MEMS Stopping Structure with Rounded Dome for Stress Distribution
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Solution Overview
Problem
Existing MEMS devices with cantilever-based stopping structures suffer from reduced mechanical robustness due to localized mechanical stresses, leading to potential breakdowns under shocks and vibrations.
Innovation Solution
A microelectromechanical device with a movable mass and a tunnel-type stopping structure, featuring a pair of anchor blocks and a connection element that distributes stopping forces uniformly, reducing deformations and localized stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cantilever-based stopping structure is used to limit out-of-plane movements, then the stopping function is achieved, but sharp edges are created where intense mechanical stresses are localized, reducing mechanical robustness and causing breakdowns under shocks
Solution Approach 1:
The patent replaces the sharp-edged cantilever stopper with a rounded, dome-shaped stopping element. This curvature eliminates stress concentration at sharp edges, distributing mechanical stresses more uniformly across the stopping structure. The rounded geometry specifically addresses the localization of intense mechanical stresses that cause breakdowns under shock and vibration conditions.
Solution Approach 2:
The stopping element is pre-formed with an optimized rounded geometry during the manufacturing process, rather than creating sharp edges that would later concentrate stress. This preliminary shaping ensures that the structure is inherently resistant to stress localization before any operational shocks occur.
2Strength
If a cantilever-based stopping structure is used, then the stopping function is achieved, but the overall mechanical robustness decreases due to stress concentration, leading to breakdowns following shocks and falls
Solution Approach 1:
The rounded, dome-shaped geometry of the stopping element distributes shock and vibration forces more evenly, preventing the stress concentration that occurs at sharp edges. This curvature design directly improves resistance to shock and vibration while reducing susceptibility to breakdown.
Solution Approach 2:
The patent changes the geometric parameters of the stopping element from sharp-edged cantilever dimensions to rounded dimensions with optimized radius of curvature. This parameter change transforms the stress distribution characteristics, improving mechanical robustness and reliability under shock conditions.
3Manufacturing precision
If stringent process requirements are applied in the definition of the cantilever element, then the stopping precision is achieved, but sharp edges are created that localize mechanical stresses
Solution Approach 1:
The rounded stopping element geometry provides manufacturing precision for stopping function while inherently avoiding sharp edges. The curvature radius can be precisely controlled during manufacturing, achieving both stopping precision and stress distribution without the need for stringent edge-definition processes.
Solution Approach 2:
The patent changes the geometric parameters from sharp-edged dimensions to rounded dimensions, allowing manufacturing precision to be achieved through curvature control rather than edge definition. This parameter transformation eliminates stress localization while maintaining stopping precision.
Data Source
Figure 1~2
Figure 3a~3d
Figure 3e~3g
AI summary
A microelectromechanical device (1) includes: a supporting body (2), containing semiconductor material; a movable mass (3), constrained to the supporting body (2) with a relative degree of freedom with respect to a first motion direction (D1) perpendicular to the supporting body (2); and at least one stopping structure (5), configured to limit out-of-plane movements of the movable mass (3) along the first motion direction (D1). The stopping structure (5) includes: first elements (6), extending parallel to the first motion direction (D1) and anchoring the stopping structure (5) to the supporting body (2); and a second element (7), extending transversally to the first elements (6), surmounting and connecting the first elements (6).