MEMS Microphone Stop Member Diaphragm Protection
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Solution Overview
Problem
MEMS microphones are vulnerable to damage from sudden high pressure events due to the potential for excessive movement of their fragile diaphragm and springs, which can occur when exposed to external acoustic signals.
Innovation Solution
Incorporating a stop member positioned between the diaphragm and the backplate to limit the diaphragm's orthogonal movement to a safe distance, preventing damage from high pressure events, and ensuring the stop member has a floating potential to minimize interference with the microphone's operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the diaphragm is allowed to move freely in response to acoustic signals, then the microphone can accurately capture sound, but the diaphragm is vulnerable to damage from high pressure events
Solution Approach 1:
A stop member is introduced as an intermediary element between the diaphragm and the backplate. This stop member limits the maximum displacement of the diaphragm during high pressure events while allowing free movement during normal acoustic operation, thus protecting the diaphragm without interfering with its primary function
Solution Approach 2:
The stop member is positioned in advance at a predetermined distance from the diaphragm to provide protective limitation before damage can occur. This pre-positioned structural element ensures that even during sudden high pressure events, the diaphragm cannot travel beyond a safe displacement distance
2Reliability
If a stop member is added to limit diaphragm movement, then protection from high pressure events is improved, but the device complexity increases
Solution Approach 1:
The stop member is integrated with existing microphone structures in multiple ways: it can be formed as part of the backplate, attached to the package housing, or combined with the suspension structure. This merging approach adds protection functionality without significantly increasing overall device complexity
Solution Approach 2:
The stop member serves multiple functions: it limits diaphragm displacement during high pressure events, maintains the back volume geometry, and can be integrated with electrical connection structures. This multi-functionality reduces the need for separate protective components
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 stop member effectively prevents diaphragm movement beyond a damaging range, enhancing the structural integrity and longevity of the microphone by limiting displacement to a safe distance, thus protecting the microstructure from shock-induced damage.
Implementation Method 1
MEMS microphones are vulnerable to damage from sudden high pressure events due to the potential for excessive movement of their fragile diaphragm and springs
Implementation Method 2
The stop member may be spaced a given distance (e.g., between about 5 and about 16 microns) from the generally planar top surface of the diaphragm to limit orthogonal movement of the diaphragm
Implementation Method 3
The microphone die has a diaphragm suspended by at least one spring, and a backplate that forms a variable capacitor with the diaphragm. The spring permits the diaphragm to move a maximum distance
Data Source
AI summary
A microphone system has a package with an interior chamber and an inlet aperture for receiving an acoustic signal, and a microphone die having a backplate and a diaphragm. The microphone is positioned within the package interior to form a front volume between the diaphragm and the inlet aperture. Accordingly, the microphone is positioned to form a back volume defined in part by the diaphragm within the interior chamber. The system also has a stop member positioned in the back volume so that the diaphragm is between the stop member and the backplate.