WO1996037340A1 - Interactive system for lapping transducers - Google Patents

Abstract

A system for lapping transducers (28) has an abrasive surface (22) that communicates with the transducers to provide information for controlling the lapping of the transducer. The lapping body (20) communicates with a transducer (28) with a signal that the transducer is designed to read or write. For lapping a magnetic head or slider, the lapping body contains a magnetic medium layer (23) that is prerecorded or written by the head during lapping, while the signal received by the head is monitored by a processor (32) in order to terminate lapping.

Description

Interactive System For Lapping Transducers

Technical Field

The present invention is generally directed to the manufacture of transducers for

information storage systems such as disk or tape drives, with particular emphasis on

methods and apparatuses for lapping transducers employed in rigid magnetic disk drives.

Background of the Invention

In rigid magnetic media disk drives, the transducer, for writing and reading

information on the media, typically is formed on or attached to a ceramic carrier, a

"slider," which is supported by a flexible suspension, which is in turn mounted on an arm

of an actuator assembly. The magnetic pole or poles of the transducer are positioned

coplanar with the surface of the slider, which confronts the media. In the past, such

sliders have been designed to "fly" above the surface of the rotating media at the minimum "flying height" consistent with the need to maintain sufficient separation in

order to avoid catastrophic wear and achieve long term reliability. The need to fly low, in

order to increase recording density and performance, is thus in conflict with constraints

imposed by mechanical and interface considerations. The latter relate to a variety of

design, manufacturing and quality control issues, not only of the slider but also of the

surface properties of the media. In particular, tight tolerances are required in creating the "air bearing surface," configuring the "ramp," controlling "throat height" and "pole tip recession" and attaching the slider to the gimbal suspension structure. The allowable recording density increased over the years, presenting greater and greater challenges to manufacture.

It should be noted, in passing, that similar considerations and limitations can be

involved in the design and manufacture of all systems which utilize transducers to sense

or record images from or to a medium. That is, the resolution of such systems is

inversely related to the spacing separating the resolving elements of the transducer, e.g.,

an aperture in a near-field optical system, from the medium. As will become apparent,

the present invention may be applicable to any system in which the particular geometry of

a transmitting or receiving terminal of the transducer is important to signal transmission. A particular manufacturing process that has been employed in defining critical

features of transducers or heads used in magnetic read/write disk drive systems is the

lapping of the transducers by an abrasive surface. With the typical heads of such systems

that are designed to "fly" on an air layer during reading or writing operations with a disk,

such lapping has been used to form the air bearing surfaces and ramps of sliders. A

particular problem encountered in mass production of such heads is the differential extent

to which a row of heads may be lapped, due to "bowing" of the row and other factors. In

U.S. Pat. No. 5,321,882, Zarouri et al. propose that the lapping of a group of air bearing

sliders is more advantageously accomplished by holding the sliders in a column rather

than a row. On the other hand, Bischoff et al., in U.S. Pat. No. 5,117,589, disclose a

device for adjusting the bowing of a row of sliders held by the device during lapping, by

mechanically or electronically compensating for bowing. Commonly, such lapping of flying heads includes an electrical lapping guide

attached to or incorporated in the device holding the transducers in an attempt to

determine when optimal material has been removed, for example, for the throat height of

the heads. As noted in U.S. Pat. No. 4,675,986 to Yen, electrical lapping devices have a

graded resistance at a surface of the holding device in order to measure the lapping of the

heads by measuring the resistance of the holding device. U.S. Pat. No. 5,175,938 to

Smith teaches means for improving the accuracy of an electrical lapping guide by

combining different types of graded resistors. Similarly, in U.S. Pat. No. 4,914,868,

Church et al. disclose a lapping control system for magnetoresitive transducers that

measures the resistance of those transducers to determine lapping height. And Zammit

teaches, in U.S. Pat. No. 5,065,483, a method for lapping thin film heads that compares a

resistive lapping guide with a finished lapping guide in order to calculate appropriate

lapping amounts of the heads.

Another approach to achieving smaller tolerances for head throat heights is to

perform an additional step for adjusting throat heights after lapping. Amin et al., in U.S.

Pat. No. 5,137,750, teach a method of making pole heads that may be etched after lapping

to create contoured pole tips. U.S. Pat. No. 5,283,942 to Chen et al. similarly discloses

an etching step which controls planarization of a gap layer at a pole tip. And in U.S. Pat.

No. 5,327,638, Haines et al. teaches first lapping a magnetic core for a vertical recording

head and then winding an electrical coil around the core.

Despite these advancements, a need for ever more accurate transducer dimensions

calls for continued improvement in the processes used for their manufacture. Moreover, a dramatic recent departure from the conventional magnetic recording technology has

resolved the conflicting demands between the reduction in flying height needed to

increase data storage density and the increased tendency to crash as flying height is

reduced. This conflict is resolved by adopting a fundamentally new slider/suspension

design logic, which assumes at the outset the possibility of reliably operating the

slider/transducer in continuous sliding contact, and is of key importance in U.S. Pat. No.

5,041,932 to Hamilton for INTEGRATED MAGNETIC

READ/WRITE/FLEXURE/CONDUCTOR STRUCTURE, assigned to the assignee of

the present invention. This new technology has demonstrated, in many hundreds of thousands of hours of cumulative testing, virtual freedom from "head crash" and the

capability for reliable, long term operation of sliders in continuous sliding contact with the media. In consequence of these developments, the magnetic spacing loss has been

reduced dramatically while the recording density has been correspondingly increased, and

the manufacture of head/suspension structures has been greatly simplified. It is with the preparation of a transducer surface for optimal conformation and

operational confrontation with a media surface that the present invention is concerned.

Therefore, it is a general objective of this invention to facilitate the manufacture of

transducers so as to increase yield and operational performance and decrease costs. A

specific objective of this invention is to provide simple, cost effective means and methods

of preparing the media-confronting surface of sliding and flying heads in concert with

their suspension structures, termed "sliders", so as to enable optimal magnetic interaction

with the media. Summary of the Invention

The above objects have been achieved with a system for lapping transducers

which employs an abrasive surface that transmits a signal during lapping, while

monitoring the transducer during lapping for an indication derived from the signal that

the transducer has been optimally lapped. To perfect a pole tip for a magnetic head, for

instance, a slider surface is lapped sufficiently to either expose the magnetic pole or to

optimize a throat height for magnetic interaction with an information storage medium.

The optimal amount of lapping is determined directly by reading information from and/or

recording information to a body having a relatively moving abrasive surface, which

serves simultaneously as an abrader and an information storage device.

Such a system for determining when to terminate the lapping of slider surfaces in order to optimize mechanical and recording performance has many advantages, the most important of which may be that reading and/or recording performance is by far the most sensitive measure of the point at which the magnetic pole or poles of the transducer come

into optimal relationship with the media. Another advantage that can be achieved with

such an interactive lapping system is the ability to test a transducer for mechanical and

electromagnetic performance characteristics following lapping, testing which may be

accomplished with the same device used for lapping.

In a preferred embodiment, magnetically active lapping disks having surface

coatings with topographies and molecular structures forming superhard materials

specifically optimized for lapping are employed. Superhard materials are defined in this

application as having a hardness greater than 400 kg(force)/mm . Lapping may be performed in steps with a plurality of disks having decreasing roughness and/or hardness,

so that transducer machining progresses generally from rough lapping to polishing.

Individual lapping bodies such as disks may also be constructed to have a graded

roughness, so that a transducer may be moved from a rough to a smooth portion of the

body according to signals received from the transducer.

In a mass production lapping environment, upon receipt of signals indicating that

an individual transducer has been appropriately lapped, that transducer may be

individually removed from the lapping body, thereby eliminating the problems of the

prior art with uneven lapping of a row of transducers. Moreover, preparing the slider

surface while mounted on an individual suspension rather than a row bar affords an

opportunity not only to individually control the lapping operation for each of many slider

suspension structures in an automated process, but also to automatically test and grade

each head for read/write performance. Performing lapping as one of the final steps in transducer fabrication also allows automatic testing and grading of dynamic mechanical performance of each slider suspension structure while in sliding contact operation with a

disk surface, while flying slightly above the surface for the case of flying heads or while

in "pseudo contact" somewhat between flying and sliding for tail dragging heads. In each

of these situations, transducer signal information may be utilized in combination with

electromechanical transducers, e.g., laser Doppler vibrometers, and signal processing and

analysis.

In addition to the advantages mentioned above, the improvements in machining

tolerances and transducer performance testing are achieved in a relatively simple system that does not require extra etching steps or the electrical lapping guides taught in the prior

art of lapping magnetic sliders. In this context, the present invention not only offers a

means for optimizing throat height and similar dimensions by using the most sensitive

and accurate measurement of those dimensions, but allows for integrated testing of

individual transducer characteristics to determine whether each transducer, slider and

suspension conforms to required specifications, in an automated system which

individually controls lapping and testing of multiple transducers simultaneously, yet

simplifies the lapping process.

Brief Description of the Drawings

Fig. 1 is a perspective plan view of a simple interactive lapping system of the present invention.

Fig. 2 is a plot of an increasing amplitude electronic signal received from a

transducer being lapped in the system of claim 1. Fig. 3 is a fragmentary, expanded, cross-sectional view of a portion of the lapping system of Fig. 1.

Fig. 4 is a fragmentary, expanded, cross-sectional view of a portion of a

conventional flying head being lapped by the system of claim 1.

Fig. 5 is a plot of a surface topography of an interactive rough lapping disk of the

present invention.

Fig. 6 is a plot of a surface topography of an interactive smooth lapping disk of

the present invention. Fig. 7 is a fragmentary top view of a row of transducers being simultaneously

lapped on an interactive lapping disk of Fig. 5 or Fig. 6 while individually controlled by a

processor.

Fig. 8 is a superimposed plot of increasing amplitude electronic signals from the

transducers of Fig. 7 received by the processor during lapping.

Fig. 9 is a plot of the shape of an isolated pulse signal from a transducer received

by the. processor during lapping.

Fig. 10 is a perspective view of a row of transducers connected to flexible support

beams for simultaneous interactive lapping.

Fig. 11 is an expanded, cross-sectional, cut-away view of a system for holding and

communicating with the transducers of Fig. 10 during lapping and for removing the

transducers upon achieving individually optimized lapping.

Fig. 12 is a fragmentary perspective plan view of an interactive lapping drum

employed for lapping a row of single pad transducers. Fig. 13 is a fragmentary cross-sectional view of a pair of transducers and pads of

Fig. 12 being tilted during lapping for rounding of the pads.

Fig. 14 is a simplified plan view of an interactive lapping tape system of the

present invention.

Fig. 15 is a plot of a signal from a transducer being analyzed for performance

characteristics and displaying an amplitude modulation indicating that the transducer is

defective. Best Mode for Carrying Out the Invention

Referring now to Fig. 1, a lapping disk 20 having an abrasive surface 22 is shown

rotating in a direction of arrow A. Associated with the surface 22 is a magnetizable

medium 23, which may be formed at the surface 22 or may be disposed beneath the

surface at a distance which affords communication of magnetic signals through the

surface. A substrate 24 is disposed beneath the medium layer 23 and connected to a

conventional means for rotating the disk such as an electric motor 21. For clarity of

illustration the medium layer 23 is shown in Fig. 1 at an exaggerated distance beneath the

surface 22, separated by a hard protective layer 26. Alternatively, the surface 22 may be

associated with another communication medium, such as an electrical or optical storage medium, for lapping transducers employed in information storage systems of those media.

Projecting inwardly over the surface 22 is a support bar 25 which, for simplicity, is shown to be holding a single transducer 28 via a flexure beam 30, the beam connected

to the bar 25 along with a positioning mechanism 31 located near the juncture of the

beam 30 and the bar 25. An electromagnetic signal 29 is shown schematically in this

plan view as providing communication between the transducer 28 and the media 23 in

order to provide information to a processor 32 regarding the lapping of the transducer 28.

The transducer 28 in this embodiment is designed for contact reading and writing with

rigid magnetic storage media, such as described in the above mentioned U.S. Pat. No.

5,041,932, in co-pending U.S. Pat. Application Serial No. 08/338,394, entitled:

TRANSDUCER/FLEXURE/CONDUCTOR STRUCTURE FOR ELECTROMAGNETIC READ/WRITE SYSTEM and in co-pending U.S. Pat.

Application Serial No. 08/408,036, entitled: CONTACT INTERFACE, SYSTEM AND

MEDIUM IN ELECTROMAGNETIC, READ/WRITE, RIGID-RECORDING-MEDIA

ENVIRONMENT, which are hereby incorporated by reference.

The beam 30 and bar 25 include conductive elements that can carry signals

between transducer 28 and processor 32, which is shown simply as a box in this plan

view. The processor 32 monitors the transducer 28 during lapping with the disk 20, so

that upon receiving a signal from the transducer indicating that an optimal amount of

lapping has occurred, the processor sends a signal to the positioning element 31 , which

causes the positioning element to lift the flexure beam 30 and transducer 28 from the

surface 22, terminating lapping. The positioning element may be a piezoelectric body,

spring loaded switch, vacuum lift or other mechanism which lifts the beam 30 upon

receiving a signal from the processor 32. Alternatively, the signal can be manually monitored for a visible or audible signal at which point the lapping bar 25 can be manually raised, lifting the transducer from the disk to terminate lapping.

Fig. 2 shows a plot 33 of an electronic signal received at processor 32 during

lapping of transducer 28 with lapping disk 20. Typically, little or no signal is obtained

initially from the transducer 28. As the lapping proceeds, a small signal is generated,

after which the signal amplitude increases rapidly as shown by the steeply sloped portion

34 ofthe amplitude plot 33. Subsequent amplitude growth is minimal. The signal

amplitude increases during lapping as material impeding transmission ofthe signal 29 is

removed from a terminal of the transducer 28 by lapping, allowing closer spacing between the terminal and the medium. The appropriate time at which to terminate

lapping depends on a number of factors, and may occur during or just following the

steeply sloped section 34 of the signal amplitude plot 33, as delineated by time 35 of

about 2 minutes. The signal received by the transducer 28 from the lapping disk 20 can

be from a signal that was previously written on the disk or a signal that is written on the

disk 20 by the transducer 28 during lapping. This latter method of writing and reading

the disk 20 during lapping is preferable as the signal increases with lapping due to

increasing both writing and reading signals, thereby enhancing sensitivity. The

simultaneous writing and reading during lapping also provides a method for testing the

writing capability ofthe transducer 28, as well as simplifying the lapping procedure by eliminating prewriting ofthe disk 20.

Fig. 3 shows a more detailed view ofthe structure ofthe transducer 28 and the

lapping disk 20. The disk substrate 24 is formed of a self-supporting material such as an

aluminum alloy. Another hard layer 27 may be deposited atop the substrate 24 and textured before the magnetic layer 23 is sputtered thereon, the texture being substantially

reflected in both the magnetic layer 23 and the hard coating 26, and therefore providing a

texture to the surface 22. For the alternative situation in which the hard coating is formed

directly atop the medium 23, the substrate is first textured in order to obtain a similarly

textured surface 22.

As is known in the formation of rigid magnetic disks, the magnetic layer 23 may

be made of, for example, alloys or lattice superstructures of iron, nickel, cobalt, palladium

or platinum. For a rough lapping disk, the thickness of layer 23 may be over twice that typical for magnetic disks, or as much as about 1000-2000 angstroms, in order to allow a

thicker coating layer. Layer 23 is shown as a single layer, which would be appropriate

for longitudinal recording, while for peφendicular recording a dual magnetic layer would

typically be formed. In the latter case, the stiffening layer 27, the stiffening layer may

become a second magnetically soft (although mechanically hard) layer for use in

peφendicular recording.

The hard protective layer 26 may be formed of diamond-like-carbon (DLC),

silicon carbide, boron carbide or other superhard materials. It is important that this layer

26 be hard for durability ofthe lapping disk 20, thin enough to allow magnetic

communication between the transducer 28 and the magnetic medium 23, and have a

surface 22 texture or topography optimized for lapping the transducer. For the case of a

rough lapping disk, hard coating layer 26 may have a thickness of between 500 and 2000

angstroms, and preferably approximately 1000 angstroms or less. For a smooth lapping

disk the coating layer 26 is substantially thinner, preferably about 200 to 300 angstroms

or less, allowing for more sensitive communication with a transducer 28 and more

accurate testing of various transducer parameters.

The transducer 28 has a head 36 containing a pole 37 for communication with

both the magnetic medium layer 23 of lapping disk 20 and a magnetic medium of a rigid

storage disk or drum, not shown. Pole 46 is surrounded by a hard, wear-resistant, non-

magnetic material 38 such as DLC, which obstructs pole 37 from communicating with

layer 23 or other magnetic media by a layer of the hard material 38 having a thickness T.

Although a single pole is shown in this figure, which is appropriate for vertical recording and reading of a magnetic storage medium, transducer 28 may contain an adjacent pole,

not shown, the gap therebetween utilized for longitudinal reading and writing of a storage

medium. Alternatively, structures associated with a magnetoresistive sensor may be

present in addition to, or in place of, the aforementioned pole or poles. In an upper

portion of transducer 28, a soft magnetic core 40 connected with pole 37 is surrounded

with a helical series of conductive elements 42 to form a helical winding used for

inductively reading or writing through the pole 37 or poles. Alternatively, a spiral or

pancake coil structure, not shown, may be utilized. Transducer 28 is attached to flexure

beam 30, with conductors in the beam 30 connecting with ends of the helical winding

and, at an opposite end, with bar 25 and processor 32 shown in Fig. 1.

The use of progressively smoother lapping disks offers a significant reduction in

pole tip recession, which can be augmented by rounding of the pole tips by lapping

techniques discussed below, including tilting of single pad transducers and lapping with a

tape that tends to conform to the pad or pads. Note that the interactive lapping ofthe

present invention is performed without water or other lubricants or slurry. An electrolyte

solution, however, may be distributed on the surface of a final stage lapping or polishing

disk, and a voltage provided between the transducer and disk, in order to grow the

exposed magnetic pole or poles so that pole tip recession is eliminated. In other words,

after lapping is completed pole 37 terminates coextensively with hard wear material 38 at

essentially the same distance from the surface 22 and medium layer 23 as the remainder

ofthe head 36, eliminating the problem of pole tip recession in the fabrication of

transducers. It is also possible to distribute a solution that selectively etches the hard wear material 38 compared to that of the pole 37 and surface 22. Pole tip recession in

prior art devices presents a problem in both flying type heads and contact heads by

spacing the tip of the pole further from the magnetic medium, thereby decreasing the

resolution at which magnetic data can be written and read.

Fig. 4 illustrates the employment ofthe interactive lapping of the present

invention for a magnetic read/write head 44 designed to fly over a storage surface. The

elements ofthe interactive lapping disk 20 denoted previously are shown here without

delineation for brevity. The head 44 is attached to a slider 45 having an air bearing

surface 47 which is lapped along with the head 44, which can be seen to offer an

extension ofthe air bearing surface 47. A pair of soft magnetic poles 49 and 50 extend

to the bearing surface 47, separated by a gap G at that surface that forms magnetic fields employed typically in longitudinal recording. A number of conductive elements 52 are

wound between the poles 49 and 50 for inductive coupling to those poles to read and/or

write magnetic information to a rigid disk. Critical to the performance ofthe head 44 is

the throat height Th, as the magnetic coupling of signals is stronger as the throat height

Th is reduced, but reduction of the throat height Th to a point at which the gap G widens

destroys the data resolution capability ofthe transducer. By monitoring signals from the

head 44 during the lapping process, critical dimensions of the throat height Th and gap G

can be sensitively optimized for performance and longevity. Although not shown, note

that a transducer designed for "pseudo-contact" or "tail-dragging" operation can be

advantageously fabricated with the present invention, in particular with regard to configuring the throat, which is located at the tail and dragged or bounced against a disk

during operation.

As previously mentioned, a transducer or transducers can be machined with the

interactive lapping technique of the present invention in a plurality of steps, using

successively smoother lapping bodies. In this fashion, pole tip recession can be reduced

and performance testing facilitated. An abrasive surface 53 of a rough lapping disk that

would be used in an initial step of lapping magnetic heads or sliders for communication

with hard magnetic disks is shown in schematic or ideallized form a greatly enlarged

cross-section in Fig. 5 to have series of peaks 54 and valleys 55. Note that the horizontal

axis is denoted in microns while the vertical axis is denoted in nanometers. The surface

53 represents the exposed portion of a hard coating layer 26 having a thickness of

approximately 80 nanometers, which is not shown in this figure in order to better

illustrate the roughness of surface 53. Disposed beneath the hard coating layer 26 is a

medium layer 23 which also has a thickness of about 80 nanometers and is not shown in

this figure, and which has a texture at the interface with the hard layer 26 which is similar

but may be smoother or rougher than that ofthe exposed surface 53, depending upon

formation characteristics. Below the medium layer 23, the substrate 24 is adjoined with a

texture that reflects that ofthe surface 53 and the interface between the hard coating 26

and the medium 23, but which may be smoother or rougher still.

Formation ofthe rough lapping surface 53 begins by roughening or texturing at

least one major surface of a substrate 24 made of aluminum alloy, for example. Such

texturing can be accomplished effectively by rubbing an abrasive tape on the surface, preferably in a radial direction as the disk is rotated more slowly or in discrete steps to

effect roughening on all but an inner core. The roughness imparted to the disk substrate

at this stage may need to be greater or less than that desired for the surface 53, as the

subsequent deposition of the medium layer 23 and then the hard coating layer 26 retains

major features of the substrate roughness but may increase, decrease or substantially

parallel smaller feature roughness, depending upon formation processes and materials.

Atop the roughened substrate 24 is sputter deposited the medium layer, which may be

formed of alloys or superlattice structures of iron, nickel, cobalt, platinum, palladium or

other magnetic materials known in the art. Atop the medium layer 23, the hard coating

layer 26 may be formed of DLC, cathodic arc carbon, silicon carbide, boron carbide or

other superhard materials. To form the hard layer 26 of DLC, for example, plasma

enhanced chemical vapor deposition (CVD) or sputtering may be employed. It should be

noted that DLC is an essentially amoφhous mixture containing carbon atoms with bonds

ranging from SP orientations characteristic of diamond, to SP bonds such as are found

in graphite, to SP bonds characteristic of polymers, including from about 2% to about

30% (by mole) hydrocarbons. By varying the process parameters during deposition, the

material characteristics of layer 26 and surface 53, including hardness, roughness and

durability can be tailored to match the lapping needs ofthe transducers being worked.

Formation ofthe hard coating 26 of cathodic arc carbon, silicon carbide or boron carbide

is instead accomplished by sputtering, with attention again being paid to process

parameters in order to achieve the surface 53 characteristics desired. We have determined that the roughness ofthe upper reaches of the surface 53 are

of key importance for lapping puφoses. In this regard, a preferable rough lapping surface

is characterized by having peaks 54 (especially those terminating in the highest few

percent of the surface 53) with radii of curvature less than one-half micron, while the

vertical peak 54 to valley 55 height does not substantially exceed about 100 nanometers.

Another topographic characterization of a preferred rough lapping surface 53 is that the

peaks 54 that terminate in an upper five percent ofthe surface area differ in height by at

least 5 nm, and preferably over 10 nm, within a 100 μm² overall surface area.

A smoother, subsequent lapping disk surface 56 shown in Fig. 6 may be

characterized by peaks 57 terminating in the highest few percent ofthe surface 56 that

have radii of curvature generally between one-fifth and two microns, while the vertical

peak 57 to valley 58 height, as before, does not exceed 100 nanometers. Alternatively,

the peaks 54 of smooth lapping surface 56 that terminate in an upper one percent ofthe

surface area differ in height by between 2 and 10 nanometers within a 100 μm surface area.

Smooth lapping surface 56 is formed in a manner similar to that described above

for rough lapping surface 53. It should be noted, however, that the substrate 24 is

roughened a significantly lesser amount for a smooth surface 56 than for a rough surface

53, due to both a need for a smoother surface and a much thinner medium layer 23 and

hard coating layer 26 which tend to mimic the texture ofthe substrate 24 more closely. In

a preferred embodiment of a smooth lapping surface 56 to be employed for interactive lapping of magnetic transducers, a medium layer 23 and a hard coating layer 26 each may

have a thickness of about 200 to 400 angstroms.

Referring now to Fig. 7, the support bar 25 holds a number of beams 60-65 and

transducers 70-75 to lapping disk 20 for simultaneous lapping as the disk revolves in a

direction indicated by arrow B. The transducers 70-75 are each independently connected

to processor 32 so that the transducers 70-75 can be individually lifted from the lapping

surface 22 as needed in response to signals received at processor 32 indicating that

optimal lapping has occurred. In this manner, the prior art problem of row bar bowing is

eliminated, as each ofthe transducers is individually controlled for optimal lapping, while

numerous transducers can be lapped simultaneously, speeding manufacture.

Plots of signals from transducers 70-75 are shown superimposed on a single graph

in Fig. 8, to demonstrate the different times at which the signals from the various

transducers 70-75 may increase in amplitude. Plot 80 represents a signal received from

transducer 75, which ramps up in amplitude earlier than the other transducers and

achieves a relatively high signal amplitude. Plot 81, corresponding to transducer 74, is

the next signal to increase, but reaches a relatively low maximum value and may, for this

reason, be discarded. Plots 82, 83 and 84 correspond to transducers 70, 71 and 72

respectively, which increase in amplitude later and reach a satisfactory value, while plot

85 corresponds to transducer 73, which is the last transducer to signal an increase in

amplitude, and may result in transducer 73 being discarded due to the low value of

amplitude achieved in plot 85. In practice, amplitude plots from a number of transducers may begin to increase simultaneously during lapping, while proceeding at different rates

and reaching differing maximum amplitudes.

Fig. 9 shows an alternative preferred method of monitoring transducer signals for

determining optimal lapping amounts by looking to a shape of pulse waveforms

transmitted to the processor 32 from an individual transducer 28 during lapping. In this

system a signal is preferably written to the lapping disk 20 during lapping in order to

optimize the pole tip for writing as well as reading, although the disk may instead be

prewritten. For the situation in which the disk is prewritten, it is preferable to utilize the

same spindle for writing as for reading. For the case in which the transducer 28 being

lapped writes as well as reads signals during lapping, a series of isolated pulses are

written by the transducer in a given disk track during one revolution of the disk, and during a subsequent revolution the transducer reads these isolated pulses. The resolution

ofthe transducer 28 in both reading and writing is reflected by the shape of these isolated

pulses, as narrower pulse widths correspond with higher resolution. Thus waveform 90,

which can be seen to be relatively low and spread out in amplitude, may occur as lapping

has proceeded sufficiently to allow a signal to be written and read by the transducer 28.

As lapping continues the signal grows and narrows, as depicted in waveform 92, which is

dashed in order to distinguish it from other superimposed curves. In waveform 94 the

signal has become shaφer still, reflecting a very high resolution, and has reached a shape

where the transducer 28 will be lifted from the lapping disk. If transducer 28 is lapped

too much, the amplitude ofthe pulse may continue to increase for a period of time, and

then decrease as the shape of the pulse broadens, indicating reduced resolution. The appropriate time for termination of lapping can be indicated by the slowing and then

cessation of the increase in signal sharpness, by a certain threshold PW50 or by a

threshold narrowness in pulse time at half-maximum amplitude (e.g., 10 to 100

nanoseconds). Alternatively, performance tests generally employed in the recording

industry, such as overwrite, bit-shift, 747 and others, may be employed during interactive

lapping, and may be employed in concert.

Fig. 9 can also be used to illustrate another aspect ofthe current invention, as the

waveforms 90, 92 and 94 can represent signals from different transducers, such as

transducers 60, 61 and 62, respectively. In this situation, the waveforms 90, 92 and 94, if

they represent the shaφest signals from transducers 60, 61 and 62, can be used to

determine whether those transducers have acceptable resolution or are defective and should be discarded.

Since the resolution at which signals can be written and read is of a paramount

importance in an information storage system, the above described method of determining

when appropriate lapping has been achieved by monitoring pulse width resolution is

ideally matched to the needs of many information storage systems. For example, the

present invention may be directed to rigid disk storage systems, flexible disk storage

systems, tape drive systems, card based media systems and essentially any other storage

system that involves a transducer for reading and/or writing information with a relatively

moving storage medium. Focusing on the context of a rigid disk magnetic drive system

the present invention can be used for lapping sliders and/or heads for conventional flying heads, or for lapping heads for contact based communication between the transducer and

the media.

Moreover, since virtually any transducer used for reading information can be

thought of as a part of an information storage system, an information storage system is

defined for the puφose of this invention to include all types of systems for

communicating with a storage medium. For instance, an angular or linear motion

detecting instrument may include a transducer for detecting relative positions, which can

be seen to be a type of stored information. Similarly, an optical fiber can be used as an

electro-optical transducer for obtaining information about the interior of a person^'s body,

which can be seen to represent another form of communication with an information

storage system. Sensors of magnetic, inductive, capacitative, electrically conductive, optical, radioactive, and other forms of information can be fabricated with the interactive

system ofthe present invention.

Figs. 10 and 11 show a means for monitoring and lifting transducers from a

lapping plate on an individual basis. A strong, conductive plate 100 formed of stainless

steel, beryllium copper, doped silicon or other materials has been micromachined or

etched into a number of individual cantilevered beams 102, each of which has been

dissected with a longitudinal cut 104, to form a pair of prongs 106 and 108.

Conductively bonded to a bottom of the each ofthe beams 102 near a tip ofthe prongs

106 and 108 is a transducer 110 which has been formed to include magnetic reading and

writing and mechanical elements as described in the aforementioned co-pending U.S. Pat.

App. Serial No. 08/338,394, for TRANSDUCER/FLEXURE/CONDUCTOR STRUCTURE FOR ELECTROMAGNETIC READ/WRITE SYSTEM. Each of the

transducers 1 10 includes on a bottom surface having a pad 1 12 for contact with a rigid

magnetic disk, not shown in this figure, the pad containing a pole for writing and reading

to and from the magnetic disk.

Fig. 1 1 shows a portion of a lapping disk 120 including a substrate 123, a

magnetic recording layer 125 adjoining the substrate 123 and a hard abrasive layer 128

disposed on the magnetic layer having a surface 130 for lapping or polishing a transducer

110. Only one transducer 110 and beam 102 are shown Fig. 1 1 for clarity, while one

should note that sets often or more beams 102 and transducers 110, as shown in Fig. 10,

are preferably lapped simultaneously. The transducer 110 of this embodiment has three

triangularly spaced pads for contact with a disk 120, one ofthe non-polebearing pads

(113) being hidden from view in this figure by another non-polebearing pad 114. A

gimbal bump 116 allows the three pads 112-114 to be in simultaneous contact with the

rigid magnetic recording disk despite small surface variations. The prongs 106 and 108

are connected to each transducer 110 to provide an electrical circuit for sending and

receiving signals to and from the disk 120. The surface 130 is moving relative to a beam

102 attached to the transducer at a speed which may vary between 150 and 1500 inches

per second in a direction indicated by arrow B, which is generally along a lengthwise

direction ofthe beam 102. The beam 102 meets the disk 120 at an angle alpha relative to

a plane ofthe surface 130 that may range between -3 and +3 degrees for lapping of a

main contact area of the wear pad. As described in the above mentioned pending U.S. Pat. App. Serial No. 08/338,394, other gimbal and beam structures may be

advantageously employed, but is not shown here for brevity.

An upper plate 133 of a clamp 135 that holds the beam 102 extends further along

the beam 102 than a lower plate 137 of that clamp so that a communication pin 140 can

press against a conductive lead ofthe beam 102 for transmitting signals between the

transducer 1 10 and a processor, not shown in this figure. Although only one pin 140 is

shown in Fig. 8, a second pin is also employed for communication with each of the

prongs 104 and 106 of the beams 102 shown in Fig. 10, so that each transducer 1 10 has a

pair of leads for independent communication with a processor regarding appropriate

lapping time and test characteristics. A removal block 142 has an air duct 144 which is

connected to a vacuum source, not shown, with a solenoid valve that is controlled by the

transducer to be opened when the transducer receives a signal that lapping should be

terminated. When the valve is opened the differential air pressure caused by

communication between the vacuum source and the air duct 144 causes beam 102 to be

pulled to the block 142 and transducer 110 to be removed from the lapping process. The

block 142 has a different air duct for each beam 102 so that the various transducers 1 10

can be removed on an individual basis according to their individual optimal lapping

needs.

Referring now to Figs. 12 and 13, a lapping drum 148 may be employed in

machining transducers 150 having single contact pad 152 containing a magnetic pole

structure, not shown in this figure. The drum 148 offers a uniform lapping speed to each

ofthe transducers 150 or other items being lapped in a row, and rotates in this example in a direction of arrow C. Transducers 150 are disposed at ends of flexible beams 155, and

can be rounded at the tip of the pads 152 by tilting the beams 155 and by moving the

beams forward and backward relative to the drum 148 so that different parts ofthe pads

are tangent to the drum 148 during lapping. This is important for a single pad contact

magnetic read-write head in order to ensure close proximity between the pole disposed

within the head and the medium even in situations in which the pad contacts the surface

ofthe recording disk at an angle to normal. Rounding of front and back facets of the

single pad 152 can also be accomplished by varying the angle at which a plane containing

the beams 157 addresses the lapping drum 148, a technique similarly applicable to

lapping with a disk.

Also applicable to a lapping disk environment is the rounding of side facets ofthe pads 152 by tilting a series of transducers 150 each having a single pad 152, which can be

achieved by holding each beam 157 with a clamp that can rotate somewhat about the long axis ofthe beam, not shown. Note that only one side ofthe clamp needs to rotate if the

other side has a semicylindrical surface 158, and that the elements of each clamp that

rotate may be each pivotally attached to a bar in a series, not shown. Another advantage

ofthe faceting or rounding of pads 150 as discussed above is not only the elimination of

pole tip recession in transducer formation but the converse creation of pole tip protrusion.

Instead of interactively lapping transducers with a rigid body such as a disk or

drum as described in previous embodiments, it may be advantageous to employ a flexible

lapping medium such as a tape 160, as shown in a simplified view in Fig. 14. In this

embodiment, the abrasive magnetic storage tape 160 is wound from a first reel 162 to a second reel 164 in a direction shown by arrow V, while a row of transducers 166, each

held by a beam 168, are pressed against the tape. An adjustable platen 169 disposed on

an opposite side of the tape from the transducers 166 provides backing for lapping. The

tape 160 and transducers 166 may be designed for longitudinal or peφendicular

communication with the tape, that is, storage of magnetic information in domains having

remnant magnetization oriented generally parallel or peφendicular to the plane of the

tape. The transducers 166 are each connected with a processor 170 via a bar 172, the

processor individually monitoring communication between each transducer 166 and the

tape 160 in order to individually control lapping of each transducer 166. A row of

recording heads 173 may be positioned along the tape upstream ofthe transducers 166 in

order to write data tracks to the tape 160 for communication with the transducers. A

positioning element 174 is attached to each beam 168 and the bar 172 and electronically

connected to the processor 170 for removal ofthe transducers 166, individually or as a

group, upon actuation by the processor, as determined by signals received at the

processor from the tape via the transducers.

Employment of an interactive lapping tape rather than a disk or drum offers a

number of potential advantages, not the least of which is that the tape may be cost

effective, so that it can easily be replaced when worn out. In addition, due to the

flexibility of the tape 160, it tends to conform somewhat to the item being lapped, which

is desirable for rounding edges of that item in particular for a final stage of lapping in

order to counteract pole tip recession. For instance, a transducer having a single wear pad

with an embedded magnetic pole for contact communication with a medium may be rounded in this manner to avoid separation of the pole from the medium during tilting of

the transducer. Alternatively, flying heads for which edge blending or rounding is

desired may be advantageously finished with such a tape 160. Furthermore, transducer

heads designed for end user employment in tape drives may benefit from such interactive

tape lapping, as such heads often are rounded.

Another potential advantage of an interactive, tape based lapping system may be

the ability to closely control the pressure of lapping, for example by employing a capstan

177 that provides an adjustable backing to the tape 160, in concert with or in the absence

of platen 169. Alternatively, variable air pressure may be used to adjust the pressure felt

by the transducers 166 during lapping. The tension provided to the tape 160 provides a

means for controlling both the pressure on the transducers 166 and the degree of conformance ofthe tape to the transducers, thereby controlling the amount that transducer

edges are rounded. In this regard it should be noted that rounding of corners may occur differentially for corners that are oriented along the direction of tape motion as compared

with corners oriented essentially peφendicular to the direction of tape, due to differing

tension of the tape in those different directions.

Although a reel-to-reel lapping system is depicted in Fig. 14, in many cases a

continuous or endless loop interactive lapping tape may be advantageously employed. It

should be noted that a tape lapping body, like a drum lapping body, has the advantage of

uniform lapping speed for a number of items being lapped. One should also note that

oscillating or vibrating lapping motion is possible with any ofthe lapping bodies

described so far (disk, tape and drum), rather than the unidirectional motion previously described, and such alternative motions may also be utilized with other lapping bodies,

such as a card, plank, plate or irregularly shaped body.

Fig. 15 illustrates another aspect of the present invention - the ability to test

transducers for electrical, magnetic, mechanical, dynamic, optical or other performance

characteristics of a transducer at the time of lapping, again offering a substantial savings

in time and equipment while potentially improving performance. Sinusoidally varying

curve 180 is a plot of the signal received by a transducer during lapping with a body

having an alternating signal written to a medium of that body, as can be the situation, for

example, with magnetic data storage. The curve 180 has a signal amplitude modulation

represented by dashed lines 182 and 184, which form an envelope for the curve 180. This

amplitude modulation may be caused by vibration ofthe transducer being tested, or

electronic or magnetic problems ofthe transducer, for instance. Note that the particular

signal amplitudes and times shown in Fig. 15 are merely representative of a specific

transducer with specific performance traits, and that such amplitudes and times may vary

greatly depending upon the transducer. Alternatively, lines 182 and 184 may represent

aerodynamic characteristics of a flying head slider that has been lapped and is pitching or

rolling during flight. For the testing of a flying head and slider, the transducer is first

lapped by an appropriate amount by employing the interactive technique taught above,

after which the slider may be tested for aerodynamic characteristics by increasing the

rotational speed ofthe disk and/or reducing the load applied to the transducer that holds it

to the disk during lapping. Should the signal received from the transducer appear as

displayed in curves 182 and 184, which can be detected with filtering or amplitude demodulation, for example, an unstable transducer head or slider structure is indicated,

which would potentially result in a crash of the transducer and disk that would destroy the

drive system.

For situations in which a second lapping or test disk is employed that is smoother

than the first and essentially free of lapping debris, testing of various characteristics ofthe

transducer or transducers can be advantageously accomplished. This second lapping disk

may be useful, for example, for the situation in which the transducer is designed for

contact based communication with a disk, tape, drum or other media, since the roughness

of the first lapping disk may make testing of performance characteristics of the transducer

with the rough disk difficult. Alternatively, for the case of a flying head, testing

performed at a separate disk may allow for more realistic testing of critical dynamic

performance characteristics that occur during takeoff and landing ofthe head. Note also that the performance testing and grading may be accomplished in serial or parallel tests

on multiple transducers with a single lapping or testing apparatus, in order to

simultaneously optimize multiple performance parameters.

Claims

1. A method of making a transducer for communication with a medium comprising

providing a partially fabricated transducer having an information-

transmissive terminal being impeded by a material disposed near an end of said terminal,

removing said material while positioning said transducer adjacent to a

body communicating with said transducer, and

monitoring said transducer during said removing for a signal from said

body indicating that a desired amount of said material has been removed.

2. The method of claim 1, wherein said removing includes lapping said transducer with said body.

3. The method of claim 2, further comprising forming an abrasive surface on said body, prior to said lapping.

4. The method of claim 1 , further comprising writing information to at least a

portion of said body with said transducer.

5. The method of claim 1, wherein said monitoring includes analyzing an amplitude

of said signal from said body.

6. The method of claim 1, wherein said monitoring includes analyzing a waveform

of said signal from said body.

7. The method of claim 1, wherein said monitoring includes detecting a magnetic

pattern from said body.

8. The method of claim 1, further comprising testing a performance characteristic of

said transducer, including analyzing said signal from said body.

9. The method of claim 1 , further comprising storing information in at least a portion

of said body, prior to said removing.

10. The method of claim 1 , further comprising

providing a plurality of partially completed transducers having individual communication terminals being impeded by material disposed near ends of said terminals,

removing said material while positioning said terminals adjacent to said

body communicating with said transducer, and

monitoring said transducers individually during said removing for

individual signals indicating that desired amounts of said material have been removed

from each said terminal.

11. A process for enhancing, by the act of material removal, the communication-

performance capability of a transducer relative to an information storage medium, said

process comprising

subjecting such a transducer to a selected material-removal operation

while communicating with such a medium, and

while so subjecting the transducer, monitoring at least one aspect of its

communication-performance capability as an indicator of desired enhancement.

12. A method of forming a transducer for an information storage system comprising forming a transducer having magnetic pole impeded at a tip portion,

lapping said transducer with a body having a magnetic region associated

with a lapping surface, and

monitoring said transducer for a signal from said region indicating that a

desired amount of said tip portion has been removed.

13. The method of claim 12, further comprising writing information to said region

during said lapping.

14. The method of claim 12, wherein said lapping includes forming a slider.

15. The method of claim 12, wherein said forming includes fabricating said

transducer for communication with a layer of magnetic media having an easy axis of

magnetization oriented substantially within a plane defined by said layer.

16. The method of claim 12, wherein said forming includes fabricating said terminal

for communication with a layer of magnetic media having an easy axis of magnetization

orientated transversely to a plane defined by said layer.

17. The method of claim 12, wherein said forming includes fabricating said terminal

for communication with a rigid magnetic storage medium.

18. The method of claim 12, wherein said forming includes fabricating said terminal

for communication with a flexible magnetic storage medium.

19. The method of claim 12, wherein said forming includes fabricating said terminal

for communication with a card having an associated storage medium.

20. The method of claim 12, wherein said body is a tape and said lapping includes

producing relative motion between said transducer and said tape.

21. The method of claim 12, wherein said body is a disk and said lapping includes

rotating said disk relative to said transducer.

22. The method of claim 12, wherein said body is a drum and said lapping includes

rotating said drum relative to said transducer.

23. A device for fabricating a transducer comprising a body with an abrasive surface

for removing excess material from the transducer, said body having a communicative

portion transmitting a signal via said surface to the transducer indicating removal ofthe

excess material.

24. The device of claim 23, wherein said surface is generally flat.

25. The device of claim 23, wherein said surface is generally cylindrical.

26. The device of claim 23, wherein said body is a tape.

27. The device of claim 23, wherein said communicative portion is magnetic.

28. The device of claim 23, further comprising a processor connected to the

transducer and detecting said signal.

29. The device of claim 23, wherein said processor includes means for analyzing

performance characteristics ofthe transducer.

30. The device of claim 23, further comprising a motor connected to said body and

effecting motion relative to the transducer, whereby the transducer is lapped with said

surface.

31. The device of claim 23, further comprising a mechanism, connected to said

processor, holding the transducer against said surface during said removing, and holding

the transducer away from said body upon detection of said signal.

32. The device of claim 23, wherein said surface is superhard.

33. In a lapping machine having a moveable body with an abrasive work surface, an

implement for holding a workpiece and a mechanism for moving the body relative to the

workpiece, the improvement comprising

a communication signal transmitted by said body via said surface for controlling lapping of said workpiece.

34. The improvement of claim 33 wherein said signal is derived from a magnetic

pattern of said body.

35. The improvement of claim 33 wherein said signal is derived from an electrical

pattern of said body.

36. A system for enhancing, by the act of material removal, the communication-

performance capability of a transducer relative to an information storage medium, said

system comprising

an abrader defining a work zone for the selected removal of material from

such a transducer positioned within said zone, and

communication structure operatively associated with said abrader within

said zone, such that communication between said structure and the transducer is

indicative of a communication-performance enhancement of the transducer.

37. The system of claim 36, wherein said communication structure includes a

magnetic medium layer.

38. A system for machining a transducer comprising a body having an abrasive surface and transmitting a communication

signal via said surface,

positioning means for holding the transducer and for affecting relative

movement between the transducer and said surface, and

processing means, connected to the transducer and to said positioning

means, for analyzing information from the transducer regarding said signal and for

controlling said positioning means.

39. The system of claim 38, wherein said system has means for simultaneously

lapping a plurality of transducers while individually determining when each of said

plurality of transducers has been optimally lapped and thereupon individually terminating

said lapping.