PCB Vibration Attenuation for Microphone Noise Isolation

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Solution Overview

Problem

Microphones mounted on printed circuit boards (PCBs) in electronic devices, such as mobile phones, pick up noise and vibration from the device housing, leading to acoustic coupling issues that affect reliability, cost, manufacturability, and packaging.

Innovation Solution

A vibration attenuation system is implemented on the PCB, featuring apertures or perforations that reduce acoustic coupling by breaking the sound wave path between different PCB portions, and the use of shock-absorbing materials to isolate vibrations, allowing for improved microphone placement and reduced noise interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the microphone is mounted directly on the PCB, then the device complexity and manufacturing cost are reduced, but the microphone picks up noise and vibration from the housing leading to poor reliability

Engineering Contradiction:

Improvemicrophone mounting structureVSAvoidmicrophone noise pickup

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The PCB is divided into two separate portions with a vibration attenuation portion positioned between them. This segmentation creates physical separation to isolate the microphone from vibrations originating from the housing, reducing noise pickup while maintaining direct mounting on the PCB.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A vibration attenuation portion is introduced as an intermediary element between the first PCB portion (where vibrations originate) and the second PCB portion (where the microphone is mounted). This intermediary structure blocks vibration transmission while allowing electrical connections to pass through.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If a separate daughter PCB with flex circuit is used to isolate the microphone, then reliability and noise reduction are improved, but device size, manufacturing complexity, and cost increase

Engineering Contradiction:

Improvemicrophone noise isolationVSAvoiddevice size

Core Design Contradiction:

ReliabilityVSVolume of moving object

Solution Approach 1:

The vibration attenuation structure is merged directly into the PCB substrate rather than being a separate component. The PCB serves dual functions as both the structural support and the vibration isolation medium, eliminating the need for separate daughter PCBs and flex circuits.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The PCB is designed to perform multiple functions simultaneously: providing structural support, enabling electrical connections, and acting as a vibration isolation barrier. This multi-functionality consolidates what would traditionally require separate components into a single integrated structure.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If vibration attenuation structures are added to the PCB, then acoustic coupling is reduced, but manufacturing precision requirements and device complexity increase

Engineering Contradiction:

Improveacoustic coupling reductionVSAvoidPCB structure precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The vibration attenuation portion is implemented using a porous or perforated structure that allows sound waves to be dissipated while maintaining mechanical integrity. This approach provides effective vibration isolation without requiring high-precision manufacturing, as the porous structure can be created using standard PCB fabrication techniques.

Inventive Principle:

Principle #31Porous materials

Solution Approach 2:

The vibration attenuation is achieved by changing the physical parameters of the PCB structure (adding perforations, changing material density, or modifying layer composition) rather than requiring precise positioning or complex geometries. This allows effective vibration isolation to be achieved through material and structural parameter adjustments that are compatible with standard manufacturing processes.

Inventive Principle:

Principle #35Parameter changes

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

This solution effectively reduces acoustic coupling and vibrations, enhancing the reliability and manufacturability of microphone placement on PCBs while minimizing noise interference, thus improving the overall performance and cost-effectiveness of electronic devices.

Implementation Method 1

a vibration attenuation portion 504 configured to attenuate vibrations from a first portion 506 of the printed circuit board 502 to a second portion 508

Methodology Applied

Scientific EffectVibration attenuation: Damping

Implementation Method 2

apertures or perforations that reduce acoustic coupling by breaking the sound wave path between different PCB portions

Methodology Applied

Scientific EffectAcoustic absorption: Acoustic Absorption

Data Source

PatentUS8259982B2Reducing acoustic coupling to microphone on printed circuit board

Publication Date: 2012.09.04 QUALCOMM INC

AI summary

A mobile computing device comprises a printed circuit board, a processing circuit, a surface mount microphone, and a vibration attenuation portion. The processing circuit is disposed on a first portion of the printed circuit board. The surface mount microphone is disposed on a second portion of the printed circuit board. The vibration attenuation portion of the board is configured to attenuate vibrations from the first to the second portion of the printed circuit board.