Piezoresistive Z-Axis Accelerometer with Multi-Beam Stress Distribution

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Z-axis accelerometers with single cantilever beam connections are prone to mechanical damage and reliability issues due to excessive sensitivity, affecting their performance over time.

Innovation Solution

Implementing multiple cantilever beams to connect the proof mass to anchors, distributing stress and reducing mechanical damage by using multiple piezoresistive material layers in a Wheatstone bridge configuration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a single cantilever beam is used to connect the proof mass to the anchor, then the accelerometer achieves high sensitivity, but the structure becomes prone to mechanical damage and reliability issues

Engineering Contradiction:

ImprovesensitivityVSAvoidmechanical damage resistance

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The single cantilever beam connection is segmented into multiple cantilever beams (typically four) connecting the proof mass to anchors at different locations. This segmentation distributes the mechanical stress across multiple structural elements, preventing excessive stress concentration on a single beam while maintaining the sensitivity required for accurate measurement.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the proof mass are connected through cantilever beams with locally optimized properties. The cantilever beams are positioned at specific locations on the proof mass where they provide optimal stress distribution and sensitivity. The local quality of the connection points is optimized to balance mechanical strength and sensing capability.

Inventive Principle:

Principle #3Local quality

2Reliability

If multiple cantilever beams are used to connect the proof mass to anchors, then the mechanical stress is distributed and reliability is improved, but the device complexity increases

Engineering Contradiction:

Improvemechanical stress distributionVSAvoidnumber of cantilever beams

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The multiple cantilever beams serve multiple functions simultaneously: they provide structural support to hold the proof mass, distribute mechanical stress during acceleration events, and act as piezoresistive sensing elements. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity despite using multiple beams.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The structural support function and the sensing function are merged into the same cantilever beam elements. The piezoresistive material is integrated directly into the cantilever beams, allowing these structural components to serve dual purposes: mechanical support and acceleration sensing. This merging reduces overall device complexity compared to having separate structural and sensing components.

Inventive Principle:

Principle #5Merging (Combining)

3Measurement precision

If piezoresistive material is used in the cantilever beams, then the sensitivity is enhanced, but the material is more susceptible to mechanical damage and cracking

Engineering Contradiction:

ImprovesensitivityVSAvoidcrack resistance

Core Design Contradiction:

Measurement precisionVSStrength

Solution Approach 1:

The piezoresistive material in the cantilever beams is designed to operate within controlled stress ranges that prevent excessive mechanical damage. The multiple beam configuration provides beforehand cushioning by distributing stresses before they can cause cracking. The material is protected from extreme mechanical damage through the redundant multi-beam structure that cushions against over-stressing.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The cantilever beams utilize composite material structures combining piezoresistive materials with structurally robust materials. This composite approach integrates the high sensitivity of piezoresistive materials with the mechanical strength and crack resistance of structural materials, creating a hybrid component that achieves both sensing performance and mechanical durability.

Inventive Principle:

Principle #40Composite materials

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

Enhances the reliability and sensitivity control of Z-axis accelerometers by reducing mechanical stress and preventing cracking, thereby improving their operational lifespan and accuracy.

Implementation Method 1

the cantilever beams comprise a piezoresistive material; and the accelerometer senses a movement of the proof mass by the piezoresistive material

Methodology Applied

Scientific EffectPiezoresistive effect: Piezoresistive Effect

Data Source

PatentUS9052332B2Piezoresistive type Z-axis accelerometer

Publication Date: 2015.06.09 RICHWAVE TECH CORP

AI summary

A pizeoresistive type Z-axis accelerometer is provided, including a substrate; a plurality of anchors formed over the substrate; a plurality of cantilever beams, wherein the cantilever beams include a piezoresistive material; and a proof mass, wherein the proof mass is suspended over the substrate by respectively connecting the proof mass with the anchors, and the accelerometer senses a movement of the proof mass by the piezoresistive material.