Metal working – Method of mechanical manufacture – Electrical device making
Utility Patent
1997-05-01
2001-01-02
Young, Lee (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S603150, C029S603180, C427S131000, C216S022000
Utility Patent
active
06167611
ABSTRACT:
DESCRIPTION
1. Technical Field
The present invention relates to a vertical magnetic head and to its production process.
A preferred application is in general public video recording, but it can also be used in other fields, such as data backups and computer memories.
2. Prior Art
A magnetic recording support for video equipment, data backups or computer memories consists of numerous tracks on which are entered informations in the form of magnetic fields.
In order to increase the information density, not only is there an increase in the number of informations per unit length, but also in the number of tracks. For this purpose, there is a decrease in the width of the tracks and simultaneously the gap separating them until they are rendered contiguous.
Nowadays, in order to meet these requirements, there are mainly two types of head on the market, namely so-called metal-in-gap heads and so-called sandwich heads.
FIG. 1
shows an example of a head of the second type. This head has a substrate
2
supporting a magnetic circuit
4
constituted by a magnetic layer deposited on the upper face of the substrate, said circuit having at the front two pole pieces
5
and
7
separated by a head gap
6
formed by an amagnetic spacer. Above the magnetic circuit, said head also has an amagnetic superstrate
2
. The head also has an opening
8
made through the magnetic layer, the substrate and the superstrate, as well as a conductor winding
9
using the opening
8
.
The head shown in
FIG. 1
is intended to cooperate with a recording support
20
oriented perpendicular to the substrate or, what amounts to the same thing, parallel to its edge.
Such heads can be called “vertical” in the sense that the active surface is perpendicular to the surface of the initial substrate.
The width of the head gap designated l is counted perpendicular to the substrate or, what amounts to the same thing, parallel to the recording support. This width l essentially corresponds to the respective width of the support tracks. Its length designated L is counted in the direction of the relative displacement of the head and the recording support
20
. With regards to the height of the head gap h, it is counted parallel to the face of the substrate supporting the magnetic circuit.
Such heads cannot be confused with so-called “horizontal” heads, where the head gap is level on a face parallel to the substrate and where the recording support is moved parallel to said substrate face. A horizontal head is e.g. described in FR-A-2 604 021.
One of the essential differences between vertical heads of the sandwich type and horizontal heads (other than the obvious differences in their structure and their production process) is due to the fact that in the latter case, the width of the gap (corresponding to the track width) is defined by lithography, whereas the dimension affected during wear to the head is defined by the thickness of the deposited magnetic material. In vertical heads of the sandwich type, like that of
FIG. 1
, it is the width of the gap l which is defined by the thickness of the deposited magnetic material, whereas the wear affects the height h, which is adjusted by lithography.
The practical implementation of vertical sandwich heads like that of
FIG. 1
involves a large number of micromechanical and high temperature welding operations and construction is usually unitary, i.e. non-collective.
Certain production processes are described in the work entitled “Recent magnetics for electronics”, JARECT, vol. 10, chapter 11, pp 121-133, 1983, published by Y. SAKURAI, North-Holland, as well as in the work entitled “The complete handbook of magnetic recording”, F. JORGENSEN, chapter 9, pp 196-216, 1988, published by TAS BOOKS Inc.
However, international application WO 92/02015 also proposes a process for the production of magnetic heads of the sandwich type making it possible to obtain a very well controlled vertical head gap, whose width is equal to that of the track to be read or written, the alignment of the pole pieces being easily obtained. These magnetic heads accept the inevitable wear linked with the friction of the magnetic support on the head.
The enclosed FIGS.
2
a
to
2
d
diagrammatically illustrate the known process. One starts with a substrate
16
and by different etching operations, some of which are anisotropic, as well as a thermal oxidation process, a vertical wall
24
is formed on the substrate (FIG.
2
a
). When the substrate is made from silicon, said wall
24
is of silicon oxide, or in other words silica.
A magnetic layer
26
is then deposited on either side of the wall
24
and is then planarized (FIG.
2
b
). The wall
24
will serve as an amagnetic spacer and its width perpendicular to the substrate is designated l. The magnetic: circuit
28
is then defined in its overall form by photolithography (FIG.
2
c
).
Everything is then covered by a not shown superstrate and an opening
34
is made therein (FIG.
2
d
). Two notches
36
are machined and a conductor wire
38
is passed into the opening
34
and into the notches
36
and wound around the magnetic circuit
28
. The friction circuit
41
is then machined. This surface is perpendicular to the upper face of the substrate. Thus, the spacer
24
is level with the edge of the machined substrate and parallel to the not shown recording support.
Although satisfactory in certain respects, this process has a problem due to the difficulty in producing a satisfactory magnetic material. Thus, beyond the usual magnetic properties required in producing a magnetic circuit, it is necessary to have a material resisting wear and which is sufficiently resistive to avoid problems associated with eddy currents when the head operates at high frequency. A magnetic material satisfying all these conditions can only be obtained by vapour deposition, e.g. cathodic sputtering. However, the thus obtained layers, which are necessarily thin, have problems linked with the expansion coefficient difference between the substrate and the magnetic material and which gives rise to separation between the layers.
The present invention solves this problem by using two magnetic materials instead of one, which are of different types, in the area of the head gap. Before giving information on the conditions under which these two materials are used, it is pointed out that magnetic heads having two materials are already known, but in the horizontal variant referred to hereinbefore and not in the vertical variant to which the present invention relates.
Such horizontal heads having two magnetic materials are desribed in FR-A-2 658 646 (or its corresponding U.S. Pat. No. 5,224,260). The enclosed
FIGS. 3 and 4
illustrate two variants of these heads.
Firstly,
FIG. 3
shows in section a horizontal head comprising a lower magnetic part
50
, two magnetic pillars
51
,
52
, a conductor winding
54
embedded in an insulator
56
, two magnetic concentrators
55
,
56
and two upper pole pieces respectively constituted by a first magnetic material
57
,
58
electrolytically deposited on a conductive underlayer
59
and a second magnetic circuit
61
,
62
deposited by cathodic sputtering. These two pole pieces are separated by an amagnetic spacer
64
. The assembly is embedded in an insulating layer
66
. The recording support
70
is parallel to the upper surface of the head, as for all horizontal heads.
FIG. 4
shows another variant, where similar components are encountered and for this reason carry the same references, but where the two magnetic materials are arranged differently. The first material
57
,
58
which has been deposited electrolytically is placed on either side of the spacer
64
, whereas the second material
61
,
62
is outside the first.
FIG. 4
also shows the friction surface
67
on which slides the recording support
70
.
In the variant of
FIG. 3
, the magnetic material
61
,
62
to be in contact with the recording support
70
has a thickness close to 1 &mgr;m and good magnetic and mechanical characteristics. This variant is suitable for recording systems wh
Gaud Pierre
Louis Christine
Sibuet Henri
Vallet Nathalie
Commissariat A l'Energie Atomique
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Tugbang A. Dexter
Young Lee
LandOfFree
Process for producing a vertical magnetic head does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for producing a vertical magnetic head, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for producing a vertical magnetic head will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2454218