Abrading – Abrading process – Glass or stone abrading
Reexamination Certificate
2001-01-12
2003-12-09
Hail, III, Joseph J. (Department: 3723)
Abrading
Abrading process
Glass or stone abrading
C451S053000, C451S054000, C451S063000, C451S397000
Reexamination Certificate
active
06659845
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a grinding method in which the grinding operation is performed on a plurality of workpieces having different thicknesses with one end surface in the thickness direction of each workpiece constituting a surface to be ground. More particularly, the present invention relates to an improvement in achieving uniform grinding with respect to a plurality of workpieces.
The present invention also relates to an electronic component, such as a variable capacitor, provided with an element ground by the grinding method described above.
2. Description of the Related Art
Electronic components, to which the present invention is related, and more specifically, variable capacitors, are disclosed, for example, in Japanese Unexamined Patent Application Publication Nos. 6-290994 and 10-321467. The variable capacitors disclosed in these patent application publications include substantially the same elements. The variable capacitor described in Japanese Unexamined Patent Application Publication No. 10-321467 is shown in
FIGS. 2
to
4
.
FIG. 2
is a perspective view showing a variable capacitor
1
,
FIG. 3
is a perspective view of the variable capacitor
1
shown in
FIG. 2
, viewed from the bottom side, and
FIG. 4
is a sectional view of the variable capacitor
1
shown in FIG.
2
.
The variable capacitor
1
includes a stator
2
, a rotor
3
, and a cover
4
.
The stator
2
composed of a ceramic dielectric member, and stator electrodes
5
and
6
are arranged side by side therein. Stator terminals
7
and
8
composed of conductive films are provided on the outer surfaces of the edges of the stator
2
to be electrically connected to the stator electrodes
5
and
6
, respectively.
Two stator electrodes
5
and
6
and two stator terminals
7
and
8
are configured as described above such that the stator
2
has a symmetrical structure, and the variable capacitor
1
is assembled using the stator
2
without taking the direction of the stator
2
into consideration. In the assembled state shown in
FIGS. 2
to
4
, the stator electrode
5
and the stator terminal
7
function and the stator electrode
6
and the stator terminal
8
do not function.
A protruding section
9
is provided on the lower surface of the stator
2
so as to longitudinally extend in the central portion thereof.
The rotor
3
is composed of a conductive metal, and is provided on an upper end surface
10
in the thickness direction of the stator
2
. A substantially semicircular rotor electrode
11
having a protruding step is provided on the lower surface of the rotor
3
. A protrusion
12
having the same height as that of the rotor electrode
11
is also provided on the lower surface of the rotor
3
, thus preventing the rotor
3
from tilting due to the presence of the rotor electrode
11
. The rotor
3
is also provided with a driver recess
13
to permit the insertion of a tool, such as a screwdriver, for rotating the rotor
3
.
The cover
4
is composed of a conductive metal, and is fixed to the stator
2
while accommodating the rotor
3
. The rotor
3
is supported by the cover
4
to be rotatable relative to the stator
2
.
An adjustment hole
14
to expose the driver recess
13
of the rotor
3
is provided in the cover
4
. A spring-action portion
15
, which is in contact with the rotor
3
and brings the rotor
3
into pressure contact with the stator
2
, is provided at the periphery of the adjustment hole
14
. The spring-action portion
15
extends downward toward the center at the periphery of the adjustment hole
14
, and is provided with a plurality of protrusions
16
.
Engaging sections
17
and
18
are provided on opposite sides of the cover
4
and extend downward. The engaging sections
17
and
18
are bent to be engaged with the lower surface of the stator
2
. Thus, the cover
4
is fastened to the stator
2
via the engaging sections
17
and
18
. The protruding section
9
provided on the lower surface of the stator
2
protrudes by substantially the same amount as that of the protrusions of the engaging sections
17
and
18
, and thus the variable capacitor
1
is securely mounted on an appropriate wiring substrate (not shown in the drawing).
A rotor terminal
19
is also provided on the cover
4
and extends downward.
In the variable capacitor
1
having the structure described above, the rotor electrode
11
is opposed to the stator electrode
5
with a portion of the ceramic dielectric member defining the stator
2
therebetween, and thus capacitance is provided. The rotor
3
is rotated to change the effective overlapping area between the rotor electrode
11
and the stator electrode
5
to vary the capacitance. The adjusted capacitance is produced between the stator terminal
7
, which is electrically connected to the stator electrode
5
, and the rotor terminal
19
provided on the cover
4
which is in contact with the rotor
3
on which the rotor electrode
11
is provided.
In the variable capacitor
1
, to increase the maximum capacitance and to obtain stable capacitance, the end surface
10
of the stator
2
is ground, and thus the thickness of the dielectric member between the end surface
10
and the stator electrodes
5
and
6
is decreased, and also a smoother surface is obtained on the end surface
10
in contact with the rotor electrode
11
.
When the end surface
10
of the stator
2
is ground, to efficiently perform the grinding operation, a plurality of stators
2
are usually ground simultaneously.
FIGS. 5A and 5B
show a conventional grinding method used for the grinding operation as described above. A workpiece
21
to be ground corresponds to the stator
2
and is schematically illustrated. ;The workpiece
21
shown in the drawing has a surface
22
to be ground on the lower surface in the thickness direction, and the surface
22
to be ground corresponds to the end surface
10
. In the workpiece
21
, an electrode
23
corresponding to the stator electrodes
5
and
6
extends parallel to the surface
22
to be ground. In the workpiece
21
, a protruding section
24
corresponding to the protruding section
9
is also provided.
As shown in
FIG. 5A
, a holder
26
having a planar holding surface
25
is prepared and a plurality of workpieces
21
is prepared. The workpieces
21
have different thicknesses due to the fabricating method therefor.
Next, the workpieces
21
are held by the holder
26
with a surface
27
opposed to the surface
22
to be ground of each workpiece being in contact with the holding surface
25
of the holder
26
. Additionally, although not shown in the drawing, to fix the individual workpieces
21
on the holding surface
25
, for example, adhesion is provided.
The surfaces
22
of the workpieces
21
are ground by a grinder
28
. In
FIG. 5A
, the position of the grinder
28
after grinding is performed is shown by the broken line. Consequently, the amount of grinding performed corresponding to the distance between the solid line, which shows the grinder
28
before grinding, and the broken line.
FIG. 5B
shows the ground workpieces
21
. As shown in the drawing, in the conventional grinding method, since the grinding operation is performed based on the opposite surfaces
27
, the difference in the overall thicknesses of workpieces
21
leads to variations in the distances between the surfaces
22
to be ground and the electrodes
23
in the finished individual workpieces. Therefore, variations in capacitance occur in the variable capacitor
1
.
To overcome the drawbacks described above, a grinding method as shown in
FIGS. 6A
to
6
C has also been disclosed. In
FIGS. 6A
to
6
C, the same reference numerals are used for the elements corresponding to the elements shown in
FIGS. 5A and 5B
, and the description thereof is omitted.
As shown in
FIG. 6A
, a first holder
30
having a planar holding surface
29
, and a plurality of workpieces
21
are provided.
Next, the workpieces
21
are held by the first holder
30
with a surface
22
to be g
Kishishita Hiroyuki
Kita Hidetoshi
Morita Keizo
Takeda Hiromichi
Grant Alvin J.
Hail III Joseph J.
Keating & Bennett LLP
Murata Manufacturing Co. Ltd.
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