Under-Display Ultrasonic Fingerprint Chip Layout for High-Voltage Isolation
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Solution Overview
Problem
The integration of a piezoelectric transducer and an ultrasonic fingerprint chip in ultrasonic fingerprint apparatuses is challenging, particularly due to the high voltage driving signals that can interfere with and cause electrical breakdown in the ultrasonic fingerprint chip.
Innovation Solution
The ultrasonic fingerprint apparatus includes a piezoelectric transducer with an upper electrode extending into a window in a passivation layer to connect with drive traces on a metal layer, allowing for electrical integration with the ultrasonic fingerprint chip, and uses a silicon substrate for bonding processes, along with grounded metal layers and shielding to prevent interference and breakdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If optical sensors are used for fingerprint recognition, then recognition speed is fast, but they cannot penetrate through glass or plastic covers
Solution Approach 1:
The patent replaces optical sensing with ultrasonic sensing. The ultrasonic sensor emits ultrasonic waves that can penetrate through glass and plastic covers to detect fingerprint ridges and valleys, solving the limitation of optical sensors而无法穿透覆盖层的问题。This substitution enables the system to work through various cover materials while maintaining recognition capability.
Solution Approach 2:
The patent changes the sensing parameter from optical wavelength to ultrasonic frequency. By using ultrasonic waves with frequencies beyond human hearing, the system achieves penetration through materials that block visible light, while the high frequency allows for detailed fingerprint pattern detection.
2Adaptability or versatility
If ultrasonic sensors are used to penetrate through covers, then recognition capability is improved, but the sensor size becomes large
Solution Approach 1:
The patent divides the ultrasonic sensing function into multiple small sensor elements arranged in an array. Each element is tiny, but collectively they provide comprehensive fingerprint coverage. This segmentation allows the system to maintain small individual sensor size while achieving large effective sensing area through coordinated operation of multiple elements.
Solution Approach 2:
The patent transitions from a single-point ultrasonic sensor to a two-dimensional array of sensor elements. This dimensional expansion allows the system to cover the entire fingerprint area using multiple small elements rather than requiring a single large sensor, enabling penetration capability without increasing individual sensor footprint.
3Object-affected harmful factors
If contactless ultrasonic sensing is implemented, then hygiene is improved, but recognition accuracy decreases due to inability to apply pressure
Solution Approach 1:
The patent makes the ultrasonic sensor dynamic by enabling it to scan and move across the fingerprint surface rather than requiring static contact. The sensor can dynamically adjust its position and scanning pattern to capture fingerprint details without physical contact, maintaining hygiene while achieving sufficient recognition accuracy through motion-based data collection.
Solution Approach 2:
The patent performs preliminary scanning and mapping of the fingerprint surface before final recognition. By first capturing the overall fingerprint pattern through contactless ultrasonic waves and then focusing on specific ridge and valley features, the system achieves accurate recognition without requiring the sensor to physically press against the finger, thus maintaining hygiene while ensuring precision.
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 enables reliable electrical connection and signal transmission while ensuring the safety and integrity of the ultrasonic fingerprint chip, facilitating under-display fingerprint identification.
Implementation Method 1
the sensor head 121 may include a contactless ultrasonic sensor that penetrates through a glass or plastic cover to recognize a fingerprint
Implementation Method 2
the sensor head 121 may include a contactless ultrasonic sensor that penetrates through a glass or plastic cover to recognize a fingerprint... the second fingerprint sensing area 1222, which corresponds to the second region 122 of the sensor head 121 and senses an applied pressure through a piezoelectric element
Data Source
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AI summary
The present disclosure provides an ultrasonic fingerprint apparatus and an electronic device. The ultrasonic fingerprint apparatus is arranged below a display screen of an electronic device to implement under-display ultrasonic fingerprint identification, the ultrasonic fingerprint apparatus includes an ultrasonic fingerprint chip and a piezoelectric transducer arranged above the ultrasonic fingerprint chip; the piezoelectric transducer includes a piezoelectric layer, an upper electrode located above the piezoelectric layer, and a lower electrode located below the piezoelectric layer; the ultrasonic fingerprint chip includes a substrate and a plurality of metal layers arranged in a first region of the substrate, the lower electrode is located above a second region of the substrate, a top metal layer among the plurality of metal layers includes N drive traces, N=1 or N is a positive integer greater than 1, a passivation layer is provided above the top metal layer, a first window corresponding to the N drive traces is provided above the passivation layer, and the upper electrode extends from an upper surface of the piezoelectric layer into the first window for connection to respective first connection regions of the N drive traces located in the first window.