MEMS Microphone Back Plate Arc Surface Stress Distribution
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Solution Overview
Problem
MEMS microphones face reliability issues due to stress concentration at right-angle connections between the back plate and substrate, leading to potential breakage under high sound pressure.
Innovation Solution
The design incorporates a back plate with a fixing portion featuring first and second arc surfaces that protrude and extend towards the substrate, improving stress distribution and connection reliability, including a connecting surface that is either perpendicular or circular arc, to enhance the structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the back plate is connected to the substrate in a right-angle manner, then the manufacturing process is simple, but stress concentration occurs at the connection leading to reduced reliability
Solution Approach 1:
The patent applies curvature by replacing the right-angle connection with an arc-shaped connecting portion. The first arc surface and second arc surface create a curved transition between the back plate body and the fixing portion, eliminating the sharp corner that causes stress concentration. This curved design distributes stress more evenly across the connection area, improving reliability while maintaining manufacturing feasibility through standard micro-machining techniques.
2Device complexity
If the connecting portion is made perpendicular to the body part, then the structural design is simple, but the back plate is prone to breakage under high sound pressure
Solution Approach 1:
The connecting portion incorporates arc surfaces that curve between the body part and fixing portion, replacing the perpendicular rigid connection. The first arc surface extends from the body part while the second arc surface connects to the fixing portion, creating a flexible stress-distributing pathway that prevents breakage under high sound pressure without significantly complicating the overall structure.
Solution Approach 2:
The patent changes the geometric parameters of the connecting portion by introducing arc radii and curved profiles instead of straight perpendicular lines. This parameter modification alters the stress distribution characteristics, allowing the structure to better withstand high sound pressure while maintaining reasonable design complexity within the micro-machining process capabilities.
Data Source
AI summary
The present disclosure discloses a MEMS microphone including a substrate with a back cavity, and an electric capacitance system arranged on the substrate. The electric capacitance system includes a back plate and a diaphragm opposite to the back plate. The back plate includes a body part, a fixing portion connected to the substrate, and a connecting portion connecting the body part and the fixing portion. The diaphragm is fixed to the substrate and located at a side of the back plate close to the substrate. The fixing portion includes a first surface away from the substrate, the first surface includes a first arc surface connected with the body part, the first arc surface protrudes toward a direction away from the substrate. Compared with the related art, MEMS microphone disclosed by the present disclosure has a better reliability.