MEMS Sound Transducer Spacer Element for Mechanical Overload Protection

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Solution Overview

Problem

MEMS sound transducers lack robustness against mechanical loading, particularly due to the risk of membrane damage during overloads such as those encountered during compressed air cleaning or drop tests.

Innovation Solution

Incorporating a spacer element with a greater height than the elevation element between the membrane and the supporting structure, which limits further deflection and reduces mechanical loading on the membrane, thereby enhancing robustness against mechanical overloads.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the membrane is made deflectable toward the backplate for normal operation, then the sound transducer function is improved, but the membrane becomes vulnerable to mechanical damage during overload

Engineering Contradiction:

Improverobustness against mechanical loadingVSAvoidmembrane resistance to mechanical damage

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The spacer element is positioned between the membrane and supporting structure to provide protective cushioning before mechanical overload occurs. During normal operation, the spacer element remains non-contacting, but during overload events such as drop tests or compressed air cleaning, it prevents excessive membrane deflection and reduces mechanical loading, thereby protecting the membrane from damage

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The spacer element acts as an intermediary component between the membrane and the supporting structure. It mediates the interaction during overload events by providing a physical barrier that limits membrane deflection toward the supporting structure, thereby reducing the direct mechanical stress on the membrane while allowing normal operation to proceed unaffected

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the spacer element height is increased to protect against overload, then robustness is improved, but the device complexity increases

Engineering Contradiction:

Improverobustness against mechanical overloadVSAvoidstructural complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The protective function is segmented into two distinct elements with different heights: the elevation element (first height) and the spacer element (second height greater than the first). This segmentation allows the spacer element to provide overload protection at a greater height while the elevation element maintains normal operational characteristics, thereby protecting against overload without significantly increasing overall device complexity

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS10638236B2MEMS sound transducer, MEMS microphone and method for providing a MEMS sound transducer

Publication Date: 2020.04.28 INFINEON TECHNOLOGIES AG

AI summary

A MEMS sound transducer includes a backplate and a membrane held by an edge fixing such that the membrane is deflectable along a deflection direction toward the backplate. The MEMS sound transducer further includes an elevation element arranged between the membrane and the backplate and having a first height along the deflection direction. The MEMS sound transducer also includes a supporting structure and a spacer element arranged between the membrane and the supporting structure and having a second height along the deflection direction, the second height being greater than the first height. The supporting structure is the backplate or is a supporting element arranged opposite the backplate, such that the membrane is arranged between the backplate and the supporting element.