Planar HGA for Pico/Nano slider

A head gimbal assembly is provided using a laminated load beam with electrical conductors etched in a copper layer of the load beam. A stiffening member is provided attached to the laminated load beam, the stiffener member being capable of being fabricated into a desired shape by a stamping process.

TECHNICAL FIELD 
This invention relates to a slider-suspension assembly for data recording 
disk files. In particular, the invention relates to an improved head 
gimbal slider-suspension assembly (HGA) for use with very small sliders, 
such as Pico-sized or Nano-sized. 
BACKGROUND OF THE INVENTION 
Disk files are information storage devices which use at least one rotatable 
disk with concentric data tracks containing the information. Also included 
is a transducer for reading data from or writing data to various tracks on 
the rotatable disk. A head or transducer-positioning actuator connected to 
the head for moving it to the desired track and maintaining it over the 
track's central line during read or write operations is also included. 
The transducer is attached to a slider which has an air-bearing surface. 
This surface rides on a cushion of air that is generated when the disk is 
rotating. The surface of the slider opposite to the air-bearing surface is 
attached to the suspension, and the suspension is attached to a support of 
the head-positioning actuator. A Pico-size slider may be 1.25 mm.times.1 
mm.times.0.3 mm thick. The exact size of the Pico slider has not yet been 
firmly standardized. However, the examples given indicate the order of 
magnitude and it is clear that one has to deal with apparatus having 
extremely small dimensions. 
The suspension provides dimensional stability between the slider and the 
actuator arm. It controls flexibility in pitch-and-roll motion of the 
slider relative to its direction of motion on the rotating disk. The 
suspension also provides resistance to yaw motion. 
Typically, a suspension provides a load or force against the slider which 
is directed against the force of the air bearing between the slider's 
air-bearing surface and the disk surface. In this manner, the slider is 
maintained in extremely close proximity to--but out of contact with--the 
data surface of the disk. 
Conventional suspensions typically are comprised of a load beam, which is 
mounted at one end to the actuator arm, and a flexure element or flexure 
which is attached to the other end of the load beam and supports the 
slider. The flexure element generally has a gimbal arrangement for 
permitting the slider to assume the respective different angular positions 
with respect to the data surface of the rotating disk. 
The load beam provides the resilient spring action which biases the slider 
toward the surface of the disk, while (as noted above) the flexure 
provides flexibility for the slider as the slider rides on a cushion of 
air between the air-bearing surface and the rotating disk. Such a 
suspension is described in U.S. Pat. No. 4,167,765, assigned to the same 
assignee as the present application. A conventional slider is described in 
U.S. Pat. No. 3,823,416, also assigned to the same assignee as the present 
application. 
The design of a suspension for a Pico-sized slider is particularly 
difficult due to the load gimbal stiffness, the size of the slider bonding 
pad, and the desire to utilize as much of the disk's real estate as 
possible. Furthermore, such a suspension must be robust so as to be able 
to withstand rough handling and shipping damage, among its other concerns. 
The gimbal design is also demanding because the required pitch-and-roll 
stiffness, including wires, have to be of the order of 60 mN-mm/Rad. A 
Nano-sized slider's requirements are twice or even three times higher. 
The normal way of reducing stiffness is to make the gimbal features 
thinner, about 0.020 mm thick, and longer. This leads to fragility and 
because of the larger features, it also does not properly utilize the 
available disk's real estate areas. It is obvious that fragility is 
undesirable because it would be unable to withstand shock and handling 
damage. Furthermore, if a thin separate flexure is welded to the load 
beam, distortions can occur because of heat dissipation and clamping 
forces. Obviously, the handling of very small pieces may also pose 
additional difficulties. 
An integral flexure approach has been developed which avoids these problems 
by using laminated suspensions. In the laminated suspensions, the 
electrical lead lines are integrated in the load beam so that the wiring 
issue is already taken care of. An integral flexure is a flexure that is a 
single piece with the load beam and not a separate part that is added to 
the load beam and welded thereto. 
The laminated suspensions generally includes three layers, such as steel, 
insulating polyimide and copper. The electrical lead lines can be etched 
into the copper layer, while the polyimide layer can provide insulation. 
The steel layer can also be etched to provide strength characteristics for 
the suspension. 
One of the problems in using the laminated suspensions of the above-noted 
type is the fact that such three-layer material is not well suited for a 
stamping/fabricating process. For example, in some suspensions it is also 
desirable to be able to stamp some formed portions, such as a pivoting 
dimple or flanges to provide rigidity to the overall suspension structure. 
There are also other problems which arise when there is a need for 
unloading the suspension from the disk file for shipping or to avoid 
shock. For this purpose, a tab may be provided on the suspension so that 
the slider-suspension assembly can be moved outside the disk's real estate 
to prevent disk damage by the slider. 
SUMMARY OF THE INVENTION 
The invention is directed to an improved slider-suspension assembly which 
overcomes the disadvantages noted above for Pico-sized sliders. 
An embodiment of the present invention includes a slider-suspension 
assembly for use with Pico-sized and Nano-sized sliders for a data disk 
file. The assembly includes a laminated load beam having a plurality of 
layers, adapted to have a slider mounted at one end thereof opposite the 
file actuator support. The laminated beam has at least one electrically 
conductive layer in which electrical lead lines have been formed for 
connection to the slider. A stiffener member is attached to the laminated 
load beam to provide stiffening to the overall assembly. The stiffener 
member is capable of being fabricated into a desired shape by a stamping 
process. 
In a further preferred embodiment of the present invention, the electrical 
lead lines are etched into the electrically conductive layer to provide 
connections between the slider and the load arm actuator support. 
In another embodiment, the stiffener member may be attached to the steel 
layer of the load beam and be provided in an elongated form having flanges 
of substantially Z-shaped cross-section. 
In still another embodiment the stiffener member arrangement can be formed 
with a dimple adapted to contact the slider for providing appropriate 
motion of the assembly with respect to the slider. 
For full understanding of the nature and advantages of the present 
invention, reference should be made to the following detailed description, 
taken in conjunction with the accompanying drawings.

DESCRIPTION OF THE INVENTION 
Referring to the drawings and, more particularly the FIGS. 1-3, it can be 
seen that the load beam 20 is made up of a steel substrate 10, an 
insulating polyimide layer 11, and a copper layer 12. Mounted on the upper 
steel layer 10 is the stiffener 13. The stiffener 13 is mounted on the 
load beam 20 by means of welding, with weld spots 16 being distributed 
along the outer edge portions of the stiffener. 
It can be seen that the weld spots 16 are spaced away from the edge of the 
load beam 20 containing the slider and its connections thereto. This is 
the rigid section of the suspension, away from the gimbal area. 
Accordingly, the gimbal has no weldment distortions. Relief holes 17 are 
included both in the stiffener and in the load beam 20 to reduce mass. The 
locations of the relief holes, as well as the locations of the weld spots 
16, can be tailored to optimize dynamics. As will be subsequently 
explained, the stiffener 13 can be formed with several different 
cross-sectional arrangements. 
As can best be seen in FIG. 2, the stiffener 13 in this environment 
includes flanges 18 which are generally Z-shaped. The steel layer 10 is 
partially etched at the slider end and has a flexure 19 due to such 
partial etching (FIG. 3). The slider itself, shown in outline 30 (FIG. 
1B), is connected to the load beam by connecting to the slider bonding pad 
21. 
Referring to FIG. 5(a), an enlarged view of the slider end of the assembly 
is shown. In this arrangement, the steel layer 10 has been partially 
etched away to form the flexure elements 32 and 33, and the bonding pad 
21. As can be seen from the dotted outline, the slider 30 is supported by 
the bonding pad 21. Also shown in FIG. 5(a) are pads 36 to provide 
electrical connection to the head transducer as well as the copper traces 
37 connected thereto. The copper traces 37 transmit electric signals from 
the transducer to the head-actuating mechanism at the other end of the 
load beam. 
The bonding pad 21 can also be seen in FIG. 6 which is a cross sectional 
view taken along the line VI--VI of FIG. 5(a). Here the stiffener 13' is 
shown formed with flanges 18 and has a generally Z-shaped cross section. 
Stiffener 13' also has a formed dimple 22 in the center thereof. The 
dimple 22 rides on the steel layer 10 arranged above the insulating 
polyimide layer 11. The steel layer 10 forms the upper surface 10A of the 
slider bonding pad, while the copper layer 12 has copper pads 23 for 
making mechanical contact with a solder spacing bump 24. 
The copper layer 12 also has etched therein copper traces 37 which are used 
for making electrical connections to the slider. Thus, the slider bonding 
pad 21 includes the upper surface 10A and the lower surfaces 26 and 24. 
The surface 24, as noted above, is a spacer formed on copper pad 23. The 
slider 30 is bonded to the lower surfaces of the bonding pad. For this 
purpose, a suitable adhesive is used, such as Blackmax, manufactured by 
the Loctite Corporation. A cross-section of the adhesive is not shown in 
order to avoid unnecessarily complicating the drawing, since this is done 
in a conventional manner. 
From FIG. 6, it can be seen that the stiffener member can be formed by a 
stamping process to produce the shape, including the dimple. A plan view 
of the stiffener 13 is shown in FIG. 4, where the location of the dimple 
22 is indicated as being right above the slider bonding pad 21. As noted 
above, the stiffener 13 is welded to the steel layer 10 of the load beam. 
An assembly includes a laminated load beam that has an integral flexure 
built in and a separate stiffener piece connected to the load beam. The 
load beam has no formed areas other than the hinges that are used for 
preload. The load beam is etched in a planar material that usually is made 
of a steel substrate 10 and can be from 0.018 to 0.0762 mm thick. The 
intermediate insulating dielectric layer 11 can be from 0.005 to 0.0254 mm 
thick in this embodiment, while the conductor copper layer 12 can be from 
0.0127 to 0.0381 mm thick. It is clear that other thicknesses can also be 
accommodated. A load beam that has performed satisfactorily had a steel 
substrate 10, 0.0508 mm thick, a insulator layer 11, 0.018 mm thick and a 
copper layer 12, 0.0178 mm thick. 
To develop the gimbal area for supporting the slider bonding pad 21 and the 
slider 30, a partial etching in the steel layer 10 to about half its 
thickness can be carried out. In FIG. 3, it can be seen that the flexure 
legs 19 run around the trailing end corners of the slider. This is very 
important to maintain the required stiffness needed for Pico-sized 
sliders. 
The slider bonding pad 21, noted above, is provided at the end of the 
flexure legs. The size of the slider bonding pad matches the slider area 
for maximum ease of slider bonding. In this manner, there is no gimbal 
feature in danger of being affected adversely by adhesive oozing. As 
indicated in FIG. 6, the slider bonding pad 21 provides the resting 
surface for the dimple 22 of the stiffener member 13. 
In order to form a gap between the copper layer and the slider, solder 
bumps are deposited on copper pads under the lower bonding surface of the 
bonding pad. This gap is needed to avoid electrically shorting the copper 
traces that are used for carrying electrical signals from the transducer 
mounted in the slider to the electronics connected to the head-actuating 
means. 
The copper traces 37 forming the electrical conductors span the hinge 40 
(FIG. 1A) by exiting on the sides of the load beam 20 and running around 
the mount plate (not shown). This avoids squeezing the copper traces 37 
between the plate and the load beam 20 if a mount plate is used to attach 
the suspension to the arm (not shown). Otherwise, the copper traces can 
span the hinge 40, running between them by using a gentle loop midway to 
better absorb the hinge-forming curvature changes. 
In the above-noted embodiment, the stiffener 13 can be a separate steel 
piece, 0.0305 mm (1.2 mil) or 0.0635 mm (2.5 mil) thick. As shown in FIGS. 
1 and 6, the stiffener 13 and 13' has flanges 18 formed in a "Z" fashion 
with simple bends which run longitudinally to form the stiffening ribs. A 
dimple 22 can be stamped at the slider end, as shown in FIGS. 4 and 6. 
A different arrangement for the stiffener and the slider bonding pad is 
shown in the cross-sectional view of FIG. 7. Here the stiffener 13" is 
arranged without a dimple and has a substantially flat surface 31, 
substantially parallel to the top surface of the slider 30. In this 
arrangement, the steel layer 10' has been partially etched away at the 
slider bonding pad area 21' so that only a small area in the center forms, 
effectively, a partially etched dimple 22' in the slider bonding pad 21'. 
The surrounding partially etched area provides clearance needed for 
gimbaling to permit the tilting of the slider 30. 
For the suspension shown in FIG. 1, the solid height is the sum of the 
slider 30 thickness (0.3 mm), the solder bump spacer 24 (0.015 mm), the 
laminate thickness (0.0508 mm steel substrate 10, 0.0165 mm polyimide 
layer 11, 0.0178 mm copper layer 12), the dimple 22 height (0.025 mm), the 
stiffener 13 thickness (0.0381 mm), and the flanges 18 height (0.125 mm). 
Thus, the solid height is a total of 0.588 mm. 
This solid height of the suspension can be reduced in several ways. If the 
preload is not too high, on the order of 4 gm or less, the height of the 
flanges 18 of the stiffener 13 can be cut to 0.1 mm. In the illustrated 
embodiment, the suspension has a length of 18.04 mm from the dimple to the 
swage hole center. If the suspension is shorter, an even shallower height 
flange 18 height can be contemplated for the stiffener 13. 
The arrangement shown in FIG. 7, which partially etches away the steel 10' 
in the bonding pad 21' area, will provide a lower overall height since the 
dimple 22' formed in the stiffener 13" is contained in the thickness of 
the steel substrate 10'. The partially etched area around the center of 
the top surface of the steel bonding pad 21' provides the clearance, as 
noted above, for the gimbaling. The formed dimple 22, as shown in FIG. 6, 
is removed from the stiffener 13" and its height is removed from the list 
of solid height contributors. Alternatively, the bonding pad 21' itself 
can be partially etched to a smaller thickness so that the dimple rests on 
the reduced thickness bonding pad 21'. Then the partial etch thickness of 
the steel substrate 10', will be the only contribution of the steel 
substrate 10' to the overall solid height. 
If the disk's real estate will permit, the copper traces 37 for providing 
the electrical connections from the slider 30 to the electronics of the 
head-actuating member can be routed outside the slider border (not shown). 
This will save the thickness of the polyimide 11 and the copper 12 layers. 
FIG. 8, including sub-FIGS. 8(A), 8(B), and 8(C), shows a different 
arrangement for the stiffener 13. In this arrangement, as can be seen in 
FIG. 8(A), the stiffener 13 will form essentially a box-shaped 
cross-section with the load beam 20 that is arranged below FIG. 8(A). FIG. 
8(B) shows the dimple 22 arrangement provided at the bond pad 21 of the 
stiffener 13. In the stiffener 13 shown in FIGS. 8 and 9, the stiffener 13 
has been extended beyond the bond pad 21 to provide a load/unload tab 25. 
FIG. 8(C) is a cross-section of the load/unload tab 25 of the stiffener 
13. 
Referring now to FIG. 10, the slider-suspension assembly 20 of FIG. 1 is 
shown mounted in operative relationship with a magnetic disk data storage 
system 40 having a plurality of disks 50. While the assembly 20 is shown 
facing the upper surface of the top disk 50 it can be appreciated that 
each of the disks 50 has a separate assembly. Of course, only a single 
magnetic disk may be used with a single slider-suspension assembly 
depending on the storage and space requirements. 
As is well known, each of the disks 50 has a plurality of concentric data 
tracks. The disks are mounted on a spindle shaft 51 which is connected to 
a spindle motor (not shown). The assembly 20 is mounted on an actuator arm 
52 in turn coupled to an actuator 53. The actuator 52 moves the arm or 
arms 52 in a radial direction across the respective disk when data is to 
be read from or written on to the disk. 
The load/unload tab 25, as mentioned above, is utilized when it is desired 
to move the slider away from the rotating disk 50, when the apparatus is 
not being used, or when the apparatus is being shipped or otherwise 
mechanically handled. This avoids any mechanical damage to the sensitive 
slider 30 and flexure elements 32 and 33. 
It should be appreciated that the invention can be easily extended to the 
Nano-sized slider in the various versions available. The utilization of 
the disk's real estate is improved in the case of the Nano-sized slider 
because the flexure elements 32 and 33 can be contained within the slider 
30 footprint. It is clear that the present invention can also be applied 
to conventional suspensions having discrete wires rather than etched 
copper traces 37. 
In the above manner, it is seen that a head gimbal assembly can be provided 
which includes the advantages of size and the strength of the load beam 20 
combined with the stiffener 13 which may be formed by a stamping process. 
An additional requirement arises when there is a need for a ship/shock and 
static friction protection in the disk file. Usually, this is taken care 
of by adding a load/unload tab 25 to the suspension. This tab slides on a 
ramp outside of the periphery of the disk and allows the suspension to 
move outside the disk, thereby preventing disk damage by the slider 30. As 
noted above, the load/unload tab is connected to the rigid section of the 
stiffener 13, which is attached to the load beam 20, and extends above the 
slider 30 a certain distance beyond its trailing edge. The load/unload tab 
25 is located above the slider 30 in order to save disk real estate. 
However, because it is above, it adds to the solid height of the 
suspension. It should be noted that the measurement of solid height is the 
distance from the air-bearing surface of the slider 30 to the most distant 
suspension feature above the slider 30. 
While the preferred embodiments of the present invention have been 
illustrated in detail, it should be apparent that modifications and 
adaptations to those embodiments may occur to those skilled in the art 
without departing from the spirit and scope of the present invention as 
set forth in the following claims.