Resonant Accelerometer Single Anchor Package Stress
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Solution Overview
Problem
Conventional resonant accelerometers suffer from significant measurement errors due to packaging-induced stress and thermal stress, which affect the accuracy of acceleration measurements, especially in high-frequency sensing applications.
Innovation Solution
A resonant accelerometer design featuring a single anchor and a proof mass suspended above a substrate with four beams, minimizing the impact of packaging stress and allowing for dual-axis differential acceleration sensing with reduced thermal stress effects, utilizing microelectromechanical systems (MEMS) technology and silicon on insulator (SOI) fabrication processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional accelerometer designs with multiple anchors are used, then structural stability is improved, but sensitivity to package stress and thermal stress increases significantly
Solution Approach 1:
The patent uses a single anchor point instead of multiple anchors, creating an asymmetric configuration that eliminates differential stress effects. This asymmetric design with one anchor and four beams allows the structure to expand and contract uniformly with thermal changes without generating measurement errors, while maintaining structural stability through the symmetric arrangement of the four beams around the proof mass.
Solution Approach 2:
The patent changes the structural parameter from multiple anchors to a single anchor configuration. This parameter change fundamentally alters how stress is distributed in the system, transforming the multi-point constraint into a single-point constraint that is insensitive to package stress while maintaining thermal stability through the beam geometry and material selection.
2Speed
If resonant sensing is used to achieve high-frequency sensing capability, then sensing frequency range is improved, but sensitivity to package-induced stress increases
Solution Approach 1:
The single anchor configuration creates an asymmetric support structure that allows the resonant elements to vibrate freely without introducing package stress artifacts. This asymmetric design enables high-frequency resonant sensing while maintaining measurement accuracy by eliminating the stress coupling that plagues conventional multi-anchor designs.
Solution Approach 2:
The patent segments the sensing function into four separate beams that operate in parallel, each contributing to the overall resonant response. This segmentation allows the system to achieve high-frequency sensing capability while the single anchor point ensures that package stress does not differentially affect each segment, maintaining measurement precision.
3Volume of moving object
If small-size accelerometer design is implemented, then device miniaturization is achieved, but measurement accuracy deteriorates due to dominant package stress
Solution Approach 1:
The single anchor configuration is particularly effective in small-size designs because it eliminates the leverage effects that amplify package stress in compact geometries. The asymmetric single-point support allows the small proof mass to be suspended without introducing significant stress sensitivity, enabling miniaturization while maintaining measurement accuracy.
Solution Approach 2:
The patent changes the constraint parameter from multiple anchor points to a single anchor point, which fundamentally alters the stress distribution in the miniaturized structure. This parameter change allows small-size implementation by eliminating the geometric amplification of package stress that occurs in conventional multi-anchor compact designs.
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 design achieves high-performance, low-sensitivity acceleration measurements with minimal package stress impact, enabling accurate sensing of frequencies up to ten kilohertz and reduced thermal stress errors, thus improving measurement reliability.
Implementation Method 1
Resonant sensing of accelerations can be classified under the category of force sensing since the input acceleration is detected in terms of a shift in the resonant characteristics of a sensing device coupled to a proof mass
Implementation Method 2
A force, which may be electrostatic, electromagnetic or piezoelectric, is applied to the beams to cause them to vibrate transversely at a resonant frequency
Implementation Method 3
A force, which may be electrostatic, electromagnetic or piezoelectric, is applied to the beams to cause them to vibrate transversely at a resonant frequency
Implementation Method 4
A force, which may be electrostatic, electromagnetic or piezoelectric, is applied to the beams to cause them to vibrate transversely at a resonant frequency
Data Source
AI summary
A resonant accelerometer (24) includes a single anchor (28) fixed to a substrate (32). A proof mass (34) is positioned above a surface (30) of the substrate (32) and is positioned symmetrically about the anchor (28). The proof mass (34) has a central opening (38). Each of a number of suspension beams (42, 44, 46, 48) resides in the central opening (38) and has one end (50) affixed to the anchor (28) and another end (52) attached to an inner peripheral wall (40) of the proof mass (34). A resonant frequency of the beams (42, 44) in a direction (64) aligned with a common axis (58) of the beams (42, 44) changes according to acceleration in the direction (64). A resonant frequency of the beams (46, 48) in a direction (66) aligned with a common axis (62) of the beams (46, 48) changes according to acceleration in the direction (66).