MEMS Sense Plate Stop Structures for Shock Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Micro-Electro-Mechanical Systems (MEMS) sensors, such as gyroscopes and accelerometers, face operational disruptions due to contact between the proof mass and sense plates during high shock or vibration, leading to signal loss and non-operational periods when acceleration forces exceed certain levels.
Innovation Solution
Incorporating stop structures on the sense plates, electrically isolated but at the same potential as the proof mass, to prevent contact and minimize energy exchange, allowing the MEMS devices to operate robustly through severe shock and acceleration events by constraining vertical and horizontal motion without electrical or mechanical disruption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If proof mass supporting springs are used to prevent contact between proof mass and sense plates, then contact prevention is achieved under normal operation, but the solution fails when acceleration forces exceed certain levels during high shock or vibration
Solution Approach 1:
The sense plate is segmented into multiple regions: an inner region that faces the proof mass and an outer region that is offset radially. Stop structures are positioned at the interface between these regions, creating a mechanical barrier that prevents proof mass contact with the sense plate during high acceleration events while maintaining capacitive coupling during normal operation.
Solution Approach 2:
Stop structures serve as intermediary elements between the proof mass and the sense plate. These structures physically intercept the proof mass before it can contact the sense plate, while being electrically isolated from the sense plate to maintain the capacitive sensor functionality. The stop structures transfer mechanical load without disrupting the electrical field necessary for sensing.
2Reliability
If electrical damping or gas damping is used to prevent proof mass touch, then contact prevention is achieved, but these solutions are defeated when acceleration forces exceed certain levels
Solution Approach 1:
Stop structures are pre-positioned on the sense plate at locations that will be reached by the proof mass during extreme acceleration events. These structures provide a mechanical cushion or barrier before contact can occur, preventing the proof mass from reaching the sense plate under high g-force conditions where electrical or gas damping would fail.
3Reliability
If the proof mass is held stationary during high adverse acceleration, then contact is prevented, but the sensor becomes non-operational during the disturbance period
Solution Approach 1:
The stop structures are positioned in the radial direction offset from the central sensing region, allowing the proof mass to maintain its capacitive coupling with the inner region of the sense plate while being mechanically constrained. This spatial arrangement enables the sensor to remain operational during disturbances by preventing contact in the vertical dimension while preserving horizontal capacitive coupling.
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 stop structures effectively prevent proof mass contact with sense plates during shock, maintaining sensor operation by minimizing frictional loss and ensuring restorative forces, thus enhancing operational tolerance during high-acceleration events.
Implementation Method 1
The stop structures are dimensioned to minimize energy exchange upon contact with the proof mass during a shock or acceleration event
Implementation Method 2
A MEMS gyroscope or accelerometer may include microstructure sense elements such as a proof pass interposed between a pair of sense plates, forming a capacitive sensor
Data Source
AI summary
A micro-electro-mechanical systems (MEMS) device comprises at least one proof mass configured to have a first voltage and a motor motion in a first horizontal direction. At least one sense plate is separated from the proof mass by a sense gap, with the sense plate having an inner surface facing the proof mass and a second voltage different than the first voltage. A set of stop structures are on the inner surface of the sense plate and are electrically isolated from the sense plate. The stop structures are configured to prevent contact of the inner surface of the sense plate with the proof mass in a vertical direction. The stop structures have substantially the same voltage as that of the proof mass, and are dimensioned to minimize energy exchange upon contact with the proof mass during a shock or acceleration event.