Side-Ported MEMS Microphone Acoustic Path Design
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Solution Overview
Problem
Conventional MEMS microphone packages face challenges in achieving a low profile due to the height of the microphone package and daughter board, and side-ported designs often result in degraded audio quality due to the audio response characteristics of the chamber.
Innovation Solution
A side-ported MEMS microphone package is designed with a substrate that defines an acoustic path oriented parallel to the substrate surface, incorporating a hollow passage and aperture to acoustically couple the microphone die with the microphone port, allowing for a lower profile mounting and improved audio quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional MEMS microphone package is mounted on a daughter board to orient the aperture in line with the port, then the microphone can detect sound effectively, but the height of the structure increases and the device becomes thicker
Solution Approach 1:
The patent reorients the acoustic path from a vertical orientation (perpendicular to the substrate) to a horizontal orientation (parallel to the substrate surface). This dimensional change allows the microphone aperture to be aligned with side ports without requiring a daughter board, thereby reducing the overall height of the microphone structure while maintaining effective sound detection.
Solution Approach 2:
The patent integrates the acoustic path definition directly into the substrate structure itself, eliminating the need for a separate daughter board. The substrate simultaneously provides mechanical support, electrical connections, and acoustic guidance, merging multiple functions into a single component and reducing overall structure height.
2Length of moving object
If apertures are defined in the sides of package lids to achieve a low profile, then the device thickness is reduced, but manufacturing becomes difficult and expensive
Solution Approach 1:
Instead of defining apertures in the side of the package lid as in conventional designs, the patent inverts the approach by defining the acoustic path and aperture directly in the substrate. This inversion simplifies manufacturing because the substrate is already being processed for other purposes (mounting the microphone die, providing electrical connections), and the acoustic path can be defined using standard substrate fabrication techniques.
Solution Approach 2:
The substrate is designed to serve multiple functions simultaneously: providing mechanical support, establishing electrical connections through contact pads, and defining the acoustic path for sound propagation. This multi-functionality eliminates the need for specialized processing to create side apertures in the lid, as the acoustic function is integrated into the substrate fabrication process.
3Shape
If the acoustic path is oriented perpendicular to the substrate surface, then the structure maintains simple geometry, but the device cannot achieve a thin profile when mounted on the main circuit board
Solution Approach 1:
The patent transitions the acoustic path orientation from the vertical dimension (perpendicular to substrate) to the horizontal dimension (parallel to substrate surface). This allows the acoustic energy to propagate laterally through the substrate to reach side-mounted ports, enabling a thin device profile while maintaining an effective acoustic path.
Solution Approach 2:
The substrate structure is designed to be acoustically dynamic, allowing sound waves to propagate through the substrate material itself rather than requiring a rigid vertical chamber. The substrate's material properties and geometry are optimized to guide acoustic energy horizontally, enabling flexibility in port placement and device 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
The solution enables a thinner electronic device design while maintaining effective sound propagation to the microphone die, overcoming the height and audio quality issues of traditional designs.
Implementation Method 1
The substrate may at least partially define an acoustic path from outside the chamber to the microphone die
Data Source
AI summary
A side-ported MEMS microphone package defines an acoustic path from a side of the package substrate to a microphone die disposed within a chamber defined by the substrate and a lid attached to the substrate. Optionally or alternatively, a circuit board, to which the microphone package is mounted, may define an acoustic path from an edge of the circuit board to a location under the microphone package, adjacent a bottom port on the microphone package. In either case, the acoustic path may be a hollow passage through at least a portion of the substrate or the circuit board. The passage may be defined by holes, channels, notches, etc. defined in each of several layers of a laminated substrate or circuit board, or the passage may be defined by holes drilled, molded or otherwise formed in a solid or laminated substrate or circuit board.