MEMS Microphone Package Ingress Protection via Internal Shield
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Solution Overview
Problem
Conventional MEMS microphones face challenges in effectively protecting the MEMS microphone die and ASIC from environmental contaminants, electromagnetic interference, and physical damage, while maintaining proper acoustic operation.
Innovation Solution
The implementation of a surface-mount package with an acoustic port featuring a flange or extension in the cover, combined with an internal shield or shallow cavity, to limit the entry of contaminants and provide electromagnetic interference suppression, while allowing acoustic energy to reach the MEMS microphone die.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an acoustic port is provided in the cover to allow acoustic energy to reach the MEMS microphone die, then acoustic operation is enabled, but environmental contaminants can enter the acoustic chamber and damage the MEMS microphone die or ASIC
Solution Approach 1:
An internal shield is introduced as an intermediary component within the acoustic chamber. This shield acts as a mediator that blocks contaminants from reaching the MEMS microphone die and ASIC while allowing acoustic energy to pass through to the diaphragm, thus resolving the contradiction between enabling acoustic operation and preventing contaminant infiltration.
Solution Approach 2:
The acoustic chamber is segmented into different zones by the internal shield. The shield divides the chamber such that the acoustic port opens into a first volume where contaminants are trapped, while a second volume contains the MEMS microphone die and ASIC. This segmentation allows acoustic energy to reach the diaphragm while preventing contaminant access to sensitive components.
2Use of energy by moving object
If the acoustic port is opened directly to the acoustic chamber, then acoustic energy can reach the MEMS microphone die, but dust and particles can intrude into the acoustic chamber
Solution Approach 1:
The internal shield serves as a mediator structure that intercepts dust and particles before they can reach the MEMS microphone die and ASIC. The shield's positioning and design allow it to block particulate matter while maintaining acoustic energy transmission to the diaphragm, thus resolving the contradiction between acoustic energy transmission and particle intrusion prevention.
3Reliability
If a shield or formed member is added to the acoustic port to prevent contaminant entry, then protection is improved, but the structure becomes more complex
Solution Approach 1:
The internal shield is merged with the cover assembly, integrating the protective function into the existing package structure. This merging approach provides contaminant protection while minimizing additional structural complexity, as the shield becomes part of the cover rather than a completely separate component.
Data Source
AI summary
A surface-mountable MEMS microphone comprising a MEMS microphone die and an application-specific integrated circuit (ASIC) mounted inside a surface-mountable package housing, and fully enclosed therein. The surface-mountable package is a single, self-contained housing that provides an electrical interface to external circuitry for the enclosed MEMS microphone die and the ASIC, and provides electrical, physical, and environmental protection for the MEMS microphone die and the ASIC. The surface-mountable package allows external acoustic energy to enter the package interior via one or more acoustic ports and impinge on the diaphragm of the MEMS microphone die. The cover of the surface-mountable package comprises an acoustic port with ingress protection to limit dust and particle intrusion. The ingress protection can be a formed member that is part of the cover of the surface-mountable package having various shapes, an internal shield, or a combination of both a formed member and internal shield.