Ultrasonic Device Electrode Configuration for Sensitivity
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Solution Overview
Problem
The existing ultrasonic devices face a challenge in maintaining transmission/reception sensitivity due to the hindrance caused by insulating films and conduction wires, which affect the deformation of piezoelectric bodies and vibration portions, leading to deteriorated ultrasonic wave sensitivity.
Innovation Solution
The ultrasonic device is designed with a piezoelectric element configuration where the outer circumferential edge of the first electrode is larger than the piezoelectric body, incorporating an extraction portion connected to the active portion and extending both inside and outside the vibration portion, with a second electrode provided on both areas, eliminating the need for a separate insulating film and minimizing the width of the extraction portion to prevent vibration hindrance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an insulating film is provided to cover the first electrode, piezoelectric body, and second electrode, then insulation between electrodes is ensured, but deformation of the piezoelectric body or vibration portion is hindered, deteriorating transmission/reception sensitivity
Solution Approach 1:
The insulating film is extracted from covering the vibration portion and active portion, being present only on the extraction portion. This removes the harmful rigid constraint on the vibration portion while maintaining insulation where needed (between electrodes on the extraction portion), thereby resolving the contradiction between insulation reliability and vibration sensitivity.
Solution Approach 2:
The insulating film is selectively applied only to the extraction portion rather than uniformly across the entire piezoelectric element. This local application provides insulation exactly where electrodes are present (on the extraction portion) while leaving the vibration portion and active portion free to deform, thus balancing insulation requirements with vibration freedom.
2Area of stationary object
If the outer circumferential edge of the first electrode is made larger than the piezoelectric body, then the drive region area is increased, but the rigidity of the electrode structure increases, potentially hindering vibration
Solution Approach 1:
The first electrode is designed with non-uniform dimensions: it has a larger outer circumferential edge to maximize the drive region area, but the insulating film is selectively applied only to the extraction portion where the electrode extends beyond the piezoelectric body. This local differentiation allows the electrode to provide both large drive area and vibration freedom in critical regions.
3Ease of manufacture
If conduction wires are formed on the insulating film over the inside and outside of the vibration portion, then multiple second electrodes can be connected, but the rigidity of the conduction wire hinders deformation of the vibration portion
Solution Approach 1:
The conduction wires are extracted from being formed over the vibration portion and active portion, being present only on the extraction portion. This removes the rigid constraint on vibration while maintaining electrical connection functionality where needed, resolving the contradiction between ease of manufacturing connections and deformation capability.
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 configuration enhances the transmission/reception sensitivity of the ultrasonic device by increasing the drive region area, reducing the risk of vibration hindrance, and alleviating stress on the vibration portion, thereby improving the overall performance and reliability of ultrasonic measurements.
Implementation Method 1
Each of the piezoelectric elements is formed by sequentially laminating a first electrode, a piezoelectric body, and a second electrode in this order from the vibration portion side. The ultrasonic device is driven when a voltage is applied between the first electrode and the second electrode, and transmits an ultrasonic wave.
Implementation Method 2
The ultrasonic device outputs a change in a potential difference between the first electrode and the second electrode as a received signal of the ultrasonic wave when the ultrasonic wave is received.
Data Source
AI summary
An ultrasonic device includes a vibration portion, a first electrode, a piezoelectric body, and a second electrode which are laminated in this order in a laminate direction, in which an outer circumferential edge of the first electrode is larger than an outer circumferential edge of the piezoelectric body in a plan view across the laminate direction, in which the piezoelectric body includes an active portion that is provided in the vibration portion, and an extraction portion that is connected to the active portion and is provided over the inside and the outside of the vibration portion, in which a width dimension of the extraction portion is smaller than a width dimension of the active portion, and in which the second electrode is provided on the active portion and the extraction portion.