Electroacoustic Transducer Gap Structure for Low Squeeze-Film Noise
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Solution Overview
Problem
Capacitive detection microphones suffer from squeeze-film damping, which generates mechanical noise and decreases performance due to air being squeezed between the piston and the frame during operation.
Innovation Solution
A manufacturing method involving the formation of a sacrificial layer with varying thicknesses to increase the distance between the substrate and the membrane, reducing squeeze-film damping by creating a cavity in the substrate and using a thicker portion of the sacrificial layer to enhance the gap between the membrane and the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the membrane is placed close to the substrate, then the device structure is compact, but squeeze-film damping occurs causing mechanical noise and performance degradation
Solution Approach 1:
The patent applies preliminary action by forming a sacrificial layer of specific thickness before depositing the membrane during the manufacturing process. This sacrificial layer is strategically positioned between the substrate and the membrane to pre-establish the optimal gap distance, preventing squeeze-film damping before the device operates. The sacrificial layer is later removed to create the final air gap, ensuring the membrane is positioned at the correct distance from the substrate to minimize mechanical noise while maintaining compact dimensions.
2Ease of manufacture
If a uniform thickness sacrificial layer is used, then the manufacturing process is simple, but the distance between substrate and membrane cannot be optimized to reduce squeeze-film damping
Solution Approach 1:
The patent applies local quality by using a sacrificial layer with non-uniform thickness, where the thickness varies in different regions to achieve optimal local gap distances. The sacrificial layer is designed with greater thickness in areas where squeeze-film damping is most problematic, allowing the membrane to be positioned farther from the substrate in those specific locations. This localized variation in sacrificial layer thickness enables targeted reduction of squeeze-film damping while maintaining manufacturing feasibility through standard deposition techniques.
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 method significantly reduces mechanical noise by increasing the gap between the membrane and the substrate, thereby minimizing squeeze-film damping and enhancing the performance of the electroacoustic transducer.
Implementation Method 1
Such a capacitive detection microphone may suffer from squeeze-film damping, which is caused by air being squeezed between the piston and the frame upon operating the microphone. Squeeze-film damping generates mechanical noise and leads to a decrease in microphone performance.
Data Source
AI summary
A method for manufacturing an electroacoustic transducer includes a frame; an element movable relative to the frame, the movable element including a membrane and a membrane rigidifying structure; a first transmission arm, the movable element being coupled to one end of the first transmission arm; in which method the membrane of the movable element is moved away from the frame by using a sacrificial layer of greater thickness at least at the periphery of the membrane.