Capacitive Sensor Side-Acoustic Channel for Compact MEMS Design
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Solution Overview
Problem
Conventional acoustic sensors face challenges in miniaturization due to large acoustic channel volumes and difficulties in fabricating metal covers with acoustic ports, leading to poor product yield and limited size reduction.
Innovation Solution
A capacitive sensor design featuring channels within a carrier and conductive bumps connecting the capacitive sensing element, allowing external waves to be transmitted without increasing the sensor's volume, and enabling directional sensing by varying channel lengths or using mechanical screens, with the option of forming channels or holes in the carrier or cover.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an acoustic channel is reserved in the cover to transmit sound waves to the MEMS microphone, then sound quality is improved, but the volume of the acoustic sensor becomes too large to be disposed into electronic products with limited inner space
Solution Approach 1:
The acoustic channel is repositioned from the cover (top surface) to the side surface of the sensor package. This dimensional change allows the acoustic channel to be formed in a direction perpendicular to the main sensing element, reducing the height requirement while maintaining acoustic transmission functionality. The side surface placement enables the acoustic channel to extend laterally rather than vertically, thus reducing overall sensor volume.
Solution Approach 2:
The acoustic channel is integrated within the existing sensor package structure by forming it in the side surface of the cover or package body. The acoustic channel path is nested within the lateral dimensions of the package rather than extending the height, allowing sound wave transmission without increasing the vertical profile of the sensor.
2Volume of stationary object
If the acoustic port is formed in a side surface of the metal cover, then the sensor volume is reduced, but the size of the acoustic port is limited by the height of the metal cover
Solution Approach 1:
The acoustic transmission function is segmented into multiple pathways: the acoustic port in the side surface provides primary sound entry, while the acoustic channel extends internally to reach the MEMS microphone. This segmentation allows the acoustic port area to be small (limited by side surface dimensions) while the internal channel provides the necessary transmission path length, separating the functions of sound entry and sound transmission.
3Measurement precision
If the acoustic port is disposed at the top of the metal cover, then sound waves can reach the MEMS microphone effectively, but the adsorption range of the packaging machine covers the acoustic port, damaging the membrane and resulting in poor product yield
Solution Approach 1:
The acoustic port function is extracted from the top surface of the cover and relocated to the side surface. This extraction removes the conflict between the acoustic port position and the packaging machine's adsorption range. The side surface placement ensures that the top surface remains clear for machine adsorption while the acoustic port on the side surface continues to allow effective sound wave transmission to the MEMS microphone through the lateral acoustic channel.
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
Enables the creation of a compact, directional capacitive sensor with improved process yield and suitability for light and thin electronic products, maintaining high signal quality while preventing dust contamination.
Implementation Method 1
a capacitive sensor... a capacitive sensing element disposed on the carrier... The capacitive sensing element has a membrane
Data Source
AI summary
A sensor including a carrier, a plurality of conductive bumps, a capacitive sensing element connected to the carrier through the conductive bumps, and a cover is provided. The capacitive sensing element has a membrane, and a channel is formed among the capacitive sensing element, the conductive bumps, and the carrier. The cover is disposed on the carrier for covering the capacitive sensing element. A chamber is formed between the capacitive sensing element and the cover. The chamber and the channel are respectively located at two sides of the membrane.