Ultrasound Transducer Insulating Layer Charge Stabilization

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Solution Overview

Problem

Capacitance type ultrasound transducers face challenges in maintaining stable characteristics due to charge accumulation in insulating layers, affecting the transducer's performance and diagnostic image quality in ultrasound endoscopes.

Innovation Solution

The ultrasound transducer design features a laminated structure with different materials and thicknesses for the lower and upper insulating layers, ensuring a specific relationship between their charge density distributions and relative dielectric constants to stabilize the effective charge amounts, preventing charge accumulation and enhancing membrane stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a single insulating layer is used in the capacitance type ultrasound transducer, then the structure is simple and manufacturing is easier, but charge accumulation occurs in the insulating layer which destabilizes transducer characteristics

Engineering Contradiction:

Improveinsulating layer structureVSAvoidtransducer characteristics stability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The insulating layer is divided into multiple sub-layers (first insulating layer and second insulating layer) with different materials and thicknesses. This segmentation prevents charge accumulation by creating distinct regions with different dielectric properties, thereby stabilizing transducer characteristics while maintaining manufacturability through systematic layering.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different insulating materials are used in the first and second insulating layers to create a composite structure. The composite materials have different dielectric constants and charge trapping characteristics, which together prevent charge accumulation and stabilize transducer performance better than a single material could achieve.

Inventive Principle:

Principle #40Composite materials

2Reliability

If the insulating layer thickness is increased to reduce charge density, then charge accumulation is reduced, but the space between electrodes increases which affects ultrasound transmission efficiency

Engineering Contradiction:

Improvecharge accumulation preventionVSAvoidultrasound transmission efficiency

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

Different regions of the insulating structure have different thicknesses and materials optimized for their specific functions. The first insulating layer has different properties than the second layer, with each layer locally optimized to balance charge prevention and ultrasound transmission requirements.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The dielectric constant and thickness parameters are optimized for each insulating layer to achieve the desired balance. By changing material composition and thickness parameters systematically, the design achieves both charge accumulation prevention and maintained ultrasound transmission efficiency.

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 design stabilizes the transducer characteristics by maintaining equivalent influences of charges on potential, resulting in improved ultrasound diagnostic image quality and reliability.

Implementation Method 1

The c-MUT applies a voltage between a fixed electrode and a movable electrode opposed via an insulating layer to vibrate the movable electrode and generate ultrasound

Methodology Applied

Scientific EffectCapacitive Micromachined Ultrasonic Transducer (c-MUT):

Implementation Method 2

When a space between both the electrodes changes according to incident of ultrasound, the c-MUT detects a fluctuating capacitance value to detect the ultrasound

Methodology Applied

Scientific EffectCapacitance detection: Capacitance

Implementation Method 3

different materials and thicknesses for the lower and upper insulating layers, ensuring a specific relationship between their charge density distributions and relative dielectric constants to stabilize the effective charge amounts

Methodology Applied

Scientific EffectDielectric properties: Dielectric

Data Source

PatentEP2595412B1Ultrasound transducer and ultrasound diagnostic apparatus

Publication Date: 2015.10.21 OLYMPUS CORPORATION(JP)

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AI summary

An ultrasound transducer includes a substrate and a lower electrode layer, a lower insulating layer, an upper insulating layer, and an upper electrode layer laminated in order on the substrate. The lower insulating layer and the upper insulating layer are arranged to be opposed to each other via an air gap section. The upper insulating layer and the lower insulating layer are different in a material and thickness and satisfy Equation 1 below. In Equation 1, K1 represents a relative dielectric constant of the lower insulating layer, K2 represents a relative dielectric constant of the upper insulating layer, T1 represents layer thickness of the lower insulating layer, T2 represents layer thickness of the upper insulating layer, ρ1(x) represents a charge density distribution in the lower insulating layer (x represents a distance from the lower electrode layer), and ρ2(y) represents a charge density distribution in the upper insulating layer (y represents a distance from the upper electrode layer).