Out-of-Plane MEMS Hinge Layout for Internal Stress Compensation
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Solution Overview
Problem
Microelectromechanical systems (MEMS) face deformation and sensitivity issues due to internal stresses generated during manufacturing, particularly from stress differences in layers with varying expansion coefficients and doping, leading to misalignment and reduced measurement accuracy.
Innovation Solution
An out-of-plane hinge design featuring two bending beams arranged head-to-toe to cancel out internal stresses orthogonal to the axis of rotation, with torsion elements to manage stresses along the axis of rotation, ensuring minimal deformation and maintaining the movable part's alignment with abutments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If internal stresses are released during structure release, then manufacturing completeness is improved, but structural deformation worsens
Solution Approach 1:
The invention converts the harmful internal stresses into a beneficial self-compensating mechanism. By arranging bending beams in configurations where their stress-induced deformations oppose each other (head-to-toe arrangement, opposed orientation), the stresses that would normally cause deformation are transformed into a self-balancing system where deformations cancel out, maintaining manufacturing precision while completing the structure release.
Solution Approach 2:
The bending beams are arranged in asymmetric configurations relative to the axis of rotation (opposed orientations, T-shaped arrangements) that exploit the symmetry of stress distribution. This asymmetric arrangement ensures that stress-induced deformations in opposite directions cancel each other, preventing net deformation while allowing complete stress release.
2Ease of manufacture
If the mass is tilted due to stress release, then stress relief is improved, but measurement accuracy deteriorates
Solution Approach 1:
The invention converts the harmful tilting effect into a beneficial self-compensating mechanism. By arranging bending beams in configurations where their stress-induced deformations oppose each other, the system transforms what would be a harmful tilt into a balanced state where deformations cancel out, maintaining mass alignment accuracy while achieving complete stress relief.
3Length of moving object
If bending beam thickness is reduced to minimize out-of-plane rigidification, then out-of-plane displacement freedom is improved, but in-plane rigidity deteriorates
Solution Approach 1:
The bending element is segmented into multiple bending beams arranged in specific configurations. This segmentation allows the use of thinner individual beams that permit out-of-plane displacement, while the collective arrangement of multiple beams maintains the required in-plane rigidity through their combined structural contribution.
Solution Approach 2:
Multiple bending beams are merged into a single bending element that functions as an integrated structure. The combined arrangement of these beams provides both the out-of-plane flexibility of thin beams and the in-plane rigidity of a multi-beam assembly, resolving the contradiction between displacement freedom and rigidity.
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 hinge design significantly reduces the impact of internal stresses on the structure, maintaining the movable part's central position relative to abutments and minimizing stress on gauges, thereby enhancing measurement accuracy and preventing excessive stress ranges.
Implementation Method 1
During the release of the structure, the stresses in the beams expand/retract
Implementation Method 2
two piezoresistive gauges 1010 that make it possible to measure the displacement of the mass
Implementation Method 3
at least one element configured to be deformed in torsion and aligned along the axis of rotation of the articulation
Implementation Method 4
at least one element configured to be deformed in bending and extending perpendicularly to the axis of rotation of the articulation
Data Source
AI summary
A hinge between a support and a movable part in an out-of-plane direction of a microelectromechanical structure includes two torsion beams, and two bending elements connecting the movable part and the support and each comprising two beams extending perpendicularly to the axis of rotation. Each beam is connected to the support by a first end and to the movable part by a second end, the first ends and the second ends of the beams being disposed with respect to one another in such a way that the orientation of the first end towards the second end of one beam is opposite to the orientation of the first end towards the second end of the other beam.