Capacitive Transducer Pressure Relief via Segmented Airflow
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Solution Overview
Problem
Capacitive transducers fabricated using MEMS technology are prone to deformation and breakage under excessive pressure, which degrades their frequency characteristics and sensitivity, especially in low-frequency sound ranges, and existing pressure relief mechanisms complicate manufacturing and reliability.
Innovation Solution
A capacitive transducer design featuring a vibration electrode film with a protrusion integral to the back plate and an airflow channel defined by a gap, where the film moves relative to the protrusion and an extension with slits to increase air flow area, relieving pressure and preventing deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pressure relief hole is formed in the vibration electrode film, then the film is protected from breaking under excessive pressure, but the frequency characteristics and low-frequency sensitivity are degraded
Solution Approach 1:
The pressure relief hole is segmented into two functional zones: an upper portion that remains blocked by the protrusion to maintain acoustic sealing and frequency characteristics, and a lower portion that provides pressure relief when excessive pressure deforms the film downward. This segmentation allows the hole to serve dual purposes without compromising either reliability or measurement precision.
Solution Approach 2:
The protrusion dynamically blocks the pressure relief hole under normal operating conditions, maintaining acoustic integrity. When excessive pressure causes the vibration electrode film to deform downward, the protrusion is pushed aside, dynamically opening the pressure relief path. This dynamic behavior ensures the hole only activates when needed, preserving frequency characteristics while providing protection.
2Reliability
If a plug portion and support are used as separate components for pressure relief, then pressure can be relieved, but the manufacturing process becomes complicated and reliability is reduced
Solution Approach 1:
The plug portion and support are merged into a single integral protrusion structure formed directly on the back plate. This eliminates the need for separate components and their associated assembly steps, simplifying manufacturing while maintaining the pressure relief functionality. The integral structure also eliminates the risk of the plug falling off the support, enhancing reliability.
Solution Approach 2:
The integral protrusion serves multiple functions: it provides structural support for the vibration electrode film, defines the airflow channel geometry, and acts as a movable block for the pressure relief hole. This multi-functionality reduces the number of components needed and simplifies the overall device structure while maintaining reliable pressure relief.
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 design maintains good frequency characteristics, prevents deformation and breakage under high pressure, and simplifies the structure while enhancing reliability by efficiently relieving pressure through increased airflow.
Implementation Method 1
A capacitive transducer converts a displacement of a vibration electrode film into a change in capacitance between the vibration electrode film and a back plate
Implementation Method 2
the vibration electrode film moves relative to a protrusion integral with the back plate. This increases an area of air flow in an airflow channel defined by a gap between the protrusion and a part of the vibration electrode film to relieve pressure applied to the vibration electrode film
Data Source
AI summary
A capacitive transducer includes a substrate having an opening in a surface thereof, a back plate facing the opening in the substrate, a vibration electrode film facing the back plate across a space, the vibration electrode film being displaceable to have a displacement converted into a change in capacitance between the vibration electrode film and the back plate, an airflow channel defined by a gap between a protrusion integral with the back plate and a part of the vibration electrode film, the airflow channel being configured to increase an area of air flow when the vibration electrode film deforms under pressure to move relative to the protrusion integral with the back plate and relieve the pressure applied to the vibration electrode film to serve as a pressure relief channel, and an extension formed at a periphery of a hole in the vibration electrode film defining the pressure relief channel.