MEMS Micro-Mirror Stopper Design for Shock Immunity
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Solution Overview
Problem
MEMS micro-mirror devices are susceptible to structural damage from mechanical shock, particularly in large scanning applications, where flexures with low spring constants are more prone to shock-induced damage, and existing technologies fail to provide adequate shock immunity.
Innovation Solution
A micro-electromechanical system (MEMS) micro-mirror device is designed with at least one stopper and flexure configuration, including upper and lower caps with recesses and protrusions, to prevent the micro-mirror plate from moving out of plane and absorb shock, thereby preventing flexure damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If flexures with low spring constants are used to enable large scanning angles, then scanning range is improved, but shock immunity deteriorates
Solution Approach 1:
The patent introduces stoppers positioned below the movable mirror plate that engage with the flexures to prevent excessive downward movement during mechanical shock events. This beforehand protective measure allows the flexures to maintain low spring constants for large scanning angles while being protected from shock-induced damage by the stoppers acting as mechanical limits.
2Reliability
If stoppers are added to prevent out-of-plane movement, then shock immunity is improved, but device complexity increases
Solution Approach 1:
The stoppers are integrated into the substrate structure, and the caps are bonded to the substrate to form a unified housing. This merging of components reduces the overall device complexity despite adding the stopper function, as the stoppers become part of the existing structural framework rather than separate add-on elements.
Solution Approach 2:
The substrate serves multiple functions: it provides mechanical support, houses the stoppers for shock protection, and serves as the bonding surface for the caps. This multi-functionality reduces the need for additional dedicated components, thereby limiting the increase in device complexity while achieving improved shock immunity.
3Reliability
If caps with recesses are added to protect flexures, then shock immunity is improved, but manufacturing complexity increases
Solution Approach 1:
The recesses are pre-formed into the cap structures during manufacturing, creating built-in protective features that guide and limit flexure movement before shock damage can occur. This preliminary structural preparation integrates protection into the manufacturing process itself, reducing the need for additional assembly steps or complex manufacturing procedures.
Data Source
AI summary
A MEMS micro-mirror device includes a middle substrate, a movable structure, at least one stopper coupled with the movable structure, at least one flexure, an upper cap, and a lower cap. The movable structure includes a micro-mirror plate having a reflective surface. The flexure connects the stopper and the middle substrate. The upper cap, bonded with the middle substrate, has a first opening for allowing the movable structure's movement and has at least one first recess facing a first side of the flexure and a first side of the stopper. The lower cap, bonded with the middle substrate, has a second opening for allowing space for the movement and has at least one second recess facing a second side of the flexure and a second side of the stopper.