MEMS Microphone Embedded in PCB Borehole for Height Reduction
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Solution Overview
Problem
Existing microphone designs for mobile communications devices are limited in miniaturization due to the height of the MEMS chip, which restricts the overall thickness of the printed-circuit board when mounted.
Innovation Solution
A microphone design where the electro-acoustic transducer is embedded within a borehole in the printed-circuit board, with a cap providing electromagnetic shielding and a carrier substrate that holds the MEMS chip, reducing the total height by utilizing the board's thickness, and allowing additional electrical components to be integrated for enhanced functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the MEMS chip is mounted on the surface of the printed-circuit board, then the microphone function is achieved, but the total structural height is increased
Solution Approach 1:
The electro-acoustic transducer is nested within a borehole in the printed-circuit board, with the carrier substrate and cap forming a nested structure that utilizes the board's thickness to house the MEMS chip, thereby reducing the overall height of the assembly
Solution Approach 2:
The design transitions from surface mounting to through-hole embedding, utilizing the vertical dimension of the printed-circuit board thickness to accommodate the transducer, effectively moving the component from a two-dimensional surface to a three-dimensional space within the board
2Length of stationary object
If the electro-acoustic transducer is embedded in the printed-circuit board, then the total height is reduced, but electromagnetic shielding is compromised
Solution Approach 1:
A cap with metallic layers is introduced as an intermediary element that provides electromagnetic shielding for the embedded transducer, while allowing the overall height to remain compact by utilizing the space within the carrier substrate and cap assembly
Solution Approach 2:
The cap is constructed with composite material structure, combining non-metallic carrier material with metallic coating layers, providing both electromagnetic shielding functionality and mechanical protection while maintaining a compact form factor
3Adaptability or versatility
If additional electrical components are integrated on the carrier substrate, then functionality is enhanced, but device complexity increases
Solution Approach 1:
Additional electrical components such as impedance transducers, amplifiers, and ESD protective components are merged onto the same carrier substrate as the electro-acoustic transducer, creating an integrated module that enhances functionality while maintaining a compact single-substrate design
Solution Approach 2:
The carrier substrate serves multiple functions: it provides mechanical support for the transducer, electrical connections through contact surfaces, mounting for additional components, and structural integration with the printed-circuit board, thereby reducing the need for separate components and assemblies
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
This design minimizes the total height of the microphone assembly, enabling it to be mounted on the back side of the printed-circuit board, reducing the overall structural height and allowing for additional components like impedance transducers and amplifiers to be integrated, while maintaining effective electromagnetic shielding.
Implementation Method 1
The cap has at least one metallic layer for the electromagnetic shielding of the electro-acoustic transducer
Implementation Method 2
capacitive transducers in particular
Implementation Method 3
those operating especially on the piezoelectric principle
Data Source
AI summary
A microphone in a miniaturized form is described herein. The microphone includes a flat carrier substrate having a first recess extending through the carrier substrate. The microphone includes a first electro-acoustic transducer on a first surface of the carrier substrate and at least partially overlapping the first recess. The microphone also includes a cap on a second surface opposite the first surface having a tight seal with the second surface and spanning the first recess. The cap includes at least one metallic layer for electromagnetic shielding.