U.S. patent application number 09/255762 was filed with the patent office on 2001-06-21 for method of making a patterned magnetic recording head.
Invention is credited to DUGAS, MATTHEW P..
Application Number | 20010003862 09/255762 |
Document ID | / |
Family ID | 22969744 |
Filed Date | 2001-06-21 |
United States Patent
Application |
20010003862 |
Kind Code |
A1 |
DUGAS, MATTHEW P. |
June 21, 2001 |
METHOD OF MAKING A PATTERNED MAGNETIC RECORDING HEAD
Abstract
A thin film magnetic recording head utilizing a timing based
servo pattern is fabricated using a focused ion beam (FIB). The
recording head is fabricated by sputtering a magnetically permeable
thin film onto a substrate. A gap pattern, preferably a timing
based pattern, is defined on the thin film and the FIB cuts a gap
through the thin film based on that pattern. Once completed, the
recording head is used to write a servo track onto magnetic tape.
The timing based servo track then allows for the precise alignment
of data read heads based on the positional information obtained by
a servo read head which scans the continuously variable servo
track.
Inventors: |
DUGAS, MATTHEW P.; (ST.
PAUL, MN) |
Correspondence
Address: |
DANIEL G CHAPIK
OPPENHEIMER WOLFF & DONNELLY
PLAZA VII SUITE 3400
45 SOUTH SEVENTH STREET
MINNEAPOLIS
MN
55402
|
Family ID: |
22969744 |
Appl. No.: |
09/255762 |
Filed: |
February 23, 1999 |
Current U.S.
Class: |
29/603.15 ;
29/603.12; 29/603.13; G9B/5.082; G9B/5.094; G9B/5.202;
G9B/5.203 |
Current CPC
Class: |
G11B 5/3166 20130101;
G11B 5/3116 20130101; G11B 5/232 20130101; G11B 5/3163 20130101;
G11B 5/3183 20130101; G11B 5/23 20130101; Y10T 29/49057 20150115;
G11B 5/59633 20130101; Y10T 29/49067 20150115; Y10T 29/49046
20150115; G11B 5/58 20130101; G11B 5/295 20130101; Y10T 29/49043
20150115; Y10T 428/31826 20150401; Y10T 29/49055 20150115; G11B
5/3133 20130101; Y10T 29/49048 20150115; Y10T 29/49041 20150115;
Y10T 29/4906 20150115; G11B 5/584 20130101 |
Class at
Publication: |
29/603.15 ;
29/603.13; 29/603.12 |
International
Class: |
H04R 031/00; G11B
005/127 |
Claims
I claim:
1. A method for fabricating a magnetic recording head comprising:
providing a substrate; depositing a magnetically permeable thin
film onto the substrate; defining a gap pattern; milling the gap
pattern with a focused ion beam.
2. The method of claim 1, further comprising coupling the substrate
to a coil which controllably causes magnetic flux to flow through
the substrate and the thin film.
3. The method of claim 1, wherein providing a substrate further
comprises: bonding two ferrite blocks to a ceramic member; and
polishing an upper surface of the bonded blocks and ceramic
member.
4. The method of claim 3, further comprising grinding the upper
surface to produce a curvature, prior to polishing.
5. The method of claim 1, wherein depositing a thin film further
includes sputtering a material onto the substrate to produce the
thin film.
6. The method of claim 5 wherein the sputtered material has a high
magnetic moment density.
7. The method of claim 5 wherein the sputtered material is chosen
from the family of iron nitride alloys.
8. The method of claim 5 wherein the material is FeXN.
9. The method of claim 5 wherein the material is FeAlN.
10. The method of claim 5 wherein the material is FeTaN.
11. The method of claim 5 wherein the material is sputtered to form
a thin film having a thickness between 1 to 5 .mu.m.
12. The method of claim 1 wherein the gap pattern defined is a
timing based servo pattern.
13. The method of claim 1 wherein defining a gap pattern further
includes providing a visual indication of the pattern on the thin
film.
14. The method of claim 13 wherein the gap pattern defined is a
timing based servo pattern.
15. The method of claim 13 wherein the visual indication is
provided by: applying a layer of photoresist over at least a
portion of the thin film; masking the photoresist; and removing a
portion of the photoresist using known chemical processes.
16. The method of claim 15 wherein the gap pattern defined is a
timing based servo pattern.
17. The method of claim 1 wherein defining a gap pattern further
includes entering the numerical coordinates of the gap pattern into
a control system of the focused ion beam.
18. The method of claim 17 wherein the gap pattern defined is a
timing based servo pattern.
19. The method of claim 1 wherein the focused ion beam is
substantially perpendicular to an upper major surface of the thin
film during milling.
20. The method of claim 19 wherein the gap has nearly vertical side
walls.
21. The method of claim 1 wherein the gap has nearly vertical side
walls.
22. A magnetic recording head made by the method of claim 1.
23. A method of fabricating a magnetic recording head for timing
based servo tracks comprising: providing a magnetically permeable
substrate by glass bonding two ferrite blocks to a medially
disposed ceramic member; sputtering a magnetically permeable thin
film onto one surface of the substrate thereby providing a major
surface; defining a timing based gap pattern; rastering a focused
ion beam in a plane orthogonal to the plane of the major surface of
the thin film, milling out the thin film in the defined gap
pattern; coupling the substrate to a coil which controllably causes
magnetic flux to flow through the substrate and the thin film.
24. The method of claim 23 wherein the thin film is FeXN.
25. The method of claim 23 wherein the thin film is FeAlN.
26. The method of claim 23 wherein the thin film is FeTaN.
27. The method of claim 23 wherein the gap pattern is defined by:
depositing a layer of photoresist to at least a portion of the thin
film; masking the photoresist; removing a portion of the
photoresist using photolithography.
28. The method of claim 23 wherein the gap pattern is defined by
providing a visual indication of the pattern on the thin film.
29. The method of claim 23 wherein the pattern is defined within a
control system of the focused ion beam.
30. The method of claim 23 wherein the pattern is defined within
the control system by entering the numerical coordinates of the gap
to be milled.
31. The method of claim 23 wherein the gap has nearly vertical side
walls.
32. A magnetic recording head made by the method of claim 23.
Description
FIELD OF THE INVENTION
[0001] This invention relates generally to magnetic recording heads
and more particularly to a method of making thin-film magnetic
heads for imprinting time based servo patterns on a magnetic
media.
BACKGROUND OF THE INVENTION
[0002] While a variety of data storage mediums are available,
magnetic tape remains a preferred forum for economically storing
large amounts of data. In order to facilitate the efficient use of
this media, magnetic tape will have a plurality of data tracks
extending in a transducing direction of the tape. Once data is
recorded onto the tape, one or more data read heads will read the
data from those tracks as the tape advances, in the transducing
direction, over the read head. It is generally not feasible to
provide a separate read head for each data track, therefore, the
read head(s) must move across the width of the tape (in a
translating direction), and center themselves over individual data
tracks. This translational movement must occur rapidly and
accurately.
[0003] In order to facilitate the controlled movement of a read
head across the width of the media, a servo control system is
generally implemented. The servo control system consists of a
dedicated servo track embedded in the magnetic media and a
corresponding servo read head which correlates the movement of the
data read heads.
[0004] The servo track contains data, which when read by the servo
read head is indicative of the relative position of the servo read
head with respect to the magnetic media in a translating direction.
In one type of traditional arrangement, the servo track was divided
in half. Data was recorded in each half track, at different
frequencies. The servo read head was approximately as wide as the
width of a single half track. Therefore, the servo read head could
determine its relative position by moving in a translating
direction across the two half tracks. The relative strength of a
particular frequency of data would indicate how much of the servo
read head was located within that particular half track.
[0005] While the half track servo system is operable, it is better
suited to magnetic media where there is no contact between the
storage medium and the read head. In the case of magnetic tape, the
tape actually contacts the head as it moves in a transducing
direction. Both the tape and the head will deteriorate as a result
of this frictional engagement; thus producing a relatively dirty
environment. As such, debris will tend to accumulate on the read
head which in turn causes the head to wear even more rapidly. Both
the presence of debris and the wearing of the head have a tendency
to reduce the efficiency and accuracy of the half track servo
system.
[0006] Recently, a new type of servo control system was created
which allows for a more reliable positional determination by
reducing the signal error traditionally generated by debris
accumulation and head wear. U.S. Pat. No. 5,689,384, issued to
Albrect et al. on Nov. 19, 1997, introduces the concept of a timing
based servo pattern, and is herein incorporated by reference in its
entirety.
[0007] In a timing based servo pattern, magnetic marks
(transitions) are recorded in pairs within the servo track. Each
mark of the pair will be angularly offset from the other. Virtually
any pattern, other than parallel marks, could be used. For example,
a diamond pattern has been suggested and employed with great
success. The diamond will extend across the servo track in the
translating direction. As the tape advances, the servo read head
will detect a signal or pulse generated by the first edge of the
first mark. Then, as the head passes over the second edge of the
first mark, a signal of opposite polarity will be generated. Now,
as the tape progresses no signal is generated until the first edge
of the second mark is reached. Once again, as the head passes the
second edge of the second mark, a pulse of opposite polarity will
be generated. This pattern is repeated indefinitely along the
length of the servo track. Therefore, after the head has passed the
second edge of the second mark, it will eventually arrive at
another pair of marks. At this point, the time it took to move from
the first mark to the second mark is recorded. Additionally, the
time it took to move from the first mark (of the first pair) to the
first mark of the second pair is similarly recorded.
[0008] By comparing these two time components, a ratio is
determined. This ratio will be indicative of the position of the
read head within the servo track, in the translating direction. As
the read head moves in the translating direction, this ratio will
vary continuously because of the angular offset of the marks. It
should be noted that the servo read head is relatively small
compared to the width of the servo track. Ideally, the servo head
will also be smaller than one half the width of a data track.
Because position is determined by analyzing a ratio of two
time/distance measurements, taken relatively close together, the
system is able to provide accurate positional data, independent of
the speed (or variance in speed) of the media.
[0009] By providing more than one pair of marks in each grouping,
the system can further reduce the chance of error. As the servo
read head scans the grouping, a known number of marks should be
encountered. If that number is not detected, the system knows an
error has occurred and various corrective measures may be
employed.
[0010] Of course, once the position of the servo read head is
accurately determined, the position of the various data read heads
can be controlled and adjusted with a similar degree of
accuracy.
[0011] When producing magnetic tape (or any other magnetic media)
the servo track is generally written by the manufacturer. This
results in a more consistent and continuous servo track, over time.
To write the timing based servo track described above, a magnetic
recording head bearing the particular angular pattern as its gap
structure, must be utilized. As it is advantageous to minimize the
amount of tape that is dedicated to servo tracks, to allow for
increased data storage, and it is necessary to write a very
accurate pattern, a very small and very precise servo recording
head must be fabricated.
[0012] Historically, servo recording heads having a timing based
pattern have been created utilizing known plating and
photolithographic techniques. A head substrate is created to form
the base of the recording head. Then, a pattern of photoresist is
deposited onto that substrate. The photoresist pattern essentially
forms the gap in the head. Therefore, the pattern will replicate
the eventual timing based pattern. After the pattern has been
applied a magnetically permeable material such as NiFe is plated
around the photoresist pattern. Once so formed, the photoresist is
washed away leaving a head having a thin film magnetic substrate
with a predefined recording gap.
[0013] Alternatively, the ion milling is used to form a first layer
having a relatively large gap. A pattern of photoresist is applied
in an inverse of the above described pattern. That is, photoresist
is applied everywhere except where the timing based pattern (gap)
is to be formed. Ion milling is used to cut the gap through the
first layer. Then an additional layer of the magnetically permeable
material is deposited by plating over the first layer and a narrow
gap is formed into this layer by the above described
photolithographic process. This approach produces a more efficient
head by creating a thicker magnetic pole system.
[0014] While the above techniques are useful in producing timing
based recording heads, they also limit the design characteristics
of the final product. In the first method, only materials which may
be plated can be utilized, such as NiFe (Permalloy). Generally,
these materials do not produce heads which have a high wear
tolerance. As such, these heads will tend to wear out in a
relatively short time. In addition, this class of materials have a
low magnetic moment density (10 kGauss for NiFe), or saturation
flux density, which limits their ability to record on very high
coercivity media.
[0015] The second method also relies on plating for the top
magnetic layer and is therefore limited to the same class of
materials. In addition, the use of ion milling makes the
fabrication of such a head overly complex. The photoresist pattern
can be applied relatively precisely; thereby forming a channel over
the gap. However, the traditional ion milling technique is rather
imprecise and as the ions pass through that channel they are
continuously being deflected. Conceptually, in any recording gap,
so cut, the relative aspect ratios involved prevent a precise gap
from being defined. In other words, this is a shadowing effect
created by the photoresist and causes the gap in the magnetically
permeable material to be angled. Generally, the sidewalls of the
gap will range between 45.degree.-60.degree.from horizontal. This
introduces a variance into the magnetic flux as it exits the gap,
resulting in a less precise timing based pattern being recorded
onto the servo track.
[0016] Therefore, there exists a need to provide a magnetic
recording head capable of producing a precise timing based pattern.
Furthermore, it would be advantageous to produce such a head having
a tape bearing surface which is magnetically efficient as well as
wear resistant and hence a choice of sputtered rather than plated
materials are required. Thus, it is proposed to use a fully dry
process to fabricate a time based head using predominantly iron
nitride based alloys.
SUMMARY OF THE INVENTION
[0017] The present invention relates to a method of fabricating a
magnetic recording head, and more particularly a recording head for
producing a time based servo pattern.
[0018] A substrate consisting of a ceramic member, glass bonded
between a pair of ferrite blocks is prepared. The substrate is then
cleaned, polished and if desired, ground to a particular curvature.
On top of this substrate, a magnetically permeable thin film is
deposited, preferably by a sputtering process. The thin film is
selected from a class of materials having a high wear tolerance as
well as a high magnetic moment density, such as FeN. The alloys in
this class of materials need to be sputtered onto the substrate, as
other thin film deposition techniques, such as plating, are
incompatible with these materials.
[0019] Once the thin film is present, the substrate is placed
within the path of a focused ion beam (FIB) orthogonally oriented
to the major surface of the thin film. The FIB is used to mill a
complex patterned gap though the thin film layer. This gap is
extremely precise and will allow the recording head to accurately
produce a similar pattern on magnetic tape.
[0020] The FIB must be controlled to only mill the patterned gap
and no other portion of the thin film. To define these parameters
within the FIB control system, several techniques are available. In
general, a non-destructive pattern is applied to the surface of the
thin film. A graphical interface within the FIB control system
allows the operator to visually align the pattern with the FIB
milling path. One way to accomplish this is to apply a very thin
layer of photoresist to the thin film. A mask is then employed to
create the very precise gap pattern. Because photoresist is
visually distinct from the remainder of the substrate, the FIB can
be aligned with this pattern. As opposed to the usual thick film
photoresist used in traditional ion milling as a protective layer
(or selectively etched layer), the photoresist in the present
invention will serve no other purpose in the milling process.
Alternatively, numerical coordinates, representing the gap to be
cut, can be directly entered into the FIB control system.
[0021] Once the gap or gaps have been cut into the thin film, the
substrate is coupled with a coil to produce a functional recording
head.
[0022] It is an object of the present invention to provide a method
of making a magnetic recording head having a precisely defined gap
structure.
[0023] It is another object of the present invention to produce a
magnetic recording head utilizing a focused ion beam to define the
gap and track width structure.
[0024] It is still another object of the present invention to
simultaneously define and create all three dimensions of a gap
structure in a magnetic head.
[0025] It is yet still another object of the present invention to
fabricate a magnetic recording head wherein the gap depth is
determined primarily by the thickness of the deposited thin
film.
[0026] It is yet another object of the invention to use a focused
ion beam to produce a thin film magnetic recording head employing a
timing based servo pattern.
[0027] It is yet still another object of the present invention to
produce a thin film magnetic recording head having a highly wear
resistant tape bearing surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1 is a side planar view of a substrate bearing a
magnetic thin film.
[0029] FIG. 2 is a top planar view of the substrate shown in FIG.
1.
[0030] FIG. 3 is top planar view of a portion of thin film, bearing
indicia of a gap to be milled.
[0031] FIG. 4 is a schematic diagram of a FIB milling a gap into a
thin film.
[0032] FIG. 5 is a top planar view of a thin film having gaps
milled by a FIB.
[0033] FIG. 6 is a side sectional view taken about line VI-VI.
[0034] FIG. 7 is a top planar view of a thin film having gaps
milled by a FIB.
[0035] FIG. 8 is side sectional view taken about line VII-VII.
[0036] FIG. 9 is a top planar view of a portion of thin film having
a gap and endpoints milled by a FIB.
[0037] FIG. 10 is a top planar view of a substrate bearing gaps and
air bleed slots.
[0038] FIG. 11 is an end planar view of a substrate bearing air
bleed slots.
[0039] FIG. 12 is a side planar view of a magnetic recording
head.
[0040] FIG. 13 is an end planar view of a magnetic recording
head.
[0041] FIG. 14 is a partial perspective view of thin film layer
bearing a set of time based or angled recording gap pairs.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0042] The present invention is a method of making a thin film
magnetic recording head using a focused ion beam (FIB) to mill out
gaps in the tape bearing surface. Referring to FIG. 1, a substrate
10 is created by glass bonding two C-shaped ferrite blocks 12 to a
medially disposed ceramic member 14. The sizes and relative
proportions of the ferrite blocks 12 and ceramic member 14 may vary
as dictated by the desired parameters of the completed recording
head. Furthermore, the choice of materials may also vary so long as
blocks 12 remain magnetic while member 14 remains magnetically
impermeable.
[0043] A layer of magnetically permeable material is deposited as a
thin film 16 across an upper surface of each of the ferrite blocks
12, as well as the upper surface of the ceramic member 14. The
magnetically permeable thin film 16 will become the tape bearing
and data writing surface for the magnetic head 5 (see FIGS. 12
& 13). As such, it is desirable to form the layer of thin film
16 from a material which has a relatively high magnetic moment
density (greater or equal to about 15 kGauss) and is also wear
resistant. An exemplary material for this purpose is FeN or
alternatively Sendust.TM.. For example, FeN has a magnetic moment
density on the order of 19 to 20 kGauss and is resistant to the
frictional deterioration caused by continuous tape engagement. Any
of the alloys in the iron nitride family, such as iron aluminum
nitride, iron tantalum nitride, etc., and including any number of
elements, are also ideally suited. FeXN denotes the members of this
family, wherein X is a single element or a combination of elements,
as is known in the art.
[0044] FeXN is created by sputtering a FeX alloy (or simply Fe) in
a nitrogen rich environment. It is not available in quantities
sufficient for plating. Furthermore, even if so available, the FeXN
would decompose during the electrolytic plating process. This is in
stark contrast to the simple alloys which may be readily utilized
in electrolytic plating techniques. Therefore, while it is
advantageous to use alloys, such as FeXN, magnetic recording heads
cannot be formed with them, in any previously known plating
process. In addition, the most desirable alloys to use are often
composed of three of more elements. Plating is generally limited to
the so called binary alloys, and as explained above is not
conducive to binary gaseous alloys, such as FeN. The use of
sputtering in combination with the use of a FIB, not only allows
any of these materials to be used but also produces a better
wearing magnetic thin film with a higher saturation flux density
and of sufficient permeability for use as a servo write head.
[0045] Referring again to FIG. 1, the thin film 16 is sputtered
onto the surface of the ferrite blocks 12 and the ceramic member
14. Prior to the sputtering process, the surface is polished and
prepared in a manner known to those skilled in the art. If desired,
the surface may be ground to produce a slight curvature. This
curvature will facilitate smooth contact between the tape and the
completed head 5 as the tape moves across the tape bearing
surface.
[0046] The thickness of the deposited thin film 16 determines the
efficiency of the magnetic head and also its predicted wear life.
The thicker the tape bearing surface (thin film 16) is, the longer
the head will last. Conversely, the thicker the magnetic film, the
longer it will take to process or etch with a FIB and it will also
process less precisely. Therefore, the thin film should be
deposited in a thickness of about 1 to 5 .mu.m. Ideally, the
thickness will be about 2 to 3 .mu.m.
[0047] FIG. 2 is a top view of the substrate 10 and in particular
the major surface of magnetic thin film 16 with the underlying
ceramic member 14 shown in dashed lines. The area 18 is defined by
the upper surface of the ceramic member 14 (the magnetic sub-gap)
and is where the appropriate gaps will eventually be milled.
[0048] Referring to FIG. 3, only area 18 is shown. Within area 18,
some indicia 20 of the eventual gap positions are laid down. It
should be noted that two diamond shaped gaps are to be milled as
shown in FIG. 3; however any shape and any number of gaps could be
created. Indicia 20 is simply an indication of where the FIB is to
mill. One way of accomplishing this is to place a layer of
photoresist 22 down and define the indicia 20 with a mask. Using
the known techniques of photolithography, a layer of photoresist 22
will remain in all of area 18 except in the thin diamond defined by
indicia 20. Alternatively, the photoresist area could be
substantially smaller than area 18, so long as it is sufficient to
define indicia 20. The photoresist differs in color and height from
the thin film 16 and therefore produces the visually discernible
pattern. This pattern is then registered with the FIB control
system through a graphical interface; thus delineating where the
FIB is to mill. The photoresist serves no other purpose, in this
process, than to visually identify a pattern. As such, many
alternatives are available. Any high resolution printing technique
capable of marking (without abrading) the surface of the thin film
16 could be used. Alternatively, the pattern could be created
completely within the FIB control system. That is, numerical
coordinates controlling the path of the FIB and representing the
pattern could be entered; thus, obviating the need for any visual
indicia to be placed onto the magnetic thin film 16. Finally, a
visual pattern could be superimposed optically onto the FIB
graphical image of the substrate 10, thereby producing a visually
definable region to mill without actually imprinting any indicia
onto the substrate 10.
[0049] In any of the above described ways, the FIB 24 is programmed
to trace a predefined pattern, such as the diamond indicia 20 shown
in FIG. 3. The FIB will be orientated in a plane orthogonal to the
major surface of the thin film 16.
[0050] FIG. 4 is a sectional view of FIG. 3, taken about line IV-IV
and illustrates the milling process utilizing FIB 24. The upper
surface of the thin film 16 has been coated with a thin layer of
photoresist 22. The visual indicia 20 of the diamond pattern is
present, due to the area of that indicia 20 being void of
photoresist. The FIB 24 has already milled a portion of the pattern
forming gap 30. The FIB as shown has just begun to mill the right
half of the pattern. The beam of ions 26 is precisely controlled by
the predefined pattern which has been entered into the FIB's
control system. As such, the beam 26 will raster back and forth
within the area indicated by indicia 20. The beam 26 will generally
not contact a significant amount of the photoresist 22 and will
create a gap 30 having vertical or nearly vertical side walls. The
width of the ion beam is controllable and could be set to leave a
predefined amount of space between the edge of the side wall and
the edge of the indicia 20. The FIB 24 will raster back and forth
until all of the indicia 20 have been milled for that particular
head.
[0051] After the FIB 24 has milled all of the gap(s) 30, the
photoresist 22 is washed away. Alternatively, any other indicia
used would likewise be removed. FIG. 5 illustrates area 18 of
substrate 10 after the photo resist 22 has been removed. Thin film
16 is exposed and has precisely defined gaps 30 milled through its
entire depth, down to the ceramic member 14. FIG. 6 is a sectional
view of FIG. 5 taken about line VI-VI of FIG. 5 and illustrates the
milled surface of gap 30. The gap 30 is precisely defined, having
vertical or nearly vertical walls.
[0052] Referring to FIG. 14, a partial perspective view of a time
based recording head 5 is shown. The major surface 50 of thin film
16 lies in a plane defined by width W, length L, and depth D. D is
the deposited thickness of the magnetic film 16. The FIB will
always mill through thin film 16 through a plane perpendicular to
the major surface 50 which would also be parallel to depth D. By
conventional standards, the gap 30 will have a magnetic gap depth
equal to depth D and a gap width equal to width W and a gap length
(L')equal to the span of gap 30.
[0053] The upper surface of thin film 16, shown in FIG. 7,
represents one of many alternative time based patterns which may be
created using a FIB 24. Here, gaps 30 will be milled in exactly the
same fashion as described above, except that indicia 20, when
utilized, would have formed the pattern shown in FIG. 7. FIG. 8 is
a sectional view taken about line VII-VII of FIG. 7 and shows how
gap 30 continues to have precisely defined vertical sidewalls.
Furthermore, the upper horizontal surface 32 of ceramic member 14
is also precisely defined.
[0054] FIG. 9 illustrates yet another pattern which may be defined
using FIB 24. Here, gap 30 is in the shape of an augmented diamond.
Rather than defining a diamond having connected corners, gap 30 is
milled to have termination cells or endpoints 34, 35, 36 and 37.
Creating endpoints 34, 35, 36 and 37 increases the definition of
the finished recorded pattern near the ends of the track.
[0055] The next step in the fabrication process is to create air
bleed slots 40 in the tape bearing surface of the substrate 10, as
shown in FIG. 10. Once substrate 10 has been fabricated into a
recording head, magnetic tape will move across its upper surface in
a transducing direction, as shown by Arrow B. Therefore, the air
bleed slots 40 are cut perpendicular to the transducing direction.
As the tape moves over the recording head at relatively high speed,
air entrainment occurs. That is, air is trapped between the lower
surface of the tape and the upper surface of the recording head.
This results from the magnetic tape, comprised of magnetic
particles affixed to a substrate, being substantially non-planar on
a microscopic level. As the tape moves over the recording head, the
first air bleed slot encountered serves to skive off the trapped
air. The second and subsequent slots continue this effect, thus
serving to allow the tape to closely contact the recording head. As
the tape passes over the recording gap(s) 30, it is also held in
place by the other negative pressure slot 42,43 encountered on the
opposite side of the gap(s) 30. Therefore, there is a negative
pressure slot 42,43 located on each side of the recording gap(s)
30.
[0056] FIG. 11 is a side view of the substrate 10, as shown in FIG.
10. The upper surface of the substrate 10 has a slight curvature or
contour. This acts in concert with the air bleed slots to help
maintain contact with the magnetic tape. The air bleed slots 40 are
cut into the substrate 10 with a precise circular saw, as is known
by those skilled in the art. The air bleed slots 40 are cut through
thin film 16, which is present but not visible in FIG. 11.
Alternatively, the air bleed slots 40 could be cut prior to the
thin film 16 having been deposited.
[0057] Substrate 10 has been longitudinally cut, thus removing a
substantial portion of the coupled C-shaped ferrite blocks 12 and
ceramic member 14. This is an optional step which results in an
easier integration of the coils and ferrite blocks. FIG. 13
illustrate how a backing block 46 is bonded to substrate 10. The
backing block 46 is composed of ferrite or another suitable
magnetic material. Wiring is wrapped about the backing block 46
thus forming an electrical coil 48. With this step, the fabrication
process has been completed and a magnetic recording head 5 has been
produced.
[0058] In operation, magnetic recording head 5 is secured to an
appropriate head mount. Magnetic tape is caused to move over and in
contact with the tape bearing surface of the head 5, which happens
to be the thin film layer 16. At the appropriate periodic interval,
electrical current is caused to flow through the coil 48. As a
result, magnetic flux is caused to flow (clockwise or
counterclockwise in FIG. 13) through the back block 46, through the
ferrite blocks 12, and through the magnetic thin film 16 (as the
ceramic member 14 minimizes a direct flow from one ferrite block 12
to the other causing the magnetic flux to shunt through the
permeable magnetic film). As the magnetic flux travels through the
magnetic thin film 16, it leaks out through the patterned gaps 30,
thus causing magnetic transitions to occur on the surface of the
magnetic tape, in the same pattern and configuration as the gap 30
itself.
[0059] Referring to FIGS. 10 and 12, it can be seen that the width
of the head 5 (or substrate 10) is substantially larger than a
single patterned gap 30. This allows the recording head to bear a
plurality of patterned gaps 30. For example, FIG. 10 illustrate a
substrate 10 having five recording gaps 30 which could then write
five servo tracks simultaneously. More or less can be utilized as
desired and the final size of the head 5 can be adjusted to
whatever parameters are required.
[0060] Rather than cutting the substrate 10 as shown in FIG. 11 and
applying a coil as shown in FIG. 13, the substrate 10 could remain
whole and the coils could be added to the C-shaped ferrite blocks
12, as they are shown in FIG. 1.
[0061] The above head fabrication process has been described with
respect to a magnetic recording head employing a timing based servo
patter. However, the process could be applied equally well to any
type of thin film recording head. That is, those of ordinary skill
in the art will appreciate that the FIB milling of the gaps could
accommodate any shape or pattern, including the traditional single
gap used in half-track servo tracks.
[0062] Those skilled in the art will further appreciate that the
present invention may be embodied in other specific forms without
departing from the spirit or central attributes thereof. In that
the foregoing description of the present invention discloses only
exemplary embodiments thereof, it is to be understood that other
variations are contemplated as being within the scope of the
present invention. Accordingly, the present invention is not
limited in the particular embodiments which have been described in
detail therein. Rather, reference should be made to the appended
claims as indicative of the scope and content of the present
invention.
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