Capacitive MEMS Switch with Dual-Spring Fast Release
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Solution Overview
Problem
Capacitive MEMS relays face limitations in generating sufficient restoring forces for efficient switch-off operations due to the low and non-linear force characteristics, leading to slow switch-off and reduced service life of relay contacts.
Innovation Solution
Incorporating a second spring structure that is either anchored to the substrate or part of the switch element, which engages before contact closure, allowing for a significant increase in restoring force, especially in the switching state, enabling faster switch-off and reducing flashovers by generating a high restoring force at the start of the return movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single spring suspension is used for the switch element, then the device complexity is reduced, but the restoring force is insufficient and the switch-off operation becomes slow
Solution Approach 1:
The single spring suspension is segmented into multiple spring elements (first spring and second spring) that act on the switch element at different stages of deflection. The first spring provides initial restoring force while the second spring engages later to provide enhanced restoring force during the switching state, thereby increasing switch-off speed without excessive complexity.
Solution Approach 2:
The spring system transitions from a static single-spring configuration to a dynamic multi-spring configuration where springs engage and disengage at different deflection stages. The second spring is designed to engage only when the switch element reaches a certain deflection position, creating a dynamic restoring force profile that adapts to the switching state.
2Speed
If the restoring force is increased to improve switch-off speed, then the switch-off operation becomes faster, but the capacitive drive cannot generate sufficient force due to its non-linear characteristic
Solution Approach 1:
The second spring acts as a counterweight mechanism that compensates for the insufficient restoring force of the capacitive drive. By engaging the second spring at the appropriate deflection stage, the system generates additional restoring force that counterbalances the weak capacitive restoring capability, enabling faster switch-off without requiring the capacitive drive to generate impossible forces.
Solution Approach 2:
The second spring is pre-positioned and pre-loaded in such a way that it engages the switch element at a specific deflection point before the switching state is fully reached. This preliminary engagement ensures that the enhanced restoring force is available exactly when needed, maximizing switch-off speed while minimizing the workload on the capacitive drive.
3Ease of operation
If a soft spring configuration is used, then the switch element can be easily deflected, but the restoring force is too low to enable rapid switch-off operations
Solution Approach 1:
The spring system transitions from a static single-spring configuration to a dynamic multi-spring configuration where springs engage and disengage at different deflection stages. The second spring is designed to engage only when the switch element reaches a certain deflection position, creating a dynamic restoring force profile that adapts to the switching state.
Solution Approach 2:
The second spring is pre-positioned and pre-loaded in such a way that it engages the switch element at a specific deflection point before the switching state is fully reached. This preliminary engagement ensures that the enhanced restoring force is available exactly when needed, maximizing switch-off speed while minimizing the workload on the capacitive drive.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The enhanced restoring force structure enables rapid switch-off operations and minimizes flashovers, improving the service life of relay contacts by ensuring a high acceleration of the switch element during the return movement, thus maintaining contact integrity.
Implementation Method 1
the first spring is deflected and exerts a first restoring force, the second spring being deflected and exerting a second restoring force
Implementation Method 2
The force of the capacitor is proportional to the reciprocal distance
Data Source
AI summary
A MEMS switch having a substrate, a micromechanical function layer situated above the substrate, and a fixed part and an electrically operable, deflectable switch element are developed in the micromechanical function layer, the switch element for closing an electrically conductive contact with the fixed part being suspended on at least one first spring in a deflectable manner. In a first operating state, the switch element is in a first position at a first distance from the fixed part, and the electrical contact is open. In a second operating state, the switch element is in a second position at a second distance from the fixed part, and the first spring is deflected and exerts a first restoring force, and the switch element establishes an operative connection with at least one second spring and the electrical contact is open. In a third operating state, the switch element is in a third position.