Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H57/00—Electrostrictive relays; Piezoelectric relays
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H59/00—Electrostatic relays; Electro-adhesion relays
  • H01H59/0009—Electrostatic relays; Electro-adhesion relays making use of micromechanics
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H1/00—Contacts
  • H01H1/12—Contacts characterised by the manner in which co-operating contacts engage
  • H01H1/14—Contacts characterised by the manner in which co-operating contacts engage by abutting
  • H01H1/20—Bridging contacts
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H1/00—Contacts
  • H01H1/50—Means for increasing contact pressure, preventing vibration of contacts, holding contacts together after engagement, or biasing contacts to the open position
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H1/00—Contacts
  • H01H1/0036—Switches making use of microelectromechanical systems [MEMS]
  • H01H2001/0052—Special contact materials used for MEMS
  • H01H2001/0057—Special contact materials used for MEMS the contact materials containing refractory materials, e.g. tungsten
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H1/00—Contacts
  • H01H1/0036—Switches making use of microelectromechanical systems [MEMS]
  • H01H2001/0084—Switches making use of microelectromechanical systems [MEMS] with perpendicular movement of the movable contact relative to the substrate
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H57/00—Electrostrictive relays; Piezoelectric relays
  • H01H2057/006—Micromechanical piezoelectric relay
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H59/00—Electrostatic relays; Electro-adhesion relays
  • H01H59/0009—Electrostatic relays; Electro-adhesion relays making use of micromechanics
  • H01H2059/0081—Electrostatic relays; Electro-adhesion relays making use of micromechanics with a tapered air-gap between fixed and movable electrodes

Definitions

• the invention relates to a micromechanical relay with a base substrate, which carries a flat base electrode and at least one fixed mating contact piece, and with at least one armature, which is elastically connected to a carrier in the form of a tongue on one side and an armature electrode opposite the base electrode and has an armature contact piece opposite the mating contact piece, such that when an electrical voltage is applied between the armature electrode and the base electrode, the armature is attracted to the base.
• a micromechanical relay with an electrostatic drive is known, for example, from an article by Minoru Sakata: "An Electrostatic Microactuator for Electro-Mechanical Relay", IEEE Micro Electro Mechanical Systems, February 1989, pages 149 to 151.
• the substrate-etched armature is supported on two torsion bars in a center line in such a way that each of its two wings faces an underlying base electrode.
• voltage is applied between the armature electrode and one of the two base electrodes, so that the armature optionally carries out a pivoting movement to one side or the other. Because of the distance between the torsion bearing and the base, a certain wedge-shaped air gap remains between the electrodes even after the pivoting movement, so that the electrostatic attraction remains relatively low. This also results in a relatively low contact force.
• an electrostatic drive for relays has the disadvantage that at the beginning of the armature movement, that is to say with a large distance between the electrodes, the attraction force is relatively low, so that the relay responds only slowly or requires high response voltages.
• the aim of the present invention is therefore to develop a micromechanical relay of the type mentioned at the outset in such a way that the response characteristic is improved so that the advantages of the electrostatic drive - a relatively high contact force when the armature is attracted - are retained, but at the same time the Forces are increased at the beginning of the response.
• this aim is achieved in that the armature is at least partially provided with a piezo layer acting as a bending transducer, the bending force of which, when excited, supports the electrostatic attraction between the base electrode and the armature electrode.
• the armature is therefore provided with a piezo drive in addition to the electrostatic drive.
• the piezo drive can move the armature by a large distance or over a large switching stroke, but generates at large anchor deflection, ie in the working position, only a small force.
• the electrostatic drive produces in Working position, ie when the armature is attracted, a large contact force, but the electrostatic attraction force at the start of the armature movement, that is to say with large electrode spacings, is only slight.
• the armature in the form of a tongue carrying the armature electrode and the piezo layer is pivotally connected on one side to an armature substrate.
• the base electrode is preferably arranged on an obliquely etched section of the base substrate in such a way that the armature electrode forms the wedge-shaped air gap mentioned with it in the idle state and rests approximately parallel to it in the excited state. Since no air gap remains after the armature has been tightened between the electrodes, apart from the necessary thin insulating layers, relatively high contact forces can be obtained.
• FIG. 1 shows a hybrid relay with a tongue-shaped armature mounted on one side
• FIG. 2 shows an enlarged sectional view, not to scale, of the layers in the armature and base substrate of a relay according to FIG. 1,
• FIG. 3 shows a schematic control circuit for a hybrid relay
• FIG. 4 shows a schematic force diagram for a hybrid relay.
• a micromechanical hybrid relay is shown schematically in FIG. 1, the actual size relationships being neglected in favor of clarity.
• a base substrate 51 is provided, which can be made, for example, of silicon, but preferably also of Pyrex glass.
• An armature substrate 52 which can preferably consist of silicon, is arranged and fastened on this base substrate 51.
• a tongue-shaped armature 53 is formed as a surface area that is etched free.
• the base substrate 51 and the armature substrate 52 are connected to etched areas at their edges so that the armature 53 lies in a closed contact space 54.
• the armature has an armature contact piece 55 which interacts with a fixed mating contact element 56 of the base substrate. Furthermore, an armature electrode 57 in the form of a metal layer is arranged on the armature at its surface area facing the base, which in turn opposes a base electrode 58 of the base substrate. These two electrodes 57 and 58 form an electrostatic drive for the relay.
• the base electrode 58 is arranged on a bevelled section 59 of the base substrate, so that the armature electrode 57, when the armature * is drawn on, as shown in FIG. 1, rests continuously on the base electrode 58 in parallel.
• the armature 53 has a piezoelectric drive in the form of a piezo layer 60, which works as a bending transducer and, above all, applies the required tightening force for the armature at the beginning of the armature movement.
• the tongue end provided with the contact piece 55 could bend elastically to increase the contact force, while the lateral tongue ends with the electrode layer lying thereon lie flat on the base electrode 58. Only for the sake of completeness should it be mentioned that the insulation of layers of different potential is ensured by suitable insulation layers, although these layers are not shown specifically.
• the two parts forming the relay are shown again in a somewhat enlarged representation before assembly in order to emphasize the layers somewhat more clearly.
• the geometric relationships do not correspond to the actual lengths and thicknesses of the individual layers.
• An SiO 2 layer is produced thereon as an insulation layer, and a metal layer is applied to this layer, which layer consists, for example, of aluminum and on the one hand the anchor electrode 57, but on the other hand also the feed line for the contact piece 55 and the inner electrode 61 for the same ⁇ forms to be applied piezoelectric layer 60.
• a metal layer is applied to this layer, which layer consists, for example, of aluminum and on the one hand the anchor electrode 57, but on the other hand also the feed line for the contact piece 55 and the inner electrode 61 for the same ⁇ forms to be applied piezoelectric layer 60.
• the piezoelectric layer 60 its outer electrode 62 is also a metal layer upset.
• the contact piece 55 is applied galvanically.
• the front end of the tongue can be divided by two slots into a switching spring and two electrostatic anchor elements located on the side.
• the base is also produced from a base substrate 51 by etching from silicon or from Pyrex glass.
• a trough 54a is produced anisotropically or isotropically, the bottom of which is parallel to the wafer surface.
• a wedge-shaped recess for producing the bevel 59 is then etched into the trough base using a technique known per se, which is inclined at a flat angle against the surface of the substrate. The inclination is exaggerated in the drawing. In a practical example, the angle is on the order of 3 °.
• a metal layer is then produced on the etched surface shape to form the base electrode 58 and the necessary supply lines.
• the contact piece 56 is generated galvanically.
• an insulation layer 63 for example made of SiO 2 is applied in a conventional manner.
• the piezoelectric layer 60 can also extend over the entire length of the tongue. In this case, it would act as an insulation layer between the electrodes 57 and 58, so that the additional insulation layer 63 would be unnecessary.
• the two substrates 51 and 52 are joined together in a known manner, for example by anodic bonding.
• the corresponding supply lines to the metal layers are also provided without this needing to be shown in more detail in the figure.
• FIG. 3 shows a simple circuit for a hybrid drive according to FIG. 1.
• a base electrode 11 lies parallel to an armature electrode 23, which face one another in the form of a plate and, when a voltage is applied, from the voltage source 40 serve as an electrostatic drive.
• Parallel to this electrostatic drive is a piezo transducer 41 with its electrodes 42 and 43, the electrode 43 being able to be formed from the same layer as the electrode 23.
• the electrostatic drive with the electrodes 11 and 23 and the piezo drive with the electrodes 42 and 43 can be applied in parallel to the voltage source 40 via the switch 44. Both drives respond simultaneously and overlap their forces to close the respective contact.
• the characteristic of the two drives is shown schematically in FIG. 4.
• the force F is plotted over an axis for the anchor spacing s.
• the electrostatic force denoted by fl is relatively low; it increases as the armature approaches the base electrode and reaches a high value when the distance s approaches 0.
• the piezoelectric attraction, designated f2 is greatest at the beginning of the armature movement, that is to say when the armature distance is large. It becomes smaller with increasing deflection of the bending transducer towards the base electrode.
• the piezoelectric force f2 at the large armature distance a compensates for the low value of fl, while the electrostatic force fl after the armature closes compensates for the small value of the piezoelectric force f2.
• the result is an overall course of the forces f3, which can overcome the counteracting spring force f4 of the elastic bearing strips over the entire path and can generate a large contact force when the armature is closed.

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• Micromachines (AREA)
• Coupling Device And Connection With Printed Circuit (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 1994
  • 1994-02-14 US US08/505,312 patent/US5666258A/en not_active Expired - Fee Related
  • 1994-02-14 EP EP94906870A patent/EP0685109B1/fr not_active Expired - Lifetime
  • 1994-02-14 WO PCT/DE1994/000152 patent/WO1994019819A1/fr active IP Right Grant
  • 1994-02-14 DE DE59403733T patent/DE59403733D1/de not_active Expired - Fee Related
  • 1994-02-14 JP JP6518543A patent/JPH08506690A/ja not_active Ceased
  • 1994-02-14 AT AT94906870T patent/ATE156934T1/de not_active IP Right Cessation
  • 1994-02-14 CA CA002156257A patent/CA2156257A1/fr not_active Abandoned
  • 1994-02-14 CN CN94191220A patent/CN1040049C/zh not_active Expired - Fee Related

Non-Patent Citations (1)

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