Composite Diaphragm Stress Balancing for Acoustic Transducers
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Solution Overview
Problem
Microphone assemblies with diaphragms face challenges in controlling tensile stress, which affects sensitivity and is difficult to manage, especially at lower tension values, leading to poor process control and bowing issues in multilayered diaphragms.
Innovation Solution
The implementation of a diaphragm with an outer and inner portion having different stresses, where the outer portion extends radially from the inner portion to reduce overall tensile stress, thereby increasing compliance and reducing bowing without increasing fabrication complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a diaphragm is made with multilayered structure to control stress, then stress control is improved, but device complexity and fabrication difficulty increase
Solution Approach 1:
The diaphragm is segmented into two distinct portions: an inner portion with first stress characteristics and an outer portion with second stress characteristics. This segmentation allows independent stress optimization in each region without requiring multiple material layers, thereby controlling overall tensile stress while avoiding the complexity of multilayered structures.
Solution Approach 2:
Different portions of the diaphragm are assigned different stress properties: the inner portion has a first stress (tensile or compressive) and the outer portion has a second stress (different from the first). This local differentiation enables precise control of stress distribution across the diaphragm surface, improving sensitivity and compliance without increasing overall device complexity.
2Reliability
If diaphragm tension is reduced to increase sensitivity, then sensitivity is improved, but process control becomes difficult
Solution Approach 1:
The invention changes the stress parameter distribution across the diaphragm by creating an inner portion with a first stress and an outer portion with a second stress. This parameter differentiation allows the overall diaphragm tension to be reduced for improved sensitivity while the specific stress distribution maintains manufacturability and process control, as each portion can be independently optimized during fabrication.
3Stability of the object's composition
If diaphragm tension is reduced to increase compliance, then compliance is improved, but bowing issues occur
Solution Approach 1:
The inner and outer portions of the diaphragm are designed with opposing or balanced stress characteristics. The first stress in the inner portion counterbalances the second stress in the outer portion, creating a net reduction in overall tensile stress that increases compliance while preventing bowing. This stress balancing acts as a counterweight mechanism that eliminates shape distortion.
Data Source
AI summary
An acoustic transducer comprises a transducer substrate defining an aperture therein. A diaphragm is disposed on the transducer substrate. The diaphragm comprises a diaphragm inner portion disposed over the aperture such that an outer edge of the diaphragm inner portion is located radially inwards of a rim of the aperture, the diaphragm inner portion having a first stress. A diaphragm outer portion extends radially from the outer edge of the diaphragm inner portion to at least the rim of the aperture, the diaphragm outer portion having a second stress different from the first stress.