Electricity: measuring and testing – Magnetic – Magnetic information storage element testing
Reexamination Certificate
2001-10-25
2004-07-20
Snow, Walter E. (Department: 2862)
Electricity: measuring and testing
Magnetic
Magnetic information storage element testing
C360S031000
Reexamination Certificate
active
06765379
ABSTRACT:
TECHNICAL FIELD
This invention relates to methods and devices for testing heads for use in sealed hard drive assemblies.
BACKGROUND
Hard drive assemblies (HDAs), otherwise known as disk drives, are commonly used for mass storage of computer programs and data. Magnetic recording media (“disks”) are coated with a magnetic material. Data is stored (“written”) on a disk by magnetizing spots on the coating with changes in polarity corresponding to binary bits.
Referring to
FIG. 1
, the data is written and read by spinning the disk
10
while a magnetic head
12
, mounted on a load beam
16
, “flies” over the upper surface
18
of the disk. The head (a hydrodynamic air bearing slider) flies as a result of a gliding action caused by compression of a layer of air that is dragged along by the spinning disk surface. The air layer is compressed between the upper surface
18
of the disk and the adjacent lower, air-bearing surface
20
of the head.
The head flies very close to the surface of the disk, without touching the disk surface. Referring again to
FIG. 1
, the distance H between the lower, air-bearing surface
20
of the head
12
and the upper surface
18
of disk
10
is referred to as the “flying height”.
Recently, proposals have been made to design sealed hard drive assemblies (HDAs) that enclose a pure helium atmosphere. It is necessary to test heads that are to be used in sealed HDAs using standard single head dynamic electrical testing (DET). Because the environment in which a head is used affects the way that it will perform, e.g., by changing the flying height of the head, testing should be done with the head in a helium atmosphere.
Heads can be tested in a helium atmosphere by putting a hermetic chamber around the DET tester and filling it with helium. However, almost all DET testers use air bearing spindles that exhaust air, and thus the tester tends to contaminate the helium atmosphere in the chamber. Running the spindle with helium instead of air requires a heavy consumption of helium. The exhaust from the spindle could be ducted outside of the chamber, but this would be mechanically difficult to retrofit onto most common spinstands.
The chamber approach also requires that parts to be tested be transferred into and out of the chamber. Most production DET loads the heads onto the tester manually, so some form of access into the chamber must be provided. Opening the chamber is undesirable due to the loss of helium (typically on the order of several cubic feet), increasing the production cost of the heads. Moreover, purging the air and refilling the chamber with helium is time consuming. Test time in mass production is very expensive, costing on the order of tens of thousands of dollars per second (i.e., one second of test time is equivalent to several tester-months per program), and thus lost time also significantly increases the cost of the heads.
SUMMARY
The invention provides methods and devices that allow heads to be tested in a helium environment in a cost-effective way with little or no impact on test time and with minimal consumption of helium. In some implementations, the helium environment adds only a penny or less to the cost of a sealed drive.
In one aspect, the invention features a method of testing a head to be used in a sealed disk drive, including directing a flow of a gas across the head while subjecting the head to electrical testing.
Some implementations may include one or more of the following features. The gas includes helium. The method further includes causing the gas to flow between the head and a disk that is being used in the electrical testing. The method further includes causing the gas to flow out of a manifold. The method includes causing the gas to flow at a flow rate of from about 40 to 60 ft
3
/hr. The method further includes causing the gas to flow across the head for a predetermined time substantially equal to the time required for dynamic electrical testing, e.g., less than 30 seconds, typically less than 15 seconds. The manifold includes an exit through which the gas flows, and the method further includes positioning the exit from about 0.005 to 0.010 inch above the surface of a disk that is being used in the electrical testing. The head and equipment used for electrical testing are exposed to the ambient atmosphere. The electrical testing comprises dynamic electrical testing. The head is surrounded by a shroud.
In another aspect, the invention features a device for testing a head to be used in a sealed disk drive to read/write data of a storage disk. The device includes a manifold having at least one opening for providing a flow of gas from a source of gas, the at least one opening being positioned to direct the flow of gas to a surface of a storage disk positioned adjacent to the head.
Other features and advantages of the invention will be apparent from the description and drawings, and from the claims.
REFERENCES:
patent: 5914594 (1999-06-01), Mian
patent: 6057975 (2000-05-01), Yaeger et al.
patent: 6112582 (2000-09-01), Yao et al.
patent: 6178059 (2001-01-01), Frees
Mallary Michael
Marshall Steven B.
Martin Richard E.
Maxtor Corporation
Sigmond David M.
Snow Walter E.
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