Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2000-07-10
2004-03-23
Arbes, Carl J. (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S603010, C029S603040, C029S603070, C029S428000, C360S245900, C360S100100
Reexamination Certificate
active
06708389
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to fabrication and testing of magnetic head suspension assemblies.
BACKGROUND OF THE INVENTION
FIG. 1
shows a fragmentary view of a prior art disk drive having an actuator arm assembly
2
and a stack of spaced apart disks
4
rotatable about a common spindle
5
as represented by the arrow
20
. The actuator arm assembly
2
is also rotatable about an actuator arm axis
6
. The arm assembly
2
includes a plurality of actuator arms
8
A-
8
C which extend into the spaces between the disks
4
A and
4
B. Attached to each of the actuator arms
8
A-
8
C is a magnetic head suspension assembly
10
, which comprises a resilient load beam
12
, a flexure
14
and a slider
16
. Each load beam
12
is attached to one of the actuator arms
8
A-
8
C via a base plate
25
having a boss
40
snugly inserted into the actuator hole
42
as shown in FIG.
1
.
FIG. 2
shows the magnetic head suspension assembly
10
in further detail. The load beam
12
is made of resilient material which is slightly bent toward the disk surface
18
(FIG.
1
). Underneath the distal end of the load beam
12
is the flexure
14
. An alignment hole
33
in the load beam
12
is provided for the alignment of the corresponding hole in the flexure
14
, thereby orienting the flexure
14
in a proper location. The flexure
14
is fixedly attached onto the load beam
12
in the area surrounding the alignment hole
33
via welding.
The flexure
14
has an integrally formed tongue portion
26
. Fixedly attached to the tongue portion
26
is the slider
16
. Stamped at the end of the load beam
12
is a dimple
28
which is urged against the tongue portion
26
of the flexure
14
. The dimple
28
acts as the fulcrum for the resilient flexure
14
to provide gimbaling action. At the edge of the slider
16
is a magnetic head transducer
24
. Electrical signals written in or read out of the transducer
24
are conducted by wires
30
disposed on the load beam
12
and guided by one of the load beam ribs
32
A. As an alternative, a flex circuit
34
is used in lieu of the wires
30
. Instead, electrical signals are sent or received through the traces
36
(shown partially as a representation in phantom) embedded on the flex substrate
38
of the flex circuit
34
.
The topology of the disk surface
18
, though highly polished, is not at all uniform at microscopic scale. Very often, the disks
4
A and
4
B are not rotating about the spindle at a perfectly perpendicular angle. A minute angular deviation would translate into varying disk-to-slider distances while the disks
4
A and
4
B are spinning. For reliable data writing and reading, the slider
16
thus has to faithfully follow the topology of the spinning disks
4
A and
4
B, without ever contacting the disk surfaces
18
. The head gimbal assembly
22
is employed to accommodate the disk surface topology. Basically, the gimbal assembly
22
is designed to dynamically adjust the position of the slider
16
to conform to the irregular disk surface
18
while the disk is spinning. To meet this end, the flexure inside the gimbal assembly
22
must be sufficiently flexible and agile on one hand, yet stiff enough to resist physical deformation on the other hand.
The magnetic suspension assembly
10
, which includes the slider
16
, the flexure
14
,the load beam
12
, the baseplate
25
, and either the wires
30
or the flex circuit
34
, needs to be tested prior to installation to a disk drive. Heretofore, testing of the magnetic head suspension assembly
10
involved inserting the entire assembly
10
into the arm of a spin station which performs the tests. Of all the constituent parts of the suspension assembly
10
, the transducer
24
is the most delicately fabricated component. Often, the failure of the assembly
10
is the electrical malfunctioning of the transducer
24
. Since the magnetic head suspension assembly
10
is permanently attached, the entire assembly
10
has to be rejected as a consequence.
The technological trend in disk drive manufacturing is toward miniaturization. As a consequence, sliders are reduced in size. A fixed area of a wafer can now yield more sliders than in the past. Accordingly, costs for each slider fabricated with the transducer
24
decrease. Instead, a greater portion of the manufacturing cost shifts to the other components of the assembly
10
. Thus, rejecting the entire assembly
10
which includes the base plate
25
, the load beam
12
, the flexure
14
and the flex circuit
34
is wasteful and unnecessarily increases manufacturing costs.
There is also a trend toward new designs which include active integrated circuits (not shown) disposed near the transducer
24
. For example, integrated circuits may be placed on the flex circuit
34
or the load beam
12
. Weak signals picked up by the transducer are immediately amplified by the integrated circuits before the next stage of signal amplification during data reading, for instance. Placing the active circuits close to transducer
24
substantially improves the signal-to-noise ratio (SNR) of the magnetic head assembly
10
. Adopting the prior art approach of testing and manufacturing of the assembly
10
would further aggravate the situation and is even more wasteful because the active circuits also need to be discarded in the event of test failure. Accordingly, there has been a long-felt need for building magnetic head suspension assemblies without the aforementioned problems.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a method of prescreening defective components prior to final assembly in the manufacturing of magnetic head suspension assemblies, thereby improving production yield and reducing manufacturing costs.
In accordance with the invention, a slider is fabricated with a magnetic head transducer and then attached to an intermediate flexible circuit. The combination is thereafter inserted into a spin stand tester for the testing of various electrical parameters. If the attached combination fails the test, it is discarded. On the other hand, if the attached combination passes the test, it is mounted onto a load beam to form the magnetic head suspension assembly. In one embodiment, the intermediate flexible circuit affixed with the slider is attached to a load beam having a flexure. In another embodiment, the intermediate flexible circuit is attached to a load beam having no pre-disposed flexure, wherein the intermediate flexible circuit acts as the flexure in the final assembly.
Accordingly, the magnetic heads, which normally experience the highest failure rate, are isolated and rejected prior to final assembly, without affecting the associated components which are more expensive.
REFERENCES:
patent: 5404636 (1995-04-01), Stefansky et al.
patent: 5574234 (1996-11-01), Schudel
patent: 5589771 (1996-12-01), Chur
patent: 5758406 (1998-06-01), Hunsaker et al.
patent: 6173485 (2001-01-01), Shiraishi et al.
patent: 6237215 (2001-05-01), Hunsaker et al.
Carlson Carl J.
Schott Daniel P.
Arbes Carl J.
Kallman Nathan N.
Phan Tim
Western Digital (Fremont) Inc.
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