Dynamic magnetic information storage or retrieval – Fluid bearing head support – Disk record
Reexamination Certificate
2000-03-14
2002-04-16
Heinz, A. J. (Department: 2652)
Dynamic magnetic information storage or retrieval
Fluid bearing head support
Disk record
C360S245800
Reexamination Certificate
active
06373660
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 or trace-suspension assembly.
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 (AMR) 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
typically provided in order to couple the MR sensor
30
to the remaining electronics (not shown).
The conventional suspension assembly
50
is preferably used with a flex-on suspension (FOS) developed by Read-Rite Corporation of Milpitas, California, in a trace suspension assembly (TSA), or in a cable on suspension (COS). 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
typically includes a metal arm (not shown) and typically is mechanically coupled with the slider
1
. 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 polyimide and includes two layers of kapton. 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 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 with current high-density recording media.
During manufacture of the conventional suspension assembly
50
, the MR head
10
is tested. Consequently, a testing portion
70
of the conventional assembly is typically provided. The testing portion
70
includes test pads
72
,
74
,
76
and
78
coupled with leads
82
,
84
,
86
and
88
, respectively, that are on a portion of insulating material. Generally, the insulating material is continuous. Thus, the insulating in the testing portion
70
is generally also made of kapton. The first test pad
72
and the second test pad
76
are coupled with the MR sensor
30
via leads
82
and
84
, leads
52
and
54
, and pads
42
and
44
, respectively. The third test pad
76
and the fourth test pad
78
are coupled with the write head via leads
86
and
88
, leads
56
and
58
, and pads
46
and
48
, respectively. Using the first test pad
72
and the second test pad
74
the MR head
10
is tested. Typically, the testing includes a magnetic test and a quasi-static test. In the quasi-static test, the environment in which the slider
1
will function is simulated and the response of the MR sensor
30
tested. In the magnetic test, the slider
1
is actually flown over a disk and the response of the MR sensor
30
tested. Thus, it can be determined whether the MR head
10
functions prior to providing the conventional suspension assembly
50
to a customer.
Although the conventional suspension assembly
50
functions in FOS and TSA embodiments, one of ordinary skill in the art will readily realize that the conventional suspension assembly
50
and head
10
are subject to 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 are 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 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 electrostatic discharge.
For example, during manufacture, electrical contact is often made to the test pads
72
,
74
,
76
or
78
. When a charged metal fixture touches the test pad
72
or
74
, the charge can be transferred to the test pad
72
or
74
. The charge on the test pad
72
or
74
could cause a large transient current to flow through the MR sensor
30
as the charge is discharged. The transient current can easily destroy the MR sensor
30
. Thus, the MR sensor
30
may be damaged or destroyed due to electrostatic discharge (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
or the leads
82
and
84
. The conductor typically has a resistance of only a few ohms or less. In other words, the leads
52
and
54
or
82
and
84
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 the leads
82
and
84
, or between one of the leads
52
,
54
,
82
or
84
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. For example, refer to
FIG. 2
, which depicts a conventional suspension assembly
50
′ described in co-pending U.S. patent application Ser. No. 08/055,729 entitled “SHORTING BAR AND TEST CLIP FOR PROTECTING MAGNETIC HEADS FROM DAMAGE CAUSED BY ELECTROSTATIC DISCHARGE DURING MANUFACTURE” and assigned to the assignee of the present invention. Also depicted is the slider
1
and MR head
10
. Most of the components of the conventional suspension assembly
50
′ are the same as those of the conventional assembly
50
, depicted in FIG.
1
. Consequently, the components are labeled similarly to the conventional suspension assembly
50
. For example, the MR head
10
′ in the conventional suspension assembly
50
′ corresponds to the MR head
10
in the conventional suspension assembly
50
.
The conventional suspension assembly
50
′ includes a low resistance conductive shunt
92
on an insulating material
90
that is coupled with the testing portion
70
′. Typically, the insulating material
90
is an additional piece of kapton that is generally made by lengthening the insulating material for the testing portion
70
′. The kapton
90
is flexible and c
Chang Caleb Kai-lo
Chim Seila Chao
Lam Chung Fai
Martinez Dino Tommy Anthony
Meyer Dallas W.
Heinz A. J.
Read-Rite Corporation
Sawyer Law Group LLP
LandOfFree
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