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DE-102024210916-A1 - Micromechanical switch

DE102024210916A1DE 102024210916 A1DE102024210916 A1DE 102024210916A1DE-102024210916-A1

Abstract

The invention relates to a micromechanical switch with a substrate (10) and a micromechanical functional layer (20) arranged above and parallel to a main extension plane (100) of the substrate, wherein a deflectable micromechanical switching element (30) and a capacitive actuator (40) for electrically actuating the micromechanical switching element are formed in the micromechanical functional layer. The core of the invention consists in the fact that the capacitive actuator has capacitor plates (42, 44) with variable contact area.

Inventors

  • Manuel Glueck

Assignees

  • Robert Bosch Gesellschaft mit beschränkter Haftung

Dates

Publication Date
20260513
Application Date
20241113

Claims (8)

  1. Micromechanical switch with a substrate (10), and with a micromechanical functional layer (20) which is arranged over a main extension plane (100) of the substrate and parallel thereto, wherein a deflectable micromechanical switching element (30) and a capacitive actuator (40) for electrically actuating the micromechanical switching element are formed in the micromechanical functional layer, characterized in that the capacitive actuator has capacitor plates (42, 44) with variable covering area.
  2. Micromechanical switch according to Claim 1 , characterized in that at least one contact electrode (50) is formed in the micromechanical functional layer (20) and the micromechanical switching element is designed to be deflectable with the contact electrode in a first direction (110) parallel to the main extension plane (100) for closing and/or opening an electrically conductive contact.
  3. Micromechanical switch according to Claim 2 , characterized in that the contact electrode (50) is firmly anchored to the substrate (10) by means of an anchor.
  4. Micromechanical switch according to Claim 2 , characterized in that the contact electrode (50) is resiliently anchored to the substrate (10) by means of at least one armature in the first direction (110) and/or that the contact electrode (50) itself is designed to be mechanically flexible.
  5. Micromechanical switch according to one of the preceding Claims 2 until 4 , characterized in that the micromechanical switching element (30) has a further contact electrode (55) which is designed to close and/or open the electrically conductive contact with the contact electrode (50).
  6. Micromechanical switch according to Claim 5 , characterized in that the further contact electrode (55) is resiliently connected to the micromechanical switching part (30) by means of a coupling spring (35).
  7. Micromechanical switch according to one of the preceding Claims 5 or 6 , characterized in that two contact electrodes (50, 50') are formed in the micromechanical functional layer (20) and the further contact electrode (55) is formed as a contact bridge (56) for closing and/or opening an electrically conductive contact between the two contact electrodes (50, 50').
  8. Micromechanical switch according to one of the preceding claims, characterized in that the capacitive actuator (40) has at least one fixed capacitor plate (42) which is fixedly connected to the substrate (10) and that the capacitive actuator has at least one movable capacitor plate (44) which is fixedly connected to the micromechanical switching part (30) and which is movable parallel to the main extension plane (100) of the substrate and parallel to a plate extension direction (120), in particular in the first direction (110) with the micromechanical switching part.

Description

State of the art The invention relates to a micromechanical switch with a substrate and a micromechanical functional layer, which is arranged above a main extension plane of the substrate and parallel to it, wherein a deflectable micromechanical switching element and a capacitive drive for electrically actuating the micromechanical switching element are formed in the micromechanical functional layer. Many different types of relays are known. Most relays have a relatively high power consumption. They are typically electromagnetically driven and require a magnetic coil for operation. This allows them to generate high forces. However, such relays have a high power consumption due to the required coil. Capacitively actuated micromechanical switches, also known as MEMS relays, have recently become available. Due to their actuation principle, they have very low power consumption. The ADGM1304 MEMS switch from Analog Devices is a well-known example ( 1 ), which is manufactured using surface micromechanics. The switching element is designed to be movable out of the substrate plane. In the publication DE 10 2021 202 238 A1 is a capacitively actuated MEMS switch with a switching element movable parallel to the substrate plane (in-plane) described ( 2 The capacitive drive works by changing the distance between the capacitor plates. A key advantage of capacitive MEMS relays is the very low moving mass due to the size of the MEMS element, enabling very fast switching operations. The MEMS elements are typically driven by parallel-plate capacitor arrays. The force F<sub>C</sub> of the capacitor is proportional to the inverse of the distance a squared: F<sub>C</sub> ~ 1/ a² . Therefore, the force is greatest when the relay is switched on. During the switching process, the moving MEMS structure gradually accelerates, reaching its highest acceleration just before the switching operation. Consequently, the contact closes at a very high speed. This is beneficial for the lifespan of the relay contacts when the relay is closed while energized, as arcing, which reduces the lifespan of the contact surfaces, can only occur for a very short time. A disadvantage of a capacitive actuator is that it can only generate small forces, and these forces do not exhibit a linear relationship with the displacement. The movable structure is retracted by a spring, which, to a good approximation, always exerts a force linearly proportional to the displacement. This behavior—where the driving force is inversely proportional to the square of the displacement and the restoring force is linearly proportional—is particularly unfavorable for the switching-off process of a relay. The switching-off process should be as fast as possible, just like the switching-on process; therefore, a large restoring force would be especially advantageous. Object of the invention An arrangement is sought for a capacitively driven micromechanical switch whose actuating force exhibits a linear behavior over the deflection. Advantages of the invention The invention relates to a micromechanical switch with a substrate and a micromechanical functional layer, which is arranged above a main extension plane of the substrate and parallel to it, wherein a deflectable micromechanical switching element and a capacitive drive for electrically actuating the micromechanical switching element are formed in the micromechanical functional layer. The core of the invention lies in the fact that the capacitive drive comprises capacitor plates with a variable overlap area. Advantageously, in the device according to the invention, the driving force behaves linearly with respect to the overlapping area of the capacitor plates. This enables more precise control of the closing and opening processes. Advantageous embodiments of the invention can be found in the dependent claims. drawing 1 Figure 1 schematically shows a micromechanical switch with a switching direction perpendicular to the substrate plane in the prior art.2 Figure 1 schematically shows a micromechanical switch with a switching movement direction parallel to the substrate plane in the prior art.3 schematically shows a micromechanical switch according to the invention in a first embodiment.4 schematically shows a micromechanical switch according to the invention in a second embodiment with a spring-loaded contact electrode.5 schematically shows a micromechanical switch according to the invention in a third embodiment with a spring-loaded additional contact electrode.6 Figure 1 schematically shows a micromechanical switch according to the invention in a fourth embodiment with two contact electrodes and a contact bridge. Description 1 Figure 1 schematically shows a prior art micromechanical switch with a switching direction perpendicular to the substrate plane. A micromechanical functional layer 20 is arranged over a silicon substrate 10, in which a micromechanical switching element 30 is formed. A fixed capacitor plate 42 and a contact