Top Port MEMS Microphone Back Volume Optimization
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Solution Overview
Problem
Conventional top port MEMS microphones have lower performance characteristics due to smaller back volumes compared to bottom port MEMS microphones of similar size, limiting their efficiency in acoustic signal processing.
Innovation Solution
The implementation of a hermetically sealed back volume within a top port MEMS microphone package, utilizing a combined air volume formed by connecting spaces between anchors on a substrate, with an acoustic seal and enclosure to enhance signal-to-noise ratio performance, similar to bottom port MEMS microphones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a top port MEMS microphone is designed with conventional structure, then the device complexity is reduced and manufacturing is easier, but the back volume is smaller and signal-to-noise ratio performance deteriorates
Solution Approach 1:
The package structure is segmented into distinct functional regions: a front volume containing the port and acoustic path, and a back volume formed by the cavity beneath the substrate. The acoustic seal divides these volumes, creating separate acoustic environments that optimize performance while maintaining manufacturability through modular assembly.
Solution Approach 2:
The invention utilizes the vertical dimension beneath the substrate to create the back volume, effectively using the third dimension (depth) to increase back volume without increasing the planar footprint. This allows top port microphones to achieve back volumes comparable to bottom port designs by exploiting the z-axis space under the package lid.
2Reliability
If the back volume is increased to improve signal-to-noise ratio, then the acoustic performance is improved, but the package size must be increased
Solution Approach 1:
The back volume is created by utilizing the vertical space beneath the substrate and package lid, converting a two-dimensional planar layout into a three-dimensional volume optimization. This allows the back volume to be increased without increasing the lateral dimensions of the package, maintaining a compact footprint while improving acoustic performance.
Solution Approach 2:
The back volume cavity is nested within the existing package structure, utilizing the space beneath the substrate and enclosed by the package lid. This nested arrangement allows the back volume to be integrated into the overall package without requiring additional external space, effectively hiding the volume increase within the existing form factor.
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
This approach improves the signal-to-noise ratio performance of top port MEMS microphones by utilizing the entire volume under the package lid as a back volume, achieving performance comparable to bottom port MEMS microphones while maintaining a compatible form factor.
Implementation Method 1
An acoustic seal can be placed, disposed, etc. on the MEMS acoustic sensor... The acoustic seal can isolate a first portion of the enclosure corresponding to a front volume from a second portion of the enclosure corresponding to the combined back volume
Implementation Method 2
Spaces between the plurality of anchors can connect a first back volume, e.g., of air, etc. corresponding to a bottom portion of the MEMS acoustic sensor with a second back volume, e.g., of air, to form a combined back volume, e.g., of air
Data Source
AI summary
A top port microelectromechanical systems (MEMS) microphone is presented herein. A device can include a substrate and a MEMS acoustic sensor mechanically attached to the substrate utilizing anchors. Spaces between the anchors can connect a first back volume corresponding to a bottom portion of the MEMS acoustic sensor with a second back volume to form a combined back volume. An acoustic seal can be placed on the MEMS acoustic sensor, and an enclosure placed on the acoustic seal and secured to the substrate. The acoustic seal can isolate a first portion of the enclosure corresponding to a front volume from a second portion of the enclosure corresponding to the combined back volume. The first portion of the enclosure can include an opening adapted to receive acoustic waves into the front volume, and the front volume can be acoustically coupled to a top portion of the MEMS acoustic sensor.