Ultrasonic Sensor Tunable Metal Layer Thickness
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Solution Overview
Problem
Existing ultrasonic sensor systems face challenges in transmitting and receiving ultrasonic waves at low frequencies, particularly below 10 MHz, due to the difficulty in uniformly printing thick silver ink layers, which affects device performance and increases manufacturing costs.
Innovation Solution
Incorporating a tunable metal layer, such as a copper layer, coupled with an acoustic layer to form a flexible copper clad laminate (FCCL) stack, which allows for frequency tuning across a wider range of ultrasonic frequencies without compromising image quality or reliability, and reducing the thickness of the electrode layer to minimize adverse effects on imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If thick silver ink layers are used to achieve low frequency operation, then the ultrasonic sensor can operate at frequencies below 10 MHz, but the manufacturing complexity and cost increase due to difficulty in uniformly printing thick layers
Solution Approach 1:
The patent divides the single thick electrode layer into two separate layers: a thin electrode layer (first electrode layer) for electrical function and a thick metal layer (second metal layer) for acoustic resonance. This segmentation allows each layer to be optimized independently - the thin layer can be printed uniformly while the thick layer provides the necessary low-frequency resonance without requiring complex printing processes.
Solution Approach 2:
The thin electrode layer acts as an intermediary between the piezoelectric layer and the thick metal layer. It provides the necessary electrical connection while allowing the thick metal layer to function as an acoustic resonator. This intermediary structure enables the system to achieve low-frequency operation without requiring the electrode layer itself to be thick and difficult to manufacture.
2Adaptability or versatility
If thick electrode layers are used to achieve low frequency operation, then the ultrasonic sensor can transmit and receive low frequency waves, but the image quality deteriorates due to pixel-to-pixel gray level differences and defects
Solution Approach 1:
By segmenting the electrode structure into a thin first electrode layer and a thick second metal layer, the patent ensures that the thin layer maintains uniform thickness for high-quality imaging, while the thick layer provides low-frequency resonance. The thin layer's uniformity prevents pixel-to-pixel gray level differences, and the thick layer's resonance enables low-frequency operation.
Solution Approach 2:
The patent applies different quality requirements to different parts of the electrode structure. The first electrode layer (in contact with piezoelectric material) is made thin and uniform for high imaging quality, while the second metal layer is made thick for acoustic resonance. Each layer has optimized local properties suitable for its specific function.
3Reliability
If the electrode layer thickness is increased to match low frequency, then the acoustic resonance is improved, but the device complexity increases
Solution Approach 1:
The electrode system is segmented into two layers with distinct functions: the first electrode layer provides electrical connection with minimal acoustic interference, while the second metal layer provides acoustic resonance. This segmentation allows the system to achieve reliable low-frequency resonance without requiring a single complex thick electrode layer.
Solution Approach 2:
The second metal layer serves multiple functions: it acts as an acoustic resonator for low-frequency operation, provides electrical connection through the conductive film, and can serve as a structural support layer. This multi-functionality reduces overall device complexity despite the additional layer.
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
The solution improves the performance of ultrasonic sensor systems by enabling operation at frequencies less than 10 MHz, reducing manufacturing costs, and enhancing image quality by minimizing pixel-to-pixel gray level differences and defects, while maintaining reliability and image uniformity.
Implementation Method 1
a piezoelectric layer coupled to the transistor layer
Implementation Method 2
a metal layer coupled to the electrode layer, where the metal layer has a thickness tuned to match a peak frequency in an ultrasonic frequency range of the ultrasonic waves transmitted by the ultrasonic sensor stack
Implementation Method 3
an ultrasonic sensor stack configured to transmit and receive ultrasonic waves
Data Source
AI summary
An apparatus includes an ultrasonic sensor stack configured to transmit and receive ultrasonic waves. The ultrasonic sensor stack includes at least a thin film transistor layer, a piezoelectric layer, and a thin electrode layer. The ultrasonic sensor stack further includes a tunable metal layer coupled to the thin electrode layer and an acoustic layer coupled to the tunable metal layer, where the tunable metal layer has a thickness greater than a thickness of the thin electrode layer. The thickness of the tunable metal layer may be configured to match a peak frequency in an ultrasonic frequency range of the ultrasonic waves transmitted by the ultrasonic sensor stack. In some implementations, the tunable metal layer includes a copper layer and the acoustic layer includes polyimide or polyethylene terephthalate.