Acoustic Sensor Back Plate Stoppers Prevent Film Damage
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Solution Overview
Problem
Capacitive transducers in acoustic sensors, manufactured using MEMS technology, are prone to deformation and damage due to excessive pressure, leading to increased internal pressure in the sensor casing, which can cause further damage to the vibration electrode film.
Innovation Solution
The implementation of projections or walls on the back plate to enclose sound holes, preventing air from passing through and thereby suppressing the increase in internal pressure, and the use of a wall or projection in the vibration electrode film to block air flow, ensuring the vibration electrode film does not come into contact with the back plate or substrate, thus preventing deformation and damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If compressed air flows through the pressure hole into the capacitive transducer, then the vibration electrode film is greatly deformed to the back plate side, but the vibration electrode film may be damaged by coming into contact with the back plate or substrate
Solution Approach 1:
The patent applies preliminary anti-action by providing stoppers that protrude from the back plate toward the vibration electrode film before excessive pressure can cause damage. These stoppers create a physical barrier that prevents the vibration electrode film from contacting the back plate or substrate during pressure equalization, thereby preventing damage before it occurs
Solution Approach 2:
The stoppers act as an intermediary element between the vibration electrode film and the back plate/substrate. During pressure equalization when air flows through the pressure hole, the stoppers mediate the interaction by providing a controlled stopping point that prevents direct contact between the deformed film and the rigid back plate or substrate surfaces
2Reliability
If the vibration electrode film is mechanically suppressed to prevent deformation, then damage due to excessive deformation is prevented, but stress concentrates on a part of the diaphragm due to contact between the diaphragm and deformation suppressing member
Solution Approach 1:
The patent segments the suppression function by providing multiple stoppers distributed across the back plate surface rather than a single continuous barrier. This segmentation allows the vibration electrode film to make contact with multiple discrete points rather than a large continuous area, distributing the stress more evenly across the film structure and preventing stress concentration at any single location
Solution Approach 2:
The stoppers are designed with specific local properties - they protrude only to a controlled height that provides suppression without excessive contact. The local quality of each stopper is optimized to provide just enough mechanical support to prevent damage while minimizing stress concentration, creating different functional zones across the back plate surface
3Reliability
If a support structure is disposed on the substrate side in the diaphragm to prevent collision, then damage due to excessive pressure is prevented, but the structure becomes complicated causing deterioration in productivity and increase in manufacturing cost
Solution Approach 1:
The patent merges the support function into the existing back plate structure by integrating stoppers that protrude from the back plate itself, rather than adding a separate support structure on the substrate side. This merging combines the back plate's structural role with the additional function of providing mechanical suppression, thereby preventing collision without increasing overall device complexity or manufacturing steps
Solution Approach 2:
The back plate is given multiple functions: it serves as both the structural base of the capacitive transducer and as the source of mechanical suppression through its protruding stoppers. This multi-functionality eliminates the need for separate support structures, maintaining simplicity in the overall device design while providing the necessary collision prevention functionality
4Volume of moving object
If the thickness of the transducer is reduced to achieve small size, then the vibration electrode film is liable to be greatly deformed and damaged when excessive pressure acts thereon
Solution Approach 1:
The patent applies beforehand cushioning by positioning stoppers that protrude from the back plate toward the vibration electrode film before excessive pressure can cause damage. These stoppers create a cushioning effect by providing a physical barrier that limits the maximum deformation of the thin film during pressure events, protecting the film from damage despite the reduced transducer thickness
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
Effectively prevents excessive deformation and damage to the vibration electrode film by blocking air flow and reducing internal pressure in the sensor casing, enhancing the durability and reliability of the acoustic sensor.
Implementation Method 1
a capacitive transducer housed in a casing, the capacitive transducer being configured in a capacitor structure formed by the MEMS technique and including a vibration electrode film and a back plate
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
Provided is a technique by which, when excessive pressure acts on an acoustic sensor, an increase in pressure in a casing is prevented to suppress excessive transformation of a vibration electrode film caused by the increased pressure. An acoustic sensor is provided with: a substrate; a back plate having sound holes that allow passage of air; a vibration electrode film disposed so as to face the back plate; and a package configured to house the substrate, the back plate, and the vibration electrode film, and having a pressure hole that allows inflow of air. The acoustic sensor is further provided with a projection configured to block a flow path for air (inhibit a flow of air) that passes through a gap between the vibration electrode film and the back plate, and a sound hole, when the vibration electrode film is transformed to come close to the back plate.