MEMS Microphone RF Shielding via Perimeter Vias and Ground Ring
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Solution Overview
Problem
MEMS microphone packages face interference from Electro-Magnetic Interference (EMI) and Radio Frequency (RF) due to the sound opening, which allows noise and external conditions to affect the device's operation, as existing RF shielding methods primarily focus on top surface protection, leaving the bottom surface uncovered.
Innovation Solution
A semiconductor package with a substrate featuring a sound opening surrounded by a first RF shield formed by vias and a metal can grounded through a ground ring, providing effective shielding around the perimeter and within the opening to reduce EMI/RF interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a sound opening is formed in the substrate to allow the microphone to receive sound waves, then the microphone can properly receive sound waves, but noise and external conditions can enter the device and interfere with operation
Solution Approach 1:
The patent applies local quality by creating an RF shield specifically around the sound opening area rather than covering the entire substrate. The shield is positioned locally where interference occurs (around the opening) while leaving the sound reception path clear. This localized shielding approach blocks RF noise from entering through the opening while maintaining acoustic transparency for valid sound signals.
Solution Approach 2:
The RF shield acts as an intermediary element between the external environment and the microphone device. It mediates by selectively blocking harmful RF noise while allowing acoustic waves to pass through to the microphone, thus protecting the device without compromising its primary function.
2Ease of manufacture
If conventional shielding methods are used, then top surface RF shielding is achieved, but comprehensive shielding around the sound opening is not provided
Solution Approach 1:
The patent merges the RF shield with the ground ring structure, combining two elements into a unified perimeter shield. The RF shield is attached to the ground ring, creating an integrated shielding system that provides both structural support and electromagnetic protection. This merged design simplifies manufacturing while ensuring reliable, comprehensive shielding around the sound opening.
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 reduces noise and RF energy interference, ensuring the proper operation of the MEMS microphone by creating a comprehensive RF shield around the sound opening, enhancing the overall shielding effectiveness of the package.
Implementation Method 1
A first RF shield is formed around a perimeter of the opening... A ground ring is formed around a perimeter of the opening... providing effective shielding around the perimeter and within the opening to reduce EMI/RF interference
Implementation Method 2
A first die is attached to the first surface of the substrate and positioned over the opening... providing effective shielding around the perimeter and within the opening to reduce EMI/RF interference
Data Source
AI summary
A semiconductor package has a substrate. An opening is formed through the substrate. A first RF shield is formed around a perimeter of the opening. A first die is attached to the first surface of the substrate and positioned over the opening.