Chip Package Encapsulation for Fingerprint Sensor Protection
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Solution Overview
Problem
Fingerprint sensing electronic products face issues with moisture and oil stains causing chip package pollution, sensor damage, and capacitance attenuation, which affect their lifespan and sensing capability.
Innovation Solution
A chip package design incorporating a chip with a sensor and conductive pad, a first isolation layer, a redistribution layer, a passivation layer, and an encapsulation layer, where the encapsulation layer covers the sensor and conductive pad, preventing pollution and providing a flat surface for assembly, and a manufacturing method involving temporary bonding, patterning, and removal of layers to form a through hole and redistribution layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the chip package is exposed to the environment for sensing operation, then the sensing capability is enabled, but moisture and oil stains cause pollution and damage to the chip package
Solution Approach 1:
The patent introduces an encapsulation layer as an intermediary between the chip package and the external environment. This encapsulation layer allows the sensor to detect external stimuli (fingerprint patterns) while preventing harmful substances (moisture, oil stains) from directly contacting and damaging the chip package components.
Solution Approach 2:
The patent employs a thin film encapsulation layer that is sufficiently thin to allow tactile sensation and capacitance coupling for fingerprint sensing, yet thick enough to provide effective protection against environmental pollution. This thin film structure enables the chip package to maintain both protection and sensing functionality.
2Ease of operation
If the sensor is exposed to the environment for fingerprint detection, then the sensing function is activated, but the sensor is physically damaged reducing product lifespan
Solution Approach 1:
The encapsulation layer serves as a protective intermediary that shields the sensor from direct physical contact with external objects while still allowing the sensor to detect capacitance changes caused by fingerprint patterns. This mediator structure prevents physical damage to the sensor during normal operation.
Solution Approach 2:
The patent provides beforehand protection by pre-installing the encapsulation layer over the sensor before the sensor can be exposed to potential physical damage. This prior cushioning structure prevents direct mechanical stress and contamination that would otherwise reduce the sensor's lifespan.
3Productivity
If the chip package structure is simplified for manufacturing, then production efficiency is improved, but capacitance attenuation occurs affecting sensing capability
Solution Approach 1:
The patent uses a thin film encapsulation layer that maintains sufficient capacitance coupling between the sensor and the external environment for effective fingerprint sensing. The thin film structure is optimized to be thin enough to prevent capacitance attenuation while still providing necessary protection, balancing manufacturing simplicity with sensing performance.
Data Source
AI summary
A manufacturing method of a chip package includes forming a temporary bonding layer on a carrier; forming an encapsulation layer on a top surface of a wafer or on the temporary bonding layer; bonding the carrier to the wafer, in which the encapsulation layer covers a sensor and a conductive pad of the wafer; patterning a bottom surface of the wafer to form a through hole, in which the conductive pad is exposed through the through hole; forming an isolation layer on the bottom surface of the wafer and a sidewall of the through hole; forming a redistribution layer on the isolation layer and the conductive pad that is in the through hole; forming a passivation layer on the isolation layer and the redistribution layer; and removing the temporary bonding layer and the carrier.