-disc interface or contact. The glide quality of a disc relates to the ability of a head to fly adjacent to the disc surface at the predetermined glide height without colliding or interfacing with the disc surface.
The glide head is supported above the disc surface at the glide height via rotation of a disc supported on a test spindle by a spindle motor. It is desirable to maintain a stable glide height for glide test operations. For operation, the spindle motor rotates the test spindle at a lower revolution per minute (RPM) than rotation or operating speeds for discs of recording head drives. Glide test operation at lower RPMs and lower glide heights increases glide height instability and likelihood of glide head collapse potentially interfering with or interrupting glide test operations. The present invention addresses these and other problems and offers solutions not previously recognized nor appreciated.
SUMMARY OF THE INVENTION
The present invention relates to a glide head supporting a glide transducer for glide test operations. The glide head includes a textured glide interface for glide height stability. The textured glide interface provides an anti-collapse protection feature for glide test operations. The present invention is characterized by these and other features as illustrated in the described embodiments.
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Kuo David S.
Yao Wei H.
Larkin Daniel S.
Seagate Technology LLC
Westman Champlin & Kelly P.A.
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