Multi-stage MEMS Stopper System with Serpentine Springs
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Solution Overview
Problem
MEMS devices face issues with shock-induced failures due to rigid stoppers causing stiction and potential breakage, as well as particle dislocation, which affects the reliability and durability of sensors like accelerometers and gyroscopes.
Innovation Solution
A multi-stage stopper system with a serpentine spring system is introduced, allowing incremental contact between the movable mass and stoppers, distributing load and reducing impact forces through compliant structures, thereby enhancing shock survivability and reducing wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If rigid stoppers are used to prevent movable mass contact during shock events, then the device structure is simple and manufacturing is easy, but the stoppers wear out quickly and cause stiction or electrostatic capture failures under continuous shock
Solution Approach 1:
The stopper system is segmented into multiple stoppers (first stopper, second stopper, third stopper) positioned at different locations, each engaging at different stages of mass displacement. This segmentation distributes the shock load across multiple contact points and reduces wear on individual stoppers, thereby improving reliability while maintaining manufacturing simplicity.
Solution Approach 2:
The stopper system transitions from static rigid contact to dynamic multi-stage engagement. The stoppers are arranged to engage sequentially as the mass displaces, creating a dynamic response to shock events. This dynamic engagement reduces impact forces and prevents stiction by allowing controlled, progressive contact rather than single-point rigid impact.
2Device complexity
If fixed rigid stoppers are used to prevent finger contact, then the device complexity is low, but excessive shock generates large impact forces that may break MEMS structures or dislocate particles
Solution Approach 1:
The stopper system divides the shock absorption function across multiple stoppers positioned at different locations around the mass. Each stopper handles a portion of the impact load, distributing the stress and preventing any single structure from experiencing excessive force that could cause breakage or particle dislocation.
Solution Approach 2:
The stoppers are pre-positioned to engage before the mass can contact critical structures or dislocate particles. The multi-stage engagement creates a cushioning effect by progressively absorbing impact energy through controlled contact at multiple points, preventing catastrophic failure modes.
3Reliability
If continuous shock keeps the mass contacting the stopper, then the stopper provides continuous protection, but the stoppers wear out and cause stiction or electrostatic capture failures
Solution Approach 1:
The stopper system segments the continuous shock absorption function across multiple stoppers. Each stopper engages only when needed based on mass displacement, distributing the cumulative wear across multiple components. This segmentation extends the operational life of the stopper system by preventing any single stopper from experiencing continuous contact and wear.
Solution Approach 2:
The stoppers engage in a periodic, sequential manner as the mass oscillates during continuous shock. Rather than continuous contact, each stopper engages intermittently when the mass reaches its displacement limit in a particular direction, reducing cumulative wear and extending the duration of effective protection.
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 solution significantly improves the reliability and durability of MEMS devices by reducing the likelihood of breakage and stiction failures, while also distributing and dissipating overload energy, thus enhancing the quality and reliability of sensing systems.
Implementation Method 1
a spring system in communication with the at least one stopper gap
Implementation Method 2
A multi-stage stopper system with a serpentine spring system is introduced, allowing incremental contact between the movable mass and stoppers, distributing load and reducing impact forces through compliant structures
Data Source
AI summary
A MEMS sensing system includes a movable mass having at least one contact surface, a stopper system for stopping the movement of the mass, the stopper system having at least one contact surface that contacts a corresponding contact surface of the mass if a sufficient movement of the mass occurs in a direction, at least one stopper gap formed between the at least one contact surface of the stopper system and the corresponding contact surface of the mass, and a spring system in communication with the at least one stopper gap.