Top Port Microphone Enlarged Back Volume
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Solution Overview
Problem
Existing microphone designs face challenges in enhancing the back volume while maintaining manufacturing ease and avoiding mechanical stress on sensitive MEMS chips, often resulting in compromised audio frequency performance and increased costs due to complex sound guiding mechanisms and size constraints.
Innovation Solution
The solution involves mounting MEMS and ASIC components on a substrate with a lid that encloses a volume, using a seal to separate partial volumes and a stopper to enhance the back volume by adding a lateral volume extension, allowing independent adjustment of front and back volumes and minimizing mechanical stress with a soft resin stopper.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If a top port microphone design is used to provide a sufficiently big back volume, then the back volume is enlarged, but electrical rewiring is necessary which increases manufacturing complexity and technical effort
Solution Approach 1:
The internal volume is segmented into a front volume and a back volume using a seal that extends from the MEMS chip to the substrate. This segmentation allows the back volume to be enlarged without requiring electrical rewiring, as the standard bottom-side component mounting is maintained.
Solution Approach 2:
The seal is extended in a lateral direction beyond the MEMS chip to define the back volume boundary. This lateral extension of the seal creates additional back volume without altering the electrical connection architecture or requiring rewiring.
2Ease of manufacture
If all internal components are mounted on the substrate with sound guided through a gap between components and substrate, then manufacturing is simplified, but the back volume cannot be enhanced
Solution Approach 1:
The seal is extended laterally beyond the MEMS chip footprint to create an enlarged back volume. This lateral extension in the horizontal dimension allows back volume enhancement while maintaining the simple manufacturing approach of guiding sound through the gap between components and substrate.
Solution Approach 2:
The seal extension segments the internal volume into distinct front and back volumes, allowing independent control of back volume size while preserving the straightforward manufacturing process.
3Ease of manufacture
If the MEMS chip is braced between substrate and lid, then manufacturing is simplified without rerouting, but the MEMS chip suffers from mechanical stress and tolerances
Solution Approach 1:
The harmful mechanical stress and tolerance issues are extracted from the MEMS chip by eliminating the bracing arrangement. Instead of bracing the MEMS chip between substrate and lid, the invention allows the chip to be mounted on the substrate with a seal extending from it, removing the compressive stress while maintaining manufacturing simplicity.
4Ease of operation
If a complex sound guiding mechanism is used to guide sound from sound port to bottom of membrane, then sound guidance is achieved, but costs increase and package size reduction is prevented
Solution Approach 1:
The gap between the MEMS chip and substrate serves its own dual function: it provides both the sound path for acoustic signal transmission and the boundary for defining the back volume. This self-service approach eliminates the need for separate complex sound guiding mechanisms while maintaining effective sound guidance.
Data Source
Figure 1a~2
Figure 3~5a
Figure 5b~6b
AI summary
A package for a top port microphone with an enlarged back volume comprises on a substrate a lid enclosing thereunder a total volume and accommodating a MEMS chip and an ASIC. A stopper seals the ASIC against the lid thereby separating and dividing the total volume under the lid in a volume extension and a remaining volume. The volume extension can be used to arbitrarily enlarge the back volume or the front volume dependent on a placement of a sound port to the volume extension or the remaining volume. A sound path connects the volume extension and a partial volume enclosed between MEMS chip and substrate.