Flexure with reduced unloaded height for hard disc drive heads

A flexure for mounting a head in a hard disc drive. The gimbal of the flexure includes a load point tab which retains the full thickness of the original flexure material for most of its area and further includes a thinned area local to and surrounding a desired location for a load point button. The thinned area is formed out-of-plane from the remainder of the flexure by approximately one-half the material thickness. The size of the thinned area is selected to be such that the thinned area is substantially non-compliant under intended load forces.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates generally to the field of hard disc drives, and more 
particularly, but not by way of limitation, to a flexure for supporting a 
head in a disc drive, the flexure having a reduced unloaded height. 
2. Brief Description of the Prior Art 
Disc drives of the type known as "Winchester" disc drives are well known in 
the industry. Such disc drive data storage devices typically contain a 
stack of rigid discs coated with a magnetic medium on which digital 
information is stored in a plurality of circular concentric tracks. The 
storage and retrieval of data--also called "writing" and "reading", 
respectively--is accomplished by an array of heads, usually one per disc 
surface, which are mounted on an actuator mechanism for movement from 
track to track. The most common form of actuator used in the current 
generation of disc drive products is the rotary voice coil actuator, which 
uses a voice coil motor (VCM) coupled via a pivot mechanism to the heads 
to access data on the disc surfaces. The structure which supports the 
heads for this movement is referred to as a head/gimbal assembly, or HGA. 
The HGA in a typical disc drive consists of three major components: 
1. a slider, which features a self-acting hydrodynamic air bearing and an 
electromagnetic transducer for recording and retrieving information on a 
spinning magnetic disc. Electrical signals are sent to and received from 
the transducer via very small twisted copper wires; 
2. a gimbal, which is attached to the slider and is compliant in the 
slider's pitch and roll axes for the slider to follow the topology of the 
disc, and is rigid in the yaw and in-plane axes for maintaining precise 
slider positioning, and; 
3. a load beam, which is attached to the gimbal and to a mounting arm which 
attaches the entire assembly to the actuator. The load beam is compliant 
in the vertical axis to, again, allow the slider to follow the topology of 
the disc, and is rigid in the in-plane axes for precise slider 
positioning. The load beam also supplies a downward force that counteracts 
the hydrodynamic lifting force developed by the slider's air bearing. 
Since the introduction of the first Winchester disc drive, the physical 
size of the slider has been progressively reduced, first from the original 
Winchester head to the so-called "mini-Winchester", and more recently to 
the 70 and 50 Series heads, which are 70% and 50% the size, respectively, 
of the mini-Winchester slider. While these size reductions are 
significant, the overall vertical dimension of the HGA has been dictated 
more by the slider-supporting mechanism than by the size of the slider 
itself. 
The load beam and gimbal comprise an assembly generally known as a head 
suspension, head flexure, or simply a flexure. An example of such a 
flexure is described in U.S. Pat. No. 4,167,765. 
Historically, the gimbal and load beam are fabricated discretely. The 
gimbal and load beam pieces are realized by chemically etching 300 series 
stainless steel foil into the desired shape, and then the two pieces are 
attached by means of laser welding. 
The general technology trend in disc drive data storage devices is 
continual shrinking of the physical size of the product while providing 
increased data storage capacity. The down-sizing of the product has 
required smaller components, especially the principal components such as 
discs, sliders and flexures. Additionally, disc drive designers seek to 
add capacity to their designs by incorporating as many discs as possible 
within defined package dimensions. As the number of discs in the unit 
increases, the spacing between the discs decreases, thus further driving 
the need for smaller sliders and flexures. 
Another industry trend is to provide the user of disc drives with high data 
storage capacity at low cost. This requires developing improved data 
recording technology and finding lower cost ways of manufacturing the 
components of the disc drive. 
The use of discrete gimbal and load beam components laser welded together, 
as shown in the '765 patent, has become problematic in disc drives of the 
current 2.5", 1.8" and 1.3" generations of disc drives. In such units, the 
flexures must become thinner in order to allow desirable close spacing of 
the discs, while the overlapping required to laser weld two discrete 
components dictates a certain minimum height for the flexure. 
Furthermore, the use of thinner gimbal and load beam components increases 
the likelihood of residual stress caused by the laser welding of the two 
components together. It has been found that laser welding produces 
residual tensile stress in the material local to the welds. This causes 
the flexure to distort. In the longitudinal direction, the flexure curls 
from the residual weld stress, and this makes it more difficult to fit the 
flexure between closely spaced discs during the manufacturing process. 
Further, if the welds are not placed symmetrically about the longitudinal 
centerline of the flexure, the residual weld stress will cause a torsional 
distortion, or twisting, of the flexure. Such an flexure is undesirable 
since the twist will create a moment, or torque, on the slider's air 
bearing, causing unwanted changes in the flying attitude of the head, and 
potentially rendering the assembly unusable. 
The welding process is also a substantial portion of the labor that goes 
into the manufacture of a flexure, and it would, thus, be advantageous to 
eliminate the practice of making discrete gimbals and load beams and 
welding the two together for cost reduction. 
Since the gimbal and load beam components must overlap in flexures of 
existing art, the emphasis on reducing the thickness of the flexure 
assembly has most often focused on reducing the thickness of the 
individual gimbal and load beam components. The thickest area of the load 
beam is the region known as the rigid beam, which usually features flanges 
along the outer edge along the longitudinal axis of the flexure. U.S. Pat. 
No. 4,996,616 teaches how a pair of drawn ribs can provide reinforcement 
of the rigid beam section of the flexure. Unfortunately, the drawn pair of 
ribs of '616 requires that the flexure material be strained to exceedingly 
high levels. Such stain can introduce cracks in the drawn material, and 
high stresses in the material near the ribs. 
Various attempts have been made to solve the problems inherent in welding a 
gimbal and load beam together by devising a flexure in which the gimbal 
and load beam are formed from a single piece of material and would thus 
require no welding. An example of such an integrated gimbal and load beam 
is presented in U.S. Pat. No. 4,245,267. A second example is known as the 
HTI Type 16, or T16, manufactured by Hutchinson Technology, Incorporated. 
Both of these flexures have a gimbal incorporated into the load beam and, 
of course, no gimbal-to-load beam welds. Both include a bonding surface on 
which adhesive is placed to secure attachment of the slider to the 
flexure. A plurality of beams, etched into the load beam, connects this 
bonding surface to the load beam portion of the flexure and provides the 
desired gimbal characteristics. 
One failing of the flexure of the '267 patent and the T16 flexure relates 
to an element of flexure design commonly referred to as "load point". 
Simply stated, load point refers to the single point of contact where the 
downward force of the load beam is applied to the slider. Proper selection 
of this load point ensures that the forces related to the hydrodynamic air 
bearing of the slider are properly balanced. In prior art flexures such as 
the one described in the '765 patent, load point is developed by forming 
an upward-extending dimple in the gimbal bonding surface. The load beam 
contacts the spherical surface of this dimple at a single point to allow 
proper gimbal action. In the case of the '267 and T16 flexures, however, a 
well defined load point is not provided, and, thus, an undesirably wide 
range of variation in slider flying characteristics is associated with 
these types of flexure. 
A second fundamental problem with the '267 and T16 types of flexures is 
that the downward force of the load beam is applied to the slider by 
placing the gimbal beams into bending mode, and the gimbal beams must 
therefore be stiff in bending mode. These same gimbal beams, however, must 
be compliant in bending mode to allow the proper gimballing action. This 
conflicting requirement results in designs that either work poorly as a 
gimbal or become deformed under load. 
A third problem with the '267 and T16 flexures is that the slider bonding 
surface, in general, covers a large area over the center of the slider. 
The slider is attached to the flexure with an adhesive epoxy, and, in 
order to reduce the cure time of the adhesive, the assembly is usually 
heated in an oven. Since the slider and flexure are made of dissimilar 
materials with different coefficients of linear thermal expansion, 
thermally induced strains develop at the bond when the assembly cools. 
These strains can distort the slider and undesirably change the flatness 
of the air bearing surface of the slider, thus, once again, introducing 
unacceptably wide variation into the flying characteristics of the heads. 
Two examples of a unitary, or one-piece, flexure which overcomes these 
deficiencies are described in co-pending U.S. patent applications No. 
07/975,352, of which this application is a continuation-in-part, and No. 
07/976,163, now U.S. Pat. No. 5,331,489, issued Jul. 19, 1994, both filed 
Nov. 12, 1992, both assigned to the assignee of the present invention and 
the latter of which is incorporated herein by reference. 
The flexures of the above-cited references are manufactured from a single 
piece of fully hardened 300 series stainless steel using the processes of 
through-etching and half-etching. That is, the overall outline and through 
openings are created by through-etching, while certain features are formed 
with a reduced material thickness brought about by the process of 
half-etching. 
In typical chemical through-etching processes, the material to be etched is 
first coated on both sides with a material called resist. The resist is 
patterned using a stencil and exposing the resist to a light source. 
Unexposed resist is then stripped away, leaving exposed metal that will be 
etched away in the presence of an acid-like etchant, while those areas of 
the material protected by the resist, or "mask", remain at their original 
thickness. Both sides of the material are treated in this manner, with the 
pattern on both sides being identical and very accurately aligned. By 
carefully controlling the strength of the etchant and the time of exposure 
of the material to the etchant, very precisely shaped and dimensioned 
parts can be realized. 
In half-etching, the pattern of the stencil on one side of the material is 
dissimilar to that on the other side. This also is a well known technique 
for etching text, art or half-tone photographs into sheet metal. It is 
known that if the area to be half-etched is large--that is, it has a 
length or diameter many times that of the material thickness--then the 
depth of the half-etching will be approximately sixty percent that of the 
material thickness. That is, during the time of immersion in the etchant 
solution which will cause through-etching in those areas where the 
etchant-resistant mask is missing on both sides of the material, those 
areas of the material which are exposed only on one side will be etched to 
about forty percent of the original material thickness. 
This half-etching process is used in the flexures disclosed in the cited 
references to reduce the thickness of a pair of gimbal beams which are 
compliant in the flexure's roll and pitch axes, and stiff in the yaw and 
in-plane axes. 
Two tabs are also formed in the disclosed flexures, with the first tab left 
at the original material thickness and used to adhesively bond the slider 
to the flexure. 
The second tab is used to support and mount the load point button which 
contacts the top of the slider and transfers the downward force of the 
flexure to the slider to counterbalance the hydrodynamic lifting force of 
the slider's air bearing. This load point tab is half-etched on the side 
toward the slider, except in that location selected for the load point, 
which retains the original material thickness. This is achieved by masking 
the location and shape of the desired load point button to prevent etching 
at that point, as described above. 
Because of the relative thinness of the load point tab of the cited 
references, this tab must be pre-formed--that is, bent at a compensating 
angle--so that when the entire assembly is placed under the designed load 
in cooperative arrangement with the surface of a disc, the load point tab 
is brought back into parallel relationship to the gimbal beams and slider 
mounting tab. Such a head/flexure assembly has a very low "loaded" height. 
It has been found, however, that the design of the flexures of the cited 
references introduces significant variability between individual units 
when produced in a high-volume manufacturing environment. Specifically, it 
is difficult to closely control the thickness of the load point tab as 
determined by the half-etching process, which leads to the necessity of 
varying the angle at which the load point tab is preformed to compensate 
for the variations in thickness. 
Additionally, since the load point tab is pre-bent to compensate for load 
on the head, the unloaded height is necessarily increased, and it is this 
unloaded height of the head/flexure assembly which determines how much 
inter-disc spacing must be allowed for assembly of the disc drive. 
A need clearly exists, therefore, for an improved slider-supporting flexure 
which reduces the overall unloaded vertical height of the HGA, as well as 
eliminates much of the individual variation between units, and which can 
be manufactured in a simple, cost-effective manner. 
SUMMARY OF THE INVENTION 
In the improved one-piece flexure assembly of the present invention, the 
majority of the load point tab is left at the full material thickness, 
while only a relatively small area local to the load point button is 
half-etched. This half-etched area, including the load point button, is 
then pressed or stamped in a secondary manufacturing step to form the load 
point button out of plane from the original material surface. In preferred 
embodiments, the amount of displacement of the half-etched area local to 
the load point button is equal to approximately one-half the original 
material thickness. The size of the half-etched area local to the load 
point is selected such that the half-etched area after forming is 
substantially non-compliant under intended load forces. The gimbal beams 
and slider mounting tab are created as in the first of the previously 
cited references. 
It is an object of the invention to provide a flexure, for mounting a head 
in a hard disc drive, which has a reduced unloaded height. 
It is another object of the invention to provide a flexure which is 
manufacturable with less unit-to-unit variation than in flexures of the 
prior art. 
It is another object of the invention to provide a flexure which is simple 
and inexpensive to fabricate. 
These and other objects and advantages of the present invention will become 
apparent in the following detailed description of the preferred 
embodiment, when read in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Turning now to the drawings and in particular to FIG. 1, shown is a disc 
drive 2 of the type in which the present invention is particularly useful. 
The disc drive 2 includes a base member 4 which, in cooperation with a top 
cover 6 (shown in partial cutaway), forms a sealed environment to protect 
the delicate internal components from outside contaminants. A number of 
rigid discs 8 coated with a magnetic medium are mounted for rotation on a 
spindle motor (shown generally at 10). The surfaces of the discs 8 hold a 
large number of concentric circular tracks to which information is written 
and from which information is read. The reading and writing of data is 
accomplished by a plurality of vertically aligned heads 12, mounted on 
flexures 14, which in turn are attached to a corresponding plurality of 
head mounting arms 16, which form part of an actuator body 18, adapted for 
rotation about a pivot shaft 20 by a voice coil motor (VCM), shown 
generally at 22. The VCM 22 thus controllably moves heads 12 along arcuate 
path 24 across the data tracks (not shown) Power for the VCM 22, as well 
as the signals used to read and write data, is passed via a printed 
circuit cable (PCC) 26. 
Turning now to FIG. 2, shown is a plan view of a flexure 30 made in 
accordance with the application of which this application is a 
continuation-in-part. The flexure 30 is substantially symmetrical about a 
longitudinal axis 31 and is made up of four distinct major areas: 
1. a gimbal/slider mounting area 32; 
2. a rigid beam 34; 
3. a pair of compliant beams 36, and; 
4. an attachment surface 38. 
The entire flexure 30 is formed from a single piece of 300 series full hard 
stainless steel, preferably 0.0025 inches in thickness, and manufactured 
using well known chemical etching processes. 
A pair of alignment holes 40, 42 aid in fixturing the flexure during the 
process of bonding the slider (not shown). 
The attachment surface 38 in the example of FIG. 2 is shaped to be attached 
to a particular type of mounting plate to provide a strong surface for 
attachment of the entire flexure head assembly to the head mounting arms 
16 of the actuator body 18. While the specific method of mounting the 
flexure is not considered a part of this invention, it should be noted 
that this attachment surface 38 could easily be adapted for use with other 
types and designs of mounting apparatus, such as that described in U.S. 
Pat. No. 5,313,355, issued May 17, 1994. 
The direction of movement of the disc relative to the flexure is shown by 
arrow A. Any slider attached to the flexure of the present invention is 
therefore assumed to have its leading edge closest to the attachment 
surface 38 and its trailing edge closest to the free end of the 
gimbal/slider mounting area 32. 
Since the present invention relates to differences in the gimbal/slider 
mounting area 32, no further discussion will be made herein of the other 
portions of the flexure. 
FIG. 3 shows a detailed view of the gimbal/slider mounting area 32 of the 
flexure of FIG. 2 with a slider 48 attached. 
The process of through- and half-etching is used to produce several of the 
features of the flexure of both the previously cited references and the 
present invention. For instance, as can be seen in FIG. 3, an H-shaped 
opening 44 has been etched completely through the material, and areas 
beside the vertical legs and on one side of the cross member of the 
H-shaped opening 44 have been half-etched. Specifically, the area shaded 
lower-left-to-upper-right is half etched on the near side of the material, 
while the area shaded lower-right-to-upper-left has been half-etched on 
the far side of the material. Since the overall thickness of the material 
is approximately 0.0025 inches, these half-etched areas are reduced in 
thickness to about 0.0010 inches thick. 
This half-etching process forms a pair of gimbal beams 58 and a slider 
mounting tab 46 to which the slider 48 is adhesively bonded. As can be 
seen in the figure, this bonding is thus done only in that area of the 
slider 48 closest to the trailing edge of the slider 48. 
The H-shaped opening 44 also forms a load point tab 50 on the opposite side 
of the cross-member of the opening from the slider mounting tab 46. The 
load point tab 50 transmits the load force of the flexure to the slider 48 
via a load point button 52, or load supporting protrusion, which is formed 
by masking the desired location and size prior to half-etching, so that 
the load point button 52 retains the full thickness of the flexure 
material. Since the majority of the load point tab 50 is half-etched on 
the far side of the material as viewed, this has the effect of creating a 
"pin" which projects toward and contacts the top of the slider 48. The 
load point button 52 should be as small in area as is possible given the 
manufacturer's capability in chemical etching. This dimension has been 
found currently to be about 0.002 inches, which causes the load force of 
the flexure to be applied to the slider at as close as possible to a 
single point. The location of this single point is selected to provide the 
desired flying characteristics for the particular design. 
Since the entire load point tab 50 with the exception of the load point 
button 52 has been reduced in thickness by half-etching, it was necessary 
to pre-form the load point tab 50 to compensate for bending which would 
occur due to the "downward" force applied by the remainder of the flexure 
to the slider. A formula for calculating the proper amount of pre-forming 
was given in the first of the previously cited references, and the 
resulting structure is illustrated in FIG. 4, which is a side sectional 
view of the gimbal/slider mounting portion of the flexure of FIG. 2. 
In FIG. 4, the desired forming of the load point tab 50 is illustrated by a 
detail sectional view taken along line 4--4 of FIG. 3. As can be seen, the 
load point tab 50 is bent in the direction of the slider (not shown) at an 
angle of approximately 3.546.degree., as calculated as an example in the 
first of the previously cited references. Because of this bending, when 
the slider is mounted on the slider mounting tab 46, and the entire 
assembly is brought into its intended relationship with the spinning disc 
of the disc drive, the bottom of the load point button 52--and thus the 
top surface of the slider--will lie substantially in the plane occupied by 
the gimbal beams 58. This relationship is best seen in FIG. 5, wherein a 
slider 48 has been bonded to the slider mounting tab 46 and the entire 
assembly brought into operational relationship to a disc 8. However, it 
must be recalled that this ideal relationship occurs only when the slider 
48 of the assembly is in the intended cooperative relationship with the 
disc 8, or in the "loaded" condition. 
Referring now to FIG. 6, shown is the flexure assembly of FIGS. 2 through 
5, with a slider 48 attached to the slider mounting tab 46. This assembly 
is shown in its unloaded condition, that is, as assembled, but not in its 
intended cooperative relationship to a disc. 
As is readily apparent from the figure, this type of flexure forces the 
slider 48 to be displaced slightly "out of plane" with the intended loaded 
configuration shown in FIG. 5, and this displacement results in an 
unloaded height, designated h.sub.u, which is significantly greater than 
the loaded height, designated h.sub.1 in FIG. 5. Once again, it should be 
noted that it is this unloaded height, h.sub.u, which determines how 
closely discs can be spaced in the disc drive, since, during the assembly 
process, a "comb" is usually inserted between the rigid beams of a stack 
of flexures to hold the heads in a separated condition, to allow the 
insertion of the heads over the discs. During this operation, no load is 
applied to the delicate gimbals and they are thus in the unloaded 
condition shown in FIG. 6. 
This relatively large unloaded height, h.sub.u, is the first of the 
drawbacks of the flexures of the previously cited references. 
A second difficulty in implementing the configuration of the previously 
cited references was found to be unexpected variability in the thickness 
of the load point tongue after etching. The preferred embodiments of the 
previously cited references feature a load point tab with a nominal 
thickness of 0.0010 inches. It was found, however, that the half-etch 
manufacturing process could be expected to produce a standard deviation in 
this thickness of 0.0001 inches, or 10%. Equation (1) of the first of the 
previously cited references describes the relationship between load point 
tab thickness and deflection under load, with equation (3) of the 
reference illustrating the case of the preferred embodiment. Table 1 below 
shows the effect of this thickness variability on load point tab 
deflection, and thus on unloaded HGA height, over a .+-.3.sigma. range. 
As can be readily seen from the table, -3.sigma. variation in the thickness 
of the load point tab results in an increase in load point tab deflection 
from 0.002066 inches at the nominal load point tab thickness of 0.0010 
inches to 0.006023 inches at a load point tab thickness of 0.0007 inches, 
or an increase in deflection of 0.003957 inches. Such an increase causes 
the amount of necessary inter-disc spacing to be increased, thus limiting 
the design of the disc drive, while the variability evident in the table 
shows the difficulty of producing consistent results. 
TABLE 1 
______________________________________ 
Load Point Tab Thickness 
Load point Tab Deflection 
______________________________________ 
0.0007 inches (-3.sigma.) 
0.006023 inches 
0.0008 inches (-2.sigma.) 
0.004035 inches 
0.0009 inches (-1.sigma.) 
0.002834 inches 
0.0010 inches (nominal) 
0.002066 inches 
0.0011 inches (+1.sigma.) 
0.001552 inches 
0.0012 inches (+2.sigma.) 
0.001195 inches 
0.0013 inches (+.sigma.) 
0.000949 inches 
______________________________________ 
Note: nominal flexure preload is assumed to be three (3) grams. 
Taking the data from Table 1 into consideration it must now also be 
considered that this variability in deflection under load must be 
compensated for in the forming process used to pre-form the load point 
tab. However, although thicker tabs require forming to less of an angle to 
compensate for loaded deflection, these same thicker tabs form with 
greater angles than do thinner tabs, all other things being equal. Thus it 
is very difficult for the manufacturer to ever find a forming process that 
is a happy compromise for both thick and thin load point tabs. 
A third difficulty with the configuration of the incorporated references 
relates to non-operating shock. Typically, the concern with non-operating 
shock is in the problem of sliders lifting off the disc surface as a 
result of the disc drive receiving a sudden shock or jolt, and then 
impacting the disc surface upon its return to the loaded position. This 
usually happens if the shock is normal to the disc surface and if the 
acceleration magnitude is greater than the load force of the flexure 
divided by the mass of the slider plus that portion of the flexure near 
the load beam. 
With the flexure configuration of the previously cited references, however, 
there is an additional concern when the shock is in a direction which 
encourages the slider toward the disc. Because the half-etched load point 
tab of the previously cited references has low out-of-plane stiffness, the 
mass near the distal end of the flexure will cause the load point tab to 
deflect during such shocks, and, if the magnitude of the shock is great 
enough, the load point tab will deflect enough to contact the upper 
surface of the slider body. This, in turn can result in a chip or particle 
breaking away from the slider body, potentially causing failure of the 
entire disc drive. 
It can be shown that the critical shock level for this mode of failure is 
described by the following relationship: 
##EQU1## 
For the example values used and described in the first of the previously 
cited references, nominal clearance between the slider and the load point 
tab is 0.0015 inches, and the lumped mass of that portion of the flexure 
near the slider is estimated at 0.015 grams. Using this information, 
critical shock levels for different load point tab thickness can be 
calculated from the above relationship, and these results are shown in 
Table 
TABLE 2 
______________________________________ 
Critical Shock 
Tab Thickness Tab Stiffness 
Level 
______________________________________ 
0.0007 inches (-3.sigma.) 
498 grams/inch 
50 G 
0.0008 inches (-2.sigma.) 
743 grams/inch 
74 G 
0.0009 inches (-1.sigma.) 
1059 grams/inch 
106 G 
0.0010 inches (nominal) 
1452 grams/inch 
145 G 
0.0011 inches (+1.sigma.) 
1933 grams/inch 
193 G 
0.0012 inches (+2.sigma.) 
2510 grams/inch 
251 G 
0.0013 inches (+3.sigma.) 
3161 grams/inch 
316 G 
______________________________________ 
In disc drives of the current 2.5" and 1.8" sizes, shock levels below 100 G 
are considered to be unacceptable, which indicates the second reason for 
concern with the completely half-etched load point tabs of the previously 
cited references. 
The flexure of the present invention provides a flexure of the type 
described in the previously cited references, without all of the 
deficiencies of load point tab design recited above. 
Turning now to FIG. 7, shown is a detail plan view of the lower side of a 
flexure including a load point tab 60 which is a part of a first 
embodiment of the flexure of the present invention. As shown, the load 
point tab 60 includes a thinned area 62 local to and surrounding the 
desired location of the load point button 64. This thinned area 62 is 
formed using the process of half-etching, as described above, and, after 
the etching process is complete, the load point button 64 retains the full 
thickness of the flexure material. 
The size of the thinned area 62 is selected such that the thinned area 62 
is small enough to not bend under intended load forces exerted on the load 
point button 64. FIG. 8 shows a detail sectional view taken along line 
8--8 of FIG. 7, and shows that the thinned area 62 is formed as a result 
of etching to displace the load point button 64 "out-of-plane" with the 
remainder of the load point tab 60. The amount of displacement is selected 
to be approximately one-half of the original material thickness The 
specific factors used to determine the size of the thinned area 62, as 
well as the minimum bend radii which will not cause excess strain in the 
materials used are also illustrated in FIG. 8, and their desired 
relationship is defined by the formulae 
EQU 2R sin.theta.=r 
EQU 2R.theta.=1.05 r 
EQU 2R(1-cos.theta.)=dimple height=0.0015" 
where: 
.theta.=the angle through which the bending is performed, in radians 
R=the radius of the bend, measured to the material centerline, and 
r=the greatest extent of the thinned area, measured from the center of the 
load point button to the outer edge. 
By applying these formulae, a thinned area which is unbendable under the 
intended load conditions and does not result in excessive material strain 
can be defined. 
Furthermore, even though the forming of the thinned area 62 is a secondary 
manufacturing operation to the etching/half-etching process used to form 
the outline and features of the flexure, the precision of the location of 
the load point button 64 is not subject to tolerance variations in the 
forming process, unlike prior art formed dimples, since the location of 
the load point button 64 is purely a function of the easily controlled 
etching/half-etching process. 
FIG. 9 shows a detail bottom plan view of a portion of a load point tab 60, 
illustrating a second possible embodiment of the present invention. In 
this embodiment, the thinned section 70 is oblong rather than circular as 
was shown in FIG. 7, and the load point button 72 is clearly shown to be 
offset from the centerline 31 of the flexure. This offset is intended to 
compensate for differences between the linear velocity of the spinning 
discs under the inner and outer air bearing surfaces of the slider, as was 
thoroughly explained in the application of which this application is a 
continuation-in-part. FIG. 9 also serves to illustrate that the specific 
shape of the thinned area 70 is not limiting to the scope of the present 
invention, so long as care is taken during the forming of the thinned area 
70 to avoid undue straining of the material. 
FIG. 10 shows a bottom plan view of a third and presently preferred 
embodiment 80 of the flexure of the present invention. Several differences 
between this embodiment and the embodiment of FIG. 7 are apparent. 
Firstly, the width of the load point tab 82 has been reduced, such that, 
when a slider (not shown) is attached, the outer lateral two-thirds of the 
slider will be accessible from the top. This will allow the attachment of 
conductive wires to head terminations on the top surface of the slider, as 
was described in detail in U.S. Pat. No. 5,331,489, previously 
incorporated herein by reference. 
Secondly, a relief slot 84 has been through-etched through the load point 
tab 86, and the thinned area 88 is now of a rectangular shape. Once again 
it should be noted that the exact shape of the thinned area is not to be 
considered limiting to the scope of the present invention, so long as care 
is taken during the forming of the thinned area to avoid excessive strain 
on the material. The forming of the thinned area 88 of the preferred 
embodiment is illustrated in FIG. 11. 
FIG. 11 is a sectional elevation view of the flexure of FIG. 10 taken along 
the line labeled 11--11 in FIG. 10. In FIG. 11, the load point tab 86 can 
be seen to be of a first material thickness, while the thinned area 88 is 
of a second, lesser thickness. This thinning of the material is 
accomplished by half-etching area 88, as described hereinabove. The 
thinned area 88 is then displaced by a secondary manufacturing step 
out-of-plane from the remainder of the load point tab 86 in the direction 
toward the side of the flexure on which the slider (not shown) will be 
mounted. The amount of deflection applied to the thinned area is 
approximately one-half the original material thickness, which results in 
the load point button 90 being displaced from the lower surface of the 
load point tab 86 by approximately one-half the original material 
thickness as well. Such an arrangement places the point of contact between 
the load point button 90 and the top surface of the slider nearly in-plane 
with the gimbal beams 58. Once again, the size of the thinned area 88 has 
been selected to make the thinned area 88 substantially non-compliant 
under intended load forces. The overall effect of the present invention is 
illustrated in FIG. 12. 
FIG. 12 is a sectional side elevation view of a flexure/slider assembly 
which includes the flexure of FIGS. 10 and 11. As shown, displacing the 
thinned area 88, with the load point button 90, approximately one-half the 
material thickness toward the slider 48, results in the slider mounting 
tab 82 being also displaced a similar vertical distance. This displacement 
is accommodated by the flexibility of the gimbal beams 58. It has been 
calculated that, since the majority of the load point tab of the present 
invention retains the full thickness of the original flexure material, the 
placing of a complete flexure/slider assembly under intended loading 
forces will result in a load point tab deflection of only 0.000132 inches, 
and a resultant tab slope of only 0.227 degrees. Therefore, the loaded 
height, h'.sub.1, and unloaded height, h'.sub.u, of the flexure/slider 
assembly of FIG. 12 are virtually identical. A comparison of FIG. 12 to 
FIGS. 5 and 6 will show that while the loaded height, h'.sub.1, of the 
present invention is slightly greater than the loaded height, h.sub.1, of 
the application of which this application is a continuation-in-part (as 
noted in FIG. 5), the unloaded height, h'.sub.u, of the present invention 
is less than the unloaded height, h.sub.u, of the previous application (as 
shown in FIG. 6). It should be recalled that it is the unloaded height of 
the flexure/slider assembly which is limiting to the interdisc spacing of 
the disc drive during assembly. 
FIG. 13 shows a third possible embodiment of the flexure of the present 
invention. In this embodiment, the thinned area 100 is in the form of a 
"stubby tab" which is in turn cantilevered from the distal end of the load 
point tab. Again, the size of the tab would be selected to be 
substantially non-compliant under intended load forces, and the thinned 
area 100 would be formed out-of-plane from the remainder of the load point 
tab by approximately one-half the material thickness. 
FIG. 14 shows a fourth possible embodiment of the flexure of the present 
invention. This embodiment is similar to the preferred embodiment of FIGS. 
10 and 11, inasmuch as the thinned area is substantially rectangular in 
shape. In the embodiment of FIG. 14, however, there are two relief slots 
104 included instead of the single relief slot of FIGS. 10 and 11. 
From the foregoing, it will be apparent that any one of several 
modifications could be made to the embodiments illustrated by a person of 
skill in the art after reading this teaching. Therefore, the scope of the 
invention is to be limited only by the accompanying claims.