Fingerprint Sensor ESD Protection via Dual Electrodes
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Solution Overview
Problem
Capacitive fingerprint sensors lack effective protection against electrostatic discharge, which can damage the device and interfere with fingerprint recognition.
Innovation Solution
A dual-layer electrostatic discharge (ESD) protection system comprising a first ESD protection electrode coplanar with the fingerprint sensor electrode array and a second ESD protection electrode connected via conductive vias, providing a low-resistance path for electrostatic current to flow to an ESD protection circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single ESD protection electrode is used, then the structure is simple, but the ESD protection performance is insufficient
Solution Approach 1:
The ESD protection electrode is divided into two separate electrodes (first ESD protection electrode and second ESD protection electrode) positioned at different locations. Each electrode independently provides ESD protection through conductive vias to the ESD protection circuit, thereby enhancing overall protection performance while maintaining reasonable structural complexity
Solution Approach 2:
The ESD protection is extended from a single-plane electrode to a multi-dimensional structure by adding the second ESD protection electrode at a different position and connecting them through conductive vias in the vertical dimension, creating a three-dimensional ESD protection network that improves protection effectiveness
2Reliability
If the ESD path has high resistance, then the structure is simpler, but the electrostatic current cannot be effectively discharged
Solution Approach 1:
Multiple conductive vias are pre-established to create low-resistance ESD paths from both the first and second ESD protection electrodes to the ESD protection circuit. This preliminary preparation ensures that when electrostatic discharge occurs, the current can immediately flow through multiple parallel low-resistance paths, effectively discharging the electrostatic charge
Solution Approach 2:
The conductive vias serve as intermediary elements that bridge the ESD protection electrodes and the ESD protection circuit, providing dedicated low-resistance connection paths. These vias act as mediators that facilitate efficient electrostatic charge discharge while maintaining clear separation between the protection electrodes and the sensitive sensor circuitry
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 dual-layer ESD protection system effectively prevents damage from electrostatic discharge, enhancing the protection performance and maintaining the accuracy of fingerprint recognition by minimizing interference.
Implementation Method 1
the first and second ESD protection electrodes are connected by the conductive via, which provides an ESD path with lower resistance for the electrostatic current
Implementation Method 2
the first ESD protection electrode is connected to an ESD protection circuit, to provide an ESD path
Data Source
AI summary
A fingerprint sensor having electrostatic discharge (ESD) protection includes a first ESD protection electrode and a second ESD protection electrode. The first ESD protection electrode is connected to an ESD protection circuit for providing an ESD path, where the first ESD protection electrode and a fingerprint sensor electrode array are formed in a same layer of the fingerprint sensor. The second ESD electrode is connected to the first ESD electrode via multiple conductive via.