Electroacoustic Transducer Gap Structure for Low Squeeze-Film Damping
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Solution Overview
Problem
Capacitive sensing microphones suffer from damping phenomena known as 'squeeze-film damping' due to air pinched between the piston and the frame, leading to mechanical noise and decreased performance.
Innovation Solution
A manufacturing process that includes forming a first sacrificial layer with varying thickness to create a larger gap between the substrate and the membrane, reducing squeeze-film damping by increasing the distance between the membrane and the frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the gap between the membrane and substrate is reduced to minimize device size, then the device dimensions are reduced, but squeeze-film damping increases causing mechanical noise and performance degradation
Solution Approach 1:
The sacrificial layer is designed with non-uniform thickness, being thicker at the periphery than at the center. This local variation in thickness creates a larger gap between the membrane and substrate at the peripheral region, specifically targeting the area where squeeze-film damping occurs most intensely, thereby reducing mechanical noise without compromising overall device miniaturization
Solution Approach 2:
The invention changes the geometric parameter of the sacrificial layer thickness from a uniform value to a gradient distribution. By controlling the thickness parameter to increase toward the periphery, the design optimizes the gap distance to minimize viscous friction effects while maintaining compact device dimensions
2Ease of manufacture
If a uniform thickness sacrificial layer is used, then the manufacturing process is simpler, but the squeeze-film damping effect is not sufficiently reduced
Solution Approach 1:
The sacrificial layer incorporates spatially varying thickness with a gradient from center to periphery. This local differentiation in thickness allows the peripheral regions to have enhanced gap distance for damping reduction, while the manufacturing process remains relatively simple by using standard deposition techniques followed by selective removal
3Object-generated harmful factors
If the gap between membrane and frame is increased to reduce damping, then mechanical noise is reduced, but the device size increases
Solution Approach 1:
The gap increase is localized to the peripheral region where the sacrificial layer is thickest, specifically targeting the area most affected by squeeze-film damping. The central region maintains a smaller gap, allowing the device to remain compact while still achieving noise reduction through the strategically enlarged peripheral gap
Solution Approach 2:
The solution addresses the gap dimension non-uniformly by introducing radial variation in the vertical dimension. Instead of a uniform gap increase throughout, the gap is selectively enlarged in the peripheral radial zone, effectively using dimensional variation to reduce damping without proportional increase in overall device volume
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 solution effectively reduces mechanical noise and improves microphone performance by minimizing squeeze-film damping, enhancing the overall operational efficiency of the electroacoustic transducer.
Implementation Method 1
Capacitive sensing microphones suffer from damping phenomena known as 'squeeze-film damping' due to air pinched between the piston and the frame
Data Source
Figure 1~2B
Figure 2C~2E
Figure 2F~2H
AI summary
The invention relates to a method for manufacturing an electroacoustic transducer (1) comprising: - a frame; - a movable element (13) relative to the frame, the movable element (13) comprising a membrane (131) and a membrane stiffening structure (132); - a first transmission arm, the movable element (13) being coupled to one end of the first transmission arm; method in which the membrane (131) of the movable element (13) is moved away from the frame by using a sacrificial layer (22) of greater thickness at least at the periphery of the membrane.