MEMS Z-axis Out-of-Plane Stopper for Shock and Electrostatic Balance
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Solution Overview
Problem
Microelectromechanical systems (MEMS) devices are susceptible to mechanical shock, which can degrade performance and cause structural damage, and existing methods to enhance shock robustness often compromise device performance or introduce electrostatic disturbances.
Innovation Solution
Incorporating z-axis out-of-plane shock stoppers and balance stoppers, where the balance stoppers are positioned underneath the proof mass and electrically coupled to a balance voltage to neutralize the electrostatic force and torque generated by the shock stoppers, thereby minimizing mechanical shock impact and electrostatic disturbance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If shock stoppers are added to protect the proof mass from mechanical shock, then shock robustness is improved, but electrostatic disturbance is introduced that degrades device performance
Solution Approach 1:
Balance stoppers act as intermediary elements that generate electrostatic force to counteract the harmful electrostatic disturbance caused by shock stoppers. The balance stoppers are positioned underneath the proof mass and electrically coupled to a balance voltage, creating a mediating electrostatic field that neutralizes the unwanted electrostatic effect while allowing the shock stoppers to maintain their mechanical protection function.
Solution Approach 2:
The invention changes the electrical parameter (voltage) applied to the balance stoppers to control and neutralize the electrostatic disturbance. By adjusting the balance voltage, the electrostatic force generated by the balance stoppers can be tuned to exactly counteract the electrostatic disturbance from the shock stoppers, thereby resolving the contradiction between shock protection and electrostatic interference.
2Strength
If elastic elements are engineered to increase robustness to sustain large shock load, then shock resistance is improved, but device performance under normal operational conditions is compromised
Solution Approach 1:
The invention segments the shock protection function into two distinct components: shock stoppers that handle mechanical shock protection and elastic elements that maintain normal operational performance. The shock stoppers are positioned to engage only during shock events, while the elastic elements continue to provide their normal mechanical support and sensing function, thereby resolving the contradiction between shock resistance and operational performance.
3Object-affected harmful factors
If a special medium is used to fill the package to dampen shock load, then shock damping is improved, but device performance is compromised
Solution Approach 1:
The invention extracts the shock damping function from the package filling medium and relocates it to dedicated shock stopper structures. By removing the dependency on special damping media and using geometric shock stoppers instead, the device maintains shock protection while eliminating the performance compromises associated with the medium's presence in the package cavity.
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 effectively protects MEMS devices from mechanical shock while maintaining normal operational performance and minimizing output offsets, ensuring reliability and sensitivity.
Implementation Method 1
Each of the plurality of balance stoppers is electrically coupled to a balance voltage and generates an electrostatic force to balance the electrostatic force generated by the plurality of shock stoppers
Implementation Method 2
the plurality of balance stoppers may generate electrostatic force and torque on the proof mass to balance the force and torque generated by the plurality of shock stoppers
Implementation Method 3
The proof mass is suspended above the sensor substrate via at least one elastic element
Data Source
AI summary
The present invention relates to a microelectromechanical structure, and more particularly, to systems, devices and methods of incorporating z-axis out-of-plane stoppers that are controlled to protect the structure from both mechanical shock and electrostatic disturbance. The z-axis out-of plane stoppers include shock stoppers and balance stoppers. The shock stoppers are arranged on a cap substrate that is used to package the structure. These shock stoppers are further aligned to a proof mass in the structure to reduce the impact of the mechanical shock. The balance stoppers are placed underneath the proof mass, and electrically coupled to a balance voltage, such that electrostatic force and torque imposed by the shock stoppers is balanced by that force and torque generated by the balance stoppers. This structure is less susceptible to mechanical shock, and shows a negligible offset that may be induced by electrostatic disturbance caused by the shock stoppers.