Microphone ESD Protection via Spark Director Air Gap

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Solution Overview

Problem

Consumer electronic devices, such as microphones in headphones, are vulnerable to damage from electrostatic discharge (ESD) due to the direct discharge of electric charges into the microphone casing, which can break the delicate components.

Innovation Solution

A spark director is positioned with a first portion away from the microphone casing and a second portion extending towards it, terminating in a tip separated by an air gap, to redirect and dissipate electric charges away from the microphone opening, potentially combined with a ground ring to attract and dissipate the charge at a location other than the opening.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a conventional microphone casing with an opening is used, then sound can be admitted to the sensing element, but electrostatic discharge can directly damage the microphone components

Engineering Contradiction:

ImproveESD damage to microphoneVSAvoidmicrophone functionality

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

A spark director is introduced as an intermediary component between the external environment and the microphone opening. The spark director includes a first portion that intercepts electrostatic discharge and a second portion that directs the spark away from the opening, preventing direct damage to the microphone while maintaining acoustic access.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The spark director converts the harmful electrostatic discharge into a controlled spark that occurs away from the microphone opening. By providing a designated path for the ESD to follow, the harmful energy is redirected to a safe location, protecting the microphone components while allowing the discharge to occur harmlessly.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Object-affected harmful factors

If a shield or conductive layer is added around the microphone, then ESD protection is improved, but the device complexity and manufacturing difficulty increase

Engineering Contradiction:

ImproveESD protectionVSAvoidmicrophone assembly structure

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The spark director is divided into two distinct portions: a first portion that intercepts the electrostatic discharge and a second portion that directs the spark away from the opening. This segmentation allows each portion to perform its specific function efficiently while keeping the overall structure relatively simple and manageable.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of protecting the microphone opening directly with a shield or conductive layer, the invention inverts the approach by placing the spark director outside the opening and redirecting the spark away from it. This indirect protection method simplifies the overall structure compared to enclosing the microphone with complex shielding.

Inventive Principle:

Principle #13The other way round (Inversion)

3Object-affected harmful factors

If the spark director tip is positioned close to the casing, then ESD protection is improved, but acoustic performance may be affected

Engineering Contradiction:

ImproveESD interception effectivenessVSAvoidacoustic opening configuration

Core Design Contradiction:

Object-affected harmful factorsVSShape

Solution Approach 1:

The spark director is positioned and configured with specific local characteristics: the tip is located at a precise distance from the opening (less than the distance from any point of the spark director to the opening centerline), and the second portion extends toward the opening without contacting it. This local configuration provides effective ESD protection while preserving the overall acoustic performance of the opening.

Inventive Principle:

Principle #3Local quality

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 design allows microphones to withstand significant electrostatic discharge without sustaining damage, reducing the risk of acoustic effects and maintaining an acoustic and water seal, while allowing for looser tolerances in construction.

Implementation Method 1

An electric charge in the first portion of the spark director will be discharged by the second portion of the spark director through the air gap into the casing at a location other than at the opening

Methodology Applied

Scientific EffectElectrostatic discharge: Electrostatic Discharge

Data Source

PatentEP3520432B1Electrostatic discharge protection of microphones

Publication Date: 2020.01.29 BOSE CORP

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AI summary

A microphone has a sensing element; a casing surrounds the microphone with an opening that admits sound to the sensing element in a first direction. A spark director includes a first portion spaced away from the casing in a direction opposite the first direction, and a second portion extending from the first portion towards the casing and terminating in a tip separated from the casing by an air gap. An electric charge in the first portion of the spark director will be discharged by the second portion of the spark director through the air gap into the casing at a location other than at the opening.