JP2000113792A - Electrostatic micro relay - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small micro relay having good high frequency characteristic by providing fixed electrodes on both sides of a signal line with equal distance and sharing it with a high frequency GND electrode. SOLUTION: Fixed electrodes 12 and two signal lines 13, 14 are respectively provided on the upper surface of a glass board 10a, and the surfaces of the fixed electrodes 12 are coated with insulating films 16, and respectively connected with connection pads 12b1-12b4 through wirings 12a1-12a4. The fixed electrodes 12 are formed on both sides of the signal lines 13, 14 with equal distance, and are simultaneously used with a high frequency GND electrode. This structure allows a characteristic impedance to be determined from a ratio of a signal line width to a gap of the fixed electrodes (GND electrode) arranged on the same plane as these signal lines, and a dielectric constant of a fixed board. Thus, even when a high frequency characteristic is increased using an insulating board such for glass as the fixed board, its thickness and the signal line width can be restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic micro relay which opens and closes contacts by being driven by electrostatic attraction.

[0002]

2. Description of the Related Art FIG. 8 shows a conventional electrostatic micro relay. This electrostatic micro relay generally includes a fixed substrate 201 and a movable substrate 202.
The fixed substrate 201 has a fixed electrode 2
04 and two signal lines 205 are formed. The signal lines 205 are provided at predetermined intervals, and the adjacent ends thereof are fixed contacts 206. The movable substrate 202 is elastically cantilevered by an anchor 207 provided on the fixed substrate 201. The movable substrate 202 has the fixed electrode 20
4 and a movable electrode 208 at a position corresponding to the fixed contact 206.
And a movable contact 209 are formed.

In this electrostatic micro relay, the fixed electrode 2
The movable contact 209 is closed to both fixed contacts 206 by applying a voltage between the fixed contact 204 and the movable electrode 208 to generate an electrostatic attraction and attracting the movable substrate 202 toward the fixed substrate 201. The signal line 205 is electrically connected. Then, by removing the voltage and eliminating the electrostatic attractive force, the movable electrode 208 is returned to the original shape by the elastic force, separated from the fixed substrate 201, and
5 is electrically disconnected.

[0004] By the way, in the electrostatic micro relay,
By using the microstrip structure, the fixed substrate 201 is used as a high-frequency GND (ground) substrate. In this case, a semiconductor such as Si or GaAs is used for the fixed substrate 201, and an insulating film 203 (several μm
(Thickness), and furthermore, the signal line 205 is disposed on the surface thereof, thereby preventing the signal line width from increasing.

[0005]

However, in the electrostatic micro relay, the fixed substrate 201 is not a semiconductor substrate but a signal line 20 in order to improve high-frequency characteristics.
It is necessary to use an insulating substrate such as a glass substrate that can neglect the capacitive coupling between the five. In this case, the characteristic impedance is
As shown in the graph of FIG. 9, the signal line width W and the substrate thickness h
However, since the substrate usually has a thickness h of about 500 μm, when trying to realize a general characteristic impedance of 50Ω and 75Ω in the microstrip structure, the signal line width becomes about 1000 μm, There is a problem that the size is increased.

Accordingly, an object of the present invention is to provide an electrostatic micro relay having a small size and excellent high frequency characteristics.

[0007]

According to the present invention, as a means for solving the above-mentioned problem, a fixed electrode of a fixed substrate and a movable electrode of a movable substrate supported on the fixed substrate via an elastic supporting portion are provided. The movable substrate is driven based on the generated electrostatic attraction, and the movable contact formed on the movable substrate via an insulating film is brought into contact with and separated from fixed contacts provided on at least two signal lines formed on the fixed substrate. Thus, in the electrostatic micro relay in which the signal line is electrically opened and closed, the fixed electrode is provided at an equal distance on both sides of the signal line and is shared with the high-frequency GND electrode.

With this configuration, the characteristic impedance is
It can be determined by the ratio of the signal line width to the gap of the fixed electrode (GND electrode) arranged on the same plane as the signal line, and the dielectric constant of the fixed substrate. This allows
The characteristic impedance is no longer affected by the thickness of the fixed substrate, and the thickness and the width of the signal line can be suppressed even if the high-frequency characteristics are increased by using an insulating substrate such as glass for the fixed substrate. Further, since the frequency of the signal applied between the electrodes is largely different between the open / close signal and the drive signal, the signals do not interfere with each other.

It is preferable to remove at least a portion of the movable substrate opposed to the signal line, since the capacitive coupling between the signal line and the movable substrate can be suppressed and the movable electrode can be prevented from being attracted to the signal line.

It is preferable that the fixed electrode is electrically connected between the fixed contacts of the fixed substrate, since capacitive coupling between the signal line and the movable substrate can be further suppressed.

It is preferable that the fixed substrate is made of glass while the movable substrate is made of single-crystal silicon, since all the substrates can be processed in a semiconductor process.

When the ratio of the width of the signal line to the distance between the signal line and the fixed electrode is 0.04 to 2.00, a structure having a predetermined characteristic impedance can be obtained.

It is preferable that a second elastic support is formed on the movable substrate, and a movable contact is formed on the elastic support via an insulating film.

According to this configuration, when a voltage is applied between the fixed electrode and the movable electrode facing each other, the first elastic support portion is bent by the electrostatic attraction, the movable electrode approaches the fixed electrode, and the movable contact contacts the fixed contact. Contact. At this time, since the distance between the movable electrode and the fixed electrode is smaller than the initial state, the distance between the movable electrode and the fixed electrode is smaller than that of the initial state.
The movable electrode is attracted to the fixed electrode. Since the second elastic support portion has a higher elastic force than the first elastic support portion, the movable contact is pressed against the fixed contact with a large load.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an electrostatic micro relay according to the present embodiment. This electrostatic micro relay is mounted on the fixed substrate 10.
Is a configuration in which the movable substrate 20 is integrated with the upper surface of the substrate.

The fixed substrate 10 is provided with a fixed electrode 12 and two signal lines 13 and 14 on the upper surface of a glass substrate 10a.

The surface of the fixed electrode 12 is covered with an insulating film 16 and wirings 12a1, 12a2, 12a3, 12a4
Through the connection pads 12b1, 12b2, 12b3, 1
2b4.

The signal lines 13 and 14 are arranged on the same straight line. One ends of the signal lines 13 and 14 are fixed contacts 13a and 14a provided at predetermined intervals. On the other hand, the other end of each of the signal lines 13 and 14 is connected to a connection pad 13b,
14b.

The fixed electrode 12 is formed on both sides of the signal lines 13 and 14 at the same distance and has a high frequency GN
A coplanar structure is formed by being also used as the D electrode. The fixed electrodes 12 located on both sides of the signal lines 13 and 14 are connected to each other between the fixed contacts 13a and 14a. As a result, the lines of electric force that generate the switching signal are terminated at the high-frequency GND electrode between the fixed contacts 13a and 14a, so that the isolation characteristics are improved.
Here, the isolation characteristics indicate how much signal leakage exists between signal lines when the contacts are opened, and improving the isolation characteristics means that signal leakage is reduced. I do. The fixed electrode 12 is formed at a position lower than the signal lines 13 and 14.

In the fixed substrate 10 having the above-described structure, as shown in FIG. 3, the characteristic impedance has the signal line width W and the fixed electrodes 12 (G) arranged on the same plane as the signal lines 13 and 14.
It is determined by the ratio (W / S) to the gap S of the ND electrode) and the dielectric constant εr of the fixed substrate 10, and is not affected by the thickness of the fixed substrate 10. Further, the fixed electrode 10 is GN
Since it is shared with the D electrode, its occupied area can be reduced. Therefore, the fixed substrate 10 can be formed compact. Note that the frequency of the signal (opening / closing signal and drive signal) applied to the electrodes is far apart (in the case of a high-frequency relay, the opening / closing signal is 100 MHz).
Even if the fixed electrode 10 is shared with a GND electrode, interference between signals does not cause a problem. Here, the open / close signal is the signal line 13, 1
4 means a signal transmitted, and the driving signal is a fixed electrode 1
2 and a signal generated between the movable electrode 23.

The movable substrate 20 elastically supports a substantially rectangular plate-like silicon substrate with anchors 21a and 21b via a first elastic support portion 22 to a movable electrode 23, and a second elastic support portion at the center thereof. In this configuration, the movable contact portion 25 is elastically supported via 24.

The anchors 21a and 21b are fixed to the fixed substrate 1.
0, and one anchor 21
b is electrically connected to a connection pad 15b via a wiring 15a provided on the upper surface of the fixed substrate 10.

The first elastic support portion 22 includes a movable substrate 20
Are formed by slits 22a provided along both side edges, and the anchors 21a and 21b are integrated with the lower surface of the end.

The movable electrode 23 faces the fixed electrode 12 and is attracted to the fixed electrode 12 by an electrostatic attraction generated by applying a voltage between the electrodes 12 and 23. The movable electrode 23 has at least a portion facing the signal lines 13 and 14 removed. Therefore, since there is no capacitive coupling between the signal lines 13 and 14 via the movable electrode 23, the isolation characteristics are improved.

The second elastic support portion 24 and the movable contact portion 2
5 is formed by a notch 26 provided from the center of both ends of the movable substrate 20 toward the center. The second elastic support portion 24 is a narrow beam that connects the movable electrode 23 and the movable contact portion 25, and is configured to obtain a larger elastic force than the first elastic support portion 22 when the contact is closed. Have been. The movable contact portion 25 has a movable contact 28 provided on the lower surface of a flat portion 25 a supported by the second elastic support portion 24 via an insulating film 27. The movable contact 28 is connected to each of the fixed contacts 13.
The signal lines 13 and 14 are electrically connected to each other by closing both the fixed contacts 13a and 14a opposite to the fixed contacts 13a and 14a.

Next, a method of manufacturing the electrostatic micro relay having the above configuration will be described with reference to FIGS.

First, as shown in FIG. 4B, a fixed electrode 12, fixed contacts 13a and 14a, signal lines 13 and 14, a glass substrate 10a such as Pyrex shown in FIG.
Wirings 12a1, 12a2, 12a3, 12a4, 15
a and connection pads 13b, 14b, 12b1, 12
b2, 12b3, 12b4, 15b are formed respectively (wirings 12a1, 12a2, 12a3, 12a4, 15a
a, connection pads 12b1, 12b2, 12b3, 12b
4, 15b are not shown. ). Then, as shown in FIG. 4C, the surface of the fixed electrode 12 is covered with an insulating film 16 to complete the fixed substrate 10.

On the other hand, as shown in FIG.
01, on the lower surface (Si layer 103) of the SOI wafer 100 including the SiO ₂ layer (oxide film) 102 and the Si layer 103,
In order to form a contact gap, for example, wet etching is performed by TMAH using a silicon oxide film as a mask to form anchors 21a and 21b projecting downward as shown in FIG. 5B. Then, as shown in FIG. 5C, a movable contact 28 is formed via the insulating film 27 at the center of the portion removed by the wet etching.

Then, as shown in FIG. 6A, the SOI wafer 10 is placed on a glass substrate 10a of the fixed substrate 10.
The zero anchors 21a and 21b are joined and integrated by anodic bonding. Then, the upper surface TMAH, KO
The oxide film 102 is etched down to a thinner thickness with an alkaline etchant such as H. Further, the Si film 1 serving as the movable electrode 23 by removing the oxide film 102 with a fluorine-based etchant
03 is exposed. Then, die cutting etching is performed by dry etching using RIE or the like, and a slit 22a and a notch 26 are provided to form the elastic support portion 22, the second elastic support portion 24, and the movable contact portion 25. At the same time, the electrostatic micro relay is completed.

Next, the operation of the electrostatic micro relay having the above configuration will be described with reference to FIG.

In the initial state where no voltage is applied between the fixed electrode 12 and the movable electrode 23, as shown in FIG. 7A, the fixed substrate 10 and the movable 28 is separated from the fixed contacts 13a and 14a.

When a voltage is applied between the movable electrode 23 and the fixed electrode 12, an electrostatic attraction is generated between the electrodes 12 and 23. As a result, as shown in FIG. 7B, the movable substrate 20 approaches the fixed substrate 10 against the elastic force of the first elastic support portion 22, and the movable contact 28 moves to the fixed contacts 13a, 13a.
4a.

As shown in FIG. 7 (c), even after the movable contact 28 contacts the fixed contacts 13a and 14a, the movable substrate 20 continues to move until the movable electrode 23 contacts the fixed electrode 12. For this reason, the movable contact 28 is fixed contact 13a,
The contact pressure is increased by applying an elastic force corresponding to the amount of deflection of the second elastic support portion 24 to the first elastic support portion 24, so that no one-side contact occurs. Therefore, when the contacts are closed, desired contact reliability can be obtained.

At this time, the first and second elastic support portions 22 and 2
4 is a force for pulling the movable electrode 23 upward, and the insulating film 1
6, the electrostatic attraction between the movable electrode 23 and the fixed electrode 12 and the drag from the surface of the insulating film 16 are represented by F _s1 , F _s2 , F
_e, there is the following relationship when the F _n, first, spring constant of the second elastic support portions 22 and 24, the movable electrode 23 fixed electrode 12
By designing the initial gap, the thickness of the contact, etc.
It is possible to make F _{n and} F _s1 small and to suppress a decrease in F _{s2 ,} that is, a decrease in the contact load (from the ideal model).

[0036]

(Equation 1)

When the applied voltage is removed, the movable substrate 20 is separated from the fixed substrate 10 by the elastic force of both the first elastic support 22 and the second elastic support 24. For this reason, this separating operation is reliably performed. Thereafter, the movable substrate 20 continues to move upward by the elastic force of only the first elastic support portion 22, the movable contact 28 is separated from the fixed contacts 13a and 14a, and returns to the initial state.

[0038]

As is clear from the above description, according to the electrostatic microrelay of the present invention, the fixed electrodes are provided at equal distances on both sides of the signal line and are shared with the high-frequency GND electrode. By using an insulating material for the fixed substrate, good high-frequency characteristics can be obtained, and the fixed substrate can be formed compactly.

Further, since at least a portion of the movable substrate facing the signal line is removed, capacitive coupling between the signal lines via the movable substrate can be suppressed, and the isolation characteristics can be improved. In addition, since the movable substrate can be prevented from approaching the fixed substrate due to the electrostatic attraction generated by the voltage applied to the signal line, the secondary withstand voltage can be improved.

Further, since the fixed electrode is electrically connected between the fixed contacts of the fixed substrate, the isolation characteristics can be further improved.

Further, while the fixed substrate is made of glass,
Since the movable substrate is made of single-crystal silicon, all can be processed in the semiconductor process, and variations in dimensional accuracy can be suppressed. In addition, single crystal silicon has fatigue resistance,
Since the creep resistance is high, the life characteristics can be improved. Moreover, since the fixed substrate is manufactured as a single glass substrate, the movable substrate made of a single-crystal silicon substrate can be integrated by anodic bonding, and the assembling work can be simplified. In addition, since the capacitance between the fixed electrode, the fixed contact, the wiring, and the connection pad on the fixed substrate can be reduced, the high-frequency characteristics can be improved.

Further, since the ratio of the width of the signal line to the distance between the signal line and the fixed electrode is set to 0.04 to 2.00, the characteristic impedance of 50Ω and 75Ω generally used is changed to other than the fixed electrode. Can be realized without forming the GND electrode.

Further, since the second elastic support portion is formed on the movable substrate and the movable contact is formed on the elastic support portion via the insulating film, it is possible to suppress a decrease in the contact load and obtain good contact reliability. Can be.

[Brief description of the drawings]

FIG. 1 is a perspective view of an electrostatic micro relay according to an embodiment.

FIG. 2 is a plan view of FIG.

FIG. 3 is a graph showing a characteristic impedance of the electrostatic micro relay of FIG. 1;

FIG. 4 is a cross-sectional view showing a processing step of the fixed substrate of FIG.

FIG. 5 is a cross-sectional view showing a processing step on the movable substrate side of FIG. 1;

FIG. 6 is a sectional view showing a processing step of the electrostatic micro relay of FIG. 1;

FIG. 7 is a schematic diagram showing an operation state of the electrostatic micro relay of FIG. 1;

FIG. 8 is a perspective view of an electrostatic micro relay according to a conventional example.

FIG. 9 is a graph showing characteristic impedance of the electrostatic micro relay of FIG. 8;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Fixed substrate 12 ... Fixed electrode 12a1, 12a2, 12a3, 12a4 ... Wiring 12b1, 12b2, 12b3, 12b4 ... Connection pad 13, 14 ... Signal line 13a, 14a ... Fixed contact 13b, 14b ... Connection pad 15a ... Wiring 15b ... Connection pad 20: movable substrate 21a, 21b: anchor 22: first elastic support 23: movable electrode 24: second elastic support 28: movable contact

Claims (6)

[Claims] A movable substrate is formed on a fixed substrate by driving the movable substrate based on an electrostatic attraction generated between a fixed electrode of the fixed substrate and a movable electrode of the movable substrate supported on the fixed substrate via an elastic supporting portion. An electrostatic micro relay that electrically opens and closes the signal line by moving a movable contact formed on the movable substrate via an insulating film to and away from a fixed contact provided on each of the at least two signal lines. 3. The electrostatic microrelay according to claim 1, wherein the fixed electrodes are provided at equal distances on both sides of the signal line and are shared with a high-frequency GND electrode. 2. The electrostatic micro relay according to claim 1, wherein at least a portion of the movable substrate facing the signal line is removed. 3. The electrostatic micro-relay according to claim 1, wherein the fixed electrode is electrically connected between fixed contacts of the fixed substrate. 4. The fixed substrate is made of glass,
The electrostatic micro relay according to any one of claims 1 to 3, wherein the movable substrate is made of single crystal silicon. 5. The electrostatic micro relay according to claim 4, wherein a ratio of a width of the signal line to a distance between the signal line and the fixed electrode is set to 0.04 to 2.00. 6. The movable substrate according to claim 1, wherein a second elastic support portion is formed on the movable substrate, and a movable contact is formed on the elastic support portion via an insulating film. An electrostatic microrelay as described.