Wave transmission lines and networks – Plural channel systems – Having branched circuits
Reexamination Certificate
2001-03-16
2002-11-19
Pascal, Robert (Department: 2817)
Wave transmission lines and networks
Plural channel systems
Having branched circuits
C333S262000, C200S181000
Reexamination Certificate
active
06483395
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a micro-machine mems switch, with electrical insulator and more particularly to a micro-machine switch used for opening and closing an electric contact.
2. Description of the Related Art
As one of conventional micro-machine switches, the micro-machine switch suggested in Japanese Unexamined Patent Publication No. 9-17300, which is based on the U.S. patent application Ser. No. 08/493,445 filed on Jun. 22, 1995 and assigned to Rockwell International Corporation, is illustrated in
FIGS. 1A and 1B
.
FIG. 1A
is a plan view of the same, and
FIG. 1B
is a cross-sectional view taken along the line
1
B—
1
B in FIG.
1
A.
An anchor
114
composed of thermosetting polyimide, a lower electrode
116
composed of gold, and a signal line
118
composed of gold are formed on a substrate
112
composed of GaAs.
A cantilever arm
120
supported at one end on the anchor
114
extends beyond the lower electrode
116
and to the signal line
118
, and faces both the lower electrode
116
and the signal line
118
with a spatial gap therebetween. The cantilever arm
120
is comprised of silicon dioxide films.
An upper electrode
124
composed of aluminum is formed on the cantilever arm
120
, extending from the anchor
114
to the lower electrode
116
.
A contact electrode
122
composed of gold is formed on a lower surface of the cantilever arm
120
in alignment with the signal line
118
.
The signal line
118
faces the contact electrode
122
with a gap therebetween. Accordingly, when no voltage is applied to the micro-machine switch, no current runs through the signal line
118
.
On application of a voltage of 30V across the upper electrode
124
and the lower electrode
116
, there is generated electrostatic force which pulls the upper electrode
124
towards the substrate
112
. Hence, the cantilever arm
120
is downwardly deformed, resulting in that the contact electrode
122
makes contact with the signal line
118
, and accordingly, a current runs through the signal line
118
.
Thus, it is possible to make a current run through the signal line
118
or stop a current from doing the same by applying a voltage across the upper electrode
124
and the lower electrode
116
or stopping application of the voltage.
However, the conventional micro-machine switch
110
illustrated in
FIGS. 1A and 1B
is accompanied with the following problems.
When the cantilever arm
120
is deformed towards the substrate
112
, the contact electrode
122
located at a distal end of the cantilever
120
first makes contact with the signal line
118
, and then, the upper electrode
124
is attracted towards the lower electrode
116
. In this situation, a force is applied to the cantilever arm
120
at a proximal end, and not at a distal end of the cantilever arm
120
.
As a result, the contact electrode
122
does not make parallel contact with the signal line
118
, but makes contact with the signal line
118
at a certain angle. That is, the contact electrode
122
makes contact with the signal line
118
only in a certain area. This causes non-uniformity in a contact resistance of the signal line
118
, and degrades an area at which the contact electrode
122
makes contact with the signal line
118
, in a lifetime test in which a load is applied to the signal line
118
.
That is, the first problem is remarkable deterioration in contact performance.
In the micro-machine switch
110
having a structure where a force is applied to the cantilever arm
120
at a proximal end thereof to thereby cause the contact electrode
122
to make contact with the signal line
118
, it is considered that the contact electrode
122
slides relative to the signal line
118
. The slide movement between the contact electrode
122
and the signal line
118
increases an adhesive force generated therebetween in dependence on materials of which the contact electrode
122
and the signal line
118
are composed and a contact force therebetween, resulting in problems of non-uniformity in a restoring voltage and troubles in operation.
In the micro-machine switch
110
, the contact electrode
122
and the signal line
118
are both composed of gold. Since gold has high electrical conductivity, it would be possible for a switch composed of gold to accomplish small insertion loss and high current-running capacity. However, since gold has a highest adhesion coefficient, gold would generate a high adhesive force.
An operational voltage at which the micro-machine switch
110
operates is dependent on a restoring force generated by the cantilever arm
120
and an electrostatic force generated between the upper electrode
124
and the lower electrode
116
.
On the other hand, a characteristic of a contact resistance between the signal line
118
and the upper electrode
122
is dependent predominantly of a contact force. One of factors for determining a contact force is a spring constant of the cantilever
120
after the contact electrode has made contact with the signal line
118
.
That is, stiffness of the cantilever arm
120
determines a characteristic of an operational voltage and a characteristic of a contact resistance. Hence, the micro-machine switch
110
has to be designed taking a balance between those characteristics into consideration, resulting in reduction in designability of the micro-machine switch
110
.
The conventional micro-switch
110
is singly fabricated on the single substrate
112
, and controls on/off of the signal line
118
. In other words, the conventional micro-machine switch
110
has only one signal-input section and only one signal-output section. Hence, if a signal was to be output into a predetermined signal line among a plurality of signal lines, it was necessary to fabricate a circuit including a plurality of the micro-machine switches
110
each formed on the substrate
112
.
However, such a circuit would increase a size of a system board including the circuit, and further increase a cost of fabricating the system board.
Japanese Unexamined Patent Publication No. 9-147720 has suggested a relay unit including a movable contact block having a movable contact at a center in an upper surface thereof and further having a movable piece deformable in a thickness-wise direction in accordance with an external signal, and a fixed contact block having a fixed contact facing the movable contact, the fixed contact being capable of making contact with and separating away from the movable contact.
Japanese Unexamined Patent Publication No. 9-269336 has suggested a micro G switch including a beam and a movable mass both fabricated by processing a silicon substrate. The movable mass is comprised of a movable contact supported by the beam, and a fixed contact formed on a glass substrate in facing relation to the movable contact. A center of gravity of the movable mass is located on a center line of the beam. The beam, the movable mass, the movable contact and the fixed contact are positioned in a hermetically sealed space formed by the silicon and glass substrates.
The above-mentioned problems remain unsolved even in the above-mentioned Publications.
SUMMARY OF THE INVENTION
In view of the above-mentioned problems in the conventional micro-machine switches, it is an object of the present invention to provide a micro-machine switch which is capable of stably operating and being fabricated in low costs.
In one aspect of the present invention, there is provided a micro-machine switch which causes a contact electrode to make contact with or separate away from a signal line formed on a substrate, to thereby turn on or off the signal line, including (a) first to N-th lower electrodes formed on the substrate, wherein N is an integer equal to or greater than 2, (b) first to N-th upper electrodes supported facing the first to N-th lower electrodes, respectively, and (c) a device for vertically raising and lowering the first to N-th upper electrodes between a first position where the contact electrode makes contact with the signal line when electro
Ide Tatsumi
Kasai Shigeru
Ota Yoshinori
Suzuki Kenichirou
Katten Muchin Zavis & Rosenman
Pascal Robert
Takaoka Dean
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