PMUT Membrane Vent Holes for Pressure Burst Dissipation

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Solution Overview

Problem

Piezoelectric micromachined ultrasonic transducers (PMUTs) are vulnerable to damage from external pressure bursts, such as those encountered in harsh environments, due to the lack of effective mechanisms for pressure dissipation.

Innovation Solution

The integration of a plurality of vent holes within the membrane of PMUTs, strategically located within inactive regions, balances robustness to applied pressure and desired ultrasonic acoustic performance by optimizing vent hole configuration, including number, size, and location.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the membrane is made robust to external pressure by adding pressure dissipation mechanisms, then reliability under pressure improves, but ultrasonic acoustic performance may deteriorate

Engineering Contradiction:

Improverobustness to external pressureVSAvoidultrasonic acoustic output

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The membrane is segmented into active regions (for ultrasonic transmission) and inactive regions (for pressure dissipation). The inactive regions contain vent holes that allow pressure equalization without interfering with the ultrasonic acoustic path through the active regions. This spatial segmentation resolves the contradiction by assigning different functional zones to different areas of the membrane.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the membrane are given different properties: active regions maintain high structural integrity and piezoelectric functionality for ultrasonic transmission, while inactive regions are designed with vent holes to provide pressure relief. This local differentiation allows each region to optimize its specific function without compromising the other.

Inventive Principle:

Principle #3Local quality

2Reliability

If vent holes are added to the membrane for pressure relief, then robustness to applied pressure improves, but ultrasonic acoustic performance may be degraded

Engineering Contradiction:

Improverobustness to applied pressureVSAvoidultrasonic acoustic performance

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The vent holes in inactive regions convert the potentially harmful effect of pressure differential into a beneficial pressure equalization mechanism. By strategically placing vent holes only in inactive regions, the design allows pressure relief while preserving the integrity and performance of active ultrasonic regions.

Inventive Principle:

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

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 approach enhances the robustness of PMUTs to external pressure bursts while maintaining high ultrasonic acoustic performance, ensuring the reliability of PMUTs in various applications.

Implementation Method 1

a piezoelectric micromachined ultrasonic transducer (PMUT) robust to an applied pressure comprises a membrane including a first electrode layer, a second electrode layer, and a piezoelectric layer between the first electrode layer and the second electrode layer, with the membrane comprising an active region configured to cause the piezoelectric layer to transmit a first ultrasonic acoustic signal based on a first electrical signal

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

configured to output a second electrical signal corresponding to the first electrode layer and the second electrode layer based on a second ultrasonic acoustic signal received by the piezoelectric layer

Methodology Applied

Scientific EffectPiezoelectric effect: Converse Piezoelectric Effect

Data Source

PatentUS20250114822A1PMUT with Plurality of Vent Holes

Publication Date: 2025.04.10 INVENSENSE INC

AI summary

A piezoelectric micromachined ultrasonic transducer (“PMUT”) sensor has a membrane that includes an active region that actively transmits and receives ultrasonic acoustic signals and an inactive region that contributes to the PMUT modeshape but does not actively transmit and receive ultrasonic acoustic signals. A plurality of vent holes are distributed throughout the membrane such as in the inactive region. The number and size of the vent holes are selected to provide a necessary dissipation of pressure bursts or transients while maintaining a transmission efficiency.