Thermal Pattern Sensor Electrode Integration
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Solution Overview
Problem
Active thermal fingerprint sensors face inefficiencies due to lateral heating of pyroelectric capacitors, which is not optimal for materials with low thermal conductivity, and the additional cost of using a separate metallic level for heating elements.
Innovation Solution
Integrating the heating element directly into one of the electrodes of the pyroelectric capacitance, allowing for closer proximity to the pyroelectric material and simplifying the design by using the same conductive layer for both heating and electrode functions, thus enhancing heat transmission and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If heating elements are produced from a separate metallic level, then heating function is achieved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent combines the heating element and electrode functions into a single metallic layer. The same conductive material serves dual purposes: as an electrode for the pyroelectric capacitor and as a heating element through Joule heating, eliminating the need for separate metallic layers and reducing manufacturing complexity
Solution Approach 2:
The metallic layer is designed to perform multiple functions simultaneously. It acts as both an electrical conductor (electrode) and a heating element, providing universal functionality that reduces the overall device complexity and manufacturing steps
2Reliability
If heating elements are positioned laterally adjacent to pyroelectric capacitors, then heating is achieved, but thermal conductivity efficiency decreases
Solution Approach 1:
The patent extracts the heating function from a separate lateral positioning and integrates it directly into the electrode structure. By making the electrode itself the heating element through Joule heating, the thermal energy is generated at the exact location where it is needed, eliminating lateral heat transfer losses
Solution Approach 2:
The metallic layer serves as an intermediary that converts electrical energy to thermal energy directly at the electrode position. This Joule heating mechanism acts as an efficient energy conversion intermediary, ensuring thermal energy is generated in-situ rather than being transferred from a lateral position
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 significantly increases heating capacity and thermal pattern detection accuracy while maintaining cost-effectiveness by eliminating the need for additional metallic layers, ensuring effective heat transfer and improved sensor performance.
Implementation Method 1
the pixels of this sensor are coupled to heating elements generally using the Joule effect which dissipates heat from a resistive element through which a current flows
Implementation Method 2
pyroelectric elements, diodes, thermistors or any other temperature-sensitive element making it possible to convert a variation in temperature into a variation in electrical potential or current
Data Source
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AI summary
The invention relates to a thermal pattern sensor (100) comprising a plurality of pixels (102), each pixel comprising at least one pyroelectric capacitor formed by at least one portion of pyroelectric material (106) arranged between a lower electrode (108) and an upper electrode (110), in which one (108) of the lower and upper electrodes corresponds to an electrode for reading the pixel and in which a heating element that can heat the portion of pyroelectric material of the pyroelectric capacitor of said pixel by Joule effect during a measurement of the thermal pattern by the pyroelectric capacitor of said pixel is formed by the other (110) of the lower and upper electrodes.