Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making electrical device
Reexamination Certificate
2000-03-06
2001-04-17
McPherson, John A. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making electrical device
C430S319000, C029S603070, C205S122000, C205S210000, C205S215000, C205S070000
Reexamination Certificate
active
06218080
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the formation of write heads for magnetic disk systems with particular reference to very narrow heads that comprise multiple layers deposited by electroplating.
BACKGROUND OF THE INVENTION
Referring to
FIG. 1
, we show, in schematic representation, a cross-sectional view of a write head for a magnetic disk system. The magnetic field needed to perform the write operation is generated by flat coil
16
made up of a number of turns (typically between about 8 and 8). Surrounding the flat coil are upper and lower pole pieces
12
and
11
respectively, made of a magnetic material such as nickel-iron. These pole pieces are joined at one end (on the left in this figure) and are separated by region
14
at the other end. The magnetic field that is generated by flat coil
16
ends up being concentrated in region
14
. It is sufficiently powerful that the fringing field that extends outwards away from
14
is capable of magnetizing the magnetic storage medium over whose surface
15
the head ‘flies’. The distance between region
14
and surface
15
is typically between about 10 and 50 nm. In practice, lower pole
11
is also used as a magnetic shield for the reading assembly that is located immediately below it. The latter can comprise many layers and is not shown in the figure. For this reason, pole
11
is usually referred to as the shared pole.
In
FIG. 2
we show a more detailed view of the parts that make up region
14
, the gap structure. Rather than being a simple gap between poles
11
and
12
, the gap structure is made up of two additional magnetic sub-components, sub-shared pole layer
21
and sub-top pole layer
22
, separated by gap layer
24
of a non-magnetic material. The area of these sub-poles is significantly less than that of the opposing flat portions of
11
and
12
that make up the gap region
14
in FIG.
1
. Thus, the introduction of sub-poles serves to concentrate the magnetic flux across gap
24
making for more intense fringing fields in its vicinity.
In U.S. Pat. No. 5,285,340 in February 1994, Ju et al. describe a pole tip structure, similar to that shown in
FIG. 2
, which can be formed by a single photolithographic process. Their basic approach was to use a photoresist mold inside which the layers
21
,
22
, and
24
could be grown by electroplating, following which the photoresist is removed in a conventional manner. While the process of Ju et al. represents a significant improvement to the art, there are associated problems. In particular, as the inside dimensions of the photoresist mold grow smaller, there is a growing tendency for the plated layers that are laid down inside it to acquire curved, non-planar surfaces. This, of course, reduces both the strength as well as the spatial resolution of the gap. The present invention provides an explanation for this problem as well as a solution for it.
A routine search of the prior art was conducted but no references that teach the solution disclosed in the present invention were encountered. Several references of interest were, however, found. For example, in U.S. Pat. No. 5,940,253, Mallary et al. show how photoresist may be used to prevent edge shorting in a laminated plated pole structure.
In U.S. Pat. No. 5,652,687, Chen et al. describe a modified sub-top pole in the shape of a U thus changing the aspect ratio of the gap. A method, based on using a very thin photoresist layer, for manufacturing this structure is disclosed in U.S. Pat. No. 5,802,700 (Chen et al.). In U.S. Pat. No. 5,812,350, Chen et al. modify the behavior of the gap by including a layer of nickel iron having a different composition from the standard Ni
81
Fe
19
.
SUMMARY OF THE INVENTION
It has been an object of the present invention to provide a process for manufacturing a write head for a magnetic disk system.
Another object of the invention has been that said process focus on the gap region of said write head with particular attention to the formation through electroplating of sub poles around the gap.
A still further object has been that said electroplated material be deposited in layers that are planar.
These objects have been achieved by growing the head structure within a photoresist mold. Prior to laying down the photoresist, a layer of copper is deposited on the substrate on which the head structure is to be grown (normally the shared pole). After the photoresist is patterned to form the mold, all exposed copper is selectively removed from the substrate a key feature being that the copper is over-etched so that some undercutting of the photoresist occurs. Then, when the layers making up the gap structure are electrodeposited inside the mold they grow away from the substrate as planar surfaces, in contrast to the curved surfaces that are obtained when processes of the prior art are used.
REFERENCES:
patent: 4339305 (1982-07-01), Jones
patent: 5126232 (1992-06-01), Gau
patent: 5285340 (1994-02-01), Ju et al.
patent: 5652687 (1997-07-01), Chen et al.
patent: 5722162 (1998-03-01), Chou et al.
patent: 5802700 (1998-09-01), Chen et al.
patent: 5812350 (1998-09-01), Chen et al.
patent: 5940253 (1999-08-01), Mallary et al.
Chang Jei-Wei
Ju Kochan
Wu Xuehua
Ackerman Stephen B.
Headway Technologies Inc.
McPherson John A.
Saile George O.
LandOfFree
Plated flat metal gap for very narrow recording heads does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Plated flat metal gap for very narrow recording heads, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Plated flat metal gap for very narrow recording heads will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2446443