MEMS Pressure Sensor Shielding Electromagnetic Interference
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Solution Overview
Problem
MEMS pressure sensors are susceptible to external electromagnetic interference due to their exposed pressure-sensitive films, which affects their sensitivity and accuracy.
Innovation Solution
An MEMS pressure sensing element is designed with a sealed cavity body containing a pressure-sensitive film and a varistor-equipped beam that bends under pressure, shielding external electromagnetic interference while maintaining pressure sensitivity through a Wheatstone bridge configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pressure-sensitive film is exposed in air to enable pressure sensitivity, then the pressure sensor can detect external air pressure, but it becomes susceptible to external electromagnetic interference
Solution Approach 1:
The device is divided into separate functional components: the pressure-sensitive film for pressure detection and the pressure-sensitive beam with varistor for signal output. This segmentation allows the pressure-sensitive film to remain exposed for pressure sensitivity while the electrical components are positioned to minimize electromagnetic interference exposure.
Solution Approach 2:
The pressure-sensitive beam acts as an intermediary between the pressure-sensitive film and the varistor. It transmits mechanical deformation from the film to the varistor, enabling indirect coupling that reduces direct electromagnetic interference on the electrical components while maintaining pressure sensitivity.
2Object-affected harmful factors
If the pressure-sensitive film is enclosed in a sealed cavity to shield electromagnetic interference, then electromagnetic interference is reduced, but the pressure-sensitive film cannot respond to external air pressure
Solution Approach 1:
The device separates the pressure-sensitive film (exposed for pressure detection) from the electrical components (protected from electromagnetic interference). The film remains accessible to external pressure while the varistor and associated electrical parts are positioned within the sealed cavity structure.
Solution Approach 2:
The pressure-sensitive beam serves as a mediator that transmits mechanical deformation from the exposed pressure-sensitive film to the protected varistor. This allows the film to remain exposed for pressure sensitivity while the electrical components remain protected within the sealed structure.
3Strength
If the pressure-sensitive beam is fixed at both ends to maintain structural stability, then structural integrity is improved, but the beam cannot bend effectively under pressure to change varistor resistance
Solution Approach 1:
The support structure provides different levels of constraint at different locations: the pressure-sensitive beam is supported at its ends to maintain overall structural integrity, but the central region remains free to bend under pressure. This local differentiation of structural properties enables both structural stability and effective pressure response.
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 shields electromagnetic interference, enhancing the precision of MEMS pressure sensors by allowing them to accurately detect external pressure while minimizing interference effects.
Implementation Method 1
when pressure acts on the pressure-sensitive film, the pressure-sensitive film will deform and drive the pressure-sensitive beam to move to cause the pressure-sensitive beam to bend, then a change of resistance values of the varistors on the pressure-sensitive beam is caused
Data Source
AI summary
An MEMS pressure sensing element is disclosed, comprising a substrate with a groove; a pressure-sensitive film on the substrate for sealing an opening of the groove to form a sealed cavity body; and a pressure-sensitive beam suspended in the sealed cavity body and parallel with the pressure-sensitive film provided with varistors, wherein a center of the pressure-sensitive beam is fixedly connected to that of the pressure-sensitive film, and a periphery is fixedly connected to a bottom wall of the groove of the substrate, such that the pressure-sensitive film drives the pressure-sensitive beam to bending deformation under an external pressure.