Pyroelectric Infrared Detection Element Thermal Expansion Suppression
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Solution Overview
Problem
Pyroelectric substrates in infrared detection elements experience deformation due to thermal expansion, leading to voltage generation as noise, which affects the accuracy and reliability of infrared detection.
Innovation Solution
A pyroelectric infrared detection element is designed with a first substrate bonded to the front side, having a thermal expansion coefficient lower than the pyroelectric substrate, and a second substrate bonded to the back side, both with a thermal expansion coefficient difference of 8.9 ppm/K or less to minimize deformation, along with a manufacturing method that includes bonding with conductive adhesive materials to further suppress substrate deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thermal expansion coefficient of the first substrate is made significantly lower than that of the pyroelectric substrate to suppress deformation, then the suppression effect is enhanced, but the thermal expansion coefficient difference becomes excessively large causing deformation due to thermal stress
Solution Approach 1:
The patent applies parameter changes by precisely controlling the thermal expansion coefficient difference between the first substrate and pyroelectric substrate to be 8.9 ppm/K or less. This quantitative parameter optimization resolves the contradiction by finding the optimal balance point where deformation is suppressed without generating excessive thermal stress that would cause new deformation issues.
2Speed
If the thickness of the pyroelectric substrate is reduced to achieve high sensitivity and high-speed response, then the response performance is improved, but piezoelectric noise increases due to deformation
Solution Approach 1:
The patent applies preliminary anti-action by bonding the first substrate to the pyroelectric substrate before operation to prevent deformation. This preventive measure counteracts the piezoelectric noise generation mechanism, allowing thin substrates to be used for high-speed response without suffering from the harmful piezoelectric noise that would normally result from thermal expansion deformation.
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 effectively reduces deformation of the pyroelectric substrate, thereby minimizing piezoelectric noise and enhancing the sensitivity and reliability of the infrared detection element, particularly in applications requiring high sensitivity and rapid response.
Implementation Method 1
a first substrate bonded to the front side of the pyroelectric substrate and having a thermal expansion coefficient lower than a thermal expansion coefficient of the pyroelectric substrate
Implementation Method 2
When deformation, such as warpage, is caused in the pyroelectric substrate used in the infrared detection element by thermal expansion, voltage is generated by a piezoelectric effect
Implementation Method 3
When a surface of the pyroelectric element is irradiated with infrared light, the temperature of the pyroelectric substrate increases. Then, the change in temperature changes spontaneous polarization, disturbs the balance of electric charge on the surface of the pyroelectric substrate, and causes generation of electric charge
Data Source
AI summary
In an infrared detection element 15, a first substrate 36 is bonded to a front side of a pyroelectric substrate 20. Since the thermal expansion coefficient of the first substrate 36 is lower than that of the pyroelectric substrate 20, deformation of the pyroelectric substrate 20 due to thermal expansion can be suppressed by the first substrate 36. Further, since a thermal expansion coefficient difference D is 8.9 ppm/K or less, the thermal expansion coefficient between the first substrate 36 and the pyroelectric substrate 20 is not excessively large, and this can suppress deformation of the infrared detection element 15 due to the thermal expansion coefficient difference between the first substrate 36 and the pyroelectric substrate 20.