Bone Conduction MEMS Package with Low-Pressure Cavity Damping Control
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Solution Overview
Problem
Existing bone conduction package structures are large in volume and exhibit poor performance due to high damping between the diaphragm and backplate, limiting their effectiveness in noisy environments.
Innovation Solution
A bone conduction package structure with a diaphragm and backplate that form sealed cavities as low-pressure areas, incorporating ventilation holes for reduced damping and improved performance, and eliminating the need for additional vibration plates and weights.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional bone conduction package structure with vibration plate, frame, and weight is used, then the device can detect bone vibrations, but the volume becomes large and performance deteriorates due to high damping
Solution Approach 1:
The patent merges the vibration detection function directly into the MEMS chip structure by integrating the diaphragm, backplate, and cavity system onto the substrate. This eliminates the need for separate vibration plates, frames, and weights, thereby reducing overall package volume while maintaining detection capability. The MEMS chip itself becomes the vibration sensing element, combining multiple functions into a single integrated component.
Solution Approach 2:
The patent replaces the traditional mechanical vibration transmission system (vibration plate connected to circuit board via frame) with a direct MEMS-based acoustic pressure detection system. Instead of mechanically coupling the vibration source to the sensor through rigid structures, the system uses acoustic pressure changes in the sealed cavity to transmit vibration information to the MEMS diaphragm, reducing mechanical damping and package size.
2Volume of stationary object
If the diaphragm and backplate are placed close together in a traditional structure, then the device size is reduced, but damping between the diaphragm and backplate increases causing poor performance
Solution Approach 1:
The patent creates a localized low-pressure environment within the sealed cavity between the diaphragm and backplate. By controlling the pressure characteristics in this specific local region, the system reduces damping effects between the diaphragm and backplate while maintaining a compact MEMS chip structure. The pressure gradient and acoustic impedance in the cavity are optimized to enhance vibration detection sensitivity despite the close proximity of the diaphragm and backplate.
Solution Approach 2:
The patent changes the physical parameters of the cavity environment by establishing a controlled pressure differential between the first cavity (low pressure) and the second cavity (atmospheric pressure). This parameter change in the gas pressure within the sealed cavity modifies the acoustic impedance and reduces damping between the diaphragm and backplate, enabling high sensitivity vibration detection in a compact structure.
3Reliability
If ventilation holes are added to equalize pressure between cavities, then the damping is reduced, but the structural complexity increases
Solution Approach 1:
The patent segments the internal volume into two distinct pressure zones: a first cavity (low pressure) and a second cavity (atmospheric pressure), separated by the diaphragm. Ventilation holes are selectively positioned to control pressure equalization between these segmented regions. This segmentation allows the system to reduce damping through controlled pressure equalization while maintaining a relatively simple overall structure by using the existing diaphragm and backplate as cavity boundaries.
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 structure achieves a smaller form factor with enhanced sensitivity and performance by reducing damping between the diaphragm and backplate, allowing for better noise isolation and improved sound quality in noisy conditions.
Implementation Method 1
A first cavity is formed between the diaphragm and the backplate... The first cavity is set as a low-pressure area below atmospheric pressure
Data Source
AI summary
The present invention provides a bone conduction package structure including a base board, a housing covered with the base board to form a receiving room, a bone conduction MEMS chip and an ASIC chip located in the receiving room. The bone conduction MEMS chip includes a substrate, a diaphragm, and a backplate. A first cavity is formed between the diaphragm and the backplate. A second cavity is formed by the diaphragm, the substrate, and the base board. And a third cavity is formed by the backplate, the housing, the substrate, and the base board. The first cavity is set as a low-pressure area below atmospheric pressure. The bone conduction package structure of the present invention sets the area between the diaphragm and the backplate as a low-pressure area to reduce damping between the diaphragm and backplate, thereby improving the performance of the bone conduction package structure.