CNT Support Posts for MEMS Microphone Durability
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Solution Overview
Problem
Capacitive MEMS microphones face durability issues due to repeated contact and separation of the vibration membrane with the fixed membrane and support post, leading to reduced sensitivity and difficulty in adjusting rigidity, especially when not driven by an applied voltage.
Innovation Solution
A high sensitivity microphone design featuring carbon nanotube (CNT) support posts that mechanically fix the vibration membrane by frictional force, providing elasticity and increased vibration displacement, and a manufacturing method involving sacrificial layers and CNT growth to form these support posts between the fixed and vibration membranes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a free-floating membrane structure is used to reduce residual stress and enhance sensitivity, then sensitivity is improved, but the vibration membrane becomes vulnerable to impact damage when not driven
Solution Approach 1:
The support post is designed with elastic properties allowing it to dynamically adapt between two states: providing mechanical support and preventing impact damage when the microphone is not driven, and yielding to allow free vibration when driven. This dynamic behavior resolves the contradiction between sensitivity enhancement through free-floating membrane and protection against impact damage.
2Stability of the object's composition
If a rigid support post is used to fix the vibration membrane, then mechanical stability is improved, but rigidity adjustment becomes difficult and sensitivity enhancement is limited
Solution Approach 1:
The support post's rigidity parameter is changed by introducing elastic properties, allowing it to transition between providing stable mechanical support and allowing free vibration. This parameter change enables both mechanical stability and rigidity adjustability, resolving the contradiction between these two features.
3Ease of operation
If the vibration membrane is repeatedly contacted and separated from the support post during driving and non-driving states, then the microphone can be driven, but durability degrades due to stress
Solution Approach 1:
The elastic support post provides beforehand cushioning by being pre-designed to yield during contact and separation cycles. This prior cushioning mechanism protects the vibration membrane from stress damage during repeated driving and non-driving states, resolving the contradiction between driving capability and durability.
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
Enhances durability and sensitivity by preventing impact damage and optimizing rigidity, allowing for increased vibration displacement and improved sound pressure conversion, thus enhancing the microphone's performance and customer satisfaction in electronic equipment applications.
Implementation Method 1
carbon nanotube (CNT) support posts that mechanically fix the vibration membrane by frictional force
Implementation Method 2
providing elasticity and increased vibration displacement
Implementation Method 3
when a sound pressure is applied to the vibration membrane, a space between the fixed membrane and the vibration membrane is changed to cause a capacitive value to be changed to generate an electrical signal
Implementation Method 4
the vibration membrane 3 is attracted toward the fixed membrane 2 due to an electrostatic force
Data Source
AI summary
A high sensitivity microphone includes a substrate having a through portion provided in a central portion thereof, a vibration membrane disposed on the substrate and covering the through portion, a fixed membrane installed above the vibration membrane, spaced apart from the vibration membrane with an air layer interposed therebetween, and having a plurality of air inlets perforated in a direction toward the air layer, and a plurality of support posts provided as vertical elastic posts between the fixed membrane and the vibration membrane and mechanically fixing the vibration membrane by a frictional force, regardless of an applied voltage.