Abrading – Abrading process – Glass or stone abrading
Reexamination Certificate
2000-09-27
2004-07-06
Hail, III, Joseph J. (Department: 3723)
Abrading
Abrading process
Glass or stone abrading
C451S286000, C451S287000, C451S270000, C451S272000
Reexamination Certificate
active
06758725
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a lapping method and lapping apparatus, and more particularly, to a lapping method and lapping apparatus used in the manufacture of slider-mounted composite magnetic heads.
2. Description of Related Art
For clarity of explanation, a description will first be given of the structure of a slider-mounted composite magnetic head used in disk drives for recording information to and/or reproducing information from a recording medium.
FIGS. 1A and 1B
are diagrams for explaining a slider-mounted composite-type magnetic head.
FIG. 1A
shows an expanded cross-sectional view of a portion of a slider-mounted composite magnetic head
1
. The slider-mounted composite magnetic head
1
has a composite magnetic head
11
at a tip of a ceramic slider
2
. The composite magnetic head
11
has a magnetoresistive head element
3
for reproducing information and an inductive head element
4
for recording information.
As shown in
FIG. 1B
, the magnetoresistive head element
3
is a thin film comprised of a magnetoresistive film
5
provided on a lower side of the head
1
that faces laterally, with a pair of conductive film terminals
6
a
,
6
b
connected to either end of the magnetoresistive film
5
. The resistance of the magnetoresistive film
5
changes depending on the external magnetic field to which it is exposed and a sense current is sent through the magnetoresistive film
5
. Thus, when the head
1
scans a disk, the resistance of the magnetoresistive film
5
changes according to the magnetization of the disk tracks T over which the head
1
scans and thus a voltage across the conductive film terminals
6
a
,
6
b
also changes, with the result that the information recorded on the disk tracks T is read out as changes in voltage.
The inductive head element
4
is also a thin film, with a lower electrode
7
, an upper electrode
8
, and a coil
9
located between the lower electrode
7
and the upper electrode
8
. When the head
1
scans the disk, signals of information to be written onto the disk are supplied to the coil
9
and a magnetic field is extruded from a lower magnetic gap
10
between the lower electrode
7
and the upper electrode
8
. This magnetic field writes information to the tracks T of the disk.
In manufacturing the slider-mounted composite magnetic head
1
having the structure described above, it is desirable that the resistance of the magnetoresistive film
5
be the same or nearly the same for all such heads so fabricated. Generally, as will be described in detail later, this uniformity of resistance is achieved by lapping so that a thickness or height
h
of the magnetoresistive film
5
is the same for all slider-mounted composite magnetic heads
1
, such that the heads
1
achieve a predetermined resistance value.
Next, a description will be given of the process of manufacturing the above-described slider-mounted composite magnetic head
1
, with reference to
FIGS. 2A
,
2
B,
2
C,
2
D,
3
A,
3
B,
4
A,
4
B and
4
C.
FIGS. 2A
,
2
B,
2
C and
2
D show initial steps in a process of manufacturing the slider-mounted composite magnetic head
1
.
FIGS. 3A and 3B
show further steps in the process of manufacturing the slider-mounted composite magnetic head
1
shown in
FIGS. 2A
,
2
B,
2
C and
2
D.
FIGS. 4A
,
4
B and
4
C show remaining steps in the process of manufacturing the slider-mounted composite magnetic head
1
shown in
FIGS. 3A and 3B
.
Generally, the manufacture of such heads involves the following steps, in the following order: Patterning, dicing, attaching, grinding, lapping, dicing, and peeling.
Initially, a pattern is formed on a ceramic wafer
20
as shown in
FIG. 2A
using thin film technology. Composite magnetic heads
11
and ELG (Electronic Lapping Guide) elements are laid down in alternate sequence as shown in
FIGS. 2B and 2C
. The wafer
20
has a thickness corresponding to a length
a
of the slider. The wafer
20
is then diced and, as shown in
FIG. 2B
, a multiplicity of row bars
22
are obtained. The row bar
22
, which as can be appreciated is in the shape of a bar, has a composite magnetic head
11
and an ELG element
21
laid down in alternate sequence, together with a margin portion
23
to be ground or lapped. It should be noted that the magnetoresistive film
5
and the ELG element
21
are both formed by thin-film technology patterning, and the magnetoresistive film
5
and ELG element
21
are positioned with a high degree of accuracy.
Next, as shown in
FIG. 3A
, the row bar
22
is attached to a tip of a transfer tool
30
using wax. A multiplicity of concave portions
31
are formed along the tip of the transfer tool
30
. The row bar
22
, as shown in
FIG. 3B
, is attached so that the ELG elements
21
are disposed opposite the concave portions
31
. The concave portions
31
are formed so as not to interfere with the dicing step to follow. The transfer tool
30
is fixedly mounted to a printed circuit board
32
. The ELG elements
21
and terminals on the printed circuit board
32
are connected, or bonded, by wire
33
as shown in
FIG. 3B
, thus connecting the ELG elements
21
and the printed circuit board
32
electrically.
Next, the transfer tool
30
to which the row bar
22
is attached is set to a grinding machine not shown in the diagram and the row bar
22
is ground down to a point indicated by a dashed line
34
in FIG.
3
B.
Next, the transfer tool
30
is removed from the sander and set to a lapping device not shown in the drawing in order to lap the ground surface of the row bar as shown in FIG.
4
A. As lapping progresses, the width, that is, the height
h
of the magnetoresistive film
5
gradually decreases, as does the height of the ELG elements
21
, and, accordingly, the magnetic resistance MRh gradually increases. Moreover, because the magnetoresistive film
5
and the ELG
21
are positioned with great precision, it is possible to know the height of the magnetoresistive film
5
from the condition of the ELG elements
21
. Therefore lapping is conducted while monitoring the magnetic resistance MRh of the ELG
21
. When this magnetic resistance MRh of the ELG elements
21
reaches a target value, lapping is discontinued. At this point in time the height
h
of the magnetoresistive film
5
should have reached its target value. This lapping process is very precise, that is, on the order of sub-microns.
Next, the transfer tool
30
is removed from the lapping device and set to a dicing device not shown in the diagram and, as shown in
FIG. 4B
, the lapped row bar
22
is cut through to the interior of the concave portions
31
using a dicing saw
35
, thus cutting out the row bar
22
ELG elements
21
. In so doing, the row bar
22
is separated into a plurality of heads
1
.
Finally, the transfer tool
30
is heated so as to melt the wax holding the row bar
22
onto the tip of the transfer tool
30
. In so doing, the plurality of heads
1
into which the cut row bar
22
has been divided peel off from the transfer tool
30
, resulting in fully formed slider-mounted composite magnetic heads
1
having a height
b
of approximately 0.3 mm and a length
a
of approximately 1.2 mm.
It will be appreciated by those skilled in the art that the production process described above is also used to fabricate giant magnetoresistive heads, or GMR heads, having a plurality of different film layers in contrast to the single layer of the magnetoresistive film characteristic of magnetoresistive heads described above.
A description will now be given of the conventional art.
FIG. 5
shows a perspective view of a conventional lapping device for lapping a row bar, as shown for example in Japanese Laid-Open Patent Application No. 10-286767. As shown in the diagram, this conventional lapping device
40
has a base
41
, a rotary plate
42
that rotates in a direction indicated by arrow A in the diagram, an arm assembly
44
supported by a shaft
43
, an oscillating mechanism
45
that swings the arm assembly
44
Sudo Koji
Sugiyama Tomokazu
Yanagida Yoshiaki
Fujitsu Limited
Greer Burns & Crain Ltd.
Hail III Joseph J.
McDonald Shantese
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