U.S. patent application number 15/041737 was filed with the patent office on 2017-08-17 for fabrication of a tape head with a monobloc closure.
The applicant listed for this patent is International Business Machines Corporation. Invention is credited to Robert G. BISKEBORN, Johan ENGELEN, Mark A. LANTZ, Hugo E. ROTHUIZEN.
Application Number | 20170236536 15/041737 |
Document ID | / |
Family ID | 59561639 |
Filed Date | 2017-08-17 |
United States Patent
Application |
20170236536 |
Kind Code |
A1 |
BISKEBORN; Robert G. ; et
al. |
August 17, 2017 |
Fabrication of a Tape Head with a Monobloc Closure
Abstract
A tape head including a body with a tape-bearing surface
configured to contact a magnetic tape, at least one transducer that
is a read or write element, configured so the tape head may read
from or write to the tape, in operation; and a monobloc closure
with a structured cross-sectional profile, so as to exhibit:
contact part, fixed on a side of the body which adjoins the
tape-bearing surface at an edge thereof, the contact part having a
top surface level with the tape-bearing surface; and connecting
part integral with the contact part, the connecting part having a
top surface recessed from the contact part's top surface,
perpendicularly to a contact plane defined by said tape-bearing
surface, so the connecting part's top surface does not contact the
tape, in operation; and a broken line of mechanical weakness that
extends at an end of said third surface.
Inventors: |
BISKEBORN; Robert G.; (San
Jose, CA) ; ENGELEN; Johan; (Rueschlikon, CH)
; LANTZ; Mark A.; (Rueschlikon, CH) ; ROTHUIZEN;
Hugo E.; (Rueschlikon, CH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
International Business Machines Corporation |
Armonk |
NY |
US |
|
|
Family ID: |
59561639 |
Appl. No.: |
15/041737 |
Filed: |
February 11, 2016 |
Current U.S.
Class: |
360/122 |
Current CPC
Class: |
G11B 5/3163 20130101;
G11B 5/255 20130101; Y10T 29/4903 20150115; G11B 5/3169 20130101;
G11B 5/00813 20130101; G11B 5/102 20130101; G11B 5/1272 20130101;
G11B 5/1871 20130101; Y10T 29/49032 20150115 |
International
Class: |
G11B 5/187 20060101
G11B005/187; G11B 5/008 20060101 G11B005/008 |
Claims
1. A method of fabrication of a tape head with a closure, the
method comprising: providing: a body with a tape-bearing surface
configured to contact a magnetic tape, the body comprising at least
one transducer that is a read element or a write element,
configured so as for the tape head to read from or write to the
tape, in operation; and a monobloc closure, having a structured
cross-sectional profile, so as to exhibit: a contact part, having a
first top surface; a breakable part, having a second top surface;
and a connecting part connecting the breakable part to the contact
part, wherein the connecting part: has a third top surface recessed
from said first top surface, perpendicularly to a contact plane
defined by said tape-bearing surface, so as to not to contact the
tape, in operation; and comprises a line of mechanical weakness
extending across said third top surface; arranging the body and the
closure on a reference surface, so as for each of the tape-bearing
surface, the first top surface and the second top surface to
contact the reference surface; fixing the contact part on a side of
the body, which side adjoins the tape-bearing surface at an edge
thereof; and removing the breakable part by breaking along the line
of mechanical weakness, to obtain a tape head wherein said first
surface is level with the tape-bearing surface.
2. The method of claim 1, wherein, at fixing, said side is a
leading side or a trailing side of the body, wherein said leading
side and said trailing side adjoin, each, the tape-bearing
surface.
3. The method of claim 1, wherein providing the monobloc closure
comprises structuring the cross-sectional profile of the closure so
as for the contact part to have a step-like cross-sectional
profile, exhibiting a riser between two treads that are
respectively formed by the first top surface and a recessed
surface, the latter recessed from the first top surface so as not
to contact the magnetic tape, in operation.
4. The method of claim 3, wherein structuring the cross-sectional
profile of the closure is carried out so as for the recessed
surface to be recessed from the first top surface by a distance h
corresponding to a height of the riser, wherein h is between 1 and
10 microns, a width w of the recessed surface along a direction
parallel to a longitudinal direction z of circulation of the tape
being between 10 and 50 microns.
5. The method of claim 3, wherein structuring the cross-sectional
profile of the closure comprises: providing a substrate; coating
the substrate provided with a photoresist; lithographically
patterning the photoresist; and transferring the photoresist
pattern accordingly obtained into the substrate, to obtain said
step-like cross-sectional profile of the contact part.
6. The method of claim 5, wherein: the substrate provided is an
Aluminum-Titanium carbide substrate, or AlTiC substrate; and the
photoresist pattern is transferred by reactive ion etching.
7. The method of claim 5, wherein structuring the cross-sectional
profile of the closure further comprises obtaining the connecting
part by cutting partially through a depth of the provided substrate
with a wafer saw, up to a level of said third top surface.
8. The method of claim 7, wherein structuring the cross-sectional
profile of the closure further comprises obtaining the line of
mechanical weakness by cutting partially through a depth of the
obtained connecting part, through the third top surface.
9. The method of claim 8, wherein cutting partially through the
depth of the connecting part is carried out so as to obtain a
residual thickness of the connecting part at the level of the line
of mechanical weakness that is between 30 and 70 microns.
10. The method of claim 1, wherein fixing comprises applying a glue
on the contact part and/or on said side of the body and curing the
applied glue.
11. The method of claim 1, wherein fixing is performed while
applying a load on the body and the closure arranged on the
reference surface.
12. A tape head, comprising: a body with a tape-bearing surface
configured to contact a magnetic tape, the body comprising at least
one transducer that is a read or write element, configured so as
for the tape head to read from or write to the tape, in operation;
and a monobloc closure, having a structured cross-sectional
profile, so as to exhibit: a contact part, fixed on a side of the
body, which side adjoins the tape-bearing surface at an edge
thereof, the contact part having a top surface level with the
tape-bearing surface; and a connecting part integral with the
contact part, wherein the connecting part has: a top surface
recessed from the top surface of the contact part, perpendicularly
to a contact plane defined by said tape-bearing surface, so as for
the top surface of the connecting part not to contact the tape, in
operation; and a broken line of mechanical weakness that extends at
an end of the top surface of the connecting part.
13. The tape head of claim 12, wherein the connecting part exhibits
fracture marks at a level of said broken line of mechanical
weakness.
14. The tape head of claim 12, wherein said side is a leading side
or a trailing side of the body, wherein said leading side and said
trailing side adjoin, each, the tape-bearing surface at an edge
thereof.
15. The tape head of claim 12, wherein the monobloc closure has a
structured cross-sectional profile so as for the contact part to
have a step-like cross-sectional profile, exhibiting a riser
between two treads, the latter respectively formed by the top
surface of the contact part and a recessed surface, the latter
recessed from the top surface of the contact part so as not to
contact the magnetic tape, in operation.
16. The tape head of claim 15, wherein the recessed surface is
recessed from the top surface of the contact part by a distance h
corresponding to a height of the riser, wherein h is between 1 and
10 microns, a width w of the recessed surface along a direction
parallel to a longitudinal direction z of circulation of the tape
being between 10 and 50 microns.
17. The tape head of claim 12, wherein the monobloc closure is a
structured substrate of Aluminum-Titanium carbide substrate.
18. The tape head of claim 12, wherein the tape head is a planar
tape head, said at least one transducer being an in-plane
transducer, whose top poles are in-plane with the tape-bearing
surface.
19. The tape head of claim 12, wherein the tape head is a servo
writer.
20. A tape head apparatus for recording and/or reproducing
multi-track tapes, comprising the tape head of claim 12.
Description
BACKGROUND
[0001] The invention relates in general to methods of fabrication
of tape heads, and more specifically to the fabrication of planar
tape heads. In particular, the invention concerns a tape head
having a closure defining a skiving edge, where the closure is
obtained without having to resort to a lapping process.
[0002] Various data storage media or recording media such as
magnetic tape, magnetic disks, optical tape, optical disks,
holographic disks or cards, and the like are known which allow for
storage and retrieval of data. In particular, in magnetic media,
data are typically stored as magnetic transitions, i.e., they are
magnetically recorded in the magnetic layer of the media. The data
stored is usually arranged in data tracks. A typical magnetic
storage medium, such as a magnetic tape, usually includes several
data tracks. Data tracks may be written and read individually, or
sets of data tracks may be written and read in parallel depending.
Transducer (read/write) heads are positioned relative to the data
tracks to read/write data along the tracks. To this aim, a tape
drive head must locate each data track and accurately follow its
path. To achieve this, servo techniques have been developed which
allow for a precise positioning of the head relative to the data
tracks. One such technique makes use of servo patterns, that is,
patterns of signals or recorded marks on the medium, which are
tracked by the head. The servo patterns are recorded on the
recording medium such as to provide a position reference for the
data tracks. In other words, a servo head reads a servo pattern,
which is then interpreted by a servo channel into a position error
signal (PES). The latter is then used to adjust the distance of the
servo head relative to the servo pattern and thereby ensure a
proper positioning of the transducers with respect to the set of
data tracks.
[0003] Essentially two technologies have been developed for
timing-based servo patterns. The first one makes use of surface
thin film servo writers, as discussed in, e.g., U.S. Pat. No.
6,021,013. The second technology relates to so-called "pure thin
film planar servo writers", see, e.g., U.S. Pat. No. 5,652,015,
U.S. Pat. No. 6,947,256, and U.S. Pat. No. 8,014,100. Pure thin
film planar servo writers potentially have several advantages over
surface thin film servo writers, such as improved servo format
quality, increased servo formatting speed, increased servo pattern
design flexibility and reduced fabrication costs.
SUMMARY
[0004] According to a first aspect, the present invention is
embodied as a method of fabrication of a tape head with a monobloc
closure. This method relies on a body (comprising the tape-bearing
surface) and a closure. The tape-hearing surface is configured to
contact a magnetic tape, in operation. The body comprises at least
one transducer, which is a read element or a write element. This
element is configured so as for the tape head to be able read from
or write to the tape, in operation. The closure has a structured
cross-sectional profile, so as to exhibit: a contact part (having a
first top surface); a breakable part (having a second top surface);
wad a connecting part, which connects the breakable part to the
contact part. The connecting part has a third top surface that is
recessed from said first top surface, perpendicularly to a contact
plane defined by said tape-bearing surface, so as for the third top
surface not to contact the tape, in operation. The connecting part
further comprises a line of mechanical weakness extending across
said third top surface. The body and the closure are arranged on a
reference surface, so as for each of the tape-bearing surface, the
first top surface and the second top surface to contact the
reference surface. Next, the contact part is fixed on a side of the
body, which side adjoins the tape-bearing surface at an edge
thereof. Finally, the breakable part is removed by breaking along
the line of mechanical weakness. This makes it possible to obtain a
tape head wherein said first surface is level with the tape-bearing
surface.
[0005] According to another aspect, the invention is embodied as a
tape head, obtainable according to a fabrication method such as
described above. The tape head comprises a body and a monobloc
closure as described above, where the contact part has a top
surface level with the tape-bearing surface. As the breakable part
is removed, the resulting tape head shows a broken surface along a
line of mechanical weakness that extends at an end of the
connecting part.
[0006] According to a final aspect, the invention is embodied as a
tape head apparatus for recording and/or reproducing multi-track
tapes, which apparatus comprises a tape head as described
above.
[0007] Devices, apparatuses, and fabrication methods embodying the
present invention will now be described, by way of non-limiting
examples, and in reference to the accompanying drawings.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
[0008] FIG. 1 is a 3D view of a planar tape head (a servo writer),
according to embodiments;
[0009] FIG. 2 is a 3D view of a monobloc closure, as used to
fabricate a planar tape head as in FIG. 1, according to
embodiments;
[0010] FIG. 3 is a 2D cross-sectional view of a (portion of a) tape
head such as depicted in FIG. 1;
[0011] FIG. 4 is a 2D cross-sectional view of an asymmetric tape
head having two monobloc closures, according to other
embodiments;
[0012] FIG. 5 is a sequence illustrating high-level fabrication
steps of a planar tape head as in FIG. 1, according to embodiments;
and
[0013] FIG. 6 schematically depicts a closure as obtained after
step S110 of FIG. 5.
[0014] The accompanying drawings show simplified representations of
devices or parts thereof, as involved in embodiments. Technical
features depicted in the drawings are not to scale. In particular,
the scales assumed for axes x and 1, differ. Similar or
functionally similar elements in the figures have been allocated
the same numeral references, unless otherwise indicated.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0015] As it can be realized, the second technology ("pure thin
film planar servo writers") referenced in the background section
may substantially suffer from friction and wear. Friction is
problematic as it results in velocity variations during servo
formatting that cause written-in velocity noise and degrade servo
performance. Wear of the servo writer is also problematic as it
limits the useful lifetime of a servo write head.
[0016] The wear robustness of a planar tape head can be
significantly improved by mounting a hard ceramic "closure" on the
leading edge (for asymmetrically wrapped heads with a trailing edge
wrap angle of <0 degrees) or on both the leading and trailing
edges for heads used in combination with a positive wrap angle on
both the leading and trailing edges. In order to assure good
contact between the tape and planar servo writer, the skiving edge
should be sharp and the tape bearing surfaces of the closure(s) and
the planar head should be co-planar. Such closures are already
known from their use in flat profile read/write heads in tape
drives (see "Hard-disk-drive technology flat heads for linear tape
recording" R. Biskeborn and J. Eaton, IBM Journal of Research and
Development, Volume: 47, Issue: 4 pp 385-400, and "Flat-profile
tape recording head", R. Biskeborn and J. Eaton, IEEE Transactions
on Magnetics, Volume: 38, Issue: 5, pp 1919-1921).
[0017] Such heads are manufactured by gluing a closure on the edge
of a tape head chip and lapping to achieve a flat planar tape
bearing surface. Good alignment (co-planarity) between the tape
bearing surface of the closure and the head chip is required to
ensure good tape-head contact (i.e., a low spacing therebetween).
For read/write heads, planarity can be achieved by lapping of the
head chip and the closure to a flat surface. In addition to making
the surfaces flat and planar, the lapping process has the added
benefit of creating a sharp skiving edge on the closure.
Unfortunately, this process is not practical for use with planar
heads as the lapping process will damage the planar write
transducers. More generally, lapping may cause damages to a
tape-bearing surface.
[0018] Having realized these potential issues, present inventors
have developed methods for mounting a closure onto a planar servo
writer, where the closure is profiled such as to make it possible
to reach co-planarity with the surface of the tape bearing, without
resorting to a lapping process. They have further devised methods
to manufacture such a profiled closure with a sharp skiving edge
and, in particular, methods to design closures so as to reduce the
friction between tape and the tape head.
[0019] The present solutions can notably find applications for
planar servo writers (e.g., thin film planar servo writers).
However, and the one skilled in the art may appreciate, the present
solutions may potentially apply to any type of tape heads and, in
particular, to planar data heads for use in tape drives.
[0020] In reference to FIG. 5 (and additionally to FIGS. 1-4), an
aspect of the invention is first described, which concerns a method
of fabrication of a tape head 1, 2 with a closure.
[0021] Basically, this method makes use of a tape bearing body 5
and a monobloc closure 50, 50a. The body 5 exhibits a tape-bearing
surface 20, which is the surface meant to contact the magnetic tape
10, in operation. The body comprises at least one transducer 22
(or, if necessary, a set of transducers [not shown]). The
transducer 22 can be a read or a write element. It is in all cases
configured in the tape head body so as for the tape head to be able
to read from or write to the tape 10, in operation. Such a
transducer is preferably partly buried in the body, the top poles
of the magnetic yoke of the transducer being in-plane with the
tape-bearing surface, as assumed in the accompanying drawings.
[0022] The monobloc closure 50, 50a needs to be specifically
profiled for the purpose of the present methods. It has a
structured cross-sectional profile, so as to exhibit various parts
51, 53, 55, as depicted in FIG. 1 or 2. It notably comprises a
contact part 51, which exhibits a top surface 51s, as well as a
breakable part 55, whose top surface is referred to by reference
55s. A middle part 53 mechanically connects the breakable part 55
to the contact part 51. The connecting part 53 is integral with the
flanks 51, 55 but has a line 54, 54s of mechanical weakness, which
line extends across a top surface 53s of the connecting part
53.
[0023] Different approaches can be used to weaken the part 53,
e.g., partial cut, regularly spaced holes (blind or through-holes),
chemical process, etc. Weakening the connecting part is needed so
that later the part 55 can be broken off.
[0024] Next, the body 5 and the closure 50, 50a are arranged (step
S80 in FIG. 5) on a reference surface 70, so as for each of the
tape-bearing surface 20, the first top surface 51s and the second
top surface 55s to contact the reference surface 70. If the two
lateral flanks have a same height, then the reference surface 70
needs to be flat, so as for each of the surfaces 51s and 55s to be
level with the tape-bearing surface 20; the top surface 55s of the
breakable flank serves to obtain a correct orientation of the
surface 51s (both surfaces are level with each other, by design).
In variants, asymmetric flanks 51, 55 (or more generally non-level
surfaces 51s, 55s) may be used but the reference surface 70 must,
in all cases, be consistent with the design of the closure 50, 50a,
so as to eventually obtain a surface 51s that is level with the
tape-hearing surface 20.
[0025] The reference surface may for instance be a glass plate or
any other hard, transparent material, in which case the first top
surface 51s and the tape-bearing surface 20 can be viewed using an
inverted microscope. Namely, interference fringes can be observed
to verify the co-planarity of the two surfaces and adjust the
alignment (and possibly a load or pressure applied onto the
elements 5. 50, 50a) before fixing.
[0026] Then, the contact part 51 is fixed at steps S90-S100 on a
side 30, 30a of the body 5. This side 30, 30a adjoins the
tape-bearing surface 20 at an edge e.sub.l, e.sub.t thereof. The
structured closure 50, 50a may for instance be fixed on a leading
side (on the side of the leading edge e.sub.l) and/or a trailing
side (on the side of the trailing edge e.sub.l) of the body. A
curable glue 60 is preferably used to that aim.
[0027] Finally, the breakable part is removed at step S110 by
breaking the connecting part along the line 54, 54s of mechanical
weakness.
[0028] Note that, in the accompanying drawings, the line 54, 54s of
mechanical weakness is systematically located on the middle,
transversal part 53. Still, the one skilled in the art will
appreciate that this line 54, 54s may actually be located on the
lateral flank 55, so as to be able to break a portion of this flank
55. In such variants, the breakable portion of the flank 55 would
nevertheless be coupled to the contact part 51 via a connecting
part (the latter comprising a lower, residual portion of the flank
55, in addition to the transversal part 53).
[0029] In all cases, breaking this line 54, 54s makes it possible
to eventually obtain a tape head wherein the first surface 51s is
level with the tape-bearing surface 20. Still, the top surface 53s
of the connecting part 53 is, by design, recessed from the surface
51s, perpendicularly to the contact plane (y, z) defined by the
tape-bearing surface 20, so as for the surface 53s not to contact
the tape, in operation.
[0030] The above method allows the closure 50, 50a to be machined
independently from the body 5. This makes it easier to obtain a
desired shape for the closure, e.g., with appropriate (sharp)
skiving edges. The closure 50, 50a is later fixed to the body 5
and, thanks to the reference surface 70 and the outermost flank 55,
the top surface 51s can be made level with the tape bearing surface
20. This, advantageously, does not require any lapping process,
which may damage the tape-bearing surface 20. This is especially
beneficial for planar tape heads, where transducers are in-plane
with the planar tape-bearing surface, as assumed in the
accompanying drawings.
[0031] Removing the breakable part 55 by breaking along the line
54, 54s of mechanical weakness typically results in fracture marks
57 on the connecting part 53, as depicted in FIG. 1 or 6.
[0032] As schematically illustrated in FIGS. 1 and 3, the side 30
of the body 5 onto which a closure 50 is fixed may be a leading
side 30 (corresponding to leading edge e.sub.l), assuming a tape
direction parallel to the axis z, as in FIG. 3. In variants, two
closures 50, 50a (each having a structured profile as described
above) may be fixed on each side 30, 30a, respectively
corresponding to the leading edges e.sub.l and the trailing edge
e.sub.t, as depicted in FIG. 4. The leading side 30 and the
trailing side 30a adjoin, each, the tape-bearing surface 20 at a
respective edge e.sub.l, e.sub.t thereof. In still other variants,
a single closure 50a may be provided on the trailing side 30a only,
for reasons explained later.
[0033] Referring now to FIG. 5: in embodiments, the monobloc
closure(s) 50, 50a may be structured S10-S20, so as to obtain a
step-like cross-sectional profile for the contact part 51 in the
plane (x, z). In particular, a sharp, skiving edge e.sub.l, e.sub.t
may be desired, as best seen in FIGS. 3, 4. A suitable, step-like
cross-sectional profile may for instance exhibit a riser 40 (FIGS.
3, 4) between two treads, which are respectively formed by the
first top surface 51s and the recessed surface 52s. The latter is
recessed from the first top surface 51s so as not to contact the
magnetic tape 10, in operation. In particular, and referring now
more specifically to FIGS. 3, 4, the closures 50, 50a may be
structured at steps S10-S30 so as for the recessed surface 52s to
be recessed from the first top surface 51s by a distance h
(corresponding to the height of the riser 40), the width of the
recessed surface 52s (along a direction z parallel to the
longitudinal direction of circulation of the tape) being chosen so
as to ensure a desired wrap angle, as explained later in
detail.
[0034] Referring back to FIG. 5, the cross-sectional profile of a
closure 50, 50a may, in embodiments, be structured as follows.
First, a substrate 50w is provided, which is then coated S10 with a
photoresist 52p. The photoresist 52p is lithographically patterned
S10, to first create notches 52s, at positions corresponding to the
step S1s-40-52s to be subsequently created (see FIGS. 3, 4). The
photoresist pattern accordingly obtained is transferred S20 into
the substrate 50w, to obtain a clean, step-like cross-sectional
profile 51s-40-52s for the contact part 51.
[0035] The substrate 50w may for instance be an Aluminum-Titanium
carbide substrate, or AlTiC substrate (e.g., a wafer that
essentially comprises Al, Ti and C elements, in an
Al.sub.2O.sub.3--TiC composition). As known per se, the photoresist
pattern can be transferred into the AlTiC substrate by reactive ion
etching. Such a process results in clean step-like structures.
[0036] In embodiments, the connecting part 53 is obtained by
cutting S40 partially through a depth of the provided substrate 50w
with a wafer saw 80, up to a level desired for said third top
surface 53s. As illustrated in FIG. 5, wide notches 52s may
initially be provided, step S20, and sawing is started S30 at the
level of a notch 52s, at an end thereof (the width of a notch being
larger than the thickness of the saw 80). Eventually, a clean,
step-like structure is obtained at step S40 for the part 51, and
hence a clean skiving edge (see FIG. 6). Sections of the wafer 50w
are typically removed using repeated passes of the wafer saw 80 to
cut partially through the depth of the wafer, as illustrated in
FIG. 5, step S40. Preferably, several closures 50 are machined in
parallel at steps S10-S60.
[0037] Note that a skiving edge may in principle be created by
cutting the-substrate 50w with a wafer saw. However, the edge that
results is typically rough and may furthermore be chipped by the
cutting process. In contrast, the etching process described above
in reference to steps S10-S20 of FIG. 5 produces clean and sharp
skiving edges, as schematically illustrated in FIG. 6.
[0038] Next, the line 54, 54s of mechanical weakness is preferably
obtained by cutting partially through a depth of the obtained
connecting part 53, through the third top surface 53s, e.g., using
the same saw 80 as before, as depicted in FIG. 5, step S60. This
results in a recessed surface 54s, forming a trench in part 54. As
mentioned earlier, one may, in variants, punch regularly spaced
holes (blind or through holes). Various mechanical weakening
techniques are otherwise known, including chemical processes.
However, using a wafer saw is certainly the simplest, especially if
the saw 80 as used at steps S30-S40 can be re-used.
[0039] Preferably, the substrate 50w is cut at step S60 partially
so as to obtain a residual thickness of the connecting part 53 (at
the level of the weak line 54, 54s) that is typically between 30
and 70 microns, to ease the subsequent breaking at step S110. No
specific tool is needed to break the part 55, e.g., a mere scalpel
may be used to achieve this. Namely, after having placed the body 5
and the closure 50 on a support, one can push on the breakaway part
55 with a sharp scalpel, preferably equally along the full width of
part 55, to get a clean, one-time break.
[0040] In embodiments, the closure is fixed at steps S90-S100 by
first applying at step S90 a glue 60 on the outer side of the
contact part 51 (and/or on a side 30, 30a of the body 5) and then
by contacting the elements and subsequently curing the glue 60 at
step 100. One may for instance use a thermosetting adhesive/coating
(epoxy resin). The glue 60 used should provide adequate stiffness
after curing. Preferably, the glue is electrically conducting after
curing, so that the closure and the head substrate are at the same
electrical potential and the closure is automatically grounded with
the head substrate.
[0041] The final fixation steps (contacting and curing, S100) are
preferably performed while applying, at step S95, a (small) load or
pressure on the body 5 and the closure 50 arranged at step S80 on
the reference surface 70, to ensure a correct orientation of the
surfaces 20 and 51s. If necessary, the orientation of the closure
and/or the body may be corrected, based on observations from an
inverted microscope, as mentioned earlier. Once the glue is cured,
the outer part 55 can be removed, step S110.
[0042] FIG. 6 schematically depicts an object as obtained after
step S110 of FIG. 5 (only the closure is depicted though, for
conciseness). As illustrated in FIG. 6, the etched edge e.sub.l is
sharp (in fact all the step profile 51s-40-52s is clean), while
other edges and surfaces as obtained by sawing are logically
rougher.
[0043] Referring now more specifically to FIGS. 1-4: according to
another aspect, the invention can be embodied as a tape head 1, 2.
The tape head 1, 2 can typically be obtained by the fabrication
methods as described above. Consistently with the fabrication
methods discussed above, tape heads according to embodiments shall
most generally be designed for reading and/or writing to a magnetic
tape 10, via the tape-bearing surface 20, which surface contacts
the tape 10, in operation of the tape head. The body 5 comprises at
least one transducer 22. In addition, the tape head comprises one
or two structured, monobloc closure(s) 50, 50a, e.g., fixed to the
body according to methods described before. Such a closure has a
structured cross-sectional profile, so as to exhibit a contact part
51, fixed on a side 30, 30a of the body 5, which side adjoins the
tape-bearing surface 20 at an edge e.sub.t, e.sub.l thereof.
Consistently with the preferred fabrication methods discussed
earlier, the contact part 51 has a top surface 51s that is level
with the tape-bearing surface 20. The connecting part 53 is
integral with the contact part 51 and has a top surface 53s
recessed from the top surface 51s of the contact part 51, so that
the surface 53s does not to contact the tape 10, in operation (to
reduce friction, damages to the tape and wear of the head).
[0044] The connecting part 53 of a closure 50, 50a further shows a
broken line 54, 54s of mechanical weakness, i.e., a broken
mechanical element 54 extending along direction y in FIG. 1, at a
distal end of the connecting part 53. The connecting part 53 may
for instance exhibit fracture marks 57 at a level of the broken
element 54. Fracture marks may notably include residual marks of
breakage, such as cleavage planes or parting breaks, etc.,
depending on the material used for the closure and the process used
to break the part 55.
[0045] As mentioned earlier, the closure 50, 50a may be mounted on
the leading side 30 or the trailing side 30a of the body 5, each of
said sides 30, 30a adjoining the tape-bearing surface 20 at a
respective edge e.sub.l, e.sub.t thereof, see FIGS. 3-4.
[0046] As per the above design, the tape-bearing surface 20 and the
adjoining surface(s) 51s form an area that is essentially flat.
This area is generally configured to contact the tape 10, in
operation. The surface 20 comprises at least one transducer 22,
which may be a read or a write element, i.e., an element configured
in the tape head to respectively read or write to the magnetic tape
10, in operation.
[0047] Still, the tape-bearing surface 20 shall typically include
several transducers. The tape-bearing surface 20 is furthermore
preferably planar. I.e., the body 5 comprises one or more in-plane
transducers 22, which are partly buried in the body. Top poles of
the transducers are mounted front-flush so as for the surface 20 to
be essentially flush.
[0048] As discussed earlier too, the monobloc closure 50, 50a may
have a step-like cross-sectional profile, exhibiting a riser 40
between two treads 51s, 52s, as respectively formed by the top
surface 51s and the recessed surface 52s. In embodiments, the
surface 52s is recessed from the top surface 51s by a distance h,
whereas the width w of the recessed surface 52s along direction z
(parallel to the direction of circulation of the tape) is such as
to ensure that a desired wrap angle can be obtained. E.g., for a
given, desired wrap angle .alpha., the ratio h/w should be larger
than or equal to tan(.alpha.), else the tape may touch the edge of
52s. For instance, h=2 .mu.m, and w=50 .mu.m may typically be used.
Smaller values of w (e.g., 10 or 20 .mu.m can be obtained). The
value of w is ideally as small as possible. The closure 50, 50a is
preferably fabricated from an AlTiC substrate, as discussed
earlier.
[0049] Because of the riser 40, the recessed surface 52s is
recessed from the contact area 20+51s by a distance 12 that
corresponds to the height of the riser 40, i.e., along x. The riser
40 and, more generally, the step-like structure 51s-40-52s can
notably be obtained according to methods described earlier in
reference to FIG. 5, which allow sharp, skiving edges e.sub.l,
e.sub.t to be obtained.
[0050] Note that the drawings are not to scale; in particular, in
FIGS. 3, 4, the scales along axes x and z differ, for the sake of
depiction).
[0051] The distance h is ideally as small as possible and, in
practice, preferably between 1 and 10 microns, to ease the transfer
process (step S20, FIG. 5). More preferably, the distance h shall
be between 3 and 7 microns. Suitable widths w for the recessed
surface 52s shall typically be between 10 and 50 microns.
[0052] Possible ranges of for dimensions for the head components
follow: [0053] The length of the leading edge e.sub.l (along axis
y) preferably corresponds to the length of the head and is
preferably larger than the width of the tape (e.g., 0.5 inch);
[0054] The width of the recessed surface 52s (along z) is
preferably between 10 and 50 .mu.m it is ideally as small as
possible). [0055] The width of the first top surface 51s (along z)
is preferably between 20 and 200 .mu.m, and is more preferably
larger than 100 .mu.m so that the tape 10 may land on the closure.
[0056] The total width of the connecting part 53 (along z) is
preferably of (approximately) 2 mm; [0057] The width of the trench
54s (along z) is preferably .about.150 .mu.m, depending on the saw
blade width; and [0058] The width of the second top surface 55s
(along z) is preferably .about.200 .mu.m.
[0059] Present tape heads 1, 2 may exhibit one (FIG. 3) or two
(FIG. 4) recessed surfaces 52s. In FIG. 4, the tape head 2 exhibit
two recessed surfaces 52s, i.e., one on the trailing side 30a and
one on the leading side 30 of the tape-bearing surface 20. In FIG.
4, the recessed 52s surface on the trailing side 30a is recessed
from the tape-bearing surface 20 by a distance h.sub.2 and has a
width w.sub.2 along z, h.sub.2 and w.sub.2 being here again
appropriately chosen so as to prevent the tape (or at least
substantially lower the chance for it) to be pushed back onto the
recessed surface 52s on the trailing side 30a, in operation of the
tape head. Again, the distance h.sub.2 shall advantageously be
between 1 and 10 microns. The fabrication of the head will be
greatly facilitated if the distances h and h.sub.2 are chosen equal
and, a fortiori, if similar closures 50 and 50a are used. Yet,
asymmetric heads may be desired, in variants, depending on the
desired wrapping of the tape 10.
[0060] Tape heads 1, 2 as described herein are preferably planar
servo write heads, i.e., planar heads comprising at least one
transducer (writer) 22, with in-plane top poles. Present tape heads
1, 2 can notably be used in tape head apparatuses for recording
and/or reproducing multi-track tapes. The present invention can
accordingly be embodied as such an apparatus.
[0061] The above embodiments have been succinctly described in
reference to the accompanying drawings and may accommodate a number
of variants. Several combinations of the above features may be
contemplated. Examples are given below.
[0062] The fabrication and assembly process is preferably as
follows. First concerning the fabrication of the closure: an AlTiC
wafer is provided that is coated with a photoresist, and
lithographically patterned, step S10. Then, S20: the pattern is
transferred into the AlTiC wafer by reactive ion etching, creating
a sharp edge e.sub.l (FIG. 6) which will later act as a skiving
edge, in operation. During steps S30-S50: sections of the wafer are
removed using repeated passes of a wafer saw to cut partially
through the depth of the wafer. At step S60: an additional deeper
cut is made with the wafer saw to produce a region with a residual
thickness of approximately 50 microns. At step S70: individual, or
"row bar", sections of closure are produced by cutting through the
full thickness of the wafer. Next, regarding the closure assembly:
a planar tape head body 5 (obtained from a wafer chip) and a
closure are placed upside-down (i.e., with the write elements and
the skiving edge down) on a flat reference surface, S80. In FIG. 5,
the planar writer is on the left and the closure is on the write.
The two parts are aligned, and glued S90 together under a small
applied load. The use of the reference surface assures the
co-planarity of the (planar) tape bearing surface and the closure's
top surfaces (upside-down). Using, for example, a glass plate (or
any other transparent material) for the reference surface, the
surfaces of the body and the closure can be viewed using an
inverted microscope, to verify the co-planarity of the surfaces and
adjust the alignment of the elements, as well as the applied load,
if necessary, before gluing. After the glued is cured at step S100,
the free, outer flank of the closure is removed at step S110 by
breaking the thinned region.
[0063] If assembly is performed at the "row bar" level, the row
bars can be cut into individual, planar servo-writers in a
subsequent step (not shown).
[0064] The closure may for instance be fixed on a leading side
and/or a trailing side of the body.
[0065] Preferably, the monobloc closure is fabricated so as to
exhibit a structured cross-sectional profile, whereby the contact
part has a step-like cross-sectional profile, with a riser between
two treads that are respectively formed by the first top surface
and a recessed surface, the latter recessed from the first top
surface so as not to contact the magnetic tape, in operation.
[0066] As mentioned earlier, said side may be a leading side or a
trailing, side of the body. Preferably, the contact part of the
monobloc closure has a step-like cross-sectional profile, as
described above. In particular, the recessed surface may be
recessed from the top surface of the contact part by a distance h
corresponding to a height of the riser, wherein h between 1 and 10
microns, whereas a width w of the recessed surface along a
direction parallel to a longitudinal direction z of circulation of
the tape is between 10 and 50 microns.
[0067] In preferred embodiments, the tape head is a planar tape
head, wherein said transducer is an in-plane transducer, in-plane
with the tape-bearing surface. The tape head is preferably a servo
writer.
[0068] While the present invention has been described with
reference to a limited number of embodiments, variants and the
accompanying drawings, it will be understood by those skilled in
the art that various changes may be made and equivalents may be
substituted without departing from the scope of the present
invention. In particular, a feature (device-like or method-like)
recited in a given embodiment, variant or shown in a drawing may be
combined with or replace another feature in another embodiment,
variant or drawing, without departing from the scope of the present
invention. Various combinations of the features described in
respect of any of the above embodiments or variants may accordingly
be contemplated, that remain within the scope of the appended
claims. In addition, many minor modifications may be made to adapt
a particular situation or material to the teachings of the present
invention without departing from its scope. Therefore, it is
intended that the present invention not be limited to the
particular embodiments disclosed, but that the present invention
will include all embodiments falling within the scope of the
appended claims. In addition, many other variants than explicitly
touched above can be contemplated. For example, other materials
than those explicitly cited may be used for the wafer 50w used to
obtain the closures.
* * * * *