Ultrasonic Fingerprint Transducer Layout for High-Voltage Isolation
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Solution Overview
Problem
The integration of a piezoelectric transducer with an ultrasonic fingerprint chip in ultrasonic fingerprint apparatuses is challenging due to the high voltage driving signals required, which can interfere with and cause electrical breakdown in the circuit, and there is a need for a compact and reliable connection mechanism.
Innovation Solution
The ultrasonic fingerprint apparatus integrates a piezoelectric transducer with an ultrasonic fingerprint chip by using a top metal layer with drive traces and a passivation layer window for the upper electrode to connect with the drive traces, ensuring a compact and reliable electrical connection, and employs grounded metal layers and shielding to prevent interference and breakdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the piezoelectric transducer is integrated with the ultrasonic fingerprint chip, then the device complexity is reduced and compactness is improved, but the high voltage driving signals may interfere with and cause electrical breakdown in the circuit
Solution Approach 1:
The patent segments the chip into distinct regions: a first region for the piezoelectric transducer and a second region for the ultrasonic fingerprint chip circuitry. This spatial segmentation isolates the high-voltage driving signals from the sensitive circuit elements, preventing electrical interference and breakdown while maintaining integration.
Solution Approach 2:
The patent introduces an intermediary structure (the passivation layer with window openings and the specific electrode configuration) that mediates between the piezoelectric transducer and the ultrasonic fingerprint chip circuit. This intermediary enables electrical connection while providing protection and isolation to prevent harmful interactions.
2Reliability
If the upper electrode extends into the first window to connect with drive traces, then the electrical connection reliability is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The passivation layer is formed with pre-defined window openings at predetermined positions before the upper electrode is deposited. This preliminary action ensures that the electrode can be accurately positioned and connected to the drive traces without requiring high-precision alignment during the final assembly, as the connection paths are already established by the window positions.
3Productivity
If high voltage driving signals are used to excite the piezoelectric transducer, then the ultrasonic signal generation efficiency is improved, but the interference with the ultrasonic fingerprint chip circuit increases
Solution Approach 1:
The patent divides the chip into separate first and second regions, placing the piezoelectric transducer in the first region and the ultrasonic fingerprint chip circuit in the second region. This segmentation allows high-voltage driving signals to be applied to the piezoelectric transducer without interfering with the sensitive circuit elements in the second region, thus maintaining both efficiency and minimizing harmful effects.
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 integration ensures safe and efficient transmission of high-voltage driving signals while minimizing interference and breakdown risks, maintaining the integrity of the ultrasonic fingerprint apparatus.
Implementation Method 1
a piezoelectric transducer arranged on the ultrasonic fingerprint chip; the piezoelectric transducer includes a piezoelectric layer, an upper electrode located on the piezoelectric layer, and a lower electrode located under the piezoelectric layer
Implementation Method 2
the top metal layer of the ultrasonic fingerprint chip includes drive traces for connection to the upper electrode... a driving signal can be transmitted from a circuit board below the ultrasonic fingerprint chip to the piezoelectric transducer through the drive traces
Data Source
AI summary
An ultrasonic fingerprint apparatus is provided. The apparatus includes a lower electrode, a piezoelectric layer and an upper electrode forming a piezoelectric transducer for emitting an ultrasonic signal and receiving an ultrasonic signal reflected from a finger. A first region of the substrate includes a plurality of metal layers, the lower electrode is disposed above a second region of the substrate, a top metal layer among the plurality of metal layers comprise a N number of drive traces, a passivation layer is provided above the top metal layer and provided with a first window corresponding to the drive traces; 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 drive traces in the first window, and a surface of each of the first connection regions in the first window has an anti-oxidative protective layer.