U.S. patent application number 10/872251 was filed with the patent office on 2004-11-18 for method and apparatus for improved static attitude of head suspension assemblies with electrical interconnects.
This patent application is currently assigned to Applied Kinetics, Inc.. Invention is credited to Girard, Mark T..
Application Number | 20040226164 10/872251 |
Document ID | / |
Family ID | 25186068 |
Filed Date | 2004-11-18 |
United States Patent
Application |
20040226164 |
Kind Code |
A1 |
Girard, Mark T. |
November 18, 2004 |
Method and apparatus for improved static attitude of head
suspension assemblies with electrical interconnects
Abstract
The present invention provides a method for improving the static
attitude of a head suspension assembly by improving the manufacture
of electrical interconnects by providing a laterally directed
tension on the electrical interconnect during manufacture, thereby
substantially inhibiting deformation of the gimbal region of the
interconnect and the creation of non-planar slider standoffs.
Inventors: |
Girard, Mark T.;
(Hutchinson, MN) |
Correspondence
Address: |
KAGAN BINDER, PLLC
SUITE 200, MAPLE ISLAND BUILDING
221 MAIN STREET NORTH
STILLWATER
MN
55082
US
|
Assignee: |
Applied Kinetics, Inc.
|
Family ID: |
25186068 |
Appl. No.: |
10/872251 |
Filed: |
June 18, 2004 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10872251 |
Jun 18, 2004 |
|
|
|
09803267 |
Mar 9, 2001 |
|
|
|
6751843 |
|
|
|
|
Current U.S.
Class: |
29/603.03 ;
29/603.06; 360/313; G9B/5.154 |
Current CPC
Class: |
Y10T 29/49032 20150115;
H05K 1/118 20130101; Y10T 29/49025 20150115; G11B 5/486 20130101;
Y10T 29/49036 20150115; Y10T 29/4903 20150115; Y10T 29/49021
20150115; Y10T 29/49027 20150115 |
Class at
Publication: |
029/603.03 ;
360/313; 029/603.06 |
International
Class: |
G11B 005/48 |
Claims
What is claimed is:
1. A method of making an electrical interconnect for a head
suspension assembly, the interconnect comprising a substrate, at
least one electrical trace, and a gimbal portion, the method
comprising: providing a web of interconnect material comprising at
least a support layer and a layer of conductive material;
selectively removing at least a portion of the conductive material
to form at least one electrical trace, selectively removing at
least a portion of the support layer to form an interconnect blank
comprising the at least one electrical trace and at least a portion
of the support layer, the interconnect blank attached to the web by
a pair of tension tabs formed from at least a portion of the
support layer and extending from the interconnect blank; and
severing the interconnect blank from the web.
2. The method of claim 1, wherein the pair of tension tabs extend
from the interconnect blank at an angle between 100.degree. and
180.degree. relative to each other.
3. The method of claim 2, wherein the pair of tension tabs extend
from the interconnect blank at 180.degree. relative to each
other.
4. The method of claim 1, wherein the web of interconnect material
further comprises a metal layer attached to the support layer.
5. The method of claim 1, wherein the metal layer comprises at
least a portion of a flexure.
Description
BACKGROUND OF THE INVENTION
[0001] Most personal computers today utilize direct access storage
devices (DASD) or rigid disk drives for data storage and retrieval.
Present disk drives include a disk rotated at high speeds and a
read/write head that, in industry parlance, "flies" a microscopic
distance above the disk surface. The disk includes a magnetic
coating that is selectively magnetizable. As the head flies over
the disk, it "writes" information, that is, data, to the hard disk
drive by selectively magnetizing small areas of the disk; in turn,
the head "reads" the data written to the disk by sensing the
previously written selective magnetizations. The read/write head is
affixed to the drive by a suspension assembly and electrically
connected to the drive electronics by an electrical interconnect.
This structure (suspension, electrical interconnect, and read/write
head) is commonly referred to in the industry as a Head Gimbal
Assembly, or HGA.
[0002] More specifically, currently manufactured and sold
read/write heads include an inductive write head and a
magnetoresistive (MR) read head or element or a "giant"
magnetoresistive (GMR) element to read data that is stored on the
magnetic media of the disk. The write head writes data to the disk
by converting an electric signal into a magnetic field and then
applying the magnetic field to the disk to magnetize it. The MR
read head reads the data on the disk as it flies above it by
sensing the changes in the magnetization of the disk as changes in
the voltage or current of a current passing through the MR head.
This fluctuating voltage in turn is converted into data. The
read/write head, along with a slider, is disposed at the distal end
of an electrical interconnect/suspension assembly.
[0003] An exploded view of a typical electrical
interconnect/suspension assembly is shown in FIG. 1, which
illustrates several components including a suspension A and an
interconnect B. It will be understood that the actual physical
structures of these components may vary in configuration depending
upon the particular disk drive manufacturer and that the assembly
shown in FIG. 1 is meant to be illustrative of the prior art only.
Typically, the suspension A will include a base plate C, a radius
(spring region) D, a load beam E, and a flexure F. At least one
tooling discontinuity 70 G may be included. An interconnect B may
include a base H, which may be a synthetic material such as a
polyimide, that supports typically a plurality of electrical traces
or leads I of the interconnect. The electrical interconnect B may
also include a polymeric cover layer that encapsulates selected
areas of the electrical traces or leads I.
[0004] Stated otherwise, suspension A is essentially a stainless
steel support structure that is secured to an armature in the disk
drive. The read/write head is attached to the tip of the suspension
A with adhesive or some other means. The aforementioned electrical
interconnect is terminated to bond pads on the read/write head and
forms an electrical path between the drive electronics and the read
and write elements in the read/write head. The electrical
interconnect is typically comprised of individual electrical
conductors supported by an insulating layer of polyimide and
typically covered by a cover layer.
[0005] As mentioned previously, the slider "flies" only a
microscopic distance--the "fly height"--above the spinning media
disk. Control of fly height is critical for the operation of a disk
drive. If the fly height is too large, the read/write head will not
be able to read or write data, and if it is to small, the slider
can hit the media surface, or crash, resulting the permanent loss
of stored data. As such, the fly height of the slider is determined
in much part by the characteristics of the head suspension assembly
to which it is mounted. The head suspension imparts a vertical
load, commonly referred to as "gram load", on the slider, normal to
the surface of the disk, in order to oppose the "lift" forces
created by the air passing between the slider and the spinning
disk. As a result, head suspension assemblies are manufactured with
a very precise gram load, typically with a tolerance of .+-.0.2
grams. Another head suspension assembly characteristic that has a
significant effect upon the fly height of a slider, is referred to
as "static attitude". Static attitude is the angular attitude of
the gimbal to which the slider is mounted. Typically, head
suspension assemblies are manufactured with tolerances for static
attitude approaching .+-.30 arc-minutes.
[0006] Successful reading or writing of data between the head and
the spinning media also requires that the head be precisely
positioned directly above the location on the disk to which data is
to be written or read. As such, great care is taken to design and
manufacture head suspension assemblies so as to optimize the
suspension's vibrational, or resonant, performance.
[0007] There are three basic configurations of electrical
interconnect/suspension assemblies that are currently utilized in
the disk drive industry. With the first, a Trace Suspension
Assembly, or TSA, the electrical interconnect is fabricated
integrally with the flexure. The TSA flexure/interconnect is
fabricated by selectively removing material from a laminate of
stainless steel, polyimide, and copper. The TSA
flexure/interconnect is then attached to a loadbeam, typically with
one or more spot welds between the stainless steel layer of the TSA
flexure/interconnect and the stainless steel of the loadbeam.
[0008] Another interconnect configuration, termed CIS, is very
similar to TSA in that the CIS interconnect is also fabricated
integrally with the flexure. However, the CIS interconnect/flexure
is fabricated with "additive" processes, rather than "subtractive"
processes. The CIS interconnect/flexure is attached to a load beam
in much the same manner as the TSA flexures and conventional
flexures are, with one or more spot welds between the stainless
steel of the flexure and that of the loadbeam.
[0009] The last interconnect configuration that is utilized today
by disk drive assemblers is essentially a flexible circuit. The
flexible circuit consists of a base polymer, typically a polyimide,
which supports copper traces, or leads. In this case, the
interconnect is fabricated independently from the flexure, and is
later adhesively attached to a conventional head suspension
assembly, to form a Flex Suspension Assembly, or FSA.
[0010] The attachment of conventional flexures to load beams with
spot welds has been practiced for years throughout the head
suspension industry and is well understood. Thus, the attachment of
a CIS or TSA interconnect/flexure to a loadbeam utilizes existing
techniques, and does not present any significant challenges for
manufacturers of head suspension assemblies. On the other hand,
adhesive attachment of flexible circuits to conventional head
suspension assemblies results in a number of issues which the
manufacturer of head suspension assemblies must address. For
example, the conventional suspension to which the electrical
interconnect is attached, is manufactured with great care to ensure
that the gimbal is at the prescribed static attitude. But when the
electrical interconnect is bonded to the conventional suspension
assembly, the static attitude of the gimbal is altered relative to
the angular attitude of the gimbal region of the electrical
interconnect, thereby increasing the static attitude variation and
changing the static attitude average of the completed head
suspension assembly/electrical interconnect.
[0011] While FSA is significantly cheaper than it's counterparts,
namely TSA and CIS, the degradation in FSA performance due to the
adhesive attachment of the flexible circuit creates a tradeoff
between cost and performance that must be considered when comparing
the competing technologies.
[0012] As such, it is the object of the present invention to
eliminate the degradation in FSA performance associated with the
adhesive attachment of the flexible circuit to the head suspension
assembly. More specifically, it is the object of the present
invention to minimize the change in static attitude of the gimbal
of a head suspension assembly during the adhesive attachment of a
flexible circuit to a head suspension assembly.
SUMMARY OF THE INVENTION
[0013] It is an object of the present invention to provide a method
of producing an electrical interconnect which is attached to a
conventional head suspension assembly without significantly
affecting the static attitude attributes of the head suspension
assembly.
[0014] It is an object of the present invention to provide an
electrical interconnect which is attached to a conventional head
suspension assembly without significantly affecting the static
attitude attributes of the head suspension assembly.
[0015] The present invention is directed to a head suspension
assembly/electrical interconnect that cantilevers a read/write
magnetic transducer head adjacent the rotating surface of a disk in
a disk drive from an actuator arm of the disk drive, and the method
of constructing the head suspension/electrical interconnect
assembly. The present invention includes both methods and designs
intended to minimize the change of the head suspension gimbal's
static attitude resulting from the adhesive attachment of an
electrical interconnect, thereby improving the manufacturing yields
and performance of the head suspension assembly/electrical
interconnect.
[0016] The present invention accomplishes the foregoing aims and
goals by providing a web out of which the electrical interconnect
is formed, the web having at least a bottom layer of a synthetic
material supporting a conductive material. The conductive layer is
selectively removed to form the electrical leads or traces, thus
forming an interconnect blank. Subsequent to the formation of the
traces, the bottom support layer is selectively removed, thus
forming an interconnect blank that is still attached to the web by
a pair of tension tabs composed of the bottom (or substrate)
material. These tabs provide a tension directed in a direction
angularly disposed to the longitudinal axis of the interconnect
blank. The interconnect blank is then severed from the web, with
the tension tabs exerting a laterally directed tension, thereby
substantially inhibiting deformation of the gimbal region of the
interconnect and the creation of non-planar slider standoffs.
[0017] The foregoing objects of the invention will become apparent
to those skilled in the art when the following detailed description
of the invention is read in conjunction with the accompanying
drawings and claims. Throughout the drawings, like numerals refer
to similar or identical parts.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is an illustrative, exploded, perspective view of a
typical suspension/interconnect assembly.
[0019] FIG. 2 is a top plan view of a hard disk drive.
[0020] FIG. 3A is a side elevation, partial view of a hard disk
drive, such as that shown in FIG. 2.
[0021] FIG. 3B is an enlarged view of the area shown in the phantom
circle in FIG. 3A.
[0022] FIG. 4 is an exploded perspective view of a
suspension/electrical interconnect.
[0023] FIG. 5 is an enlarged top plan view of the gimbal region of
a standard electrical interconnect before it has been excised from
the polyimide web.
[0024] FIG. 6 is an enlarged top plan view of the gimbal region of
an electrical interconnect in accord with the present invention as
it appears before it is excised from the polyimide web.
[0025] FIG. 7 is a partial cross sectional view taken along viewing
plane 7-7 of FIG. 6.
[0026] DETAILED DESCRIPTION OF THE INVENTION FIGS. 2, 3A, and 3B
illustrate a hard disk drive 10 in a top plan, highly schematic
view. It will be understood that many of the components found in
such a disk drive 10, such as memory cache and the various
controllers are not shown in the figure for purposes of clarity. As
illustrated, drive 10 includes at least one, and typically several,
disks 12 mounted for rotation on a spindle 14, the spindle motor
and bearing not being shown for purposes of clarity. A disk clamp
16 is used to position and retain the disk 12 on the spindle 14.
The disk drive 10 further includes an "E" block 18, best seen in
FIG. 2A. The E block 18 gets its name from its shape as viewed from
the side. It will be observed that E block 18 includes a plurality
of actuator arms 20, 22, and 24, which are supported for pivotal
motion by an actuator pivot bearing 26. A voice coil motor assembly
28 is used to control the pivoting motion of the actuator arms
20-24.
[0027] Each actuator arm 20-24 includes a head gimbal assembly 30
comprising a suspension 32, a read/write head/slider 34, and
interconnect 36 that extends from the head/slider to the actuator
flex. The dashed circle shows an expanded view of the arm 20, which
includes a substrate 40 (wherein the bracket indicates the lateral
extent of the substrate relative to the actuator arm 20 in this
particular embodiment) upon which electrical leads or traces 42 are
supported. The electrical conductors 42 are typically copper or
copper alloy with a gold plating.
[0028] The substrate 40 will substantially underlie the traces 42.
Substrate 40 may comprise a synthetic material such as polyimide,
which may be of the type sold under the brand name Kapton by I.E.
DuPont.
[0029] FIG. 4 is an example of a head suspension/electrical
interconnect assembly 44 for which the present invention is
intended. Assembly 44 may have varying configurations depending
upon the manufacturer. Assembly 44 is comprised of four primary
components: electrical interconnect 36, flexure 45, loadbeam 46,
and a baseplate (not shown for the purposes of clarity).
[0030] The loadbeam 46 can be properly described as having a
mounting region 48 (to which a baseplate is mounted), a spring
region 50, a load beam body 52, and a loadpoint 54.
[0031] Similarly, the flexure 45 is comprised of a flexure body 56
and a gimbal region 58. The flexure body 56 is rigidly affixed to
the load beam body 52, typically with one or more spot welds. As
such, the gimbal region 58 of the flexure 45 is not rigidly affixed
to the loadbeam 46. Within the gimbal region 58 of the flexure 45,
there is a support pad, commonly referred to as the tongue 60. The
tongue 60 is in point contact with the loadpoint 54, and provides
for a mounting surface to which the slider is affixed with adhesive
or some other means. The tongue 60 is connected to the flexure body
56 by resilient springs, commonly referred to as flexure arms 62.
This construction of flexure 45 and load beam 46 provides for the
tongue 60 to pivot, or gimbal, about the loadpoint 54 when a small
torque is applied. The flexure 45 and load beam 46 assembly is
referred to as a "conventional" suspension assembly. After the
electrical interconnect 36 has been applied to a conventional
suspension assembly, the assembly will more properly be referred to
as a head suspension/electrical interconnect assembly 44.
[0032] The electrical interconnect 36, as described previously,
generally consists of a base substrate 40, such as polyimide,
supporting electrical leads or traces 42. At one end of the
electrical interconnect 36 are slider termination pads 64 that form
electrical connections to the read/write head. The electrical
interconnect 36 may also have an area of substrate that is
sandwiched between the flexure tongue 60 and the read/write head
slider (not shown in these figures). The electrical interconnect 36
is attached to the conventional suspension assembly such that is
rigidly affixed to the suspension assembly in areas proximal to the
flexure body 56 and load beam body 52. The electrical interconnect
36 may also be rigidly attached to the flexure tongue 60.
[0033] It is desirable to attach the electrical interconnect 36 to
the conventional head suspension assembly as described previously,
without significantly impacting the performance of the conventional
head suspension assembly. Adhesive is used to affix the electrical
interconnect 36 to both the load beam body 52/flexure body 56 and
flexure tongue 60. If the portion of the electrical interconnect 36
that is affixed to the flexure tongue 60 is not planar with the
flexure tongue 60, the static attitude of the flexure tongue 60
will change respective of the relative stiffnesses of the flexure
45 and electrical interconnect 36 and respective of the difference
in planar angles of the flexure tongue 60 and electrical
interconnect 36. Additionally, the distribution of planar angles of
the electrical interconnect 36 serves to increase the distribution
of the gimbal static attitude of the head suspension assemblies 44
to which they are attached. As a result, it is advantageous for the
planar angles of the region of the electrical interconnect 36 which
is bonded to the flexure tongue 60 of the flexure 45 to be
consistent from part to part, that is, to have a very tight
distribution with little variation. Therefore, factors which impart
variability on the planar angles of the electrical interconnect 36
in the area of the electrical interconnect that is bonded to the
flexure tongue 60 of the flexure 45 are desirably minimized.
[0034] The electrical interconnect 36 is created from a "web" of
material by way of subtractive processes, such as etching and
blanking. The "web" is generally a comprised of at least one layer
of copper and one or more layers of polyimide, or some other
polymer. The layers of copper and polyimide are patterned and
material is selectively removed to formulate the electrical
interconnect 36. This process may include plating, spray coating,
etching, developing, exposing, stripping, and curing, without
regard for the frequency and order. Variants to this process are
obvious and well known to those skilled in the art. Many of the
processes, such as stripping and plating, utilized to manufacture
the electrical interconnect 36 exert high pressures and loads on
the web, thereby imparting significant stresses into the individual
electrical interconnects 36. This can result in significant
un-wanted yielding or bending of the electrical interconnects 36 if
the electrical interconnects 36 are not properly supported in the
web. Additionally, near the completion of the electrical
interconnect 36 manufacturing process, the individual electrical
interconnects are blanked, or sheared, from the web with blanking
dies. The blanking process again imparts significant stresses into
the web and can result in un-wanted yielding or bending of the
electrical interconnects 36. As mentioned earlier, it is
advantageous for the electrical interconnect 36, especially the
portion of the electrical interconnect that is to be affixed to the
flexure tongue 60, to be flat and very consistent within a
distribution.
[0035] Referring now to FIGS. 5, 6 and 7, the present invention
will be described in broad detail. FIGS. 5 and 6 illustrate an
enlarged top plan view of an electrical interconnect 36 as it
appears near the end of the electrical interconnect 36
manufacturing process, with the electrical interconnect still
supported by the web 70, and not yet blanked from the web 70. The
cross-hatched areas in FIGS. 5 and 6 depict areas of the web 70 in
which the polyimide has also been removed, thereby defining a hole
through both surfaces of the web and the perimeter of the
electrical interconnect 36. As discussed previously, the
interconnect 36 includes one or more slider standoffs 72, which are
the portions of the electrical interconnect 36 that are affixed to
the flexure tongue 60 on a conventional head suspension assembly.
The slider standoffs 72 should be planar with the rest of the
electrical interconnect 36 so as not to significantly affect the
static attitude of the head suspension to which it is attached.
[0036] FIG. 5 illustrates the manner in which electrical
interconnects are commonly supported by the web 70 in today's
electrical interconnect 36 manufacturing processes. Of most
interest is the tip tab 74 which connects the gimbal portion 76 of
the electrical interconnect 36 to the web 70. During the
manufacturing process, tension on the web 70 results in
corresponding tensioning of the electrical interconnect via the tip
tab 74. The direction of the tensioning imparted by the tip tab 74
as indicated by arrow 78 is in the longitudinal direction of the
electrical interconnect 36 and causes the interconnect gimbal arms
80 to be deformed, as illustrated by the dashed line 82, resulting
in a condition in which the slider standoffs 72 are non-planar with
the rest of the electrical interconnect 36. Additionally, the
blanking process employed to excise the electrical interconnect 36
from the web 70, results in a similar tensioning of the tip tab 74,
again resulting in non-planar slider standoffs 72 with respect to
the rest of the electrical interconnect 36.
[0037] FIGS. 6 and 7 illustrate one embodiment of the current
invention. Specifically, the electrical interconnect 36 is attached
to the web 70 through two lateral in-line tabs, referred to as
gimbal bar tabs 84. The gimbal bar tabs 84 are positioned on the
gimbal portion 82 of the electrical interconnect 36 such that they
are separated by a collinear continuous polyimide member 88. That
is, the tabs 74 are connected by a substantially continuous portion
or column of the substrate material such that the shearing force
applied during the severing of the interconnect from the web is not
borne by the gimbal arms 80 or slider standoffs 72. Stated
otherwise, the tensioning of the gimbal bar tabs 84, which is
indicated by arrows 86 in the lateral direction and which occurs
during the electrical interconnect 36 manufacturing process and the
blanking process, does not impart stresses into either the
interconnect gimbal arms 80 or the slider standoffs 72. As a
result, the deformation 82 which commonly occurs in the gimbal
portion 76 of the electrical interconnect 36 during the
manufacturing and blanking processes, is greatly minimized.
[0038] Referring specifically to FIG. 7, it will be noted that the
web 70 includes at least a bottom layer 90 made of synthetic
material such as polyimide. This layer 90 supports a conductive
layer 94 made of a conductive material such as copper. During
manufacture of the interconnect 36, the conductive layer 94 is
selectively removed according to the aforementioned known
processes, resulting in the formation of the traces 42 being
supported on the bottom layer 90, which forms the aforementioned
substrate 40 of the interconnect. Further processing results in the
removal of the supporting layer 90 in the cross-hatched areas 71
shown in FIGS. 5 and 6, thus leaving an interconnect blank
connected to the web by the tension tabs 84. The interconnect blank
98 is then removed from the web 70 by known means. For example, the
interconnect blank 98 shown in the Figure would be severed from the
web substantially along the cutting line 96, thus forming an
interconnect such as the interconnects shown in FIGS. 1 and 4. This
severing process would sever the tension tabs 84.
[0039] Thus the present invention employs the use of opposing
support tabs, separated by a collinear, substantially continuous
member of polyimide to connect the gimbal region 76 of the
electrical interconnect 36 to the web 70 during it's manufacturing
processes.
[0040] Other modifications, alterations, or substitutions may now
suggest themselves to those skilled in the art, all of which are
within the spirit and scope of the present invention. For example,
small holes or apertures could be present in the collinear section
of polyimide separating the opposing tabs which attach the gimbal
region of the electrical interconnect to the web. Additionally,
rather than truly being collinear, the opposing tabs could be
slightly misaligned, and still provide the same benefit (i.e.
rather than a 180 degree included angle between the two tabs, an
included angle of greater than 100 degrees would suffice).
[0041] And finally, the present invention as described herein is
applicable to any variant of the components or elements such as,
dual-layered interconnects, integrated gimbal products,
microactuated products, "Femto" products, flex gimbals, and
products intended to be used with a headlift.
[0042] The present invention having thus been described, other
modifications, alterations, or substitutions may also now suggest
themselves to those skilled in the art, all of which are within the
spirit and scope of the present invention. It is therefore intended
that the present invention be limited only by the scope of the
attached claims below.
* * * * *