Electricity: circuit makers and breakers – Electrostrictive or electrostatic
Reexamination Certificate
2002-05-20
2004-06-22
Barrera, Ramon M. (Department: 2832)
Electricity: circuit makers and breakers
Electrostrictive or electrostatic
Reexamination Certificate
active
06753487
ABSTRACT:
SPECIFICATION
1. Technical Field of Invention
The present invention relates to a static relay (an electrostatic relay) that opens and closes electrical contacts by driving a movable contact by electrostatic attraction, and a communication device using the relay. More particularly, the present invention relates to a small-size electrostatic microrelay manufactured by using micromachining technology.
2. Background of Invention
As an electrostatic microrelay, one described in the paper “Micro Machined Relay for High Frequency” (Y. Komura, et al.) has previously been known.
FIG. 1
is an exploded perspective view showing the structure of this electrostatic microrelay.
FIG. 2
is the cross-sectional view schematically showing the structure of the relay. The electrostatic microrelay substantially comprises a stationary substrate
1
and a movable substrate
2
. In the stationary substrate
1
, two signal lines
5
,
6
are formed on a substrate
3
. Ends of the signal lines
5
,
6
are opposed to each other with a small gap in between, and serve as fixed contacts
5
S,
6
S, respectively. Fixed electrodes
4
A,
4
B are disposed on both sides of the signal lines
5
,
6
. In the movable substrate
2
, movable electrodes
9
A,
9
B are formed, with resilient supporting portions
10
A,
10
B in between, on both sides of a movable contact
11
formed substantially in the center. Anchors
7
A,
7
B are provided on the movable electrodes
9
A,
9
B with resilient bending portions
8
A,
8
B in between, respectively. The movable substrate
2
is resiliently supported above the stationary substrate
1
by fixing the anchors
7
A,
7
B onto the stationary substrate
1
. The movable electrodes
9
A,
9
B are opposed to the fixed electrodes
4
A,
4
B, and the movable contact
11
is opposed so as to straddle the gap between the fixed contacts
5
S and
6
S.
In this electrostatic microrelay, by applying a voltage between the fixed electrodes
4
A,
4
B and the movable electrodes
9
A,
9
B, electrostatic attraction is caused, and by the movable substrate
2
being attracted toward the stationary substrate
1
by the electrostatic attraction, the movable contact
11
makes contact with the fixed contacts
5
S,
6
S, so that the fixed contacts
5
S,
6
S are closed to thereby electrically connect the two signal lines
5
,
6
. Then, by eliminating the electrostatic attraction by removing the voltage, the movable electrodes
9
A,
9
B are returned to the original shapes by resilience and are separated from the fixed electrodes
4
A,
4
B, so that the electrical connection between the signal lines
5
and
6
is broken.
An important property of relays is the insertion loss. The insertion loss property shows the degree of signal loss caused between the signal lines when the contacts are closed. Improvement of the insertion loss property means a reduction in the signal loss.
The insertion loss property is determined mainly by the electric resistance of the signal lines and the contact resistance between the contacts. The electric resistance of the signal lines is determined mainly by the width, length and material of the signal lines. The contact resistance between the contacts is determined by the contact force between the fixed contact and the movable contact and the material of the contacts.
To reduce the insertion loss, the above-described electrostatic microrelay operates in the following manner when the contacts are closed: When a voltage is applied between the fixed electrodes
4
A,
4
B and the movable electrodes
9
A,
9
B, electrostatic attraction is caused between the fixed electrodes
4
A,
4
B and the movable electrodes
9
A,
9
B. Then, the resilient bending portions
8
A,
8
B bend, so that the movable electrodes
9
A,
9
B approach the fixed electrodes
4
A,
4
B and the movable contact
11
is attached to the fixed contacts
5
S,
6
S. At this time, since the distance between the movable electrodes
9
A,
9
B and the fixed electrodes
4
A,
4
B is shorter than the initial one, the movable substrate
2
is attracted by a larger electrostatic attraction, so that the resilient supporting portions
10
A,
10
B bend. Consequently, the movable contact
11
makes contact with the fixed contacts
5
S,
6
S with an insulating layer in between. Since the resilient supporting portions
10
A,
10
B have a larger resilience than the resilient bending portions
8
A,
8
B, the movable contact
11
is pressed onto the fixed contacts
5
S,
6
S with a heavy load.
Since the electrostatic microrelay thus has a strong contact force between the contacts, the contact resistance between the contacts is reduced, so that the insertion loss is reduced. Moreover, an excellent insertion loss property is realized by using a low-resistance material such as gold (Au) for the signal lines and the fixed and movable contacts.
Moreover, a mounting configuration of the above-described electrostatic microrelay is such that, as shown in
FIG. 3
, the electrostatic microrelay is connected to the lead frames
12
by bonding wires
13
so that the fixed electrodes
4
A,
4
B, the movable electrodes
9
A,
9
B, the fixed contacts
5
S,
6
S, the movable contact
11
and the like are made electrically continuous with the lead frames
12
, then the electrostatic microrelay is sealed in a molded package.
However, in the electrostatic microrelay with the above-described structure and mounting configuration, since the mounting configuration uses the lead frames
12
and the bonding wires
13
, the mounting area of the electrostatic relay in the mounting configuration is large compared to the chip size and the signal line length is large, so that the insertion loss increases to degrade the high-frequency property.
In the above-described electrostatic microrelay, the insertion loss of the relay can further be reduced by suppressing the electric resistance of the signal lines by the shortening signal line length by reducing the size of the electrostatic microrelay.
However, when the size of the electrostatic microrelay is reducing, the areas of the movable and fixed electrodes are also reduced, so that the electrostatic attraction that acts between the electrodes decreases. This decreases the contact force between the contacts. Consequently, the contact resistance between the contacts increases to increase the insertion loss.
As described above, in the electrostatic microrelay of the conventional structure, since there is a tradeoff relationship between the electric resistance of the signal lines and the contact force between the contacts, size reduction of the electrostatic microrelay does not always improve the insertion loss of the electrostatic microrelay.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an electrostatic relay capable of reducing the insertion loss irrespective of the size of the relay and the contact resistance between the contacts. Another object is to provide an electrostatic relay capable of reducing the insertion loss without degrading the reliability of the contacts. Still another object is to provide a communications apparatus using the relay.
In an electrostatic relay of the present invention in which a movable electrode of a movable substrate resiliently supported so as to be opposed to a fixed electrode formed on a stationary substrate is driven based on electrostatic attraction caused between the fixed electrode and the movable electrode, and a plurality of fixed contacts provided on the stationary substrate and a movable contact provided on the movable substrate are brought into contact with each other and separated from each other; a sealing portion formed on a third substrate is provided that constitutes a portion that crosses a line connecting the fixed contacts and the movable contact outside a gap between the fixed contacts and the movable contact, and seals at least the fixed contacts and the movable contact by bonding them to the stationary substrate or to the movable substrate, and a through portion in which at least one of the signal lines connecting to the fix
Fujii Mitsuru
Sakata Minoru
Sato Shobu
Seki Tomonori
Barrera Ramon M.
Omron Corporation
Osha & May L.L.P.
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