MEMS Proof Mass Single Anchor Mounting System
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Solution Overview
Problem
MEMS devices are sensitive to strains caused by thermal expansion, residual stresses, and environmental changes, leading to bias and alignment errors that affect their performance.
Innovation Solution
A centrally located, single mounting member with isolation cuts in the proof mass provides torsional and flexural suspension, minimizing strain sensitivity by distributing anchor variances evenly and reducing asymmetric loads on the hinges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If multiple spaced apart mounting anchors are used to attach the proof mass, then the structural support is provided, but the strain sensitivity increases causing asymmetric displacement and rotational errors
Solution Approach 1:
The patent merges multiple separate mounting anchors into a single centrally located mounting member. This single mounting member is positioned at the center of the proof mass and provides both torsional and flexural support, eliminating the asymmetric strain distribution that occurs with multiple spaced anchors. The central mounting member integrates the functions of multiple anchors while minimizing strain sensitivity.
Solution Approach 2:
The patent addresses asymmetry by using symmetric placement - specifically, a single mounting member located at the geometric center of the proof mass. This central symmetric position ensures that strains are distributed evenly in all directions, preventing the asymmetric displacement that occurs when multiple anchors are spaced apart. The isolation cuts are also symmetrically arranged around the central mounting member.
2Reliability
If multiple mounting anchors are placed at finite distances apart, then the proof mass is securely attached, but thermal and environmental strains cause asymmetric displacement leading to rotational errors
Solution Approach 1:
The patent combines multiple mounting anchors into a single centrally located mounting member that provides both torsional and flexural support. This integration eliminates the relative displacement between multiple anchors that occurs under thermal and environmental strains, maintaining attachment stability while preserving geometric symmetry.
Solution Approach 2:
The central mounting member acts as an intermediary between the proof mass and the substrate, centrally positioned to evenly distribute thermal and environmental strains. The isolation cuts surrounding the mounting member further mediate strain transmission, allowing the system to maintain anchor symmetry despite external strain variations.
3Measurement precision
If a single central mounting member is used, then strain sensitivity is minimized, but the torsional and flexural support capability must be sufficient
Solution Approach 1:
The patent segments the support functionality into two distinct components: a central mounting member for minimizing strain sensitivity and isolation cuts for providing structural support. The isolation cuts are strategically positioned around the central mounting member to provide both torsional and flexural support while allowing the central member to remain strain-sensitive minimal.
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 reduces unwanted rotational displacements and motion errors in MEMS devices by distributing strain evenly across the hinges, enhancing the stability and accuracy of the sensor element.
Implementation Method 1
the bonding material used as an interface between the proof mass and the anchor member(s)
Implementation Method 2
The mounting system may include isolation cuts arranged in the proof mass to advantageously achieve a desired amount of strain isolation
Implementation Method 3
The proof mass 12 includes a necked down region 20 that operates as a torsional hinge
Data Source
AI summary
A mounting system for a MEMS device includes a proof mass selectively coupled to a substrate using a centrally located, single anchor mount that minimizes sensitivity to strain variations experienced by the MEMS device. The mounting system may include isolation cuts arranged in the proof mass to advantageously achieve a desired amount of strain isolation and to produce hinges that extend in opposite directions from the anchor mount. The single anchor mount is arranged to reduce a separation distance from a mid-point or centroid of the anchor mount to its perimeter as compared to conventional mounting schemes that have multiple anchor mounts positioned distally from a common mid-point.