Ultrasonic Transducer Electrode Overlap and Cavity Design
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Solution Overview
Problem
Piezoelectric micromachined ultrasound transducers (pMUTs) face inefficiencies in transmitting and receiving ultrasound waves due to capacitance at coupled transducer elements and interference from piezoelectricity at the edge of cavities, which degrades frequency response and causes deterioration of the transducer edges.
Innovation Solution
The ultrasonic transducer design includes a piezoelectric layer, first and second electrodes, a base layer, and a substrate with cavities, where the electrodes overlap but have a larger width than the peripheral portion, allowing for enhanced vibration and reduced capacitance at coupling points, and the substrate's cavities facilitate free vibration, improving frequency response and reducing edge deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If transducer elements are coupled with each other to form a parallel structure, then the transducer can transmit and receive ultrasound waves, but capacitance is generated at the coupling portions which decreases transmission and reception efficiency
Solution Approach 1:
The patent extracts the harmful capacitance effect by introducing cavities at the coupling portions between transducer elements. These cavities remove the piezoelectric material from the coupling regions, eliminating the parasitic capacitance that would otherwise degrade ultrasound transmission and reception efficiency.
Solution Approach 2:
The patent applies different structural qualities to different regions: the transducer elements maintain their piezoelectric structure for ultrasound generation, while the coupling portions between elements are modified with cavities to eliminate capacitance. This local differentiation optimizes both ultrasound generation and transmission efficiency.
2Reliability
If piezoelectric material is present at the edge portion of the cavity, then the transducer structure is complete, but the piezoelectricity interrupts free vibration and degrades frequency response
Solution Approach 1:
The patent removes piezoelectric material from the edge portions of cavities where it would interfere with free vibration. By extracting the harmful piezoelectric effect from these specific locations, the transducer achieves better frequency response without compromising the overall structural integrity.
Solution Approach 2:
Instead of having piezoelectric material continuously present as in conventional designs, the patent inverts the approach by strategically removing piezoelectric material from cavity edges. This inversion allows the cavity edges to vibrate freely without piezoelectric interference, improving frequency response characteristics.
3Duration of action of stationary object
If piezoelectric material is present at the edge portion of the cavity, then the transducer structure is complete, but the edge portion deteriorates over time
Solution Approach 1:
The patent extracts piezoelectric material from the vulnerable edge portions of cavities, eliminating the source of deterioration. This removal prevents the chemical and mechanical degradation that would otherwise occur at these exposed edges, thereby extending the transducer's operational lifespan.
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 enhances the sensitivity and efficiency of ultrasonic transducers by minimizing capacitance-related inefficiencies and maintaining the integrity of the transducer edges, leading to improved transmission and reception of ultrasound waves across a wider frequency bandwidth.
Implementation Method 1
a piezoelectric layer 1, a first electrode 2, and a second electrode 3. The first electrode 2 is disposed in a front side of the piezoelectric layer 1
Implementation Method 2
Expansion and contraction of the piezoelectric thin film causes an ultrasound wave to be received and transmitted
Implementation Method 3
the substrate 5 has a cavity 6 formed on a back side of the overlap area 50 of the first electrode 2 and the second electrode 3
Data Source
AI summary
An ultrasonic transducer according to an embodiment includes a piezoelectric layer, a first electrode, a second electrode, a base layer, and a substrate. The first electrode is disposed in a front side of the piezoelectric layer and extends along a first direction. The second electrode is disposed in a back side of the piezoelectric layer and extends along a second direction intersecting with the first direction. The base layer is disposed in a back side of the second electrode. The substrate is disposed in a back side of the base layer. Each of the first electrode and the second electrode includes an overlap portion where the first electrode and the second electrode overlap each other when viewed from the front side of the piezoelectric layer. The substrate is provided with a cavity on a back side of the overlap portion on each of the first electrode and the second electrode. Each of the first electrode and the second electrode has the width of the overlap portion that is larger than the width of a peripheral portion of the overlap portion.