Electricity: magnetically operated switches – magnets – and electr – Electromagnetically actuated switches – Polarity-responsive
Reexamination Certificate
2002-11-27
2004-12-07
Donovan, Lincoln (Department: 2832)
Electricity: magnetically operated switches, magnets, and electr
Electromagnetically actuated switches
Polarity-responsive
C200S181000, C361S056000
Reexamination Certificate
active
06828888
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a micro relay, and more particularly, to a micro relay that is activated by electrostatic attractive force and manufactured using semiconductor manufacturing techniques such as film forming, exposure, and etching.
2. Description of the Related Art
An ordinary relay is switched by current flowing in a winding provided therein. The current generates electromagnetic force that activates a contact point formed on a leaf spring. It is difficult to make the ordinary relay small and less power-consuming, however, due to such structure of the conventional relay. To solve this problem, a micro relay has been developed. The micro relay is manufactured using manufacturing processes of a semiconductor apparatus, such as film forming, exposure, and etching. The micro relay is activated by electrostatic attractive force, electromagnetic force, piezoelectric distortion, thermal expansion, and so forth. This micro relay is expected to break through the conventional limit in size and power consumption.
The micro relay is suitable for switching signal lines in which only weak current flows. One of the best applications of the micro relay is to switch high frequency signals. The micro relay is required to have a good isolation property. The isolation property indicates the amount of signals that leak between opening contacts. The smaller the amounts of signals that leak, the better isolation property the micro relay has.
An effective way to improve the isolation property is to reduce the areas of the opening contacts facing each other and to increase the distance between the opening contacts facing each other so as to reduce the electrostatic capacity connection between the opening contacts facing each other. In the case of the micro relay, the areas of the opening contacts facing each other are easily reduced. However, increasing the distance between the opening contacts facing each other is not easy since voltage that is practically applicable to the micro relay is limited to about 10 V, and the resulting activating force generated by the electrostatic attractive force is weak.
FIGS. 1 and 2
show a micro relay
10
that is disclosed in Japanese Laid-open Patent Application No. 2001-52587. The micro relay
10
is structured by laminating a fixed substrate
20
, a movable substrate
30
, and a cap member
40
. Signal wirings
11
,
12
and stationary contacts
13
,
14
are formed on the top face of the fixed substrate
20
. The fixed substrate
20
itself forms a stationary contact. The movable substrate
30
has a movable contact
31
on its bottom face and an upper contact unit
32
and a movable electrode
33
on its top face. The movable contact
31
and the movable electrode
33
are electrically connected to each other. The cap member
40
has a conductive layer
41
on the bottom face. When the micro relay
10
is mounted on a printed board, the conductive layer
41
is grounded.
When the micro relay
10
is activated by the applying of voltage, the electrostatic attractive force generated between the fixed substrate
20
and the movable electrode
33
bends the movable substrate
30
downward, and causes the movable contact
31
to contact the stationary contacts
13
,
14
. Accordingly, the signal wirings
11
and
12
are electrically connected by the movable contact
31
.
When the applying of voltage to micro relay
10
is discontinued, the movable substrate
30
restores itself, and the movable contact
31
separates from the stationary contacts
13
,
14
. Then, the upper contact unit
32
contacts the conductive layer
41
, and the movable contact
31
is grounded. Because the movable contact
31
is grounded, the electrostatic capacity between the movable contact
31
and the stationary contacts
13
,
14
is eliminated. Though the distance between the movable contact
31
and the stationary contacts
13
,
14
is short, the isolation property of the micro relay is good.
However, because the upper contact unit
32
contacts the conductive layer
41
, the upper contact unit
32
may stick on the conductive layer
41
. The electrostatic attractive force generated between the fixed substrate
20
and the movable electrode
33
by the voltage applied to the micro relay is not strong.
In situations where the upper contact unit
32
is stuck to the conductive layer
41
even in the least, the micro relay
10
is not activated even if the voltage is applied.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of the present invention to provide a novel and useful micro relay in which one or more of the problems described above are eliminated.
To achieve one of the above objects, a micro relay according to the present invention includes a movable contact, a stationary contact, and a ground contact opposed to said movable contact, wherein in an operating state, said movable contact touches said ground contact when said movable contact separates from said stationary contact, and in a non-operating state, said movable contact remains separated from said ground contact.
In the operating state, the movable contact touches the ground contact and is set at the ground voltage level when the movable contact separates from the stationary contact. Since no parasitic capacitance is formed between the stationary contact and the movable contact, the isolation property of the micro relay is improved.
In the non-operating state, the movable contact separates from the ground contact so that the movable contact does not stick to the ground contact. Accordingly, the micro relay operates at high reliability even at the beginning of the operation.
Other objects, features, and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.
REFERENCES:
patent: 5372515 (1994-12-01), Miller et al.
patent: 5872496 (1999-02-01), Asada et al.
patent: 6016092 (2000-01-01), Qiu et al.
patent: 6504447 (2003-01-01), Laney et al.
patent: 2002/0123270 (2002-09-01), Belopolsky
patent: 2003/0008538 (2003-01-01), Murnaghan et al.
patent: 2-100224 (1990-04-01), None
patent: 5-242788 (1993-09-01), None
patent: 9-17300 (1997-01-01), None
patent: 9-92116 (1997-04-01), None
patent: 11-260233 (1999-09-01), None
patent: 2001-52587 (2001-02-01), None
patent: WO 200167476 (2001-09-01), None
Iwata Hideki
Saso Hirofumi
Donovan Lincoln
Fujitsu Component Limited
Rojas Bernard
Staas & Halsey , LLP
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