U.S. patent application number 11/693489 was filed with the patent office on 2007-10-04 for timing-based servo verify head and method thereof.
Invention is credited to Matthew P. Dugas, Gregory L. Wagner.
Application Number | 20070230040 11/693489 |
Document ID | / |
Family ID | 34752398 |
Filed Date | 2007-10-04 |
United States Patent
Application |
20070230040 |
Kind Code |
A1 |
Dugas; Matthew P. ; et
al. |
October 4, 2007 |
TIMING-BASED SERVO VERIFY HEAD AND METHOD THEREOF
Abstract
A servo head capable of verifying at least one timing based
pattern printed on media is provided. The servo head includes a
magnetic structure having at least one magnetic element arranged
and configured to form at least one magnetic gap parallel to the
timing based pattern. In one embodiment, the magnetic element is
arranged and configured to have a plurality of magnetic gaps being
parallel to each other but not co-linear to each other. In the
second embodiment, the magnetic element is arranged and configured
to have a magnetic gap being parallel to and co-linear to the
timing based pattern.
Inventors: |
Dugas; Matthew P.; (St.
Paul, MN) ; Wagner; Gregory L.; (Roseville,
MN) |
Correspondence
Address: |
DORSEY & WHITNEY LLP;INTELLECTUAL PROPERTY DEPARTMENT
SUITE 1500
50 SOUTH SIXTH STREET
MINNEAPOLIS
MN
55402-1498
US
|
Family ID: |
34752398 |
Appl. No.: |
11/693489 |
Filed: |
March 29, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11017529 |
Dec 20, 2004 |
|
|
|
11693489 |
Mar 29, 2007 |
|
|
|
60530943 |
Dec 19, 2003 |
|
|
|
Current U.S.
Class: |
360/121 ;
G9B/5.068 |
Current CPC
Class: |
G11B 5/265 20130101;
G11B 5/584 20130101 |
Class at
Publication: |
360/121 |
International
Class: |
G11B 5/265 20060101
G11B005/265 |
Claims
1-39. (canceled)
40. A servo head capable of writing a portion of a timing based
pattern comprising at least two magnetic writing gap elements,
wherein the at least two magnetic writing gap elements are parallel
and co-linear.
41. The servo head of claim 40, wherein the at least two magnetic
writing gap elements are substantially aligned to a predetermined
angle with respect to the direction of a magnetic media
velocity.
42. The servo head of claim 40, wherein the servo head further
comprises at least one thin film head row bar comprising the at
least two magnetic writing gap elements.
43. The servo head of claim 40, wherein the servo head further
comprises at least one magnetic gap bar comprising the at least two
magnetic writing gap elements.
44. The servo head of claim 40, wherein the servo head comprises a
plurality of magnetic writing gap elements.
45. The servo head of claim 40, further comprising at least one
additional gap element, wherein the at least two magnetic writing
gap elements are substantially aligned to a predetermined angle
with the at least one additional gap element.
46. The servo head of claim 40, wherein the timing of energizing
the at least two magnetic writing gap elements is staggered to
produce an arbitrary pattern of magnetic transitions on magnetic
media.
47. The servo head of claim 45, wherein the timing of energizing
the gap elements is staggered to produce an arbitrary pattern of
magnetic transitions on magnetic media.
48. A servo head capable of writing a portion of a timing based
pattern comprising at least two magnetic writing gap elements,
wherein the at least two magnetic writing gap elements are parallel
and not co-linear.
49. The servo head of claim 48, wherein the at least two magnetic
writing gap elements are substantially aligned to a predetermined
angle with respect to the direction of a magnetic media
velocity.
50. The servo head of claim 48, wherein the servo head further
comprises a thin film head row bar comprising the at least two
magnetic writing gap elements.
51. The servo head of claim 48, wherein the servo head further
comprises a magnetic gap bar comprising the at least two magnetic
writing gap elements.
52. The servo head of claim 48, wherein the servo head comprises a
plurality of magnetic writing gap elements.
53. The servo head of claim 48, further comprising at least one
additional gap element, wherein the at least two magnetic writing
gap elements are substantially aligned to a predetermined angle
with the at least one additional gap element.
54. The servo head of claim 48, wherein the timing of energizing
the at least two magnetic writing gap elements is staggered to
produce an arbitrary pattern of magnetic transitions on magnetic
media.
55. The servo head of claim 53, wherein the timing of energizing
the gap elements is staggered to produce an arbitrary pattern of
magnetic transitions on magnetic media.
56. Magnetic media made with a servo head capable of writing a
portion of a timing based pattern comprising at least two magnetic
writing gap elements, wherein the at least two magnetic writing gap
elements are parallel and co-linear.
57. The magnetic media of claim 56, wherein the magnetic media is
magnetic tape.
58. Magnetic media made with a servo head capable of writing a
portion of a timing based pattern comprising at least two magnetic
writing gap elements, wherein the at least two magnetic writing gap
elements are parallel and not co-linear.
59. The magnetic media of claim 58, wherein the magnetic media is
magnetic tape.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application claims the benefit of U.S. Provisional
application No. 60/530,943, entitled "Time-Based Servo Heads Using
Discrete Single Channel Head Elements and Methods for Making the
Same," filed on Dec. 19, 2003, the subject matter of which is
hereby incorporated by reference herein in its entirety.
FIELD OF THE INVENTION
[0002] The present invention relates generally to recording and
reading data from magnetic storage media and, more particularly, to
a magnetic head and method thereof for verifying timing-based servo
tracks or patterns on magnetic storage media.
BACKGROUND OF THE INVENTION
[0003] Due to the density of modern magnetic data storage media,
magnetic data storage media requires servo tracks be printed onto
the media to minimize data-track registration errors. The servo
tracks are often written onto the storage media in the media
production facility, where it is necessary, after writing servo
tracks or patterns, to verify that the tracks have been properly
printed onto the media and meet the production specifications. This
verification process is accomplished by running a servo verify
magnetic recording head, e.g. read head, over the media on which
the servo tracks are printed.
[0004] A servo head, in this case particularly a servo verify head,
generally requires an ensemble of magnetic structures. Standard
processing techniques and tools for assembling magnetic structures
generally operate in an orthonormal coordinate system. Thus, the
processing of magnetic structures at an angle to the standard
processing planes poses unique challenges.
[0005] In the magnetic data storage media industry, there are many
methods of writing or implementing magnetic servo tracks on storage
media. Servo tracks have many different geometries. One specific
method and geometry is that of timing based servo (TBS). TBS
utilizes successive magnetic transitions written on the media at
non-orthogonal angles with respect to the travel direction of the
media (e.g. tape). FIG. 2a illustrates this method. Two separate
servo bands 42 are shown, with a set of four magnetic patterns or
tracks 40a and 40b at +6.degree. and -6.degree. respectively.
[0006] The uniqueness of TBS patterns is due to magnetic structures
at an angle to standard processing planes, i.e. non-orthogonal
angles with respect to the travel direction of media. To verify TBS
patterns or tracks on the media, it is desired that the magnetic
sensing regions (read gap) on a servo verify head are effectively
parallel to the corresponding magnetic transitions (servo patterns)
printed on the media. Non-parallelism between the magnetic
transition on the tape and the magnetic read head may lead to
detection inefficiencies and lower sensitivity of the resultant
signals through azimuth loss.
[0007] One method for verifying a TBS pattern is to sense or read a
full servo transition at once, a so-called full-band verify. With
this method, the full pattern width of any single transition is
detected at once. With full-band verify, it is desirable to have
good azimuth alignment between the magnetic head read gap and the
servo transition on tape. Misalignment between these will cause the
magnetic transition to be effectively smeared across the read
sensor, causing detection efficiency and sensing accuracy loss.
Severe azimuth misalignment, may even cause more than one magnetic
transition to be intersecting the read sensor (gap) simultaneously,
confusing what transition was verified.
[0008] Another method for verifying a TBS pattern is the so-called
partial-band verify. With this method, a narrow read gap magnetic
head is used. If the read gap width is sufficiently small relative
to the TBS pattern width, the amount of azimuth misalignment
acceptable is eased. In one example, a TBS pattern with a width of
190 .mu.m at an angle of 6.degree. can be verified by a read sensor
with a width of 5-10 .mu.m at an azimuth angle of 0.degree.. This
method allows the production of a servo verify head without the
complexity of processing previously mentioned. This method also
requires that the servo verify head be mechanically scanned along
the TBS pattern transition width to sample the full servo pattern.
Both the above mentioned methods have advantages and disadvantages
and are practiced in the industry.
[0009] One advantage of the full-band verify method is that the
head is stationary, eliminating the need for a scanning actuator to
move the head in the cross-track direction. Another advantage of
the full-band verify method is that the entire width of each
pattern in the servo band is verified. On the other hand, it may be
difficult for the full-band verify method to detect small localized
defects in the servo pattern. In one example, a localized defect of
5 .mu.m along a 190 .mu.m track width, which is repeated down the
servo band, may not be properly detected.
[0010] One advantage of the partial-verify method is that the
repeatable small local defects previously mentioned can be
intersected and properly detected as the head scans back and forth.
In a partial-verify method, however, an appropriate scan rate,
i.e., how long it takes to scan the width of a servo band, may be
desired in representing the fraction of any servo pattern sampled.
Large temporary defects where a significant portion of a servo
pattern is missing, and where the defects only repeat for a small
number of servo patterns, may not be intersected by the scanning
head and hence be undetected. Hence, it is desirable to detect
these defects with an appropriate scan rate and in an efficient and
capable manner in the production facility.
[0011] Also, in the processing of magnetic structures of a servo
head for verifying TBS patterns, independent channels at a
specified angle are desired. This allows each servo pattern and any
defects of that servo pattern to be detected independent of any
other servo pattern.
[0012] Further, in the processing of magnetic structures of a servo
head for verifying TBS patterns, it is desirable to assemble or
bond independent cores while maintaining multi-dimensional
tolerances.
[0013] An additional feature of a magnetic servo verify head is a
proper head to tape interface. If the head to tape interface is
poor, the tape may not contact the head appropriately, leading to
sensing inefficiency. A magnetic head surface generally requires an
appropriate geometry to obtain a good or acceptable head to tape
interface. One standard geometry for a magnetic servo head used in
the industry is a cylindrical contour. As an example, typical
cylindrical contours may have a radius from 5 mm to 25 mm. A
cylindrical contour generally limits the length of the head
(down-tape or down-track direction) to achieve a good interface.
Therefore, the spatial location acceptable for magnetic elements on
a cylindrical contour is restricted.
[0014] Thus, depending on the desirable geometry and form factor of
a magnetic servo head surface, TBS patterns may add a high degree
of complexity to processing techniques of the ensemble of magnetic
structures for a servo verify head.
[0015] Therefore, there is a need for a servo head to verify TBS
patterns printed on data storage media, and further there is a need
for a method of assembling a servo head having acceptable head
geometry and form factor of a servo head surface to be adapted for
verifying TBS patterns.
SUMMARY OF THE INVENTION
[0016] In accordance with the present invention, a servo head or
servo verify head capable of verifying at least one timing based
pattern printed on media comprises a magnetic structure including
at least one magnetic bar or magnetic element arranged and
configured to form at least one magnetic gap parallel to the timing
based pattern. In one embodiment, the magnetic element is arranged
and configured to have a plurality of magnetic gaps being parallel
to each other but not co-linear to each other. In the second
embodiment, the magnetic element is arranged and configured to have
a plurality of magnetic gaps being both parallel and co-linear to
each other.
[0017] Further in one embodiment of the present invention, the
magnetic element includes a plurality of individual gap bars bonded
to each other, each gap bar having a pair of magnetic cores bonded
together with the magnetic gap disposed therebetween. The magnetic
gap is an angled gap which is non-orthogonal to an edge of the
magnetic element.
[0018] Also, in accordance with the present invention, a method of
forming a servo head capable of verifying at least one timing based
pattern printed on media comprises the steps of: providing a
magnetic gap element having a pair of magnetic element elements
bonded together with a magnetic gap disposed therebetween, the
magnetic gap extending linearly along the element and being
parallel to the timing based pattern.
[0019] In one embodiment, the method further comprises the steps
of: dicing the magnetic gap element into individual cores at an
angle to the magnetic gap such that the magnetic gap is
non-orthogonal to an edge of the magnetic element; and assembling
the cores into a composite structure on a reference block, such
that the gaps of the cores are parallel to each other.
[0020] Still in one embodiment, the method further comprises the
steps of: bonding the cores against the reference block by spring
means; removing a portion of the composite structure to form an
azimuthal multicore which includes a plurality of magnetic
structures on one side of the azimuthal multicore, and each
magnetic structure including a magnetic gap; bonding a slider
element onto the azimuthal multicore; and exposing the magnetic
structures including the magnetic gaps, wherein the magnetic gaps
are parallel to each other.
[0021] Additionally in one embodiment, the method further comprises
the steps of: processing a second magnetic gap element having
exposed magnetic structures including magnetic gaps wherein the
magnetic gaps are parallel to each other and a slider element
bonded onto an azimuthal multicore; bonding the first magnetic gap
element and the second magnetic gap element onto a spacer disposed
therebetween.
[0022] In the second embodiment of the present invention, the
magnetic structure includes a first gap element having a first pair
of magnetic cores bonded together with a first magnetic gap
disposed therebetween, and a second gap element having a second
pair of magnetic cores bonded together with a second magnetic gap
disposed therebetween. The first and second magnetic elements are
arranged and configured to be bonded onto a spacer disposed
therebetween such that the first and second magnetic gaps are
angled and parallel to the timing based patterns on the media and
are non-orthogonal to an edge of the magnetic structure.
[0023] Also, in accordance with the second embodiment of the
present invention, the method of forming a servo head capable of
verifying at least one timing based pattern printed on media
further comprises the steps of: removing a portion of the magnetic
element to form a plurality of magnetic structures on one side of
the magnetic element, and each magnetic structure including a
magnetic gap; bonding a slider element onto the magnetic
structures; and exposing the magnetic structures including the
magnetic gaps.
[0024] Additionally in the second embodiment, the method further
comprises the steps of: processing a second magnetic gap element
having exposed magnetic structures including magnetic gaps; bonding
a second slider element onto the magnetic structures; exposing the
magnetic structures including the magnetic gaps; and bonding the
first magnetic gap element and the second magnetic gap element onto
a spacer disposed therebetween.
[0025] Further, in accordance with the present invention, the
magnetic element is a thin film head row bar.
[0026] Further in one embodiment of the present invention, one
servo verify head covers the entire length of the timing based
patterns so as to verify the timing based patterns in its entirety
at the same time. In another embodiment, a plurality of servo
verify heads cover the entire length of the timing based patterns
so as to verify the timing based patterns in its entirety at the
same time. In a third embodiment, a servo verify head covers a part
of the entire length of the timing based patterns and scans the
timing based patterns by moving the servo verify head along the
patterns.
[0027] While multiple embodiments are disclosed, still other
embodiments of the present invention will become apparent to those
skilled in the art from the following detailed description, which
shows and describes illustrative embodiments of the invention. As
will be realized, the invention is capable of modifications in
various obvious aspects, all without departing from the spirit and
scope of the present invention. Accordingly, the drawings and
detailed description are to be regarded as illustrative in nature
and not restrictive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1 illustrates a perspective view of one embodiment of a
timing-based servo verify head in accordance with the principles of
the present invention.
[0029] FIG. 2 illustrates a flow chart of one exemplary process of
forming a timing-based servo verify head in accordance with the
principles of the present invention.
[0030] FIG. 2a illustrates a top view of one embodiment of a
timing-based servo pattern on a magnetic tape.
[0031] FIG. 3 illustrates a perspective view of one embodiment of a
core bar in the process of forming a timing-based servo verify head
of FIG. 1 in accordance with the principles of the present
invention.
[0032] FIG. 4 illustrates a perspective view of one embodiment of
an individual core piece formed from the core bar of FIG. 3 in the
process of forming a timing-based servo verify head of FIG. 1 in
accordance with the principles of the present invention.
[0033] FIG. 5 illustrates a perspective view of one embodiment of a
plurality of individual core pieces of FIG. 4 attached to a
reference block to form a multicore bar in the process of forming a
timing-based servo verify head of FIG. 1 in accordance with the
principles of the present invention.
[0034] FIG. 6 illustrates a perspective view of one embodiment of a
modified multicore bar having portions of core pieces removed to
define outwardly extending magnetic elements and read gap
tolerances in accordance with the principles of the present
invention.
[0035] FIG. 7 illustrates a partially enlarged view of one of the
core bars of the multicore bar of FIG. 6 in accordance with the
principles of the present invention.
[0036] FIG. 8 illustrates a perspective view of a slider element
with a plurality of slots bonded with the modified multicore bar of
FIG. 6 in accordance with the principles of the present
invention.
[0037] FIG. 8a illustrates a backside of the perspective view of
FIG. 8.
[0038] FIG. 9 illustrates a perspective view of a structure having
portions of the slider element and multicore bar of FIG. 8 removed
to form the first half-slider of a magnetic head in accordance with
the principles of the present invention.
[0039] FIG. 9a illustrates a top down view of the structure of FIG.
9.
[0040] FIG. 10 illustrates a perspective view of one embodiment of
the first half of the servo verify head, having a support beam
attached, in accordance with the principles of the present
invention.
[0041] FIG. 11 illustrates a perspective view of one embodiment of
a servo verify head where the second half of the servo verify head
is bonded to the first half of the servo verify head in accordance
with the principles of the present invention.
[0042] FIG. 12 illustrates a top view of one embodiment of the
servo verify head of FIG. 11.
[0043] FIG. 13 illustrates a second embodiment of a timing-based
servo verify head in accordance with the principles of the present
invention.
[0044] FIG. 14 illustrates a flow chart of a second exemplary
process of forming the second embodiment of the timing-based servo
verify head of FIG. 13 in accordance with the principles of the
present invention.
[0045] FIG. 15 illustrates a perspective view of one embodiment of
a core bar in the process of forming the second embodiment of the
timing-based servo verify head of FIG. 13 in accordance with the
principles of the present invention.
[0046] FIG. 16 illustrates a perspective view of one embodiment of
the core bar having portions of core pieces removed to define
outwardly extending magnetic elements and read gap tolerances in
accordance with the principles of the present invention.
[0047] FIG. 17 illustrates a top view of the one embodiment of the
core bar shown in FIG. 16.
[0048] FIG. 18 illustrates a perspective view of a slider element
with a plurality of slots for mating with the core bar of FIG. 16
in accordance with the principles of the present invention.
[0049] FIG. 19 illustrates a perspective view of a structure having
portions of the slider element and core bar of FIG. 18 removed to
form the first half of the servo verify head in accordance with the
principles of the present invention.
[0050] FIG. 20 illustrates a top view of the structure shown in
FIG. 19.
[0051] FIG. 21 illustrates an exploded view of one embodiment of
the servo verify head shown in FIG. 13 where the second half of the
servo verify head is to be bonded to the first half of the servo
verify head in accordance with the principles of the present
invention.
[0052] FIG. 22 illustrates a bottom view of the embodiment of the
servo verify head after a plurality of magnetic u-cores are
attached to the magnetic structure of the servo verify head.
[0053] FIG. 23 illustrates a top view of one embodiment of a servo
verify head having a core bar that uses a thin film head row bar in
accordance with the principles of the present invention.
[0054] FIG. 24 illustrates an exploded view of the embodiment of
the servo verify head having the core bar that uses the thin film
head row bar of FIG. 23.
[0055] FIG. 25 illustrates a perspective view of a third embodiment
of a timing-based servo verify head using scanning head technique
in accordance with the principles of the present invention.
[0056] FIG. 26 illustrates a perspective view of one embodiment of
a core bar as shown in FIGS. 3 and 15 having portions of core
pieces removed to define outwardly extending magnetic elements and
read gap tolerances in accordance with the principles of the
present invention.
[0057] FIG. 27 illustrates a top view with a slanted angle of the
embodiment of the core bar shown in FIG. 26.
[0058] FIG. 28 illustrates a partially enlarged view of the
embodiment of the core bar shown in FIG. 26.
[0059] FIG. 29 illustrates a perspective view of a slider element
with a plurality of slots for mating with the core bar of FIG. 26
in accordance with the principles of the present invention.
[0060] FIG. 30 illustrates a perspective view of the embodiment of
the servo verify head shown in FIGS. 25-29 after a plurality of
magnetic u-cores are attached to the magnetic structure of the
servo verify head.
DETAILED DESCRIPTION
[0061] The present invention relates to heads for use with magnetic
tape, and methods for forming heads. Various embodiments of the
present invention are described herein.
[0062] FIG. 1 shows a head 10 having five channels 12 with each
channel having a first magnetic structure (first gap) 56a and a
second magnetic structure (second gap) 56b. As shown in FIG. 1,
each of the first magnetic structures 56a are parallel but not
collinear and each of the second magnetic structures 56b are
parallel but not collinear. As shown in FIG. 1, the first magnetic
structures are -6 degrees from a x-axis, and the second magnetic
structures are +6 degrees from a x-axis. Also, in head 10, each
magnetic structure is magnetically and electrically independent.
The head as shown in FIG. 1 may be used to verify a TBS pattern
written to a tape. In use, the head shown in FIG. 1 has a surface
contour that provides a good or acceptable head to tape
interface.
[0063] With reference to FIGS. 2-12, a technique to manufacture
heads having magnetic structures that include angles will be
described. The process to be described enables the manufacture of
any single magnetic line pattern that can be mechanically diced and
reassembled to have mechanically and electrically independent
channels with the line having any angle. Moreover, as will be made
clear by the manufacturing process, the resulting head may have
magnetic structures in each of the channels that are not parallel
or collinear to each other. Alternatively, the heads may be
manufactured to provide parallel and/or collinear relationships
between the magnetic structures in one or more of the channels.
Also, the process provides for a high degree of precision (e.g.,
within a micron or two).
[0064] FIG. 2 illustrates one example of the operations for forming
a magnetic tape head with discrete and independent magnetic
elements, in accordance with one embodiment of the present
invention. This process can be utilized to form a magnetic tape
head as shown in the example of FIG. 1 or other tape heads having
two or more discrete and independent magnetic elements aligned in a
precise manner.
[0065] The operations of FIG. 2 may be used to form a magnetic head
without having to bond or connect in multiple operations the
plurality of magnetic servo elements to portions of the magnetic
head. The operations of FIG. 2 provide for precise alignments of
the plurality of individual core pieces to form a magnetic head
using these operations. Accordingly, the operations of FIG. 2 can
be used to form a magnetic head having typical or standard head
geometries, without the need for the manufacturing process having
to include multiple alignment operations of each magnetic element
to one another. Hence, the operations of FIG. 2 may be used to form
a head with a typical or standard head to tape interface.
[0066] In one example, an azimuth head having a plurality of
independent and aligned magnetic structure is generally formed by
creating a first half of the head and a second half of the head,
then attaching the first half with the second half with a spacer
portion therebetween. Operations 20-34 of FIG. 2 may be used to
form the halves of the head structures, and operation 36 assembles
the halves to form the final head structure, in one example.
[0067] At operation 20, a magnetic ferrite gap bar, or core bar, is
formed with one or more magnetic gaps or cavities defined between
at least two types of magnetic materials. One example of a core bar
50 is shown in FIG. 3. In one example, the core bar may be a
generally elongated, rectangular structure, having a first portion
52, a second portion 54, and a magnetic read/write gap 56. The
first portion of the core bar may be generally rectangular and
include an interface (gap) surface for attachment to the second
portion of the core bar. The second portion of the core bar may be
a generally elongated, rectangular structure having two or more
slots 58 and 60 extending linearly along the length of the second
portion. The slot 58 will be used to wind wire to energize the
magnetic structure. The slot 60 exists to define the height of the
magnetic core when full processing is completed. The first and
second portions are bonded together using conventional glass
bonding or other conventional bonding techniques. The faces of
portions 52 and 54 where they are joined typically contain a thin
nonmagnetic spacing material. This spacing material, typically 0.3
.mu.m to a few .mu.m thick, results in the magnetic read/write gap
56.
[0068] In one example, the first 52 and second 54 portions of the
core bar may be made from magnetic ceramic materials such as NiZn
Ferrite.
[0069] At operation 22, the core bar 50 may be divided or diced
into multiple individual azimuth core pieces 62. One example of an
individual core piece is shown in FIG. 4. In one example, the core
bar is diced into individual azimuth core pieces at an angle of
+6.degree. or -6.degree. to the gap 56. These cores are then
squared or made orthogonal to the diced face 64, resulting in an
orthogonal cross-section with the angled gap 56.
[0070] At operation 24, FIG. 5, two or more core pieces 62 are
attached to a reference block 72 to form an azimuthal multicore bar
70, each core piece being accurately positioned relative to one
another on the reference block. In one example, the reference block
72 is a generally elongated L-shaped structure defining a shelf
portion upon which the core pieces are positioned. The reference
block 72 may be made from any suitable material which maintains
dimensional stability. In one example, the reference block 72 is
made from BaTiO for a stable material matched with the magnetic
ceramic 52 and 54 for thermal expansion characteristics. In this
operation, the parallelism of the gaps 56, the co-planarity of the
cores surfaces of 62, and the distance between the cores is
governed by the desired final head design requirements. In one
example, a bonding tool or fixture is used to position and
reference the core pieces on the reference block. This bonding tool
references each core independently and maintains the core
independently referenced in five degrees of freedom. The sixth
degree of freedom is also constrained, but not independently for
each core. In this dimension, the core references are coupled. Once
the cores are thus positioned, they are bonded to the reference
block to accurately secure their relative positions for further
processing. The bonding fixture allows the cores to be either epoxy
bonded or glass bonded to the reference block, with a possible
temperature range of 50-750.degree. F., while maintaining the
multidimensional reference. FIG. 5 is one example of an azimuthal
multicore bar 70, showing five cores or core pieces 62.
[0071] Operation 26, FIGS. 6 and 7, modifies the azimuthal
multicore bar 70. In one example, operation 26 removes portions of
the core pieces 62 from the azimuthal multicore bar, which may be
accomplished by machining portions of the core pieces to form
T-shaped magnetic elements outwardly extending from the reference
block. Cuts 74 and 76 are precision machined surfaces. These
surfaces define the width of the magnetic read gap 56. This
approach, machining the read gap width and position of all azimuth
cores 62 in a single operation, allows precise location and pitch
of the read gaps 56 relative to each other. The precision of this
approach is greater than that can be achieved by machining the
cores individually and then assembling them. In one example, the
width of the magnetic read gap 56 is approximately 200 .mu.m, and
the pitch between any two adjacent cores is 2.858 mm with a
precision of around 1 .mu.m.
[0072] At operation 28, FIGS. 8 and 8a, a slider element 92 is
bonded to the modified azimuth multi-core bar 80 to form a bonded
slider bar 90. In one example, the slider 92 is an elongated,
generally rectangular structure having a machined slot 96 extending
along its length, and having a plurality of partial slots 94
orthogonally oriented relative to the elongated slot. Each partial
slot 94 is adapted to receive the T-shaped magnetic elements
extending from the modified multi-core bar 80 of operation 26.
Machined slot 96 allows access to slot 58 for winding wire onto the
individual cores. The slider 92 will serve as the tape bearing
surface of the magnetic head. The slider 92 may be bonded onto the
modified azimuthal bar 80 by conventional techniques of epoxy or
glass bonding, and may be made from any suitable non magnetic
material. In one example, the slider 92 is formed from a
nonmagnetic BaTiO ceramic for thermal expansion and tape wear
characteristics.
[0073] At operation 30, FIG. 9, the bonded slider bar 90 is
machined to form a half-slider 100. In one example, portions of the
slider element, core bar, and core pieces are removed to form a
first or second half of the magnetic head. For example, the top
surface may be processed to expose the individual magnetic
structures 62 containing azimuth recording gaps 56. A portion of
the L-shaped reference block 72 (FIG. 6) may be removed along with
the remaining stock on the bottom of the bar to achieve, for
example, a series of five individual separated magnetic cores 62.
Each core contains a magnetic structure at an angle to the
orthogonal surfaces of the bar. FIG. 9a shows a top down view of
the half-slider 100.
[0074] At operation 32, FIG. 10, a support beam 112 is bonded to
the bottom of the half-slider 100 to form a half-head 110. In one
example, the support beam 112 is formed from a nonmagnetic BaTiO
ceramic for a materials match to ferrite.
[0075] At operation 34, operations 20-32 are repeated to form the
other half-head 110 for use in making the magnetic head 10. For
instance, operations 20-32 may be used to form the first half-head
110 with an azimuth angle of +6.degree. and the second half-head
110 with an azimuth angle of -6.degree..
[0076] At operation 36, FIGS. 11 and 12, the first and second
half-heads 110 are assembled to form the magnetic head 120. In one
example, the first and second halves are bonded to a spacer element
122. The spacer element 122 may be any suitable nonmagnetic
material to provide isolation between the two halves of the head
120. In one example, two thin sheets of copper 124 are bonded on
either side of the spacer element 122 to provide electrical noise
isolation between the two halves of the head. In one example, the
spacer material 122 is a nonmagnetic BaTiO ceramic, chosen for tape
wear characteristics. In one example, the first and second halves
110 are bonded together, where the angle of the magnetic structures
on one bar are different than those on the other. If desired,
contours to customize head to tape interfaces may now be machined
on the surface to produce a final device.
[0077] One example of a magnetic head formed by the operations of
FIG. 2 is shown in FIGS. 1 and 11-12, where FIG. 12 shows a top
view of the head face. In one example, the first magnetic gaps 56A
and second magnetic gaps 56B are at +6 and -6.degree. respectively.
This full head 10 or 120, may be utilized to verify a TBS pattern
on a magnetic tape, where each servo pattern and each angle of any
servo pattern may be independently verified. Independent
verification allows greater flexibility and accuracy of the servo
pattern on tape. In addition, the process described above,
resulting in gaps that are parallel but not collinear and hence
limiting the overall size of the servo head, allows for a standard
cylindrical contour to be machined onto the head face to provide a
good and acceptable head to tape interface.
[0078] If desired, the process of FIG. 2 can be utilized with any
combination of ferrite or thin film head element, which may include
inductive, AMR or GMR.
[0079] FIG. 13 illustrates another example of a magnetic head 140
having a plurality of magnetically and electrically independent
magnetic elements 144 which may be used, in one example, for
reading servo patterns on a magnetic tape. In FIG. 13, the magnetic
head includes a first set of magnetic elements and a second set of
magnetic elements, wherein the first set of magnetic gaps 162a and
the second set of magnetic gaps 162b are disposed to one another
along an angle defined by a center spacing element 148. A pair of
wedge-shaped outriggers 146 can be used to provide a generally
rectangular structure to the head, and the center spacer or center
spacing element 148 can be utilized to set the respective angles of
the magnetic read gaps 162a and 162b. In one example, each set of
magnetic read gaps 162a and 162b are parallel and collinear.
[0080] FIG. 14 illustrates an example of operations that may be
used to form a magnetic head, such as the head shown in FIG. 13.
The operations of FIG. 14 may be utilized to form a magnetic head
of, in one example, a non-standard size or a non-standard head to
tape interface.
[0081] At operation 50, FIG. 15, a core bar 160 is formed with one
or more magnetic gaps 162. The core bar 160 may have the same or
similar characteristics as the core bar 50 as described above in
FIG. 3 or as produced by operation 20 in FIG. 2. Any suitable gap
bar, such as a ferrite gap bar 160 or magnetic head row bar, such
as a section of a thin film head wafer that is diced into a row of
thin film heads forming a thin film head row bar, may be used as
the core bar.
[0082] At operation 52, FIGS. 16 and 17, a multi-core bar 170 is
formed by processing or machining the core bar 160 to have a
plurality of upwardly extending magnetic elements 172. In one
example, five upwardly extending magnetic elements 172 are
provided, wherein each of the upwardly extending portions includes
at least one magnetic gap 162. In one example, the upwardly
extending portions are rectangularly shaped with their long axis at
an azimuth angle of +6.degree. with respect to the long axis of the
multi-core bar 170. In one example, the multi-core bar edge face
174 is machined at an azimuth angle of +6.degree. with respect to
the long axis of the multi-core bar 170. This angled structure can
be seen most clearly in FIG. 17. The core bar 170 may have similar
tolerance characteristics as the core bar 80 of FIG. 6 made in
operation 26.
[0083] At operation 54, FIG. 18, a slider element 192 with a
plurality of slots 194 for mating with the extending magnetic
elements 172, is attached to the multi-core bar 170 of operation
52. The slider element 192 will serve as the tape bearing surface
and may be made from any suitable nonmagnetic and nonconductive
material. In one example, a BaTiO ceramic is used for its tape wear
characteristics and its match to the mechanical properties of
ferrite. The slider element 192 may be bonded to the core bar 170
by any suitable means, including epoxy or glass bonding, to produce
a bonded slider 190. In one example, the ends 196 of the slider
element 192 may be machined at an angle of +6.degree. to the long
axis of the slider element 192.
[0084] The bonded slider element 190 of operation 54 may have the
same or similar characteristics as described above with reference
to operation 28 of FIG. 2 or FIG. 8.
[0085] At operation 58, FIGS. 19 and 20, the structure of operation
54 is processed to form a first half-head magnetic head structure
200. In one example, the structure 200 is machined on the top
surface to expose the magnetic structures 172 and the magnetic
sensing gaps 162. The remaining stock on the bottom of the core bar
170 is also removed to achieve a series of five individual magnetic
structures or cores 172 separated by the remaining slider element
192. In one example, the long axis faces 202, 204 of the half-head
200 are machined orthogonal to the magnetic gaps 162, as can be
seen most clearly in FIG. 20.
[0086] At operation 60, the operations 50-58 are repeated to form a
second magnetic half-head.
[0087] At operation 62, FIGS. 21 and 13, first and second
half-heads 200 are assembled to form the magnetic head 140. FIG. 21
is an exploded view of FIG. 13 for illustrative purposes. In one
example, the first and second half-heads 200 formed by operations
50-60 may be attached to the wedge-shaped center spacer element
148, as shown in FIGS. 21 and 13. Further, a pair of wedge-shaped
elements or outriggers 146 can be attached to the outer portions of
the first and second magnetic half-heads to form the generally
rectangular final head 140 as shown in FIG. 13.
[0088] The angles of the magnetic structures 172 containing the
magnetic sensing gaps 162 may be set by the angles machined into
the center spacer 148, or may be free-space aligned. Complimentary
angles may be machined into the outriggers 146 so the final head
geometry is rectangular, which may provide greater tape dynamic
stability when compared with nonrectangular cross-section head
geometries. The center spacer 148 and the outriggers 146 may be
formed from any suitable nonmagnetic and electrically insulating
material. In one example, both 148 and 146 are made from a BaTiO
ceramic, chosen for its tape wear characteristics. The head 140,
shown in an exploded view in FIG. 21, may be bonded together by any
appropriate means, including either epoxy or glass bonding.
[0089] In FIG. 22, the bottom of the servo verify head 140 is shown
where magnetic u-cores 222 have been attached to the magnetic
structures 172. These u-cores 222 may be wound with wire to
complete the magnetic circuit. In one example, these u-core are
made from a magnetic NiZn ferrite. FIGS. 13 and 22 represent the
completed TBS verify head 220.
[0090] The operations of FIG. 14 may be used to reduce the
complexity in manufacture of a TBS verify head, as the contour
allows for the magnetic read gaps to be parallel and collinear. The
operations of FIG. 14 do not require the assembly of individual
azimuth cores while maintaining multidimensional tolerances. In
addition, the tolerances between and of the individual magnetic
structures can be more tightly constrained. The processes of FIGS.
2 and 14 and the device resulting thereof may also be used for the
production of a Servo Write head, or any relevant magnetic
recording read or write head used in Timing Based Servo.
[0091] As an additional example of this method, shown in FIGS.
23-24, is a head having a core bar that uses a thin film head row
bar 232a, 232b instead of a ferrite half-head bar 200. In one
example, two thin film row bars, 232a and 232b, are combined with a
center spacer 148 and two outriggers 146 to form the final head
230. The angles of the magnetic structures may be set by the angles
machined into the center spacer 148, or may be free-space aligned.
Complimentary angles may be machined into the outriggers 146 so the
final head geometry is rectangular, in one example.
[0092] FIG. 23 shows a top view of the magnetic head 230, while
FIG. 24 shows an exploded view of head 230 made according to one
example of the present invention. The final contour may be a flat
face. The center spacer 148 and the outriggers 146 may be made from
any appropriate nonmagnetic material. In one example, elements 146
and 148 are made from an AlTiC ceramic, for tape wear
characteristics and material match to the thin film row bar
substrate.
[0093] This process and device may also be used for the production
of a servo write head, or any relevant magnetic recording read or
write head used in Timing Based Servo. The thin film row bar may
contain any reasonable thin film head, which may include inductive,
AMR or GMR elements.
[0094] The processes of FIGS. 2 and 14 described previously are for
a full-band servo verification head for TBS servo patterns. The
azimuth angle of the magnetic structures is used to align the
magnetic sensor on the servo verify head to the azimuth angle of
the recorded servo pattern on the media. As an alternative to this
approach, the verify magnetic read gap may be restricted to a width
much less than the servo track width. As previously discussed, such
a structure may not suffer from azimuth alignment loss of the
sensed signal as the angle is effectively zero over such small
track widths. A verify head constructed as such, a so called
partial-band verify, would then be mechanically scanned along the
width of the pattern to be verified. Such a head, constructed of
independent read elements could be fabricated as a straight row bar
or gap bar, i.e. without the azimuth angle. In addition, such a
head would only require one magnetic sensing gap, rather than a
separate gap for each pattern angle. This head could be constructed
from any combination of ferrite or thin film head element, which
may include inductive, AMR or GMR.
[0095] FIG. 25 represents one embodiment of a servo verify head 250
using a scanning head technique wherein the magnetic servo verify
head 250 includes five independent magnetic elements 252 interlaced
between six ceramic slider elements 254. The servo verify head 250
may be formed by processing techniques similar in style to those of
FIGS. 2 and 14 previously described, with the exception that all
processing is performed in an orthogonal system. i.e. there are no
azimuth angles machined into the head.
[0096] In one example, as with the embodiments described in the
full-band servo verify heads, a ferrite gap bar which may be
similar to those of FIG. 3 or 15 is processed to form a multi-core
bar 260, FIGS. 26-28. In one embodiment, material is removed
leaving magnetic structures 252 with magnetic gaps 262. In one
embodiment, slots 264 and 266 are processed on the top of the
magnetic structures 252 producing the magnetic read gap 262 with a
width of approximately 10 .mu.m. The orthogonal processing can be
seen most clearly in FIG. 27, where the magnetic structures 252 are
orthogonal to the long axis of the ferrite gap bar. The slots 264
and 266, used to define the read sensor gap 262 width, can be seen
most clearly in FIG. 28. In one example, FIG. 26 is similar in
style to FIGS. 6 and 16.
[0097] As described in the processes of FIGS. 2 and 14, a mating
slider is attached to the multi-core bar 260. FIG. 29 shows one
embodiment of this process. A slider 292, comprising five
complimentary slots 294 is mated to the multi-core bar 260
producing the bonded slider 290. The slider 292 may be attached
using any appropriate technique such as glass or epoxy bonding, and
may be made from any suitable nonmagnetic material. In one
embodiment, the slider element 292 is made from BaTiO ceramic,
chosen for its tape wear characteristics and materials match to the
ferrite multi-core bar 260. The bonded slider 290 may be processed
similar to operations 30 and 58, FIGS. 9 and 19 respectively, to
produce the magnetic servo head 250 of FIG. 25.
[0098] FIG. 30 shows one embodiment of the partial-verify, or
scanning servo verify head 300. The magnetic head 300 has been
processed to create a cylindrical contour on the surface to obtain
a good or acceptable head to tape interface. In addition, u-cores
302 have been attached to the bottom of the head 300. Wire may be
wound on the u-cores 302 to complete the magnetic sensing
circuit.
[0099] As previously described, the partial-verify head 300 may be
scanned along the width of a TBS servo pattern. In one example, a
TBS pattern with a width of 190 .mu.m at an azimuth angle of
6.degree. can be verified by a read sensor with a width of 5-10
.mu.m at an azimuth angle of 0.degree., the head 300 being
continuously scanned back and forth along the 190 .mu.m track width
of the servo band. In this example, the partial-verify head may
sense any particular 10 .mu.m segment of the 190 .mu.m track width.
In one example, the head 300 possesses at least one magnetic
sensing element per servo band to be verified, such that all servo
patterns spanning the tape may be partial-verified in a single pass
of the media. This head could be constructed from any combination
of ferrite or thin film head element, including inductive, AMR or
GMR.
[0100] As previously mentioned, a factor of the scanning or
partial-verify method is the scan rate. The scan rate represents
the fraction of any servo band width sampled. One means of reducing
this factor is to reduce the scan rate. This may be accomplished by
a partial-verify head with more than one sensing gap per servo
band. In one example, a partial-verify head has five independent
sensing regions, each sensing region comprising two or more sensing
gaps.
[0101] In one example, two sensing gaps, each 10 .mu.m in width,
are spaced 100 .mu.m apart from center to center. In this example,
a servo pattern with a 190 .mu.m track width may be scanned in
approximately half the time as compared to the embodiment of FIG.
30, as each sensing gap would have to traverse only half the
pattern. The use of multiple sensing gaps for each servo band may
significantly reduce the scan rate of the partial-verify method,
correspondingly increasing the defect detection efficiency. This
head could be constructed from any combination of ferrite or thin
film head element, which may include inductive, AMR or GMR.
[0102] One example of a TBS system currently used in industry is
the so-called Linear Tape Open ("LTO") system. LTO utilizes a
series of five servo bands to span the tape in the cross-track
direction. The embodiments of a TBS verify magnetic head described
herein may allow all servo bands to be simultaneously and
independently verified. Such a quality is valuable in the
production environment as it combines both efficiency and
accuracy.
[0103] While the methods disclosed herein have been described and
shown with reference to particular operations performed in a
particular order, it will be understood that these operations may
be combined, sub-divided, or re-ordered to form equivalent methods
without departing from the teachings of the present invention.
Accordingly, unless specifically indicated herein, the order and
grouping of the operations is not a limitation of the present
invention.
[0104] Although the present invention has been described with
reference to preferred embodiments, persons skilled in the art will
recognize that changes may be made in form and detail without
departing from the spirit and scope of the invention.
* * * * *