RF Insensitive MEMS Microphone Package Design
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Solution Overview
Problem
Conventional MEMS microphone packages are susceptible to RF interference, requiring metal caps for protection which can introduce additional design complexities and limitations.
Innovation Solution
An RF insensitive MEMS microphone chip design that includes a conductive base, a perforated shielding layer, a diaphragm, and a back plate, along with a radio frequency attenuation circuit and a shielding cage, which filters out RF interference without the need for a metal cap, using a non-conductive substrate and cover made of materials like copper clad laminate, ceramic, or plastic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal cap is used to shield the MEMS microphone from RF interference, then RF protection is improved, but device complexity and design limitations increase
Solution Approach 1:
The patent implements a nested shielding structure where an inner shielding layer is placed within the MEMS microphone package, surrounded by an outer shielding layer. This multi-layer nested configuration provides enhanced RF protection without requiring a bulky metal cap, thereby improving reliability while controlling device complexity
Solution Approach 2:
The patent transitions from a traditional external metal cap shielding approach to an integrated multi-layer shielding structure embedded within the package dimensions. By adding shielding layers in the vertical dimension (between the diaphragm and backplate), the patent achieves RF protection without increasing the horizontal footprint or requiring a separate metal cap component
2Reliability
If a metal cap is used for RF shielding, then protection from external factors is improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges the RF shielding function with the existing package structure by integrating shielding layers into the microphone assembly. The inner and outer shielding layers are combined with the diaphragm, backplate, and housing components, eliminating the need for a separate metal cap manufacturing process and simplifying overall manufacturing
Solution Approach 2:
The shielding layers serve multiple functions simultaneously: they provide RF interference protection, act as structural components within the package, and contribute to the overall sealing and protection from external factors. This multi-functionality reduces the need for separate dedicated shielding components, easing manufacturing
3Reliability
If shielding layers are added to the MEMS microphone package, then RF interference protection is improved, but device dimensions increase
Solution Approach 1:
The patent applies shielding selectively in the regions where RF interference is most problematic, specifically placing the inner shielding layer between the diaphragm and backplate where the sensing capacitor is located. This localized shielding approach provides effective RF protection without adding shielding material throughout the entire package volume, thereby controlling the increase in device dimensions
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 effectively shields the MEMS microphone from RF interference while allowing sound to pass through, providing protection from external factors like light, particles, and mechanical damage without the need for a metal cap, enhancing the package's robustness and functionality.
Implementation Method 1
The shielding layer is supported by the conductive base and connected to a constant voltage. The diaphragm is disposed between the conductive base and the shielding layer.
Implementation Method 2
The diaphragm and the back plate form a capacitor and the capacitance thereof is inverse proportional to the space between the diaphragm and the back plate.
Implementation Method 3
The radio frequency attenuation circuit filters the signal.
Data Source
AI summary
A micro-electro-mechanical-system microphone package includes a substrate, a micro-electro-mechanical-system microphone chip mounted on the substrate, and a cover attached to the substrate to cover the micro-electro-mechanical-system microphone chip. The cover is provided with a sound inlet through which the micro-electro-mechanical-system microphone receives external sound. The micro-electro-mechanical-system microphone chip includes a conductive base connected to a constant voltage, a shielding layer supported by the conductive base and connected to the constant voltage, a diaphragm disposed between the conductive base and the shielding layer, and a back plate also disposed between the conductive base and the shielding layer.