Peltier Cooled IR Sensor Thermal Isolation
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Solution Overview
Problem
Current infrared (IR) sensors, particularly uncooled thermopile sensors, face challenges such as reduced sensitivity, self-heating noise, and increased complexity in fabrication, which affect their performance and cost-effectiveness.
Innovation Solution
An electronic device incorporating a temperature sensing semiconductor substrate with a thermopile and a cooling semiconductor substrate featuring a Peltier cooler, along with cavities for enhanced thermal isolation and a dielectric layer to reduce noise, is designed to increase sensitivity and operational efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pyroelectric detector is used for passive infrared detection, then sensitivity to infrared radiation is improved, but the device requires constant motion, has Z-directional insensitivity, is prone to false alarms, and has relatively low response time
Solution Approach 1:
The patent replaces mechanical motion requirements with a stationary microbolometer sensor that uses thermal conduction principles. The sensor detects infrared radiation through temperature changes in the bolometer element, eliminating the need for constant mechanical motion while maintaining detection capability.
Solution Approach 2:
The patent changes the detection parameter from pyroelectric effect (requiring motion) to bolometric effect (temperature-dependent resistance). By using a microbolometer with temperature-sensitive resistive elements, the system achieves infrared detection without requiring the target to be in motion, resolving the contradiction between sensitivity and operational requirements.
2Adaptability or versatility
If a microbolometer is used for thermal imaging applications, then cooling requirements are reduced, but fabrication complexity increases
Solution Approach 1:
The patent segments the microbolometer sensor into an array of independent pixel elements, each with its own readout circuit. This segmentation allows for modular fabrication processes and simplifies the overall manufacturing by enabling standardized production of individual pixels that can be assembled into complete sensor arrays.
Solution Approach 2:
The patent introduces a suspended membrane structure as an intermediary element that thermally isolates the bolometer elements from the substrate. This membrane acts as a thermal barrier, reducing heat conduction to the bulk substrate and improving sensor performance while using standard micromachining techniques to manage fabrication complexity.
3Measurement precision
If high vacuum level packaging is used to improve sensitivity, then sensitivity is improved, but product lifetime becomes problematic
Solution Approach 1:
The patent extracts the thermal isolation function from vacuum packaging by implementing a suspended membrane structure that provides thermal isolation without requiring high vacuum environments. This eliminates the reliability issues associated with vacuum sealing while maintaining the sensitivity benefits of thermal isolation.
Solution Approach 2:
The patent replaces expensive and unreliable high-vacuum packaging with a simpler, more robust sealed cavity structure that does not require maintaining high vacuum levels. The sealed cavity provides sufficient thermal isolation for improved sensitivity without the complexity and reliability problems of high-vacuum systems.
4Measurement precision
If IR filters with anti-reflective coating are used to improve sensitivity, then sensitivity is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies anti-reflective coating only to specific regions where infrared radiation enters the sensor, rather than coating entire filter surfaces. This localized application maintains the sensitivity improvement while reducing the overall manufacturing complexity and material requirements.
5Temperature
If a Peltier cooler is integrated into the same plane as thermocouples, then cooling is provided, but noise in thermocouple readout increases due to current consumption and heat generation
Solution Approach 1:
The patent positions the Peltier cooler in a different spatial plane relative to the thermocouple readout circuits, specifically placing it on the opposite side of the substrate or in a separate layer. This dimensional separation prevents the heat and electromagnetic interference from the Peltier cooler from directly affecting the sensitive thermocouple measurements, thereby reducing noise while maintaining cooling functionality.
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 solution enhances sensitivity and reduces self-heating, leading to improved operational efficiency and cost-effectiveness by effectively managing thermal isolation and noise in IR sensors.
Implementation Method 1
a cooling semiconductor substrate having a upper surface coupled to a lower surface of the temperature sensing semiconductor substrate and comprising a Peltier cooler
Implementation Method 2
A pyroelectric detector is typically constructed from lead zirconate titanate (PZT) using a sol-gel deposition method
Implementation Method 3
At least one of the temperature sensing semiconductor substrate, and the cooling semiconductor substrate may have a cavity therein beneath the thermopile and aligned therewith
Data Source
AI summary
An electronic device may include a temperature sensing semiconductor substrate, that may include a thermal sensor at an upper surface thereof, and a cooling semiconductor substrate having an upper surface coupled to a lower surface of the temperature sensing semiconductor substrate. The cooling semiconductor substrate may include a Peltier cooler. At least one of the temperature sensing semiconductor substrate and the cooling semiconductor substrate may have a cavity therein beneath the thermopile and aligned therewith.