EP1269506B1 - Microactuator arrangement - Google Patents

Abstract

The invention relates to a micro reactor arrangement, particularly for a micro relay. It comprises a substrate (1) with two thermomechanical micro actuators (3, 4). In response to thermal stimulation, the first micro actuator (3) performs a movement in parallel with the substrate surface (2), while the second micro actuator moves in a direction orthogonal on the substrate surface (2). Both thermomechanical micro actuators are so disposed relative to each other that the first micro actuator (3), in the extended state, reaches under the second micro actuator (4). With these provisions, the first micro actuator (3) can be maintained in this position without supply of power when the second micro actuator (4) is de-energized. With the present micro actuator arrangement, one can achieve the advantages of a high activation force and long positioning travels of thermomechanical micro actuators for micro relays, without the necessity to supply energy for maintaining the individual switching states.

Description

Technical application

The present invention relates to a microactuator arrangement with a substrate having a first thermo-mechanical microactuator and a second thermo-mechanical microactuator, wherein the first thermo-mechanical microactuator is deflected in a thermal excitation substantially parallel to the surface of the substrate. The Mikroaktoranordnung is particularly suitable for use as a micro-relay.

Micro-relays are increasingly replacing conventional electromechanical relays because they can be manufactured at a lower cost and with less space required, and because of their size also achieve shorter switching times. Currently, these micro-relays are usually realized on the basis of microactuators, which operate on the electrostatic action principle. However, these electrostatic micro-relays are characterized by relatively small travel ranges and small actuating forces of the microactuators, which on the one hand leads to problems with regard to the dielectric strength of the microrelay and, on the other hand, to problems due to increased contact wear.

In contrast, thermomechanical microactuators, which are used in other areas of microsystems technology, are distinguished above all by the generation of comparatively large actuating forces and travel ranges with at the same time moderate power consumption. In microsystem technology, they are used primarily for the construction of micro-actuators that require the greatest possible actuating forces and travel ranges. An example of this is the use in microvalves. Since for the operation of thermal microactuators usually electrical power in the range of a few 100 mW are required, thermal drives are mainly primarily for the construction of individual control elements in question.
However, a particular disadvantage of thermo-mechanical microactuators proves that a thermomechanical microactuator for holding its deflected state induced by thermal excitation (ON state) must be heated continuously by supplying energy. For this reason, thermo-mechanical micro-sensors in micro-relays as well as for a variety of other applications are not used or only in exceptional cases.

State of the art

US 5,909,078 shows an example of a Mikroaktoranordnung with thermo-mechanical microactuators according to the preamble of claim 1. As a microactuator here is a single or a plurality of juxtaposed bar-shaped elements used parallel to a substrate surface at both ends clamped to the substrate and in a Preferred direction are biased parallel to the substrate surface. By heating the beam-shaped elements they expand in the clamped state, so that a deflection in the preferred direction results parallel to the substrate surface. This deflection movement can be used, for example, to open or close a valve opening in the substrate.
However, the thermo-mechanical microactuators of this document can not be used without the above disadvantages in a micro-relay, in which individual switching states must be kept for a long time.
The same disadvantage is exhibited by the thermomechanical microrelay disclosed in J.-Y. Lee et al., "A characterization of thermal parameters of thermally driven polysilicon microbridge actuators using electrical impedance analysis", Sensors and Actuators A75 (1999), 86-92. In this relay, a bridge-shaped polysilicon membrane is deflected by heating perpendicular to the substrate surface to connect electrical contacts. However, keeping this connection requires constant power input.

From WO 99/16096 a micro-relay of a plurality of identically constructed thermo-mechanical actuators is known, which are clamped on bar-shaped elements at both ends of the substrate. By heating the bar-shaped elements, a deflection of the two actuators is caused parallel to the substrate surface. About a mechanical locking mechanism, a lateral hooking with the second actuator, one of the actuators can be held without current in a certain position. The lock can be released again by actuating the second actuator.

Based on this prior art, the object of the present invention is to provide a further Mikroaktoranordnung that allows switching between at least two switching states with great force and large travel, the respective switching states can be held without power.

Presentation of the invention

The object is achieved with the Mikroaktoranordnung according to claim 1. Advantageous embodiments of the Mikroaktoranordnung are the subject of the dependent claims.

The present microactuator arrangement consists of a substrate with at least two thermomechanical microactuators. A first thermomechanical microactuator is arranged in a manner known from the prior art on the substrate, wherein it is deflected in a thermal excitation substantially parallel to the surface of the substrate, that carries out its actuating movement substantially parallel to the surface. According to the invention, the second thermomechanical microactuator on the one hand is designed such that it is deflected at a thermal excitation substantially perpendicular to the surface of the substrate, ie performs its adjusting movement substantially perpendicular to the substrate surface. On the other hand, the second thermo-mechanical microactuator is arranged relative to the first thermomechanical microactuator such that a portion of the first thermo-mechanical microactuator at a thermal excitation to below a portion of the second thermo-mechanical microactuator - in the deflected state - extends. Thus, because the second thermomechanical microactuator performs an actuator motion substantially perpendicular to the substrate surface, a portion of the first thermo-mechanical microactuator is in a deflected state between a portion of the second thermo-mechanical microactuator and the substrate surface, such that that portion of the first thermo-mechanical microactuator will shut off the second thermo-mechanical microactuator thermomechanical microactuator is clamped by this.

This arrangement of two thermo-mechanical microactuators thus makes it possible to keep the switching state (ON state) of the first thermo-mechanical microactuator powerless. When switching from the idle state (OFF state) to the ON state, first both thermo-mechanical microactuators are switched on, ie thermally excited, so that a first section of the first thermo-mechanical microactuator moves below a second section of the second thermo-mechanical microactuator. Subsequently, the second thermo-mechanical microactuator is turned off, thereby clamping the first portion of the first thermo-mechanical microactuator. If this is then also switched off by interrupting the supply of heat, it remains in the deflected position, since it is held in this position by the clamping action of the switched-off second thermo-mechanical microactuator. This holding position is on the one hand by the friction between the two microactuators and on the other hand by the high restoring force, with the second thermal Mikroaktor takes his rest position allows. In this way, the deflected state of the first thermo-mechanical microactuator is held without further energy supply, that is, without power. To release this holding position, it is only necessary to briefly turn on the second thermo-mechanical microactuator, whereby the holding position is released and the first thermo-mechanical microactuator returns to its rest position (OFF state), in which he also remains without energy.

By virtue of this feature of the microactuator arrangement according to the invention, in order to be able to use two switching states with the aid of thermomechanical microactuators, it is possible to use the large actuating forces and actuating strokes of thermomechanical microactuators even in areas for which they were hitherto unsuitable. The present Mikroaktoranordnung is particularly suitable for use in micro-relays, but can of course be used for other applications such as micro valves. The use of the present microactuator arrangement makes it possible, especially when used in micro-relays, to combine comparatively large travel ranges with a relatively large contact pressure on the contacts to be bridged. The first thermomechanical actuator, also referred to below as a lateral actuator, can in this case be designed so that it enables strokes or travel ranges of 50-80 μm. Through these large travel paths, the electrical contacts in the relay can have a greater mutual distance, so that on the one hand increases the dielectric strength of the relay and on the other hand, a crosstalk between each Lines is reduced. At the same time, the second thermo-mechanical actuator, hereinafter also referred to as a z-actuator, which holds the lateral actuator in a deflected position develops pressure forces in the rest position in the range of 10 mN-50 mN and more. The lateral actuator thus provides for the large stroke while the z-actuator for closing the relay contacts provides the large pressure force, since he presses the lateral actuator with this pressure force against the substrate surface on which the micro-relay to be closed contacts are arranged.

The electrical power of about 200 - 300 mW for switching the micro-relay is required only during the short switching phases, while the individual switching states can be held without power. The space required for the two microactuators on the substrate is usually about 2 mm x 1 mm and is therefore comparable to the areas required for microrelays according to the electrostatic action principle. The present microactuator arrangement is thus clearly superior to any hitherto known micro-relay concept with regard to the achievable switching forces and the achievable switching strokes.

It goes without saying, however, that the microactuator arrangement according to the invention is also suitable for other applications in which, on the one hand, at least two switching states must be held without power and, on the other hand, large actuating forces and travel paths are required.

Another advantage of the microactuator arrangement according to the invention is that with this arrangement not only two but also further switching states can be realized and kept without power. This only requires that the lateral actuator at different deflections, which are generated by different degrees of thermal excitation, each with a portion extends below the z-actuator. This can be achieved for example by a correspondingly long boom on the lateral actuator, which extends in the deflection direction. In this way, the lateral actuator can be held by the z-actuator in any deflection position. This embodiment enables a multiplicity of switching connections in a microrelay equipped with the microactuator arrangement according to the invention.

A further preferred embodiment of the present microactuator arrangement is characterized in that the two microactuators interlock when the holding position is taken. This allows a very secure holding position, in which the friction between the two actuators does not matter. This hooking can be realized in that the two overlapping in the holding position portions of the lateral actuator and the z-actuator engage, for example by one of the two sections has a recess into which engages a survey of the other of the two sections. Of course, other geometrical configurations are conceivable, which lead to a corresponding entanglement or to a corresponding interlocking. The person skilled in the art knows such embodiments from many areas of the technique. In the case of a plurality of shift positions to be held, different holding positions can be predetermined by corresponding geometric design of the sections, with the two sections meshing with one another.

The production and the different design possibilities of thermomechanical microactuators are known to the person skilled in the art. Preferably, in the present Mikroaktoranordnung also a bar-shaped element is used as a basic element of the single microactuator, as is known for example from US 5,909,078. This bar-shaped element is preferably etched out of the substrate such that it remains clamped on both sides of the substrate. Also, the second thermo-mechanical actuator, that is, the z-actuator, consists of such an element which is connected in the form of a bridge to the substrate.
The thermal excitation of the two elements can be done in a variety of ways. Examples of thermal excitations, such as irradiation, arranging a heating element on the substrate, direct heating by current flow through the actuator element or attaching a Heizleitungsschicht on the actuator element are known in the art. Preferably, the last option in the present microactuator arrangement is used by applying to the beam-shaped elements a corresponding heating conductor layer, for example of polysilicon.

The microactuator arrangement is not limited to a lateral and a z-actuator. Thus, several such actuators in a corresponding arrangement be used for the substrate. Likewise, a mechanical coupling of different lateral actuators is possible, as is known from the mentioned in the introductory part US-Script.

When used as a micro-relay to be switched, that is to be electrically bridged conductor tracks or contact surfaces are applied to the substrate. To bridge the interruptions between these contact surfaces corresponding contact bridges are provided from a highly conductive material on the underside of the lateral actuator. The actuator itself or the bar-shaped elements of the actuator can in this case consist of other materials. Preferably, however, nickel is used as the material for the beam-shaped elements, since this has good thermo-mechanical properties and is suitable for building the elements in the required dimensions by known means of microstructure technology. In this case, the electrically conductive contact bridges and the heating conductor layer are additionally insulated from the nickel via an intermediate layer.

Methods for producing such thermomechanical microactuators on a substrate can be taken from the specialist literature at any time. This is usually a combination of photolithography, galvanic deposition and etching.

Fig. 1

schematisch ein Beispiel für eine erfindungsgemäße Mikroaktoranordnung; und

Fig. 2

ein weiteres Beispiel für eine erfindungsgemäße Mikroaktoranordnung in der Anwendung als Mikrorelais.

The present microactuator arrangement will now be described by way of embodiments in conjunction with the drawings without limiting the general inventive concept again explained in more detail. Hereby show:

Fig. 1

schematically an example of a microactuator arrangement according to the invention; and

Fig. 2

a further example of a Mikroaktoranordnung invention in the application as a micro-relay.

Ways to carry out the invention

FIG. 1 shows a three-dimensional view of a microactuator arrangement according to a first exemplary embodiment. The microactuator arrangement consists of the substrate 1, a semiconductor substrate on which a lateral microactuator 3 and a z-actuator 4 are arranged. The lateral actuator 3 is composed of four bar-shaped elements 7, which are each anchored to the substrate 1 on one side. At these beam-shaped elements, a plate-shaped arm 9 is mounted, which extends in the direction of the deflection, that is, in the direction of the z-actuator 4. The lateral actuator 3 can be seen in the figure in the deflected state. In the resting state, it is located above the indicated depression 11 in the substrate surface, which is produced during the production process during the undercutting of the bar-shaped elements 7. The bar-shaped elements 7 are provided with Heizleitungsschichten (not visible in the figure), which are supplied via corresponding pads 12 with power. The bar-shaped elements hereby have dimensions of typically about 1 mm in length, 5-10 μm in width and 15-20 μm in height.

The z-actuator 4 is also composed of a bar-shaped element 8, which is clamped on both sides of the substrate 1. This z-actuator 4 is designed in the form of a Brückenaktors. The bar-shaped element 8 is also provided in this case with a corresponding, not shown, heating layer, which is supplied via connection pads 12 with power. Also on the z-actuator 4, a plate-shaped arm 10 is provided, which extends in the direction of the lateral actuator 3. Both arms 9 and 10 can be hooked together by a corresponding configuration, as shown in the enlarged portion of Figure 2.

In the resting state, the bar-shaped elements 7 of the lateral actuator 3 are located above the depression 11; the bar-shaped element 8 of the z-actuator 4 rests on the substrate 1. For the transition to the ON state of the micro-relay, both actuators are first put into operation. As a result, the lateral actuator 3 pushes its plate-shaped arm 9 under the z-actuator 4. Then, the z-actuator is first turned off and lowers with its arm 10 on the boom 9. A suitable hook-like structure prevents after switching off the lateral actuator. 3 a release of this contact. For the transition to the OFF state, both actuators are also first switched on. The lateral actuator 3 is switched off but this time before the z-actuator 4. Thereby, the plate-shaped arm 9, which is executed in this example in the form of a nickel plate, pulled out under the z-actuator 4, so that the contacts are released. The figure 1 shows the microactuator arrangement in the ON state. The bar-shaped elements 7, 8 and the arms 9, 10 of the two actuators 3, 4 are made of nickel in this example. The heating conductor extending below the bar-shaped elements is separated from this metallic structure by insulating layers.

Figure 2 shows another example of a microactuator assembly according to the present invention when used as a micro-relay. Again in this figure, the substrate 1 and the two microactuators 3, 4 with the respective bar-shaped elements 7, 8 and the arms 9, 10 can be seen. In addition, four printed conductors 13 are arranged on the substrate 1, of which - can be seen in the enlarged view - all are interrupted by a gap. At the bottom of the boom 9 of the lateral actuator 3 are contact bridges 14 for closing the open contacts. These contact bridges 14 may be formed of a good conductive material such as gold, which is isolated from the material of the actuator. As a result, smaller lead resistances can be achieved in the relay. As shown in the figure, with the present micro-relay several contacts or lines 13 can also be closed simultaneously. Even the realization of more than two switching states can be achieved with this relay structure. This would make it easy to switch from one of the lines to another.
In the figure, the ON state of the micro-relay is shown, in which the contacts of the four lines are closed in different ways, as can be seen in the enlarged view. By the high pressure force of the contact bridges 14 on the lines 13 allows a long service life of the contacts. The high pressure force is generated by the return movement of the z-actuator 4, which presses on the lateral actuator 3. In the enlarged view is also a geometric arrangement of a possible entanglement between the boom 10 of the z-actuator 4 and the boom 9 of the lateral actuator 3 can be seen.

For the construction of the microactuators, the use of a suitable metal such as nickel is recommended. Thus, in addition to the necessary strength and a good thermal conductivity of the bar-shaped elements can be achieved, so that the switching times of the relay are approximately between 10 ms and 100 ms. Due to the very good electrical conductivity of the bar-shaped elements, however, prohibits direct use as a heating element in this case. For this purpose, a heat conductor layer is preferably attached to the actual actuator element, which of course must be isolated from the actual thermoactor.

LIST OF REFERENCE NUMBERS

1

substratum

2

Surface of the substrate

3

lateral microactuator

4

z microactuator

5

first section (9)

6

second section (10)

7

bar-shaped element

8th

bar-shaped element

9

plate-shaped boom

10

plate-shaped boom

11

deepening

12

pads

13

conductor tracks

14

Contact bridges

Claims (11)

1. Micro actuator arrangement, particularly a micro relay, comprising a substrate (1) on which a first thermomechanical micro actuator (3) and a second thermomechanical micro actuator (4) are disposed, with said first thermomechanical micro actuator (3), in response to thermal stimulation, being extended in a direction substantially parallel with the surface (2) of said substrate (1),
   characterised in
   that said second thermomechanical micro actuator (4) is so configured and disposed relative to said first thermomechanical micro actuator (3) that upon thermal stimulation it is extended substantially in a direction orthogonal on the surface (2) of said substrate (1) and that, in an extended state, a first section (5) of said first thermomechanical micro actuator (3) reaches up to under a second section (6) of said second thermomechanical micro actuator (4).
2. Micro actuator arrangement according to Claim 1,
   characterised in
   that said first and/or said second thermomechanical micro actuator (3, 4) is/are composed of one or several bar-shaped elements that are clamped on both sides on said substrate (1).
3. Micro actuator arrangement according to Claim 2,
   characterised in
   that said one or several bar-shaped elements are provided with a thermal conduction layer.
4. Micro actuator arrangement according to Claim 2 or 3,
   characterised in
   that said one or several bar-shaped elements consist of an electrically conductive material.
5. Micro actuator arrangement according to any of the Claims 1 to 4,
   characterised in
   that said first section (5) of said first thermomechanical micro actuator (3) is designed as plate-shaped arm that extends along the direction of extension of said first thermomechanical micro actuator (3).
6. Micro actuator arrangement according to Claim 5,
   characterised in
   that said plate-shaped arm has such a length in the direction of extension of said first thermomechanical micro actuator (3) that, in response to different extensions of said first thermomechanical micro actuator (3), it reaches up to under said second section (6) of said second thermomechanical micro actuator (4).
7. Micro actuator arrangement according to any of the Claims 1 to 6,
   characterised in
   that said second section (6) of said second thermomechanical micro actuator (4) is designed as plate-shaped arm that extends in a direction opposite to the direction of extension of said first thermomechanical micro actuator (3).
8. Micro actuator arrangement according to any of the Claims 1 to 7,
   characterised in
   that said first and said second sections (5, 6) are so designed that they engage in each other when the thermal stimulation of said second thermomechanical micro actuator (4) is terminated while said first thermomechanical micro actuator (3) is in the extended state.
9. Micro actuator arrangement according to Claim 8,
   characterised in
   that said first section (5) has a recess into which a projection on said second section (6) engages or vice versa.
10. Micro actuator arrangement according to any of the Claims 1 to 9,
    characterised in
    that one or several conducting paths (13) and/or contact areas with one or more discontinuity (discontinuities) are provided on said substrate (1), which can be bridged by extension of said first thermomechanical micro actuator (3).
11. Micro actuator arrangement according to Claim 10,
    characterised in
    that said first thermomechanical micro actuator (3) presents one or several electrically conductive contact bridges (14) for bridging said discontinuity (discontinuities).

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