MEMS Transducer Package with Conductive Substrate for RF Shielding
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Solution Overview
Problem
MEMS transducers, particularly capacitive microphones, face challenges in protecting circuitry from radio frequency interference (RFI) due to the lateral ingress of RF radiation through the side surfaces of traditional packaging configurations, which are not adequately shielded.
Innovation Solution
A substrate with a conductive layer and isolated conductive portions supported by an insulating moulding substance is used, combined with a conductive lid structure to form a package that provides a continuous ground enclosure, effectively shielding the transducer and circuitry from RF radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a traditional package configuration with separate PCB substrate and metal lid is used, then the structure is simple and easy to manufacture, but RF radiation can laterally ingress through the side surfaces, causing audible noise
Solution Approach 1:
The patent combines the PCB substrate and metal lid into a single integrated package substrate with a conductive layer. The conductive layer is formed directly on the PCB substrate, merging the electrical connection function of the PCB with the RF shielding function of the metal lid, thereby eliminating gaps and improving shielding effectiveness without significantly increasing structural complexity
Solution Approach 2:
The conductive layer serves multiple functions simultaneously: it provides RF shielding against lateral RF radiation ingress, serves as an electrical connection path for the MEMS transducer, and can function as a ground plane. This multi-functionality improves shielding effectiveness without adding separate components that would increase device complexity
2Object-affected harmful factors
If a metal lid structure is added to provide RF shielding, then protection against RF radiation is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent replaces the mechanical metal lid structure with a conductive layer formed by deposition processes directly on the PCB substrate. This substitution eliminates the need for separate metal lid manufacturing, assembly, and mechanical fastening, thereby maintaining RF shielding effectiveness while significantly improving ease of manufacture through standard semiconductor fabrication processes
Solution Approach 2:
The patent changes the physical state and form of the shielding material from a separate metal component to a thin conductive layer deposited on the substrate. This parameter change allows the shielding function to be integrated into the substrate fabrication process, improving ease of manufacture while maintaining effective RF radiation protection
3Object-affected harmful factors
If the conductive layer is made continuous to improve shielding, then RF radiation protection is enhanced, but the electrical isolation requirements become more complex
Solution Approach 1:
The patent applies local quality by making the conductive layer continuous in regions where RF shielding is needed while providing local breaks or isolations where electrical separation is required. The conductive layer can be selectively connected or isolated in different areas of the substrate, allowing simultaneous achievement of continuous shielding and proper electrical isolation without increasing overall device complexity
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 provides enhanced protection against RF radiation, reducing audible noise and improving the overall performance of MEMS transducers by creating a more comprehensive metal shield that encapsulates the package, thereby alleviating issues related to lateral RF ingress.
Implementation Method 1
A substrate with a conductive layer and isolated conductive portions supported by an insulating moulding substance is used, combined with a conductive lid structure to form a package that provides a continuous ground enclosure, effectively shielding the transducer and circuitry from RF radiation
Data Source
AI summary
The Application describes a substrate design for a MEMS transducer package. The substrate is defined by a conductive layer which forms the upper and lower surfaces of the substrate. The substrate is also provided with a conductive portion which is electrically isolated from the rest of the conductive layer. The conductive portion is supported between a first plane defined by the upper surface of the substrate and a second plane defined by the lower surface of the substrate by an electrically insulating moulding substance.