Slit Membrane MEMS Acoustic Transducer for Low-Frequency SPL
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Solution Overview
Problem
Existing microelectromechanical electroacoustic transducers face challenges in achieving a balance between miniaturization, sound pressure level, and cost, with issues such as membrane stiffness limiting displacement, especially at low frequencies, and process variability affecting sound quality and symmetry.
Innovation Solution
A microelectromechanical electroacoustic transducer design featuring a symmetric semiconductor membrane with central connection portions and strategically placed slits, combined with piezoelectric actuators, enhances displacement and sound pressure while maintaining structural integrity and symmetry, compatible with SMT processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a continuous semiconductor membrane is used to maintain structural integrity, then manufacturing consistency is improved, but displacement capability deteriorates due to membrane stiffness especially at low frequencies
Solution Approach 1:
The membrane is divided into multiple segments by introducing radial slits that extend from the center toward the perimeter. This segmentation allows each segment to move independently with greater displacement capability while the overall membrane structure remains intact and manufacturable using standard processes
Solution Approach 2:
The membrane structure is made non-uniform by creating a central connection portion with different properties than the peripheral portions. The central area maintains continuity for manufacturing consistency while the peripheral segments gain enhanced displacement capability through the slits
2Volume of moving object
If the membrane area is reduced for miniaturization, then device size is reduced, but sound pressure level deteriorates because sound pressure is proportional to the product of area and displacement
Solution Approach 1:
By segmenting the membrane through radial slits, the patent enables greater displacement of each segment. This compensates for the reduced area in miniaturized devices, maintaining the area-displacement product and thus the sound pressure level despite the smaller overall size
Solution Approach 2:
The patent changes the mechanical parameters of the membrane by introducing slits that increase displacement capability. This allows the membrane to achieve greater amplitude of vibration, compensating for the reduced area and maintaining acoustic output in miniaturized devices
3Length of moving object
If cantilever structures are used to increase displacement and yielding, then response dynamics are improved, but process variability affects sound quality because even small differences cause uneven movements and dissymmetry
Solution Approach 1:
The patent uses symmetric radial slits arranged evenly around the center, creating a balanced structure where opposing segments move in mirror fashion. This symmetry compensates for process variations by ensuring that deviations affect opposing segments equally, maintaining overall balance and reducing dissymmetry in sound emission
Solution Approach 2:
The membrane segments are made from the same continuous semiconductor material with uniform properties, ensuring consistent mechanical behavior across all segments. This homogeneity reduces the impact of process spread by minimizing material property variations between segments
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 design achieves high sound pressure levels, especially at low frequencies, with improved manufacturing consistency and reduced defects, enabling high-performance miniaturized audio reproduction.
Implementation Method 1
a piezoelectric actuator arranged on a peripheral portion of the membrane
Data Source
Figure 1~2
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Figure 6~7
AI summary
A microelectromechanical electroacoustic transducer includes a supporting frame (12) of semiconductor material, a membrane (13) of semiconductor material, connected to the supporting frame (12) along a perimeter and having central symmetry, and a piezoelectric actuator (15) on a peripheral portion of the membrane (13). The membrane (13) has through slits (17, 18) of elongated shape arranged around a center of the membrane (13).