Note: Descriptions are shown in the official language in which they were submitted.
Ç;7~
-- 1 --
"DELTA" MAGN~TIC HEAD-SLIDER
A '~Delta slider" for flying a magnetic head on
a fluid bearing above moving magnetic recording media is
disclosed in which an air bearing surface ABS includes a
generally planar, but divergent, fluid support surface
extending generally transver~e to the direction MM of
media movement, with ABS area increasing in direction MM.
The leading-edge of this ABS is relatively narrow and
pointed. A method of making such a Delta slider is also
disclosed.
lQ The present invention relates to magnetic head-
slider assemblies, ana more particularly to air bearing
slider assemblies used for noncontact recording in
magnetic disk files and the like.
-- 2 --
Magnetic head assemblies, comprising sliders
carrying magnetic transducers, are widely and
extensively used in magnetic recording apparatus,
particularly disk recording apparatus. Various types of
head/slider arrangements that fly on a fluid or air
bearing film over the moving recording media surface are
well known in the art. In order to maximize the density
of stored data on such magnetic disks, the flying height
of the transducer above the media is made as small as
is practical, with the requirement that a substantially
constant height be maintained. Conventionally, the
sliders are designed such that they experience, from
their support arms, a constant pressure toward the disk
surface, with the lifting force of the air bearing
serving to hold the slider and transducer away from the
disk surface the desired amount when the disk is
rotating.
An object of this invention is to provide a novel
and improved air bearing slider for a flying magnetic
head assembly that maintains a substantially constant
spacing relative to a moving magnetic medium during
transducing operation.
Another object is to provide a head slider
assembly that is insensitive to skew and disk curvature
or flutter and has a high degree of bearing stiffness
and stability.
7~
-- 3 --
Magnetic head assemblies that fly relative to
magnetic media have been used extensively. The
objectives for improving the noncontact transducing
relationship between a magnetic transducer and a
magnetic recording medium, such as a rotary disk, are
to attain ~ery close spacing between the transducer and
the disk, and to maintain a stable constant spacing.
The close spacing, when used with very narrow ~ransducing
gaps and very thin magnetic record films, allows short
wavelength, high frequency signals to be recorded,
thereby affording high density, high storage capacity
recording. As the data recording technology progresses,
it becomes more desirable to fly magnetic heads more
closely to the magnetic disk surface in order to increase
data packing density.
Workers are aware of prior art techniques to
utilize magnetic head-slider assemblies. In such an
air bearing slider assembly, magnetic transducers are
affixed thereto for non-contact recording on a passing
magnetic disk. Workers know how to mount such magnetic
head assemblies (having air bearing sliders) onto
carriages -- e.g., to be used in integrated data modules
for storage of information in a magnetic disk file.
Efforts now abound to increase the density of
storage on such magnetic disks -- e.g., workers are
trying to narrow disk-track width.
.
-- 4
Among the various types of known slider
configurations are those of Garnier, et al. U.S. 3,855,625
self-loading), Roscamp, et al U.S. 4,081,846 and the
trimaran structures of Warner U.S. 3,823,416 and Piper,
S et al. 3,754,104, where the transducing head is
supported relative to a record medium by three pads
spaced apart from one another in triangular formation.
~ne type of slider which has been developed and
which may possess some self-loading characteristic is
that shown in the Garnier, et al. patent. This slider,
having what is known as a taper-flat configuration with
a ramped portion at the leading edge and two air bearing
rails extending therefrom to the trailing edge with a
rectangular recess therebetween, has provided satisfactory
operation in many respects. The structure is
substantially self-loading in that the rectangular recess
provides a low pressure area to counteract some of the
lift provided by the air bearing side rails such that
the device tends to fly a distance above the moving
media surface which can be controlled by the
relationship between the rectangular recess and the fluid
bearing rails. However, the Garnier, et al. structure
possesses several major disadvantages both in
fabrication and in operation. Since the recessed area
of that structure is rectangular and is enclosed on three
sides by walls, fabrication of the device requires
surface etching to produce the necessary configuration.
The requirement for such etching severely restricts the
~ ~ ~~7~3
types of material tha-t may be used. And, the e-lyes are
substantially perpendicular to the air bearing surface
and act as collectors of dust, debris and foreign
material. A build-up of such material in this cavi-ty
can change the operating conditions of the slider and
head assembly significantly.
Even the slider configurations of Roscamp, et al.
and Warner require expensive processes such as grinding
and lapping within confined areas between side rails.
Such requirements not only increase the manufacturing
costs but also may have adverse effects upon the
production yield.
The present invention provides a "Del-ta slider"
which overcomes many of the disadvantages of the prior
art devices. It is an object of this invention to
provide a novel Delta slider for flying a mangetic head
at a substantially constant spacing from the moving
magne-tic media during operation.
It is another object of this invention to provide
a Delta slider which resists roll.
A further object is to provide such a slider
which is easy and economical to manufac-ture.
To achieve the foregoing, as well as other objects
which will become apparent below, the present invention
provides a Delta-shaped slider Ass for flying a magnetic
head on a fluid bearing relative to magnetic recording
media moving in a predetermined direction, which slider
includes a slider ABS whose area increases as one
proceeds fore-to-aft.
-- 6 --
Embodiments of the present invention will now be
described, by way of e~ample, with reference to the
accompanying drawings (not necessarily to scale), wherein
like reference symbols denote like elements.
FIG. 1 depicts, in schematic perspective, a prior
art self-loading ("modified Winchester") type slider while
FIG. 2 similarly depicts a like known slider whose ABS
pressure profile is given in FIG. 3;
FIG. 4 depicts in plan view a like self-loading
slider, shown in side and end views respectively in FIGS.
5, 6, with different pressure profiles thereof given in
FIGS. 7 and 8, these being idealized pressure-profiles
along respective axes of this slider;
FIG. 9 schematically indicates operational attitude
(side view) of such an embodiment, while FIG. 10 indicates
the same without a back-bar;
FIG. 11 is a highly-schematic, generalized view
(plan, side) of a Delta slider with Back-bar;
FIG. 12-A is an enlarged plan view of a like
slider, shown in side view on FIG. 12-B, in associated
plan view if FIG 13-A and end-view in FIG. 13-B, with a
like plan view in FIG. 14-b and idealized pressure profile
across some portions thereof plotted in FIG. 14-A;
FIG. 15 reproduces a photograph of a Delta slider
flying over a (transparent) disk;
FIG. 16 idealizedly relates the orientation of
pressure pads on a Delta slider;
FIG. 17 very schematically shows a multi-slider
workpiece in side view; this shown in idealized
fragmentary plan view in FIGS. 1~ and 19; and
FIGS. 20/21 show respective modified Delta sliders
very schematically and in plan view.
' ~, '....
Illustrated in FIG. 1 is a prior art ~self-loading"
slider 20' of the conventional, taper-flat configuration
with ramps 22' leading into air bearing support side rails
24' which run the length of the slider. At the leading
edge of the slider a cross rail 26' (emphasizes negative
pressure and self-loading of cavity 30') extends between
the two side rails 24'. Suitable magnetic transducers
28', schematically illustrated in phantom, are provided at
the trailing edge of the transducer.
In this prior art slider 20' the flying height is
controlled by the provision of a rectangular
negative-pressure cavity 30' bounded on three sides by the
side rails 24' and the cross rail 26'. This cavity 30' is
generally formed by various etching techniques, is
disadvantageous in that the manufacturing processes form
side walls 32' and 34' between the base of the cavity 30'
and the side rails 24' and transverse rail 26', which side
walls are generally perpendicular to the surfaces of the
side rail and transverse rail. The abrupt break between
the fluid bearing support surfaces and the side walls, as
well as the corners at the leading edge of the recess 30'
have tended to trap dust and debris and to make continued
control of the flying height difficult. As noted above,
the necessity for forming such a structure by etching has
also limited the materials from which the slider could be
fabricated and has complicated the manufacturing process.
FIG. 2 shows an air bearing head slider formed from
a substantially rectangular block 110 made of ceramic, by
way of example. The slider may be configured with an air
bearing surface that is flat, taper-flat, or other
variations of geometry. The slider configuration has two
spaced side rails 112 and 114 and a cross-rail 16. The
leading portion of each rail 112 or 114, relative to a
moving data track, is formed as tapered sections 118 and
120 respectively. Between the tapered sections and at the
leading end of the slider adjacent to the cross rail 16, a
recessed step 119 is configured.
. ~
. ~
-- 8 --
Magnetic transducer elements 122a, 122b, which may
be thin film assemblies, are bonded to the ends of the
rails 112 and 114 at the trailing end 113 of the slider
relative to the path of movernent of the data tracks as
found for example on a rotating magnetic disk (not shown),
The transducing gaps of the elements 122a,b are
flush with the surface of the side rails 112 and 114. The
slider assembly, when it is urged by a load means toward
the surface of a rotating magnetic disk, establishes a
thin air lubricating film which separates the gaps of the
transducer elements from the disk by a very small, but
constant distance.
A negative pressure zons 2~ is formed by the
configuration of the side rails and cross-rail. The
negative pressure zone is rnade in the recessed region
following the cross-rail 116 and between the two side
rails 112 and 114 to the same depth as the step 119, which
may be in the order of 10 microns.
To provide optimum opposing load forces, and to
realize mechanical stability with insensitivity to skew
and disk curvature or flutter while preserving high
stiffness, reliefs or recessed areas 126 and 128 may be
formed on the exposed surfaces of the side rails and at
the air bearing surface of the slider. The recesses 126
and 128 are formed, by etching for example, to a depth in
the side rails which produces a condition of essentially
ambient or slightly subambient pressure across the side
rails in the recess areas 126, 128 during flying operation
of the head slider. The recesses 126, 128 are preferably
formed to a depth in the range of 0.5 to 3 microns. The
cross-rail 116 may also be relieved to the same depth as
the recesses below the surface of the side rails, during
the same fabrication step.
~ ~67~j~
g _
FIG. 3 depicts a trailing edge isometric view of
the pressurP profile observed with the implantation of the
inventive slider described with reference to FIG. 2. For
reference, the outer slider boundaries are at ambient
pressure. The zones between the pressure peaks (136 and
144, and 134 and 142) have average pressures essentially
equal to ambient, and relate to the side rail relieved
zones 126 and 128 respectively. The two projecting
positive pressure areas 134 and 136 relate generally to
the trailing end surfaces 138 and 140 of the side rails
112 and 114, respectfully, and the positive pressure areas
142 and 144 relate to the front portions 146 and 148
respectively of the side rails. This illustrates
"4-point" slider-record contact (see also U.S. 4,218,715).
., . ~ .
67~-~
-- 10 --
Descrl~tion of Bac~-bar; feature:
FIGS. 4-6 schematically illustrate a "self-loading"
type slider assembly 20 constructed and modified
according to a back-bar feature. This, and other related
S techniques and means discussed for all embodiments, will
generally be understood as constructed and operating as
presently known in the art, except where otherwise
specified. And, except as otherwise specified, all
materials, methods and devices and apparatus herein will
be understood as implemented by known expedients according
to present good practice.
More particularly, FIGS. 4-6 will be understood as
schematically depicting such a slider 20 which is
improved to include a prescribed "full back bar" 21 and
associated "purge channel" 23 extending transverse to
the direction of slider flight (arrow). Slider 20 will
be recognized by workers as otherwise conventional,
comprising a ceramic body 1 with a leading edge portion
20-L and a trailing edge portion 20-TR, a pair of
(positive-pressure) side-rails 20-R, 20-R' (including
projecting, ramped lead-tips 20-T, 20-T'), plus a very
shallow interior aerodynamic cavity 20-C (or "negative-
pressure channel") of prescribed precise dimensions
(usually, up to several hundred ,u-in.).
It has been found that advantageous effects may
be produced by a prescribed e~tension of the slider
length to accommodate a "back-bar" 21 and intervening
"purge channel" 23 of proper dimensions, designed to
9 ~~67~;~
reduce the pressure to zero (atmosphere) -- and yield
such effects as flushing the dirt particles away from
the transducer end. Workers know that one must guard
against detritus clogging slots P, R or cavity L le.g.,
this can lead to a catastrophic head crash). Now, some
detritus build-up is virtually certain with such
sliders. For instance, the best filters ["99.999%"
type] correctly used with such equipment will
customarily exclude all atmospheric contaminants larger
than about 12 ~u". This should eliminate most smoke
particles (usually -~250,u"). But smaller airborne
contaminants abound and can readily build-up in shallow
cavity L (especially at its trailing edge) and/or in
slots P, R [e.g., commonly: oil vapor from the disk drive
bearings, particles from the media -- also smog,
atmospheric dust and fumes, rosin smoke, metallurgical
dust and fumes, viruses, etc.]. Thus, the art needs a
better contaminant-free slider which avoids, or
mitigates, such problems. This is one salient objective
of my invention.
Thus, as one feature hereof, an improved, more
contaminant-free flying slider is provided with a
"back-bar" and associated transverse flush-cavity (purge
channel) adapted to better accommodate multiple heads at
the lowest point of slider's flying face (above disk),
to reduce pitch angle, to better "flush" the slider
(cf. more reliable way of keeping "negative-pressure-
orifice" clean), to facilitate fabrication of thin film
; ` ' g"~ 7~;~
heads (lower cost, yet high reliability due to accuracy
of masking techniques), and to effect improved
"purging" (at the R/W gap).
In particular, this allows multiple transducer
means to be located anywhere across the "back bar"
(compared with conventional sliders). This "back bar"
extends the full width of the slider (trailing edge) --
i.e., to be a "full back bar" (no advantage to less than
full width) -- and it may be of any suitable width
talong direction of axis A) depending on pitch angle
required (e.g., here, several mils width was found
suitable).
The "purge channel" 23 is cut just upstream
(forward) of the back-bar 21 along the slider ABS face
20-f. Channel 23 will be located (along axis A) such as
to terminate cavity L and to distribute positive and
negative (dynamic) forces as understood by workers.
Channel 23 may in some instances be cut in two segments.
Channel 23 is preferably cross-sectionally rectangular
(square-corners as in FIG. 5, e.g., for fabrication
convenience) or virtually any other suitable shape.
For instance, satisfactory operation has been
observed with a self-loading slider like slider 20
(FIGS. 4-6) about 170 mils in length L (Lc = 93 mils) by
40 mils in height h (hc = 25 mils), by 110 mils in width
w (WC ~ 30 mils); with rails having a width wr of about
15 mils [ramp hp about 0.175 mils in height hr;
tips 20-T about 20 mils in lengthr te ~~ bar 20-L about
~ 7~
20 mils in length, fe] with inner "flying-cavity" 20-c
about 500 micro-inch in depth dc and 80 mils in
width wc.
For this slider, under relatively conventional
"flying" conditions (e.g., disk surface-velocity at
mid-track a~out 1500 inch/sec -- 3600 rpm 4"-7" disk
band), it is found satisfactory to make "back bar" 21
about 5 mils wide (Wb) and "square" in cross-section
(cf. FIG. 5) with a purge channel 23 about 10 mils wide
(wp) and about 4 mils deep (dp) and "s~uare-cut". This
afforded a stable flying height of about 5-7 micro-inch
(at trailing edge, along back-bar), and showed fine
"self-flushing" characteristics -- such that workers
would likely be surprised.
--Operation of this Embodiment
(see FIGS. 7, 8):
FIG. 9 diagrammatically suggests how such a
slider 20 is intended to function, as opposed to a like
slider 30 lacking the "back-bar" and "purge channel"
(both sliders assumed to be flying above a disk at a
desired attitude, for read/write operations). The
trailing corner 31-Tc of conventional (self-load)
slider 30 in FIG. 10 will be visualized as allowing
relatively little air (compressed by slider flight) to
escape, and wil~ be seen as approaching so close
("trailing corner" 31-Tc of flying-face 30-f at trailing-
edge 31) to the passing disk surface (see plane M'---M')
as to readily be occluded by debris build-up -- such as
to "block" the desired, necessary purge of its
"negative-pressure-channel" 30-c.
~ 7
- 14 -
By comparison, when analogous embodiment 20 is
provided with a back-bar 21 and associated purge
channel 23 (see FIG. 9) to purge its "negative-pressure-
channel" 20-c of debris, air can readily and quickly
escape to atmosphere, so the slider 20 may purge itself
of debris quite easily. [Note the relatively "massive"
dimensions of purge-channel 23 compared with the
miniscule depth of n-p channel 20-c]. Such "purging"
along such a relatively massive channel (cut transverse
to the flying direction) is found different from (and
superior to) other proposed air escape configurations
such as "parallel slots" through bar 20-B. This proposed
design is not as practical or economical, etc., as I
would like.
Thus, this "full back-bar/transverse purge
channel" design improves operational and other
characteristics of the usual "self-load" slider, giving
a massive air purge conduit across to the air beari~g
surface (to very effectively flush cavity 20-c) and
parallel to the back-bar. The "positive pressure" and
the "negative pressure" regions provide the "net load"
across the air bearing surface (compare FIGS. 7, 8 with
FIG. 4). The positive pressure surfaces (along axis B;
cf. FIG. 8) fully flank the medial negative pressure area
(e.g., along axis A; cf. FIG. 7). The resultant (net,
loading) force due to these pressures provides a
relatively constant load over the slider bearing. Changes
in air flow or disk speed will have negligible effect on
this loading; hence, a more stable air bearing surface is
realized.
~6,7~
-- 15 --
The positive loads due to positive pressure
distribution along the side rails and the "back-bar"
control the "bearing stiffness" o the slider. The
sum of these positive loads tends to increase the "net
load", resulting in a higher air-bearing-stiffness
(see FIGS. 7, 8 for pressure profiles plotted along
axis A, axis B of slider of FIG. 4).
Workers will note that as cavity depth (cd)
increases the flying height (fh) increases and becomes
less linear vs load change -- and tends to approach the
characteristics of a more conventional slider OW
~ordinary Winchester, no Back-Bar) -- something novel
in the art -- also, suction decreases as cd increases.
Thus, a worker would likely prefer a MIN cd design
(e.g., 100 u"); however, for ease and reliability of
rendering such miniscule "cd cuts", we prefer a cd of
about 300 u" (or slightly more~.
The positive pressure distributed along the
back-bar surface will increase slider stiffness. This
added stiffness will tend to improve control of the
slider and inhibit undesirable "roll" (e.g., about
axis A, FIG. 4). The presence of such positive back-bar
pressure also acts to reduce the "pitch restoring moment",
and thus reduce "pitch angle" where pitch angle is
plotted vs load for a "zero load full back bar" slider.
Workers will be surprised to note that, unlike
the ordinary slider, such "back bar sliders" are so
relatively insensitive to changes in load (especially the
smaller cd, at least for such minor load changes). A
like (surprisingly) insensitivity to disk-velocity is
also observed (e.g., 1500-2500 ips).
7~
Initial Delta Embodiment
FIG. 11 indicates some broad features of the
subject "delta slider" here shown rather generally as
- delta slider SL depicted in pitched "flying condition"
flying on an air bearing film past associated
magnetic recording medium M. Slider SL will be
understood as pitched-up by positive hydrodynamic
~orces on forward pad PD (situated just aft of ramp R)
and supported elsewhere by the positive forces on tail
section TL as well as some forces from the rail members
l-RL enclosing cavity CV -- cavity CV acting as a
negative pressure force as with the typical self-floating
slider urging slider SL relatively toward passing
medium M~ A "Delta slider" will be understood as having
a somewhat pointed (reduced width) nose with gradually
increasing ABS area going aft therefrom. (The non-ABS
parts of the slider need not follow this Delta-profile,
though such is prefeFred).
TABLE A
As further detailed below, many desired
characteristics inhere in this "delta slider", such as:
1. It provides a slider with a "three point force
profile" and greater stability (less roll, etc; see
discussion of FIG. 13 below).
2. The delta shape provides a maximum tail area for
mounting read/write heads (as much as with the best
- conventional sliders), whereas the overall slider mass
(weight) is radically reduced (about one-half of a
conventional slider such as in FIG. 1 or in
U.S. 3,855,625, etc.).
7~
- 17 -
3. This great reduction in mass is accompanied by
a significant decrease in production cost and an
increase in the "natural frequency" of the slider --
this latter acting to increase the servo band width
associated with the head carriage (e.g., when mounted on
the same load beam as slider of U.S. 3,855,625, the
delta has a natural frequency 5% higher).
4. The delta design is particularly stable,
especially laterally and is quite resistant to
disturbance from surface asperities, being nimble in
negotiating such, without problems.
5. Delta operation is par-ticularly clean, even
"self-cleaning", since its "plow-shaped nose" is adapted
to thrust particles (dirt, etc.) to one side.
A particularly preferred version of such a delta
slider is shown in FIG. 12A in plan view as delta slider
l-SL, in associated side view in FIG. 12B and in similar
plan view in FIG . 1 3A with a schematic end view in
FIG . 1 3B showing the transducer means mounted on the
tail.
Thus, slider l-SL has a ramp means 1-R across its
forward air bearing surface ("ABS"1, terminating in a
somewhat nose portion 1-N which is somewhat pointed as
illustrated (the ramp section being relatively
conventional as known by workers, both in structure and
in function). A positive pressure pad ABS 1-PD is
provided just aft of ramp 1-R. A negative pressure
cavity l-CV is disposed aft of pad l-PD, and is defined
laterally by a pair of thin rail means l-RL.
-- 18 --
A back bar arrangement preferably terminates
this structure with a back bar slot l-CT just aft of
cavity l-CV (and adapted to "purge" l-CV), with the
other side of slot l-CT defined by a back bar member
ABS l-PB presenting a tail edge l-TL on which transducer
means are mounted (e.g., about five as shown
schematically in FIG. 13B~. Of course, features like
the Back-bar/slot, ramp, etc. are not always necessary
for a Delta slider, as workers will perceive.
The slider material may be made of any known
"slider material" as known in the art; for instance, a
ceramic like Sumitomo No. SCS-AC2 (by Sumitomo Co.)
which, as finished, in the illustrated form may be the
order of .150 to .160" long by about .120 to .130" wide
at tail l-TL and about .034" high with cavity l-CV for
instance being 350 to 400 u-in. deep and slot l-CT
being the order of .004" deep by about .010" wide.
Rail walls l-RL will be kept thin (e.g., about .005").
The angle of divergence of the sides (see AA angle,
FIG. lOA) may be the order of 20 to 22.
-~Results:
Workers will be surprised at how clean, nimble,
stable and effective a slider such as l-SL can be in
operation. For instance, FIG. 15 is a photograph taken
of such a delta slider flying above a glass disk
(photographed from under the disk) with the forward
area 12-A flying at about 14 u-in. and the tail area at
12-T flying at about 2 u-in. in very stable condition.
g.2~7~
-- 19 --
One reason for the great stability and
particularly strong resistance to roll is presented in
the analysis summarized by FIG. 14A, a plotting of
ideal pressure profiles for a slider air bearing like
5 l-SL, illustrated in associated FIG. 14~. Here, it will
be understood that the positive pressure thrusting the
slider away from the medium is principally exerked by
the "front pad" l-PD and to a lesser degree by thé aft
ABS, or "rear pad" (including back bar l-PB and rails
l-RL flanking cavity l-CV). This "rear pad" ABS pressure
profile will be seen as presenting minor peaks PK, PK'
determined principally by the additive function of rails
l-RL. These positive pressures will be understood as
resisted by the oppositely urging negative pressures of
cavity l-CV (see "cavity" in the profile plot).
TABLE B
Some novel features of this delta slider (ABS)
appear to be:
1. CLEAN: A triangular or "Delta" shape (in plan-
cross-section) together with a properly pitched flying
attitude (leading edge flies at greater height than
trailing edge above media) appears to give this design
a particular self-cleaning aspect. Any dirt particles
encountered (at head-disk interface) will likely be
deflected to either side of the slider.
2. STABLE: The slider is supported as it flies on
the medium by three main pressure points (see discussion
re FIG. llA above) with consequent great improvement in
i7~
- 20 -
slider stability, especially in the lateral direction
(vs. roll).
Thus, as opposed to a conventional "rectangular
profile" slider (as slider 20 in FIG. 1), there is
virtual complete elimination of "wobble" tendencies
(i.e., a lateral "seeking" of a plane of stabilization
while flying, with associated oscillation back and forth
in the roll direction, e.g., when one rail ABS l-RL is
not exactly coplanar with the other). Radical reduction
of rail ABS area helps to provide this stability too.
2A. SELF-RIGHTING: Pitch attitude of such a delta
slider should be largely determined by the pressure
differential under the leading pad ABS (l-PD) vs. that
of the trailing edge ABS (l-TE) -- the size of the leading
pad l-PD is probably a significant factor determining the
air bearing pressure attained (here a pitch of about 80
to 90 micro-radians is assumed).
As long as the air bearing surface adjacent the
trailing edge is sufficiently flat, the pressure peaks
near the edges of the slider should be relatively equal
(see FIG. 12, peaks PK, PK,); this balance of forces will
tend to keep the plane of the air bearing surfaces ABS
parallel to the plane of the passing disk.
Further, the fact that the forward pad l-PD has a
reduced-length lateral "lever arm" significantly reduces
roll tendencies. The pressure peak on this leading pad
will be centered on the slider's center line. If the
plane of leading pad l-PD is different than the plane of
the trailing pad, then leading pad l-PD will tend to
7~i~
- 21 -
exert a roll force on the slider. This is indicated
schematically in FIG. 3 where the large ~orce Fl on the
leading pad is directed symmetrically on ~he pad, that
is on the center line of the slider. Since there is
only one force applied to this pad, there is very little
(other than the spatial extent of the force) to affect
the orientation of the pad with respect to the disk.
The trailing pad, however, has a relatively uniform
support along the entire slider width; and this tends
to keep its ABS parallel to the disk surface. Since the
moment arm of the leading pad tending to roll the slider
is so small, the overall roll forces will always be much
reduced and relatively trivial and the slider will
typically tend to return to its "no-roll" equilibrium
state even when perturbed (a "self-righting"
characteristic).
2B. EDGE-FORCES BALANCED: Workers will understand
that as this Delta ABS rushes across a disk (or other
flat) surface, very very close thereto, a type of
"exhaust" is commonly thrown-up about its sides from air
escaping the entrapment induced by "wedging" between the
up-pitched slider and the passing record. Such "exhaust"
can readily tip a slider ABS to one side (undesired
roll) and upset stability. A Delta slider ABS is
desensitized to such exhaust-induced roll and related
instabilities. Also, the simple "cuneiform" ABS shape
makes it much easier for a worker to ascertain the
magnitude of such lateral forces.
.-~
22 -
Also, a "Delta ABS" is more stable under low
transport velocities le.g., flying a few u" above a
3~" or 5~" disk at low rpm -- cf over sputtered
recording surface).
3. NIMBLE: Such a delta slider seems to have
interesting compliance features that make it more
forgiving of media imperfection (e.g., surface
asperities~, being lighter and more nimble in dodging-
around such surface discontinuities (this also results
from its three point pressure contact as well as its
somewhat pointed nose and reduction in forward ABS area
in the lateral direction (i.e., "forward attentuation"
or "pointing").
--Alternative structures:
Where the Delta ABS pre~erably is somewhat
pointed at its leading edge (cf ramp R, FIG. 11), it may
merely be snub-nosed in appropriate cases (e.g., see
slider II, FIG. 20). hikewise, where the back-bar/slot
feature and/or the ramp are not needed, these can be
eliminated (see FIG. 20 also, where Delta slider II is
like slider I in FIG. 11 except for eliminating ramp and
back bar/slot, and exhibiting a relatively blunt nose).
Also, where symmetry of the ABS about center axis
~ ~Ax ~~ Ax FIG. 20) is commonly desired, in some instances
it may not be. For instance, one may orient the ABS
sides at different angles; e.g., to nullify unequal
"exhaust" or like lateral forces. Thus, FIG. 21 shows
a Delta ABS like II in FIG. 20 except that one side
diverges from its center axis Ax ~~ A at about 24 (aa)
- 23 -
- (vs. larger side-thrust on ABS) while the other diverges
at about 24 (bb). Likewise, the size and orientation/
shape of the side rails flanking cavity C~ may be
modified. Also, one could adapt this delta ABS for a
non-self-loading slider (cf where the cavity CV has the
blocking wall on its forward section pierced or
removed), though, as usual, such must be downward urged
for proper loading.
--Manufacturing methods:
A delta slider (e.g., like slider l-SL discussed
above) presents a number of attractive manufacturing
features as well. For instance, when using typical
slider production techniques, one may expect about twice
the yield from a given workpiece, with little or no
significant increase in manufacturing time or costs.
This is a very significant advantage of course as workers
will ~cknowledge. It is somewhat schematically
illustrated in FIG. 15 where a first linear array of
delta sliders SL will be seen as formed by common
treatment steps on a single multi-slider workpiece 15-P
(see FIGS. 17-19), being first formed there and later
cut-out or sliced away (diced). Where sliders SL
(e.g., rectangular) might convent onally be formed from
15-P, the "delta" configuration facilitates doubling the
yield approximately, to also form sliders SL', for
example. That is, a second identical set of sliders SL'
is likewise formed in the interstices between primary
sliders SL; these second sliders SL' however are faced
in the opposite direction so that their air bearing
surfaces ABS are on the opposite side of this plan view.
2~J~3~~
~ 24 -
According to known techniques, such a work-piece
15-P may be clamped at both ends, and an array of
transducers for each slider set formed along the
appropriate edge ( that is lower edge 15-E for sliders
SL and the opposite side, and upper edge for transducers
of the second slider set SL'). Work-piece 15-P may
comprise a three inch thick wafer with the thin film heads
deposited on these edges, and with both sides being
sputtered and electroplated simultaneously, or at least at
the same s*ation, thus reducing the process time by about
one-half. Both sides of the wafer would thus be masked
(resist deposition and removal in common), washed,
cleaned and annealed together, etc; these being performed
on both sides of the wafer at the same station (and
possibly simultaneously). Then t~.e two slider sets SL,
SL' could be cut away for the finished form, yielding
approximately twice the number of sliders for little more
than essentially the same processing time and
trouble-expense.
Workers will be particularly attracted to this
feature of "delta sliders", especially the possibility
of forming two sets of sliders together, with associated
transducers deposited on both sides of the wafer.
Automatic laser machining or ion etching may be
used to conveniently define the air bearing geometry.
One may typically find that the leading ABS pad
and the trailing ABS pad need not be coplanar in all
instances (vs. 4-point pressure profile, as FIG. 3
G~
25 -
which requires co-planarity) -- one other advantage of
the 3-point pressure profile of a Delta slider (see al80
FIGo 16). "Imperfect flatness" of the leading pad may
not be significant in affec~ing Delta slider attitude or
stability -- the 3-point pressure profile is more
tolerant of changes in such.
Special fixturing and transfer tooling would of
course would be advisable. Also, it might not be
feasible to attempt to obtain a precise alignment of the
"zero-throat" line on both sides of the substrate --
thus, it may be pruaent to orient the masks on the
"second side" of the workpiece 180 degrees from those on
the front side, even where trying to maintain alignment
as close as possible. Thus, it is necessary to have
access to both cut surfaces on the workpiece as each
surface will be machined to form ABS pads, though one
need not perform these operations simultaneously. After
the sliders are cut from the workpiece, each ~lider can
be marXed on a bar-by-bar basis using the negative force
cavity l-CV surface as a reference.
FIG. 17 shows a side view of such a workpiece
15-P as described above, clamped top and bottom, while
FIG. 19 shows in plan view somewhat greater detail of
such a workpiece 15-P. For instance, with a tail-spacing
16-S of about 12 mils one day typically laser-etch an
outline each of the sliders (cf step L-l) about 315 + 100
u-in. One may also laser etch the back bar channel (cf
step L-2), e.g., about 4 mils deep. One may also laser
etch the center cavity l-CV (cf. step L-3), e.g., about
350 + 50 u-in. deep.
- ~ ~!3~
-- 26 --
Thus, in summary workers will appreciate that
there has been described a novel "delta slider" and
associated advantageous manufacturing techniques and
that these involve a number of surprising features and
advantages, such as those above mentioned.
For instance, such a low mass delta slider is
appropriate for use on some state of the art disk drive
units. The slider may in some cases even be mounted on
conventional support mechanisms such as the "Watrous
flexure-load beam" or like flexure-spring cantilever.
Such a light slider will exhibit less momenttlm and be
more nimble, thus more readily negotiating a nodule on
a disk surface without being destabilized, etc. thereby.
Reduced mass will also increase the slider's natural
frequency.
The delta slider forms an advantageous "zero load"
(or negative load) air bearing member and as such it
may be appropriate for a wide range of implementations
(e.g., 3.5 in. to 14 in. disks); varying head-disk
velocities (e.g., from 500 to 2500 ips) and even for use
as a "launched" head in a disk drive unit.
And where the back bar is used it is conducive to
the placement of a plurality of read/write transducers
on the device.
The "three point" medium-contact feature will
provide greater stability and less tendency to roll.
Dust particles and the like can be more readily
negotiated and/or diverted out of the slider path by the
light slider and its pointed nose. And, the pointed
nose should slice through the air with less disturbance
and oscillation.
9 2~3~
- 27 -
Manufacturing advantages have also been mentioned
such as the fact that approximately twice the number of
sliders and associated thin film heads can be produced
on a given wafer (both sides) with a consequent
reduction in wafer cost and processing steps (e.g., heads
electroplated in a single step).
Operating with the mentioned slider embodiment
(cf. disk velocity of 1508 in/sec; positive pressure
rails 15 mil wide and 500 u-inch negative air-pressure
cavity), an escape passage 23 as in FIGS. 4-6 and 10 x 4
mils in cross section (for a flying height of 5 to 7
u-inch under the back-bar) increased bearing stiffness
(e.g., by about 10~), gave better control and less "roll",
while reducing "pitch angle" (e.g., from 130 u-radians
to 90 u-radians).
It will be understood that the preferred
embodiments described herein are only exemplary, and
that the invention is capable of many modifications
and variations in construction, arrangement and use
without departing from the spirit of the invention.
Workers will appreciate that such "Delta ABS"
features are apt for use with negative pressure type
sliders which fly at less than 10 u" (as is back bar).
Workers will also appreciate that, in appropriate
instances, one may alternatively use such design (e.g.,
and back bar/purge channel) with low flying, positive-
pressure or zero-pressure (Winchester) sliders.
2.~6~7
-- 28 --
.
Further modifications of the invention are also
possible. For example, the means and methods disclosed
herein are also applicable for flying Delta ABS over
other record surfaces. Also, the present invention is
applicable for providing a precision-flying ABS in
association with other forms of low-mass recording
and/or reproducing systems, such as those in which data
is recorded and reproduced optically.
The above examples of possible variations of
the present invention are merely illust,rative.
Accordingly, the present invention is to be considered
as including all possible modifications and variations
coming within the scope of the invention as defined by
the appended claims.
