MEMS Filter with Electrets for Particle Protection
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Solution Overview
Problem
Existing MEMS devices face performance degradation due to particle contamination through access ports, with conventional filters either allowing small particles to pass through or degrading signal quality with larger mesh holes or thicker designs.
Innovation Solution
Incorporating electrets into the filter mesh holes within the MEMS device's access port to enhance particle filtration without compromising the device's acoustic performance or reliability, using surface or bulk charged electrets arranged on the filter surfaces and walls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a filter with mesh holes is used at the port to block particles, then particle protection is improved, but small particles (PM 2.5) cannot be blocked efficiently when mesh hole sizes are 100 μm or more
Solution Approach 1:
The patent changes the parameter of mesh hole size to 10 μm or less, which is significantly smaller than conventional filters (100 μm or more). This parameter change enables efficient blocking of small particles like PM 2.5 while maintaining manufacturability through the proposed fabrication process
Solution Approach 2:
The patent replaces the purely mechanical filtration system with an electrostatic filtration system by incorporating electrets. The electrets generate electrostatic fields that attract and capture particles, substituting the reliance on mechanical mesh hole size with an electrical field-based particle capture mechanism
2Reliability
If the mesh hole size of the filter is reduced to block small particles, then particle protection is improved, but the SNR of the MEMS device decreases
Solution Approach 1:
The patent divides the filtration function into two independent components: mechanical filtration (mesh holes) and electrostatic filtration (electrets). The mesh holes provide structural support and block large particles, while the electrets handle small particle capture. This segmentation allows each component to be optimized independently, enabling small mesh holes for particle protection without the SNR penalty that would result from using a dense mechanical filter alone
3Reliability
If the thickness of the filter is increased to improve particle blocking, then particle protection is improved, but the SNR and frequency response of the MEMS device are degraded
Solution Approach 1:
The patent changes the thickness parameter of the filter to 10 μm or less, which is significantly thinner than conventional filters. The electrostatic field generated by the electrets compensates for the reduced mechanical filtering capability of the thin mesh structure, maintaining effective particle protection while minimizing the filter's acoustic impact on the MEMS device
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
Effectively blocks small particles while maintaining signal quality and frequency response, providing improved reliability and reduced yield losses in uncontrolled assembly environments.
Implementation Method 1
a port for the MEMS element to access outside, wherein the port is provided with a filter which has mesh holes and includes electrets to prevent particles from entering into the MEMS element
Data Source
AI summary
The present invention discloses a MEMS device and an electronics apparatus. The MEMS device comprises: a substrate; a MEMS element placed on the substrate; a cover encapsulating the MEMS element together with the substrate; and a port for the MEMS element to access outside, wherein the port is provided with a filter which has mesh holes and includes electrets to prevent particles from entering into the MEMS element.