Ultrasonic Element Electrode Misalignment Tolerance
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Solution Overview
Problem
The existing electrostatic capacitance type ultrasound elements face instability in characteristics due to misalignment of electrode patterns during manufacturing, leading to reduced reception sensitivity and unreliable performance in ultrasound endoscopes.
Innovation Solution
The design features a configuration where the lower electrode section is larger than the cavity, and the upper electrode section is smaller than the lower electrode but larger than the cavity, ensuring that even minor misalignments do not affect the effective electrode area, and the use of orthogonal wiring sections to minimize parasitic capacitance, maintaining high sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the upper electrode section and lower electrode section are placed in correct positions, then the effective electrode areas are maximized, but manufacturing precision requirements increase and misalignment sensitivity increases
Solution Approach 1:
The patent applies beforehand cushioning by designing the upper electrode section to extend beyond the cavity boundaries in the radial direction. This intentional overextension creates a buffer zone that compensates for potential misalignment during manufacturing. Even if the upper electrode section is not precisely positioned, the extended portions ensure that sufficient effective electrode area remains within the cavity boundaries, thereby maintaining stable characteristics without requiring high placement precision.
2Device complexity
If the upper electrode section size is reduced, then the device complexity is reduced, but the effective electrode area decreases and reception sensitivity is reduced
Solution Approach 1:
The patent applies local quality by creating a non-uniform electrode configuration where the upper electrode section has different functional zones: a central portion within the cavity that provides effective electrode area for reception sensitivity, and radial extension portions that extend beyond the cavity boundaries. This local differentiation allows the electrode structure to maintain simple overall geometry while ensuring sufficient effective area in the critical region, thus preserving reception sensitivity without increasing device complexity.
3Reliability
If the upper electrode section is larger than the cavity, then misalignment tolerance is improved, but the electrode area outside cavity increases potentially causing parasitic capacitance
Solution Approach 1:
The patent applies taking out by extracting or removing the potential harmful function of the extended electrode portions. The upper electrode section extends radially beyond the cavity boundaries, but these extension portions are designed to be electrically isolated or shielded from the lower electrode section. This separation extracts the potentially harmful parasitic capacitance effect from the overall electrode system, allowing the extended portions to serve only the beneficial function of compensating for misalignment without generating harmful electrical interactions.
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 stabilizes the characteristics of the ultrasound element and endoscope, ensuring consistent performance despite manufacturing variations and misalignment, thereby maintaining high reception sensitivity and reliability.
Implementation Method 1
The US cell vibrates a membrane (a vibration portion) including the upper electrode section by an electrostatic force by applying a voltage to between the lower electrode section and the upper electrode section, and generates ultrasound.
Implementation Method 2
When ultrasound enters from an outside, a space between both the electrodes changes, and therefore, the ultrasound is converted into an electric signal from a change of an electrostatic capacitance.
Data Source
Figure 1
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Figure 4~5
AI summary
An ultrasound element 20 includes a silicon substrate 11, a lower electrode layer 12 that has a plurality of lower electrode sections 12A, and a plurality of lower wiring sections 12B, and is connected to a lower electrode terminal 52 to which a drive signal and a bias signal are applied, a lower insulating layer 13, an upper insulating layer 15 in which a plurality of cavities 14 smaller than the respective lower electrode sections 12A are formed, an upper electrode layer 16 that has a plurality of upper electrode sections 16A that are disposed to face the respective lower electrode sections 12A via the respective cavities 14, and are smaller than the lower electrode sections 12A and larger than the cavities 14, and a plurality of upper wiring sections 16B, and is connected to an upper electrode terminal 51 at a ground potential that detects a capacitance signal, and a protection layer 17.