DE19823690C1 - Micromechanical electrostatic relay - Google Patents

Abstract

The micromechanical electrostatic relay has a base substrate with a base electrode and at least two base contact pieces, and also an armature substrate with a rib-shaped armature which is etched free and is pivotable in the region of a central pivot axis (20) via flexible bands (25, 26). The armature (21) forms on both sides of the pivot axis (20) in each case a flexible armature wing (21a, 21b) that is curved away from the base substrate in the idle state, each of which forms with the base substrate a working air gap that widens outward in the wedge shape in the idle state. When a voltage is applied between an armature electrode and a base electrode (11, 12) arranged under the respective armature wing (21a, 21b), the armature is pivoted about the pivot axis, while at the same time the relevant armature wing (21a, 21b) rolls on the base electrode and an associated one Contact closes.

Description

The invention relates to a micromechanical electrostatic relay

• - a flat base substrate, in its surface area two flat base electrodes in the longitudinal direction to each other are staggered,
• - An armature substrate with a rocker-shaped armature, which in the Area of a central swivel axis on two opposite sides over flexible bands in the anchor substrate is suspended and egg on both sides of the pivot axis NEN leaf-shaped anchor wing, each anchor wing each carries an anchor electrode section, which is opposite one of the two base electrodes stands, and
• - Wherein each anchor wing continues to move at least one Chen contact, who is in contact with at least one the base substrate arranged fixed contact cooperates.

Such a micromechanically manufactured relay with Um Switching function is basically already in EP 0 520 407 A1 shown. There is the rocker anchor suspended in the middle as rigid plate executed. He therefore has a total of a right relatively large distance between the base electrodes and the an kerelektrode, the respective armature wing also in the respective response switch position only under one spit zen angle to the counter electrode and this essentially Lichen can only touch point or line. Dar from it follows that the electrostatic drive a rela tiv requires high tension and that because of the im on only incompletely closed working air gap tes too high contact forces can not be achieved nen.  

From DE 42 05 029 C1, DE 44 37 261 C1 and DE 44 37 259 C1 However, micromechanical relays are also known to which a one-sided clamped anchor at rest forms a wedge-shaped air gap with a base electrode, so that the anchor there speaks closely to the base electrode.

The aim of the present invention is to provide a micromechanical electrostatic switching relay with the aforementioned To create structure in which with relatively little to speaking voltage high contact forces can be achieved, ver different operating modes of a switch, such as neutral, bi stable and monostable switching characteristics, on simple Are feasible.

According to the invention, this goal is achieved with the aforementioned Structure achieved in that the two anchor wings in themselves flexible and each at rest from the base Substrate are curved away, each with a wedge form the air gap with its narrowest point in is close to the swivel axis and which is towards the free end of the anchor wing continuously expanded.

The micromechanical relay according to the invention is thus the anchor can not only be swiveled over the flexible straps hung, but it is also flexible in itself and in its basic form with both wings from the respective basi selectrode curved away, so that everyone is already at rest Anchor wing with the base electrode a wedge-shaped Air gap forms. To form this wedge-shaped air gap is the anchor in the area of the swivel axis with little Distance to the plane of the base electrodes arranged so that when Applying a voltage at the beginning of the response phase an area of the armature has a small electrode gap points; this enables a quick response of the person kers and a rolling process that is from the narrowest point of the wedge-shaped air gap to the free end of the armature  continues (according to the walking wedge principle) and thereby one builds up relatively large contact force. As far as in the neren tip of the wedge-shaped air gap, ie in the area the swivel axis of the armature, due to production reasons value distance between the anchor and the plane of the base electrodes exists, this can be approximately when responding to Zero be reduced if the flexible bands of the An not only a torsion, but also a torsion Deflection perpendicular to the surface of the base substrate possible.

Due to the curvature of the anchor and the flexible hanging supply results when the relay responds both Swivel movement around the swivel axis as well as a rolling motion supply of the switching anchor wing, which from its pre curved shape changes into an elongated shape, so that it to the Conclusion of the anchor movement flat on the straight electrode of the Base substrate rests. Removed during this tightening motion because of the pivoting movement of the tensionless Anchor wing also away from the base substrate. This has the further advantage that after tightening an anchor wing the opposite anchor wing is not created by applying the normal response voltage can also be tightened, so that a safety function is provided in this way. Ge nerell is the predetermined curvature of the anchor in the area of Swivel axis strongest, and it becomes the respective free Lower end of the anchor wing. In extreme cases, the Anchor approximately a sharp one in the area of the swivel axis Kink, so that it has an approximately V-shaped profile in the longitudinal cut has.

In a further embodiment, the contact areas of the armature with the movable contacts preferably designed so that them via connecting webs ela with reduced cross-section are connected to the table and to build up the contact force ela are movable from the anchor plane.  

The movable contacts on the anchor can be provided with a feed line as individual contacts or as a common center contact, a common supply line have; the power supplies are in the usual way in the form of conductor tracks over one or both flexible banks the led. In addition, it is also possible to move the mov Chen contacts on the two anchor wings as bridge contacts to execute. In this case you do not need your own allowance tion, but they each bridge two fixed cones clock on the base substrate.

In an advantageous further development, it can also be performed hen that additional electret layers on the Base electrodes or a mono on the anchor electrodes stable or bistable switching characteristic is generated.

The invention is based on exemplary embodiments hand of the drawing explained in more detail. It shows

Fig. 1 is a perspective, schematic diagram showing the arrangement of an armature substrate with an anchor according to the invention stalteten ge over a base substrate,

Fig. 2 is a similar to FIG. 1 constructed relay in a sectional view,

Fig. 3 is a plan view of the relay of Fig. 2,

Fig. 4 shows a comparison with FIG. 3 somewhat modified exporting approximate shape of a relay in plan view,

Fig. 5 is a side view of an anchor according to FIG. 2 in the actuated state,

Fig. 6 shows an embodiment of FIG. 2 with additional electret,

Fig. 7a to 7d, the schematic representation of a Schaltab run of the relay in four phases and

Fig. 8 is a timing chart for the switching sequence shown in Fig. 7a to 7d.

The relay shown schematically views in Figs. 1 to 3 in different At comprises a base substrate 1, preferably as consisting of silicon, on which an armature substrate 2, also preferably made of silicon, angeord net and is fixed, for example by anodic bonding. The base substrate has in its surface area two flat base electrodes 11 and 12 which are offset with respect to one another in the longitudinal direction and are produced in the usual way as metallic layers. You have Steuerlei lines 11 a and 12 a, which are indicated schematically in Fig. 1 as conductor tracks. In addition, two fixed contacts 13 and 14 are arranged on the base substrate in the present example, which likewise have supply lines 13 a and 14 a in the form of conductor tracks. The specific configuration of the individual conductor tracks must be selected in individual cases depending on the circumstances; in addition, any necessary insulating layers are not shown. For this purpose, additional conductor tracks 15 and 16 are indicated in FIG. 1, which, for example, act as feed lines to the movable armature.

The armature substrate 2 , which is shown only schematically in Fig. 1 as a frame and in Figs. 2 and 3 also strongly simplified, consists, like the base substrate, preferably of silicon. From this armature substrate, a sheet-shaped armature 21 is worked out in such a way that it is only hung along a pivot axis 20 via two meandering spring bands 25 and 26 . These spring bands 25 and 26 he possible not only a torsion about the pivot axis 20 , but also a deflection downwards, so that the armature 21 can approach the base substrate 1 in the region of the pivot axis.

The armature 21 forms two armature wings 21 a and 21 b on both sides of the pivot axis 20 . The armature wings 21 a and 21 b are each curved upward away from the base substrate 1 , so that each of the two armature wings each forms a wedge-shaped air gap with the base substrate in the idle state, which starts from the region of the pivot axis towards the free ends expanded. This curvature can be caused by a targeted doping and thus generated tensile stress in individual layers of the armature substrate, as is basically mentioned, for example, in DE 42 05 029 C1. The curvature is, as indicated in Fig. 2, set in the region of the pivot axis 20 on a small radius R1, which in the ideal case could be approximately a kink, but this is not entirely possible from the manufacturing point of view, while at the free ends of the The anchor decreases the curvature, which is schematically indicated in Fig. 2 with a large radius R2; in reality, of course, it is not a circular curve, but a flattening curve that could run in a straight line towards the end of the anchor. The proportions are shown over the top. In a typical embodiment, the anchor has a length of the order of 2 mm and a width of the order of 1 mm. The thickness of the anchor then be z. B. 5-10 microns, while the contact distance at rest can be about a1 = 10 microns.

The armature 21 carries an anchor electrode 22 in the region of its underside. In the example, this extends over the entire underside of the anchor. For certain applications, for example to control both armature wings of separate circuits, electrode sections 22 a and 22 b that are insulated from one another could also be provided on the underside of the armature wings. At the lower ends of the armature wings 21 a and 21 b movable contacts 23 and 24 are also arranged, which cooperate with the fixed contacts 13 and 14 of the base substrate. The movable contacts 23 and 24 are located on the underside of contact areas 27 , which are partially separated by cuts 28 from the actual armature wing so that they are only connected to these by narrow webs 29 . This causes them to be moved with greater elasticity than the actual armature when the respective contact closes out of the armature plane and thus build up the desired contact force, while the separate armature electrode lies flat in the surrounding areas around the base electrode, as shown in Fig. 5 is shown.

From this Fig. 5, which shows the closed state of the armature wing 21 b, it can also be seen that due to the pivoting movement of the armature the left armature wing 21 a also stands out further from the base electrode, so that the Kontaktab stood a2 between the contacts 13 and 23 is greater than the contact distance a1 in the idle state of the relay according to FIG. 2. This also results in additional security against incorrect switching. This means that after tightening an armature wing, in this case the armature wing 21 b, a control of the second armature wing 21 a with the same speaking voltage to this armature wing with its contacts 13 and 23 cannot close at the same time. In a typical case, this would require approximately three times the response voltage.

The function of such a relay was based on a case game calculated in which the contact spacing k1 or k2 of the two anchor wings were 42 µm at rest. Simu A silicon was mounted over torsion springs see-saw with a thickness of 10 µm, a length of 2 × 1300 µm and a width of 1000 microns, which in the middle is curved four times more by internal tensions than in remaining area of the two wings. At the ends they have both wings a distance of 42 µm from the base. According to this relatively high contact distance, too relatively high response voltages required.

The following results were obtained, which are shown in FIGS. 7a to 7d in a schematic representation of the individual phases of the switching sequence and in FIG. 8 as an associated time diagram. In Figs. 7a-7d schematically the armature 21 with the armature wings 21 a and 21 b to the two base electrodes 11 and 12 shown. U11 means the voltage between the armature wing 21 a and the base electrode 11 , U12 the voltage between the armature wing 21 b and the base electrode 12 ; k1 is the contact distance of the armature wing 21 a, k2 is the contact distance of the armature wing 21 b from the respective base electrode. In FIG. 8, the profile of the voltages U11 and U12 and the contact spacing shown k1 and k2 over time.

7a shows the idle state with U11 = U12 = 0 as the first phase . As mentioned, in this case the idle contact distance between the two anchor wings is k1 = k2 = 42 μm. From time T1 ( FIG. 8), voltage U11 is switched on; the rocker tilts slightly towards the base electrode 11 , so that the contact distance k1 drops to approximately 36 μm and the contact distance k2 increases to approximately 46 μm ( FIG. 8). Otherwise, the idle state remains until U11 reaches the response value U11an = 64 V. At this point in time T2 the armature wing 21 a closes, ie the contact distance k1 becomes 0. At the same time the other armature wing 21 b is raised further via the rocker so that its contact distance k2 increases to 65 μm (see FIG. 7b).

A further increase from U11 to 100 V does not change the switching status. Also, the turning on of U12 between the armature wings 21b and the base electrode 12 at the same time maintaining U11 = 100 V initially does not change the switching state. Only at U12 = 190 V also includes the contact on the armature wings 21 b, as shown in Fig. 7c is shown. This simultaneous switching on of U11 and U12 corresponds to an undesired incorrect operation of the relay. However, since the value U12an = 190 V roughly corresponds to the condition U12an = 3 × U11an, a changeover relay with the structure according to the invention has a sufficiently high level of security against incorrect switching.

If the voltage U11 is reduced from the time T4, the switching state according to FIG. 7c is initially maintained until U11 has reached the drop voltage value of U11ab = 17 V (time T5 in FIG. 8). At this point in time, the anchor wing 21 a falls off, k1 rises to the value of 65 μm according to FIG. 7d. The contact on the armature wing 21 b remains closed.

This calculation example serves to demonstrate the functional sprin zips. The results also apply to smaller ones Contact spacing on the order of 10 microns, then also smaller response voltages in the range from 10 to 20 V. are enough.

The power supply for the movable contacts 23 and 24 (in Fig. 5), which are expediently connected as a center contact, takes place via a conductor track, not shown, via the underside of the spring band 25 and the conductor track 15 on the base substrate, while the control of Armature electrode 22 via an also not shown Lei terbahn on the underside of the spring band 26 to the conductor path 16 of the base substrate. If several supply lines, for example to several contacts, are required, conductor tracks would have to be routed in different layers via the spring strips.

In order to avoid a load current supply via the spring bands at all, it is also possible to design the movable contacts as bridge contacts. Such an embodiment is shown schematically in FIG. 4. There on the left armature wing 21 a two movable contacts 33 a and 33 b are connected via a bridge 33 , as are two movable contacts 34 a and 34 b on the armature wing 21 b via a bridge 34 . When switching, a contact bridge 33 or 34 can connect two stationary contacts, not shown, on the base substrate.

In Fig. 6, a development is indicated schematically, in which electrets 41 and 42 are provided above the armature electrodes 11 and 12 , which can achieve a bias with their charges and thus achieve a certain monostable or bistable switching characteristic of the relay. In the example shown, the electret layers are arranged on the base substrate above the fixed electrodes. In principle, it would of course also be possible to attach appropriate elec- tric layers either optionally or additionally to the anchor.

Depending on the type and amount of the charges in the electret layers 41 and 42 , different operating modes of the relay can be achieved, as summarized in the following tables.

Neutral relay (without electret charges):

Monostable relay:

Bistable relay:

In the tables, U11 means the total voltage between the base electrode 11 and the armature electrode 22 , and U12 the total control voltage between the base electrode 12 and the armature electrode 22 . Included in this is the electret voltage U41 of the electret 41 and U42 of the electrical circuit 42 . The control voltage to be applied from the outside is therefore half lower than U11 or U12, namely U11-U41 or U12-U42.

Otherwise means:
Uan: general response voltage
Uan0: response voltage of the neutral relay
Urück: the release voltage, in general, that is the voltage at which the anchor is no longer held and returns to the rest position,
Urück0: the dropout voltage for the neutral relay.

The equivalent electret voltages U1 for the monostable relay and U0 for the bistable relay correspond approximately to the values:
U1 <Uan0
Uan1 <U1 and
Urück0 <U0 <Uan0.

As already mentioned at the beginning, the substrates can be processed using known coating and etching methods. In particular, the armature 21 can be obtained from the armature substrate 2 using known methods. The anchor is preferably formed by a doped silicon layer in the armature substrate 2 , which is then exposed by anisotropic etching of the silicon wafer on the back with an electrochemical etching stop. However, other methods can also be used.

The design of the contact area 27 with the movable contact piece 23 or 24 shown in FIG. 1 can also be modified. In particular, designs of a contact area with spiral spring-like or sun radar term suspensions are possible, as described in DE 44 37 259 C1.

Claims (11)

1. Micromechanical electrostatic relay with

• 1. a flat base substrate ( 1 ), in the surface area of which two flat base electrodes ( 11 , 12 ) are arranged offset to one another in the longitudinal direction,
• 2. an armature substrate ( 2 ) with a rocker-shaped armature ( 21 ) which is suspended in the region of a central pivot axis ( 20 ) on two opposite sides via flexible bands ( 25 , 26 ) in the armature substrate ( 2 ) and one on each side of the pivot axis leaf-shaped armature wings ( 21 a, 21 b), each armature wing carrying an armature electrode section ( 22 a, 22 b), which in turn is opposed to each of the two base electrodes ( 11 , 12 ),
• 3. Furthermore, each anchor wing ( 21 a, 21 b) carries at least one movable contact ( 23 , 24 ; 33 a, 33 b, 34 a, 34 b), each of which is arranged with at least one on the base substrate ( 1 ) Fixed contact ( 13 , 14 ) cooperates,

characterized in that the two anchor wings ( 21 a, 21 b) are flexible in themselves and are each curved away from the base substrate ( 1 ) in the idle state, each forming a wedge-shaped air gap with the latter, the narrowest point of which is in the vicinity of the pivot axis ( 20 ) lies and which continuously widens towards the free end of the anchor wing ( 21 a, 21 b). 2. Relay according to claim 1, characterized in that the flexible belts ( 25 , 26 ) for armature suspension allow both a torsion and a deflection perpendicular to the surface of the siss substrate ( 1 ). 3. Relay according to claim 1 or 2, characterized in that the flexible strips ( 25 , 26 ) for the suspension of the armature ( 21 ) are meandering. 4. Relay according to one of claims 1 to 3, characterized in that the armature ( 21 ) in the region of the pivot axis ( 20 ) has a small radius of curvature (R1) and in the free ends of the armature wing ( 21 a, 21 b ) extending area has a large radius of curvature (R2). 5. Relay according to one of claims 1 to 4, characterized in that both armature wings ( 21 a, 21 b) have contiguous sections ( 22 a, 22 b) of a common armature electrode ( 22 ), which is a conductor track via at least one of the flexible Belts ( 26 ) guided control connection ( 16 ). 6. Relay according to one of claims 1 to 5, characterized in that two on one armature wing ( 21 a, 21 b) arranged movable contacts te ( 23 , 24 ) have a common load current connection ( 15 ) in the form of a conductor track one of the flexible bands ( 25 ) is guided. 7. Relay according to one of claims 1 to 5, characterized in that each armature wing ( 21 a, 21 b) has a movable bridge contact arrangement ( 33 , 34 ) without its own connection, which cooperates with a pair of fixed contacts. 8. Relay according to one of claims 1 to 7, characterized in that each movable contact ( 23 , 24 ) in a contact section ( 27 ) is arranged, the cross-sections via connecting webs ( 29 ) small cross-section elastically from the main plane of the respective anchor wing ( 21 a, 21 b) is movable out. 9. Relay according to one of claims 1 to 8, characterized in that at least in one of the wedge-shaped working air gaps an electret layer ( 41 , 42 ) on the base electrode ( 11 , 12 ) or on the armature electrode section ( 22 a, 22 b) is arranged . 10. Relay according to claim 9, characterized in that for the development of a monostable switching characteristic in the region of a first working air gap ( 11 , 21 a) an electret layer ( 41 ) is arranged and that between the electrodes ( 12 , 22 ) of the second working air gap ( 12 , 21 b) a control voltage (Uan1) can be applied, which is substantially greater than the elec tric voltage (U1). 11. Relay according to claim 9, characterized in that for the development of a bistable switching characteristic in the area of both working air gaps ( 11 , 21 a; 12 , 21 b) an electret layer ( 41 , 42 ) is arranged in each case and that between the electric the two Working air column optionally a control voltage (Uan2) can be applied, which is significantly larger than the electrical voltage (U0).