MEMS Microphone Particle Filter Using Thin Structured Mesh
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Solution Overview
Problem
High-end MEMS microphones face acoustic performance degradation due to particle accumulation in the air-gap, as existing filters either allow small particles to enter or increase acoustic resistance, compromising Signal-to-Noise Ratio (SNR) and Total Harmonic Distortion (THD).
Innovation Solution
A filter chip with a thin, structured mesh is integrated into the carrier board of the microphone, spanning the sound opening to prevent particle entry while minimizing acoustic resistance, using semiconductor technology to fabricate extremely thin layers with small holes that effectively detain particles without significantly impacting mechanical or electrical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a filter with small pore size (2-5 μm) is used to detain small particles, then particle filtration effectiveness is improved, but acoustic resistance increases and SNR performance deteriorates
Solution Approach 1:
The patent applies a thin film mesh structure with pore sizes of 2-5 μm that is sufficiently thin to minimize acoustic resistance while effectively filtering small particles. The mesh is integrated into the backplate structure, creating a thin barrier that does not significantly impede acoustic wave propagation while maintaining particle filtration effectiveness.
Solution Approach 2:
The patent changes the pore size parameter of the filter from traditional larger sizes (10 μm and above) to smaller sizes (2-5 μm), and simultaneously optimizes the thickness parameter to be minimal. This parameter optimization allows the filter to detain smaller particles while maintaining low acoustic resistance and preserving SNR performance.
2Reliability
If the backplate hole diameter is reduced to 2 μm to prevent particle entry, then particle filtration is improved, but SNR performance deteriorates drastically
Solution Approach 1:
Instead of having a single large backplate hole, the patent segments the opening into a mesh structure with multiple small pores of 2-5 μm diameter. This segmentation allows effective particle filtration while the overall open area of the mesh maintains adequate acoustic transmission, avoiding the drastic SNR deterioration that would result from a single 2 μm hole.
Solution Approach 2:
The patent uses a thin film mesh integrated into the backplate that provides particle filtration without significantly impeding acoustic wave propagation. The thin film structure ensures minimal acoustic resistance while maintaining the small pore size needed to prevent particle entry into the air-gap.
3Reliability
If a traditional filter is placed outside the microphone in the sound channel, then large particles are detained, but SNR is reduced due to increased resistance
Solution Approach 1:
The patent merges the filter function with the backplate structure by integrating a thin mesh directly into the backplate. This combination eliminates the need for a separate external filter in the sound channel, reducing the overall acoustic resistance while maintaining particle filtration effectiveness. The integrated design ensures that particles are detained at the backplate level rather than adding an additional resistance element in the sound path.
Data Source
AI summary
A MEMS microphone including a carrier board and a MEMS chip mounted thereon over a sound opening. A filter chip includes a bulk material with an aperture covered and closed by a mesh. The mesh includes a layer of the filter chip with parallel through-going first holes structured in the layer. The filter chip is arranged in or on the carrier board such that the mesh covers the sound opening.