Insulating Layer on Microphone Enclosure for Thermal Noise Reduction
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Solution Overview
Problem
Miniaturized MEMS microphone assemblies face noise issues due to thermal conduction from enclosures, which are prone to temperature changes from external RF signals and radiant heat, leading to increased acoustic noise.
Innovation Solution
An insulating layer is insert molded or over molded onto the enclosure to reduce heat transfer into the internal volume, with the layer not covering the portion of the sidewall that contacts the substrate, allowing for continuous contact and effective insulation while maintaining bonding integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If an insulating layer is applied to the entire enclosure including sidewalls, then thermal insulation is improved, but bonding integrity deteriorates due to interference with solder material flow
Solution Approach 1:
The insulating layer is selectively applied only to specific surfaces of the enclosure (bottom surface and top surface) while deliberately excluding the sidewalls. This local differentiation allows the insulating layer to provide thermal insulation where needed without interfering with the bonding process between the enclosure sidewalls and the substrate using solder material.
2Volume of moving object
If the enclosure is miniaturized, then device size is reduced, but noise from thermal conduction increases due to higher surface-to-volume ratio
Solution Approach 1:
The insulating layer is applied selectively to the bottom and top surfaces of the enclosure where thermal conduction paths exist, while leaving the sidewalls uncovered. This targeted approach provides effective thermal insulation to reduce noise from temperature changes without requiring complete coverage that would increase device size.
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 insulating layer significantly reduces thermal conduction and noise by providing superior thermal insulation and preventing solder material from damaging internal components, while simplifying manufacturing and reducing costs through direct molding and alignment.
Implementation Method 1
An insulating layer is insert molded or over molded onto the enclosure to reduce heat transfer into the internal volume
Data Source
AI summary
A microphone assembly comprises a substrate. An acoustic transducer is disposed on the substrate and configured to generate an electrical signal responsive to an acoustic signal. An integrated circuit is disposed on the substrate and electrically coupled to the acoustic transducer. An enclosure is disposed on the substrate, and comprises a main body, and a sidewall projecting axially from outer edges of the main body towards the substrate and contacting the substrate such that an internal volume is defined between the enclosure and the substrate. An insulating layer is insert molded on an inner surface of the enclosure, or over molded on an outer surface of the enclosure such that the insulating layer is not disposed on a portion of the sidewall proximate to the substrate.