Suspension flexure with primary and secondary stiffness control

Optimized stiffness in a disk drive suspension comprising a load beam and a flexure structure is realized by forming the flexure structure from a flexure and a flexible conductor in which the conductor is a laminate of conductive metal and plastic and has an easily controlled and relatively higher spring constant, while the flexure has a relatively lower spring constant.

REFERENCE TO RELATED APPLICATION 
This application claims the benefit of U.S. Provisional Application No. 
60/026,747, filed Sep. 26, 1996. 
BACKGROUND OF THE INVENTION 
This invention has to do with disk drive suspensions, more particularly 
with flexure and conductor assemblies for disk drive suspensions, and 
especially with the modification of flexure stiffness by fixing a flexible 
conductor having a separate stiffness thereto. Electrical connection and 
modification of the stiffness properties of the flexure are thus both 
obtained from a single arrangement of components. 
The invention enables the use of very thin flexures having improved 
performance parameters. In a specific aspect, the invention provides disk 
drive suspensions and flexures therein in which the spring constant is the 
sum of the inherent spring constant in a very thin flexure and the greater 
spring constant of a conductor laminate secured to the flexure. In a 
further aspect, the invention provides for reduction in conductor induced 
biases and certain bimetallic bending effects observed in disk drive 
suspensions by routing of the conductor as a laminate circumjacently of 
the flexure and supporting it at multiple locations, while attaching the 
laminate at a selected flexure locus where the resulting bias is 
predictable and parallel to the flexure spring. 
BRIEF SUMMARY OF THE INVENTION 
Accordingly the objects of the invention include the realization in a disk 
drive suspension the foregoing benefits and advantages over previously 
known disk drive suspensions. 
These and other objects of the invention to become apparent hereinafter are 
realized in a disk drive suspension comprising a load beam, and supported 
by the load beam a flexure structure comprising a flexure having a given 
stiffness and a flexible conductor of a separate given stiffness, the 
flexure structure having a stiffness which is the sum of the stiffhesses 
of the flexure and the flexible conductor, the flexure structure being 
adapted to support a slider and head in gimballing relation 
In this and like embodiments: the flexure has a thickness of from about 
0.0008 to about 0.0011 inch and a spring constant of less than about 2 
.mu.n-m/deg.; the flexure and the flexible conductor are adhered to each 
other in stiffness combining relation; the flexible conductor comprises at 
least one conductive wire and a plastic film laminated to the wire; the 
flexure structure has a predetermined spring constant, the flexure having 
a spring constant lower than the flexure structure predetermined spring 
constant, the flexible conductor having a spring constant higher than the 
flexure structure predetermined spring constant and sufficient when added 
to the flexure spring constant that the flexure structure has the 
predetermined spring constant; the flexure comprises a frame having a 
locus, the frame supporting at the locus a tongue for gimballing 
attachment of the slider and head, the flexible conductor lying 
circumjacent the load beam and flexure frame and attached to the flexure 
frame at the locus; the flexure defines a plurality of laterally 
projecting tabs, the flexible conductor being supported on the tabs 
circumjacently of the flexure except at the locus, whereby the flexible 
conductor bias on the flexure is parallel with the flexure tongue; the 
flexure tabs are circumferentially distributed about the flexure in 
bimetallic bending effect reducing relation; the flexure has a thickness 
of about 0.0011 inch and a spring constant of less than about 2 
.mu.n-m/deg.; and the flexure and the flexible conductor are adhered to 
each other at the flexure frame locus in stiffness combining relation. 
In a further embodiment of the disk drive suspension, the flexure structure 
has a predetermined spring constant, the flexure having a spring constant 
lower than the flexure structure predetermined spring constant, the 
flexible conductor having a spring constant higher than the flexure 
structure predetermined spring constant and sufficient when added to the 
flexure spring constant that the flexure structure has the predetermined 
spring constant. 
In this and like embodiments: the flexure comprises a frame having a locus, 
the frame supporting at the locus a tongue for gimballing attachment of 
the slider and head, the flexible conductor lying circumjacent the load 
beam and flexure frame and attached to the flexure frame at the locus; the 
flexure defines a plurality of laterally projecting tabs, the flexible 
conductor being supported on the tabs circumjacently of the flexure, 
whereby flexible conductor bias on the flexure is parallel with the 
flexure tongue; the flexure defines a plurality of laterally projecting 
tabs, the tabs being circumferentially distributed about the flexure in 
bimetallic bending effect reducing relation; the flexure has a thickness 
of about 0.0008 to about 0.0011 inch; and the flexure comprises a frame 
having a locus and a tongue depending from the frame at the locus, the 
flexible conductor and frame being adhered to each other at the flexure 
frame locus in stiffness combining relation. 
In a further embodiment, there is provided a disk drive flexure comprising 
a frame having a locus and a depending tongue at the locus for mounting a 
slider and head in gimballing relation, the flexure having a plurality of 
laterally projecting tabs for carrying a flexible conductor circumjacently 
about the flexure with the flexible conductor attached to the flexure 
frame at the locus. 
In this and like embodiments, the disk drive flexure has a thickness of 
about 0.0008 to about 0.0011 inch; and the flexure has a spring constant 
of less than about 2 .mu.n-m/deg. 
In yet a further embodiment, there is provided a disk drive flexure for 
mounting a slider and head in gimballing relation, the flexure having a 
thickness of about 0.0008 to about 0.0011 inch. 
In this and like embodiments, the disk drive flexure has spring constant of 
less than about 2 .mu.n-m/deg.; the flexure has a plurality of laterally 
projecting tabs for carrying a flexible conductor circumjacently about the 
flexure; there is further included a flexible conductor attached to the 
flexure frame, the flexible conductor having a greater spring constant 
than the flexure, whereby the assembly of the flexure and the flexible 
conductor has a spring constant which is the sum of the spring constants 
of the flexure and the flexible conductor; the flexible conductor 
comprises a plastic film and copper conductor laminate, the plastic film 
having a thickness of about 0.0005 to about 0.0020 inch and the copper 
conductor having a thickness of about 0.0002 to about 0.0007 inch. 
In a still further embodiment, the invention provides a disk drive 
suspension comprising a load beam, a flexure, a perimetrical locus 
surrounding the flexure, the flexure having a central portion including a 
head gimbal assembly for a slider carrying a head in movable relation to a 
disk, and connected to the head an electrically conductive flexible web 
disposed within the perimetrical locus and beyond the flexure center 
portion. 
In its method aspects, the invention contemplates the method of supporting 
a conductor on a disk drive suspension, including maintaining the 
conductor within a plastic film laminate, securing the laminate to the 
outer end of a flexure carried by a load beam, and routing the laminate 
circumjacent the flexure from the load beam to the flexure outer end. 
In this and like embodiments, the method further includes maintaining a 
series of tabs projecting laterally from the flexure, and carrying the 
laminate on the tab circumjacently of the flexure. 
In a further aspect, the invention provides the method of modifying the 
stiffness of a disk drive suspension flexure, including selecting a 
flexure having a frame of a given stiffness, locally securing to the 
flexure frame a laminate of a conductor and plastic film of a separate 
given stiffness than the flexure given stiffness while maintaining the 
balance of the flexure frame free of securement to the flexure frame to 
add the stiffness of the laminate to the given stiffness of the flexure 
frame. 
In a still further aspect, the invention provides a method of manufacturing 
a disk drive suspension, including mounting to a load beam a flexure with 
a flexure tongue arranged for carrying a slider and a head and depending 
from a locus on the flexure, mounting a flexible laminate of a conductor 
and a plastic film to the flexure at the flexure locus for connecting the 
conductor with the head, and routing the laminate circumjacently of the 
flexure to the load beam. 
In another method embodiment, the invention provides a method of operating 
a disk drive suspension, including maintaining a flexure and slider 
carried head connected to a conductor within a plastic laminate fixed to a 
forward locus on the flexure, and supporting the laminate rearwardly of 
the locus circumjacent the flexure.

DETAILED DESCRIPTION OF THE INVENTION 
The invention provides a number of advantages especially in the design of 
nano and pico sized slider and suspensions systems. The invention enables 
the head gimbal assembly to have electrical connections to the magnetic 
heads without causing excessive bias to the slider air bearing. The bias 
from the flexible conductor is controlled and predictable. The invention 
enables bonding of the flexible conductor circumjacently of the flexure 
and load beam and avoidance of bonding of the conductor to the top of the 
flexure or load beam. The flexible conductor is guided around the flexure 
and attached to extensions of the flexures beyond the perimeter of the 
flexure body, and fixed with epoxy adhesive or laser welding. Accordingly, 
the invention advantages include: 
1. The use of the flexible conductor eliminates the wire biases caused by 
use of 4 wires to the head. 
2. The flexible conductor bias is predictable, can be designed for, and is 
parallel with the flexure spring. 
3. Multiple attachment points of the flexible conductor to the load beam 
and flexure reduces bimetallic bending effects arising from temperature 
change in the disk drive. 
4. Flexible conductors are low cost and reliable. 
5. Multiple layers of conductors can be designed at lower cost than other 
solutions. 
6. Flexure and suspension vibration gain is dampened by use of the flexible 
conductor in accordance with the invention. 
With reference now to the drawings in detail, in FIGS. 1, 2 and 3 disk 
drive suspension 8 comprises a generally conventional load beam 10 and 
affixed thereto a flexure structure 12 according to the invention. The 
flexure structure 12 comprises the flexure 14 and the flexible conductor 
16. The flexure 14 is formed of stiff material such as a stainless steel 
having a known stiffness. It is an advantage of this invention that the 
flexure 14 can be formed thinner than heretofore and thus have increased 
responsiveness, but without loss of adequate stiffness in view of the 
combination of the flexure with the flexible conductor 16. 
Flexible conductor 16 comprises one or more conductors 18 laminated within 
opposed plastic film sheets 20 for transfer of signals from a head to be 
attached to the flexure 14 via a slider not shown. Flexible conductor 16 
has a stiffness contributed by the stiffness of the conductors 18 therein, 
by the stiffness of the film sheets 20, and by their lamination together 
as shown. The flexible conductor 16 stiffness is a known value for a given 
laminate. 
It is the availability of a known stiffness value flexible conductor 16 
which enables the controlled modification of the flexure 14 to a desired 
stiffness value above that realized from the flexure alone owing to its 
lower than normal thinness. 
The flexure structure 12 comprises the flexure 14 and the flexible 
conductor 16 attached to the flexure by welding or adhesive at the tabs 22 
which extend from the periphery 24 of the flexure frame 26. The flexible 
conductor 16 is only attached to the flexure frame 26 at the locus 30 
where its leads (not shown) are connected to the head (not shown). 
The flexure frame 26 supports the tongue 34 at the locus 30 for gimbaling 
attachment of a slider and head arrangement (not shown). The flexure 14 is 
preferably relatively thinner than the usual flexure, having a thickness 
of about 0.0008 to 0.0011 inch. In a preferred mode, the flexure 14 has a 
spring constant of less than about 2 .mu.n-m/deg. and higher than the 
spring constant of the flexure 14. The flexure frame 26 supports the 
flexible conductor 16 in circumjacent relation on the tabs 22, enabling 
the routing of the flexible conductor around rather than upon the flexure 
as described. The effect of the connection of the flexible conductor 16 at 
the locus 30 is a modification of the flexure 14 stiffness and its spring 
constant in the sense that the structure 12 which comprises the flexure 
and the flexible conductor has a stiffness and spring constant that is the 
additive result of the flexure and flexible conductor values, assuming the 
bond between them to be only a nominal factor. In general, it is desired 
to use a thinner, more flexible flexure 14, provided adequate stiffness 
can be maintained. The flexible conductor 16 provides the ability to 
obtain the degree of stiffness desired in a given thinness flexure 14. 
For example, a flexure structure formed of a stainless steel flexure 14 of 
0.0011 inch thickness having a spring constant K.sub.S to which is bonded 
a flexible conductor 16 comprised of Kapton-E of 0.0020 thickness 
laminated with a conductor of copper 0.0007 inch thickness having a spring 
constant of K.sub.flex will have a spring constant K=K.sub.S +K.sub.flex. 
As an illustration, a typical flexure will have the stiffness values in 
Column A below, a typical flexible conductor the stiffness values in 
Column B, and the flexure structure from their combination, their combined 
stiffness values as shown in Column C. 
______________________________________ 
STIFFNESS VALUES 
A + B = C 
______________________________________ 
Pitch 2.84 .mu. N.m/Deg 
+ 0.45 .mu. N.m/Deg 
= 3.29 .mu. N.m/ 
Deg 
Roll 2.15 .mu. N.m/Deg 
+ 0.27 .mu. N.m/Deg 
= 2.42 .mu. N.m/ 
Deg 
Lateral 
10.41 N/mm + 0.30 N/mm = 10.71 N/mm 
______________________________________ 
In the method aspects of the invention, the flexible conductor 16 is 
supported on the disk drive suspension 8 by including conductors 18 within 
a laminate of plastic sheets 20 to form flexible conductor 16, securing 
the flexible conductor to the locus 30 at the outer end of the flexure 14 
carried by the load beam 10, and routing the laminated flexible conductor 
across the laterally projecting tabs 22 circumjacent the flexure from the 
load beam to the locus 30. 
In a further method aspect, the stiffness of the suspension flexure 14 is 
modified by selecting a flexure 12 having a frame 26 of a given stiffness, 
locally securing, e.g. at locus 30, to the flexure a flexible conductor 16 
of a separate given stiffness than the flexure, and maintaining the 
balance of the flexible conductor free of securement to the flexure frame 
to add the stiffness of the flexible conductor to the given stiffness of 
the flexure frame. 
In a further method aspect, a method of manufacturing a disk drive 
suspension 8 is provided, including mounting to a load beam 10 a flexure 
14 with a flexure tongue 34 arranged for carrying a slider and head, and 
depending from the flexure, mounting a laminate of a conductor 18 and 
plastic film 20 to the flexure at the flexure locus 30 for connecting the 
conductor to with the head, and routing the laminate circumjacently of the 
flexure, carried on laterally projecting tabs 22. 
In the operation method of the invention, the flexure 14 adapted to carry a 
slider and head is maintained connected to a conductor 18 within a plastic 
sheet 20 laminate fixed to a forward locus 30 on the flexure, the laminate 
being supported rearwardly of the locus and circumjacent the flexure. 
The invention thus provides for the use of very thin flexures having 
improved performance parameters, including a spring constant which is the 
sum of the inherent spring constant in a very thin flexure and the greater 
spring constant of a conductor laminate secured to the flexure, a 
reduction in conductor induced biases and bimetallic bending effects by 
routing of the conductor as a laminate circumjacently of the flexure and 
supporting it at multiple locations, while attaching the laminate at a 
selected flexure locus where the resulting bias is predictable and 
parallel to the flexure spring. 
The foregoing objects of the invention are thus met.