Abrading – Precision device or process - or with condition responsive... – Computer controlled
Reexamination Certificate
2002-02-08
2003-09-23
Rachuba, M. (Department: 3723)
Abrading
Precision device or process - or with condition responsive...
Computer controlled
C451S008000, C029S603100, C029S603160
Reexamination Certificate
active
06623330
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a lapping sensor used in a height adjustment of a magnetoresistive effect (MR) film (MR-height adjustment) when a magnetic head with an MR element is fabricated, and to a lapping control method using the lapping sensor.
DESCRIPTION OF THE RELATED ART
In the MR-height adjustment process, MR heights of a plurality of MR elements are adjusted in one operation by polishing one surface (ABS, Air Bearing Surface) of a bar or block obtained by cutting a wafer so that a plurality of magnetic heads with the MR elements are aligned along the bar. In order to precisely and equally adjust MR heights of MR elements in one bar and MR heights of MR elements in bars, a lapping amount is controlled in response to electrical signals from a plurality of lapping sensors each called ELG (Electric Lapping Guide) or RLG (Resistance Lapping Guide), which are in general formed in each bar for detecting the lapped height of the bar. Bending of the bar may be additionally controlled in response to the electrical signals.
The ELG or RLG is substantially configured by a resistor film formed adjacent to and in line with the ABS to be lapped, and by a pair of connection pads electrically connected with both end sections of the resistor film. When lapping the MR height, the resistor film will be also lapped to decrease its height and to increase its electrical resistance. Thus, the lapped amount can be obtained from the change in a terminal voltage of the resistor film.
Such lapping sensors are disclosed in for example U.S. Pat. Nos. 5,065,483, 5,210,667, 5,242,524, 5,361,547, 5,997,381, 6,007,405 and 6,03,849.
In general, the pair of the connection pads for taking out the electrical signal from the resistor film of the lapping sensor are arranged on an element-forming surface of the bar side by side with terminal electrodes of magnetic heads.
FIG. 1
shows a plane view schematically illustrating an element-forming surface of a part of a conventional bar obtained by cutting in lines an wafer on which many magnetic heads are formed in matrix.
In the figure, reference numerals
10
denote magnetic head sections, and
11
denote lapping sensor sections adjacent to the respective magnetic head sections
10
. On the element-forming surface of each magnetic head section
10
, four magnetic head connection pads
13
a
-
13
d
electrically connected to a composite magnetic head element
12
consisting of an MR element and an inductive element are formed. On the element-forming surface of each lapping sensor section
11
, two resistor-film connection pads
14
a
and
14
b
electrically connected to the resistor film, for extracting an electrical signal from the resistor film are aligned perpendicular to a surface to be lapped (lapping surface)
15
of the bar.
Such conventional structure had been applicable to a 30% magnetic head slider with a size of 1.0 mm×1.235 mm×0.3 mm. However, in case of a magnetic head slider with a size smaller than that of the 30% slider such as a 20% slider of 0.7 mm×0.85 mm×0.23 mm, since the space between the upper connection pad
14
a
and the lower connection pad
14
b
and also the space between the lower connection pad
14
b
and the lapping surface
15
became extremely narrow, the following problem had been occurred.
In the lapping control process, one end terminals of a printed circuit board (PCB) with the other end terminals to be electrically connected to a lapping control device are electrically connected to the resistor-film connection pads
14
a
and
14
b
by wires in general. If these spaces are too narrow, because a wire bonding machine has a limited accuracy in bonding, a wire
16
bonded to the lower connection pad
14
b
may come into contact with the upper connection pad
14
a
as shown in
FIG. 2
causing a short circuit to occur, or a wire
17
bonded to the lower connection pad
14
b
may come into contact with a lapping plate touched with the lapping surface
15
as shown in
FIG. 2
If the resistor-film connection pads
14
a
and
14
b
are short-circuited by the wire
16
, the measured resistance of the lapping sensor will become lower than its actual resistance and thus an excess lapping may be occurred. Also, if the wire
17
touches the lapping plate, noises may be mixed in the measured signal due to current flowing into the lapping plate via the wire
17
. Then, a correct resistance of the lapping sensor cannot be measured and a correct lapping cannot be expected.
In order to solve such problem, there may be an arrangement in which resistor-film connection pads
34
a
and
34
b
of the lapping sensor are aligned in parallel with a lapped surface
35
of a bar by forming the connection pad
34
a
over a lapping sensor section
31
and a magnetic head section
30
as shown in FIG.
3
. However, this arrangement will make the layout design of magnetic head connection pads very difficult and also will expose the section of the resistor-film connection pad
34
a
when the magnetic head section
30
is separated by cutting from the section
31
.
There may be another arrangement in which resistor-film connection pads
44
a
and
44
b
of one lapping sensor are aligned in parallel with a surface to be lapped
45
of a bar by forming the connection pad
44
a
in one lapping sensor section
41
and by forming the other connection pad
44
b
in another lapping sensor section
41
as shown in FIG.
4
. However, this arrangement will make the resistance of the lapping sensor to increase because of a long lead conductor
48
for connecting the resistor film of the lapping sensor with the connection pad
44
b,
and also will expose the section of the lead line
48
when the magnetic head section
40
is separated by cutting from the lapping sensor section
41
.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a lapping sensor which can surely and stably detect a correct lapping amount even when a magnetic head slider is to be fabricated is downsized.
Another object of the present invention is to provide a lapping control method using a lapping sensor, whereby an MR height can be surely and stably adjusted to a correct value.
According to the present invention, a lapping sensor used in fabrication of a magnetic head with an MR element includes a resistor film with a resistance that varies depending upon a lapping amount, and a pair of connection pads formed on a element-forming surface of the magnetic head and electrically connected to both end sections of the resistor film. The pair of connection pads consist of a first connection pad and a second connection pad located nearer to a lapping surface than the first connection pad. One edge of the first connection pad is faced to one edge of the second connection pad and inclined toward the lapping surface.
One edge of the first connection pad formed far side from the lapping surface (upper connection pad) is faced to one edge of the second connection pad formed near side from the lapping surface (lower connection pad) and inclined toward the lapping surface. Thus, when wires are bonded to these connection pads, contact of the wire bonded to the lower connection pad with the upper connection pad can be prevented. Namely, by routing the wire bonded to the lower connection pad run along the inclined edge of the upper connection pad, a possibility of contact of this wire with the upper connection pad can be extremely reduced. As a result, a correct lapping amount can be always provided, and therefore an MR height can be surely and stably adjusted to a correct value even when a magnetic head slider to be fabricated is downsized.
It is preferred that the one edge of the first connection pad (upper connection pad) has a linear shape. In this case, more preferably, the one edge of the second connection pad (lower connection pad) has also a linear shape parallel to the one edge of the first connection pad (upper connection pad). Thus, the space between the upper connection pad and the lower connection pad and the space b
Rachuba M.
SAE Magnetics (H. K.) Ltd.
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