Method and system for providing ESD protection using diodes...

Details Method and system for providing ESD protection using diodes... Method and system for providing ESD protection using diodes...

2000-08-16

2004-03-09

Heinz, A. J. (Department: 2652)

Dynamic magnetic information storage or retrieval

Head

Magnetoresistive reproducing head

Reexamination Certificate

active

06704173

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to magnetoresistive heads and more particularly to a method and system for providing electrostatic discharge protection for magnetoresistive heads, particularly in devices using a flex-on-suspension (FOS) or trace-suspension-assembly (TSA) in a head-gimbal-assembly (HGA).
BACKGROUND OF THE INVENTION
FIG. 1
is a block diagram of a portion of a suspension assembly used in magnetoresistive (MR) technology. Depicted with the suspension assembly
50
is a slider
1
including an MR head
10
used in reading magnetic recording media. Typically, the slider
1
includes a merged head. Thus, the MR head
10
is part of a merged head that also includes a write head. However, for clarity, only the MR head
10
is shown. The MR head
10
includes an MR sensor
30
. Typically, the MR sensor
10
is an anisotropic magnetoresistive (MR) sensor or a giant magnetoresistive (GMR) sensor. The slider
1
also includes pads
42
,
44
,
46
and
48
. Two pads
42
and
44
are used for making electrical contact to the MR sensor
30
from other portions of the suspension assembly
50
. The other two pads
46
and
48
may be used in making electrical contact to the write head.
In order to use the MR head
10
in a disk drive, electrical connection is made to the MR sensor
30
via the pads
42
and
44
. In some conventional systems, a twisted pair of wires is used to connect to the leads
42
and
44
. However, the conventional suspension assembly
50
is typically provided in order to couple the MR sensor
30
to the remaining electronics (not shown).
The conventional suspension assembly
50
may include a flex-on-suspension (FOS) developed by Read-Rite Corporation of Milpitas, Calif., in a trace-suspension-assembly (TSA), in a chip on suspension (COS) or in a bridge-flex-circuit (BFC). Note that the BFC is typically coupled with the MR head
10
through the FOS, TSA or COS. Thus, as used herein a suspension assembly can refer to any combination of a FOS, a TSA, a COS, a BFC or similar structure for making electrical contact to the MR head
10
. The conventional suspension assembly
50
has a wireless electrical connection with the MR head
10
that allows for a smaller form factor for the head and head-gimbal-assembly. The conventional suspension assembly
50
is typically significantly longer than the slider
1
.
The conventional suspension assembly
50
is typically mechanically coupled with the slider
1
via a metal arm (not shown). The conventional suspension assembly
50
includes a first lead
52
, a second lead
54
, a third lead
56
and a fourth lead
58
. Note, however, that the third lead
56
and fourth lead
58
may be omitted if the slider assembly
1
does not include a write head. The leads are typically surrounded by an insulating film
60
. The insulating film
60
is typically made of two layers of polyimide. The film
60
generally surrounds the leads
52
,
54
,
56
and
58
. Thus, in the conventional suspension assembly
50
the leads
52
,
54
,
56
and
58
are typically sandwiched between two layers of film
60
. The conventional suspension assembly
50
also includes four head gimbal assembly (HGA) pads
62
,
64
,
66
and
68
coupled with the leads
52
,
54
,
56
and
58
, respectively. The leads
52
and
54
are also electrically coupled with the MR sensor
30
, preferably through pads
42
and
44
. Thus, electrical connection can be made to the MR sensor
30
even when the MR head
10
is sufficiently small for use in present disk drives.
Although the conventional suspension assembly
50
functions, one of ordinary skill in the art will readily realize that the conventional suspension assembly
50
and head
10
are subject to electrostatic discharge (ESD) failure. During fabrication, the MR sensor
30
is often rendered inoperative. In some cases, losses may be as high as ten to twenty percent. It has been determined that these losses may be due to tribo-charging of the film
60
in the suspension assembly
50
. As higher density recording media is used, the MR head
10
is built smaller to be capable of reading narrow track signals from high-density recording media. As the MR head
10
is reduced in size, more damage to the MR sensor
30
can be caused by smaller transient currents due to ESD.
For example, during manufacture, electrical contact is often made to a portion of the conventional suspension assembly
50
, such as the HGA pads
62
or
64
. When a charged metal fixture touches the pad
62
or
64
, the charge can be transferred to the HGA pad
62
or
64
. The charge on the HGA pad
62
or
64
could cause a large transient current to flow through the MR sensor
30
as the charge is discharged. Charge could be similarly transferred to the leads
52
and
54
, resulting in a transient current which flows through the MR sensor
30
. The transient current can easily destroy the MR sensor
30
. Thus, the MR sensor
30
may be damaged or destroyed due to ESD.
Many conventional systems have been developed for protecting the MR head
10
from damage due to ESD. Some conventional methods connect a very low resistance conductor between the leads
52
and
54
. The conductor typically has a resistance of only a few ohms or less. In other words, the leads
52
and
54
are shorted. As a result, the transient current can be prevented. Other conventional methods connect a very high resistance shunt between the leads
52
and
54
, or between one of the leads
52
and
54
and ground. The high resistance shunt is typically on the order of 10
6
Ohms. The high resistance shunt allows any charge accumulated on the conventional suspension assembly
50
to be slowly dissipated. Thus, the MR sensor
30
may be preserved.
Although the very high resistance and very low resistance shunts can function, one of ordinary skill in the art will readily recognize that such shunts are typically temporary and, therefore, removable. As a result, the protection provided from ESD damage is also temporary. For example, prior to contacting a shunt with the HGA pads
62
and
64
, the MR sensor
30
is not protected. Thus, the MR head
10
may still be subject to failure due to ESD induced damage during manufacture.
Accordingly, what is needed is a system and method for providing ESD protection for MR heads during fabrication. The present invention addresses such a need.
SUMMARY OF THE INVENTION
The present invention provides a method and system for providing a suspension assembly which includes a mechanism for protecting a magnetoresistive (MR) head from electrostatic discharge damage. The MR head includes an MR sensor having a first end and a second end. The method and system comprise providing a first lead and a second lead. The method and system also comprise providing an insulating film that substantially supports a first portion of the first lead and a second portion of the second lead. The MR head is coupled with the suspension assembly. The first and second ends of the MR sensor are coupled with the first and second leads, respectively. The method and system also comprise providing a conductive strip coupled with the insulating film. In one aspect, the method and system comprise providing at least one diode electrically coupling the first lead and the second lead. In another aspect, the method and system also comprise electrically coupling first lead with the conductive strip. In another aspect, the method and system also comprise electrically coupling first lead with the conductive strip and electrically coupling the first and second lead. In another aspect, the method and system comprise electrically coupling first and second leads with the conductive strip. Preferably, electric coupling is provided using at least one diode.
According to the system and method disclosed herein, the present invention provides greater robustness against damage due to electrostatic discharge.


REFERENCES:
patent: 5614727 (1997-03-01), Mauri et al.
patent: 5638237 (1997-06-01), Phipps et al.
patent: 5757590 (1998-05-01), Phipps et al.
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