Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – For fault location
Reexamination Certificate
2001-03-23
2003-05-27
Oda, Christine (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
For fault location
C324S212000
Reexamination Certificate
active
06570391
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the manufacture of disc drives. More particularly, the present invention relates to a method of manufacturing disc drives with improved bits error rate.
BACKGROUND OF THE INVENTION
Disc drives perform write, read, and servo operations when storing and retrieving data. Generally, a write operation includes receiving data from a host system and storing the data in the random access memory (RAM). The microprocessor schedules a series of events to allow the information to be transferred from the RAM to the discs through the write channel. Before the data is transferred, the read/ write heads are positioned on the appropriate track and the appropriate sector of the track is located. The data from the RAM is then communicated to the write channel as a digital write signal. The preamplifier processes the digital write signal coming from the write channel and generates a write current to the appropriate writer.
In a read operation, the appropriate sector to be read is located and data that has been previously written to the discs is read. The appropriate reader senses the changes in the magnetic flux and generates a corresponding analog read signal. The analog read signal is provided back to the electronic circuitry where the pre-amplifier amplifies the analog read signal. The amplified analog read signal is then provided to the read channel where the read channel conditions the signal and detects “zeros” and “ones” from the signal to generate a digital read signal. The digital read signal is then transferred from the read channel and is stored in the RAM. The microprocessor may then communicate to the host system that data is ready to be transferred.
Electrical noise is often present in the read/write signals. More specifically, noise is coupled into the analog read signal during read operations between the reader and the read pre-amplifier, and between the read pre-amplifier and the read channel. For example, any noise that is coupled into the read path will be amplified by the read pre-amplifier. Similarly, noise is introduced into the write path. Overall, this results in a decrease in the signal-to-noise ratio (SNR) and decrease in bit error rate (BER).
Disc drive manufacturers strive to provide drives that operate at a high SNR and a good BER. Traditionally, the BER performance is obtained after assembly to assess whether the disc drive meets predetermined standards. The cost of rejecting a disc drive at such a late stage of the manufacturing process is high, but deemed inevitable since only an assembled disc drive can be used to produce the BER which is used for assessing the SNR characteristics of the disc drive.
There is therefore a need for an improved method of screening defective disc drives at lower cost to the manufacturer. The following describes how the present invention provides this and other advantages over the prior art.
SUMMARY OF THE INVENTION
The present invention relates to a method of manufacturing disc drives which provides an improved solution to the above-mentioned problem.
In accordance with one embodiment of the invention, before a pivot cartridge is assembled into a disc drive, impedance readings of the pivot cartridge are taken, preferably, at more than one rotational position and across a frequency range. The pivot cartridge is accepted for assembly into the disc drive only if its impedance readings compare favorably with readings taken of a good pivot cartridge. Otherwise, the pivot cartridge is rejected and the impedance readings are analyzed to provide identification of the defect in the pivot cartridge.
The present invention also can be implemented as a computer-readable program storage device which tangibly embodies a program of instructions executable by a computer system to perform the method of screening pivot cartridges and pin-pointing the causes of defects. In addition, the invention also can be implemented as a testing apparatus.
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.
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Chew Victor Wengkhin
Gan Kah Liang
Liang Lim Bernard Tuang
Lim Eng Hock
Ngwe Myint
Kerveros James
McCarthy Mitchell K.
Oda Christine
Seagate Technology LLC
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