CN113284755B - Torsional micro-mechanical switch with perforation structure - Google Patents
Torsional micro-mechanical switch with perforation structure Download PDFInfo
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- CN113284755B CN113284755B CN202110359304.7A CN202110359304A CN113284755B CN 113284755 B CN113284755 B CN 113284755B CN 202110359304 A CN202110359304 A CN 202110359304A CN 113284755 B CN113284755 B CN 113284755B
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- 238000013016 damping Methods 0.000 abstract description 32
- 239000000758 substrate Substances 0.000 abstract description 10
- 238000001125 extrusion Methods 0.000 abstract description 7
- 230000000694 effects Effects 0.000 description 8
- 238000000034 method Methods 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000001133 acceleration Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 239000002210 silicon-based material Substances 0.000 description 1
- 238000013022 venting Methods 0.000 description 1
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H19/00—Switches operated by an operating part which is rotatable about a longitudinal axis thereof and which is acted upon directly by a solid body external to the switch, e.g. by a hand
- H01H19/02—Details
- H01H19/10—Movable parts; Contacts mounted thereon
- H01H19/14—Operating parts, e.g. turn knob
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- Micromachines (AREA)
Abstract
The invention discloses a torsion type micro-mechanical switch with a perforation structure, which comprises: a torsion plate with staggered perforations, two torsion support beams, two fixed supports, a fixed electrode and a substrate. And applying driving voltage between the staggered perforated rectangular flat plates and the substrate, and twisting the flat plates to perform torsion movement. The traditional rectangular plate has no perforation, and the non-perforated plate has large moment of inertia and large damping of the extrusion film, so that the switch has slow response, large energy loss and low application value. The present invention proposes a torsion micro-switch with perforated structure, which holes reduce the moment of inertia of the plate, making the device response faster. Perforation also reduces squeeze film damping, greatly reducing time lag caused by damping force. The invention provides a rectangular flat plate with perforation ratio of 0.45, the damping of an extrusion film is reduced by more than ten times, the moment of inertia is reduced by 20%, and the pull-in voltage is only increased by 10%.
Description
Technical Field
The invention relates to the field of micro-mechanical electronic systems (MEMS), in particular to a torsion type micro-mechanical switch with a perforation structure.
Background
The torsional rectangular plate capacitance is the core of many micromechanical switches. The micro-switch is generally made of silicon materials, and has small volume, simple structure and wide application. The torsion rectangular flat plate of the micro switch is an upper polar plate, the substrate is a lower polar plate, and an input voltage is arranged between the upper polar plate and the lower polar plate. The torsion plate is rigid and is supported by torsion support beams. The torsion supporting beam generates elastic torsion deformation under the action of electrostatic torque and drives the torsion flat plate to generate torsion displacement by taking the torsion supporting beam as a rotation center.
When the input voltage is smaller, the electrostatic moment formed between the upper polar plate and the lower polar plate is equal to the torsion support counter moment of the torsion support beam, the torsion deformation of the upper polar plate is relatively smaller, and the upper polar plate is not contacted with the lower polar plate. When the input voltage increases to a certain value, that is, when the electrostatic moment increases to just above the torsion support moment of the torsion support beam, one side of the upper rotatable plate is pulled towards the lower plate and is attracted with the lower plate. In document 1 (C.N.Nielson, G.Barbastathis, dynamic pull-in of parallel-plate and torsional electr)ostatic MEMS actuactors, IEEE Journal of Microelectromechanical System,2006,15 (4), pp.811-821.), are described as follows: the voltage corresponding to this Pull-in phenomenon is referred to as the "Pull-in (Pull-in) voltage", and the corresponding angle of rotation is referred to as the "Pull-in (Pull-in) position", which is 0.44 times the maximum mechanical angle of the torsion plate. The expression "Pull-in voltage" isWhere ε is the dielectric constant, k is the torsional stiffness, g 0 Is the plate gap when the drive voltage is zero, a=lw is the rectangular plate area, and L and W are the length (x-direction dimension) and width (y-direction dimension) of the rectangular plates. Micromechanical switches are operated using this "pull-in phenomenon".
Document 2 (s.d. senturia, microsystem design, kluwer academic publishers, 2001) describes: in order to be able to generate large drive torques with small drive voltages, the upper plate (torsion plate) and the lower plate (fixed plate) of the device must be very close.
In document 3 (R.B.Darling, C.Hivick, J.Xu, compact analytical modeling of squeeze film damping with arbitrary venting conditions using a Green's functions application, sensors & Actuators a.1998,70, pp 32-41.) and document 4 (p.li, y. Fang, an Analytical Model for Squeeze-Film Damping of Perforated Torsional Microplates Resonators, sensors,2015,15 (4), pp 7388-7411.) it is described that in this case the device has a "squeeze film damping effect", namely: when the torsion plate moves downwards, the gas in the gap is compressed and extruded. When the torsion plate moves upward, the gas in the gap is expanded, and the gas around the gap is sucked into the gap. This effect creates a pressure differential between the inside and outside of the gap. This pressure difference has a damping effect. This damping effect is squeeze film damping.
The micro switch must be able to respond quickly to the input voltage with a small time lag and converge to the equilibrium position at the opening speed. This requires the device to have a small moment of inertia and less damping. However, current device structure designs, which do not contemplate reducing moment of inertia, ignore the "squeeze film damping effect" of the device.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a torsion type micro-mechanical switch with a perforation structure, which can simultaneously reduce damping and moment of inertia of an extrusion film.
In order to solve the technical problems, the invention provides the following technical scheme:
the utility model provides a torsion type micro-mechanical switch with perforation structure, includes the basement, twists reverse dull and stereotyped, fixed support, twists reverse a supporting beam and fixed electrode plate, fixed support and fixed electrode plate set up on the basement, twist reverse dull and stereotyped parallel arrangement in fixed electrode plate top, twist reverse through between dull and stereotyped and the fixed support twists reverse a supporting beam fixed connection about can regard twists reverse a supporting beam as the center, its characterized in that: the torsion flat plate is provided with a plurality of through holes, and the through holes are uniformly distributed on the torsion flat plate according to a certain perforation ratio.
Further, the through holes are uniformly arranged according to an equilateral triangle array.
Further, the perforation ratio of the torsion plate isWherein l p Adjacent hole-to-hole spacing, l, of square through holes h Is the side length of the through hole.
Further, the perforation ratio of the torsion plate isThe number of the through holes is at least 50.
Further, the torsion flat plate is rectangular, two torsion support beams are arranged, one end of each torsion support beam is connected with the fixed support, and the other end of each torsion support beam is connected with two ends or the middle of the side edge of the torsion flat plate.
Further, the length, width, and thickness of the torsion plate are l=250 μm, w=500 μm, and T, respectively p =10 μm, torsional rigidity of 7.78x10 -9 N.m/rad, a gap between the torsion plate and the substrate of 5 μm, a via pitchl p =50 μm, the number of vias is 50.
Compared with the prior art, the invention has the beneficial effects that: 1. through hole structures are uniformly arranged on the torsion flat plate, and the mass of the torsion flat plate is greatly reduced by the aid of the porous structure, so that the moment of inertia of the torsion flat plate is reduced, and the torsion response speed of the torsion flat plate is shortened; 2. in the twisting process, the porous structure of the twisting flat plate can also enable air between the twisting flat plate and the substrate to pass through the through holes, so that the damping effect of the extrusion film is reduced, and the twisting response speed and the energy loss are further reduced; 3. the through holes are distributed in an equilateral triangle array, so that the torsion flat plate has higher rigidity, and the original shape is kept without deflection and deformation in the torsion process; 4. when the perforation ratio of the rectangular torsion flat plate is 0.45, the damping of the extrusion film is reduced by more than 10 times, the moment of inertia is reduced by 20%, the torsion response speed of the torsion flat plate is greatly improved, and the actuation voltage is only increased by 10% compared with that of the unperforated torsion flat plate, so that the influence on the driving circuit of the micromechanical switch is small, and the micromechanical switch is acceptable; 5. the arrangement of a single through hole with small area and a large number of through holes is adopted, so that the pressure in the extrusion die is uniform, and the local rigidity and strength of the torsion flat plate are maintained in the torsion process.
Drawings
FIG. 1 is a schematic diagram of the structure of the present invention;
FIG. 2 is a top view of an embodiment of the present invention;
FIG. 3 is a top view of a second embodiment of the present invention;
FIG. 4 is a top view of a third embodiment of the present invention;
FIG. 5 is a top view of a fourth embodiment of the present invention;
FIG. 6 is a graph showing the variation of squeeze film damping coefficient with perforation ratio.
Wherein: 1-a substrate; 2-fixedly supporting; 3-torsion support beams; 4-torsion plate; 5-fixing the electrode plate; 6-through holes.
Detailed Description
In order to enhance the understanding of the present invention, the present invention will be further described in detail with reference to the drawings, and the following examples are only for the purpose of illustrating the present invention and are not to be construed as limiting the scope of the present invention.
Embodiment one: as shown in fig. 1 and 2, a torsion type micro-mechanical switch with a perforation structure comprises a substrate 1, a torsion flat plate 4, a fixed support 2, a torsion support beam 3 and a fixed electrode plate 5, wherein the two fixed supports 2 and the fixed electrode plate 5 are arranged on the substrate 1, the rectangular torsion flat plate 4 is arranged above the fixed electrode plate 5 in parallel, the torsion flat plate 4 and the fixed support 2 are fixedly connected through the torsion support beam 3, one end of the torsion support beam 3 is connected with the fixed support 2, the other end is connected with the side edge of the torsion flat plate 4, the torsion flat plate 4 can twist up and down by taking the torsion support beam 3 as a center, a plurality of square through holes 6 are formed in the torsion flat plate 4, and the through holes 6 are uniformly distributed on the torsion flat plate 4 according to a certain perforation ratio. The length and width directions of the torsion flat plate 4 are x and y directions respectively, the torsion axis of the torsion flat plate 4 is y axis, and the number of rows of holes is M rows of holes calculated along the torsion axis direction, wherein m=m Odd, even +M Doll (doll) ，M Odd, even Is the total number of odd lines, M Doll (doll) Is the total number of even rows. The perforated area isWherein N is Odd, even And N Doll (doll) The number of holes, l, in odd and even rows, respectively h Is the side length of the square through hole 6. The total number of lines in the odd numbered lines is one more than the total number of lines in the even numbered lines, the number of perforations in the odd numbered lines is one more than the number of perforations in the even numbered lines, i.e. M Odd, even ＝M Doll (doll) +1 and N Odd, even ＝N Doll (doll) +1, length l=n of the corresponding torsion plate 4 Odd, even l p ，l p Is the pitch of the through holes 6; width->
Embodiment two: as shown in fig. 3, the total number of odd-numbered rows of the through holes 6 is equal to the total number of even-numbered rows, and the number of through holes 6 in each odd-numbered row is one more than the number of holes in the even-numbered rows, that is, M Odd, even ＝M Doll (doll) And N Odd, even ＝N Doll (doll) +1, the corresponding length and width, etcThe structure is the same as that of the first embodiment.
Embodiment III: as shown in fig. 4, the total number of odd-numbered rows of the through holes 6 is one more than that of even-numbered rows, but the number of through holes 6 in the odd-numbered rows is one less than that in the even-numbered rows, i.e., M Odd, even ＝M Doll (doll) +1 and N Odd, even ＝N Doll (doll) -1, corresponding length
L＝(N Odd, even +1)l p ＝N Doll (doll) l p The other structures such as the width are the same as those of the first embodiment.
Embodiment four: as shown in fig. 5, the torsion support beam 3 is fixedly connected to the middle of the side edge of the torsion plate 4, and the torsion plate 4 has a structure symmetrical to the torsion support beam 3 about a symmetry axis.
The working principle of the above embodiment is as follows: when the driving voltage is zero, the elastic torsional deformation of the torsional support beam is zero, the torsional flat plate is parallel to the substrate, and the micromechanical switch is disconnected. When the driving voltage is applied, the torsion flat plate moves downwards around the y axis under the action of electrostatic moment. When the driving voltage is equal to the pull-in voltage, the right end of the torsion plate is pulled together with the substrate, and the micromechanical switch is closed at the moment. Obviously, the smaller the moment of inertia of the torsion plate, the greater the angular acceleration, and the faster the response of the torsion plate to the electrostatic moment. In addition, when the torsion flat plate moves downwards around the torsion supporting beam, gas in the gap is extruded, and the reaction moment of the gas on the torsion flat plate also resists the movement of the pole plate, and the reaction moment has a damping moment effect (extrusion film damping), and the damping causes the response time lag of the flat plate. Obviously, an ideal switching device would have a small moment of inertia and low squeeze film damping.
The moment of inertia of the perforated torsion plate is approximately:
wherein, I h Side lengths of square through holes, ρ and T p Density and thickness of torsion plate, ρT respectively p A is the mass of the unperforated torsion plate. Obviously, the perforation size l h The bigger the torsion levelThe smaller the moment of inertia of the plate.
The perforation on the torsion flat plate can reduce the damping of the flat plate squeeze film, and the damping coefficient of the squeeze film when the perforated torsion flat plate is in torsion vibration is approximate to
Where μ is the gas viscosity coefficient,l and W are the length and width of the rectangular plate, L h Is a perforation effect term, and the expression is
In the method, in the process of the invention,T eff ＝T P +(3πb/8),/>and K (β) =4β 2 -β 4 -4lnβ-3。
Obviously, the size l of the through hole h The larger the damping coefficient c damping The smaller the moment of inertia.
However, the perforation of the torsion plate also reduces the electrode area and increases the actuation voltage. In many cases, high pull-in voltages are very detrimental to drive circuitry design. After the hole on the torsion flat plate is perforated, the pull-in voltage is
Due toIs small, the above is spread according to Taylor series, and it is onceThe approximation is
For a rectangular torsion plate, the length, width, thickness are l=250 μm, w=500 μm, and T, respectively p =10 μm, torsional rigidity of 7.78x10 -9 N·m/rad，g 0 =5 μm. Pitch of square array of holes/ p The damping coefficient of the plate was calculated using the theoretical model described above, with a hole count of 5×10=50, for example, =50 μm. FIG. 6 is a graph showing the variation of the damping coefficient with the perforation ratio of the original structure and the present invention, wherein the abscissa represents the perforation ratioThe ordinate indicates the damping coefficient. Obviously, as the perforation ratio increases, the damping coefficient of the present invention decreases rapidly. When perforation ratio->When the damping value is less than 0.1, the damping value is not greatly reduced by perforation, and no difference exists between the damping value and the non-perforation. When the perforation ratio is equal to 0.45, the damping ratio of the perforated flat plate is reduced by more than 10 times compared with the unperforated torsion flat plate, and the moment of inertia is 80% of that of unperforated flat plate. At this time, the pull-in voltage only increased by about 10% and was not much different from that of the unperforated device. Thus the perforation ratio of the torsion plate is +.>Is suitable for (I)>Most preferably.
When the required perforation area is selected, two perforation schemes are selected, namely, the number of holes is smaller, but the side length of the holes is larger; the other is that the number of holes is larger, but the side length of the holes is smaller. The second scheme is adopted in the invention, because when the number of through holes is too small, single holes are larger, the pressure in the extruded film is uneven, and the perforated flat plate is easy to skew. In addition, large perforations greatly reduce the local stiffness and strength of the panel. By adopting the second scheme, the pressure distribution in the perforated extruded film is uniform, and the local rigidity of the flat plate is high. The total number of holes is not less, the total number M of the perforation holes of the device exceeds 5 lines, and the total number of the holes is more than or equal to 50
The foregoing detailed description will set forth only for the purposes of illustrating the general principles and features of the invention, and is not meant to limit the scope of the invention in any way, but rather should be construed in view of the appended claims.
Claims (4)
1. The utility model provides a torsion type micro-mechanical switch with perforation structure, includes basement (1), twists reverse dull and stereotyped (4), fixed stay (2), twists reverse a supporting beam (3) and fixed electrode plate (5), fixed stay (2) and fixed electrode plate (5) set up on basement (1), twists reverse dull and stereotyped (4) parallel arrangement in fixed electrode plate (5) top, twists reverse through between dull and stereotyped (4) and the fixed stay (2) twists reverse a supporting beam (3) fixed connection, twists reverse dull and stereotyped (4) can use twists reverse a supporting beam (3) from top to bottom as the center, its characterized in that: a plurality of through holes (6) are formed in the torsion flat plate (4), the through holes (6) are uniformly distributed on the torsion flat plate (4) according to a certain perforation ratio, and the perforation ratio of the torsion flat plate (4) is thatWherein l p Adjacent hole-to-hole spacing, l, of square through holes (6) h Is the side length of the through holes (6), and the number of the through holes (6) is at least 50.
2. A torsional micro-mechanical switch with a perforated structure according to claim 1, characterized in that: the through holes (6) are uniformly arranged according to an equilateral triangle array.
3. A torsional micro-mechanical switch with a perforated structure according to claim 2, characterized in that: the torsion flat plate (4) is rectangular, two torsion support beams (3) are arranged, one end of each torsion support beam (3) is connected with the corresponding fixed support (2), and the other end of each torsion support beam is connected with two ends or the middle of the side edge of the torsion flat plate (4).
4. A torsional micro-mechanical switch with a perforated structure according to claim 3, characterized in that: the length, width and thickness of the torsion plate (4) are L=250 μm, W=500 μm and T, respectively p =10 μm, torsional rigidity of 7.78x10 -9 N.m/rad, the gap between the torsion plate (4) and the fixed electrode plate (5) is 5 μm, the spacing l of the through holes (6) p =50 μm, the number of through holes (6) being 50.
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| CN202110359304.7A CN113284755B (en) | 2021-04-02 | 2021-04-02 | Torsional micro-mechanical switch with perforation structure |
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TW201002606A (en) * | 2008-07-02 | 2010-01-16 | Touch Micro System Tech | Torsional MEMS device |
| CN109245602A (en) * | 2018-10-12 | 2019-01-18 | 东南大学 | A kind of low squeeze-film damping micro-resonator |
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- 2021-04-02 CN CN202110359304.7A patent/CN113284755B/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TW201002606A (en) * | 2008-07-02 | 2010-01-16 | Touch Micro System Tech | Torsional MEMS device |
| CN109245602A (en) * | 2018-10-12 | 2019-01-18 | 东南大学 | A kind of low squeeze-film damping micro-resonator |
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