Overview
IEC 62951-5:2019 is an international standard developed by the International Electrotechnical Commission (IEC) that specifies the test method for evaluating the thermal characteristics of flexible semiconductor materials. These materials, including both substrates and thin films, are subject to bending and stretching in practical applications. The standard introduces a non-contact optical thermometry technique based on temperature-dependent optical reflectance-known as thermoreflectance-to measure and analyze thermal properties with precision.
This standard covers terminology, symbols, and detailed test procedures to ensure consistent evaluation of flexible and stretchable semiconductor devices. It addresses the unique challenges posed by flexible materials, whose thermal characterization requires sensitive and accurate methods to account for their mechanical flexibility and optical properties.
Key Topics
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Thermoreflectance Principle
The test method relies on thermoreflectance, which measures changes in optical reflectance of a material surface as a function of temperature without physical contact. This technique exploits temperature-dependent variations in refractive index to determine thermal behavior.
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Material Categorization
- Substrate materials: Defined as materials thicker than approximately 12.7 µm (20 times the probing laser wavelength). Their optical reflectance typically changes linearly with temperature.
- Thin-film materials: Defined as materials thinner than approximately 12.7 µm, exhibiting highly non-linear optical reflectance behavior with temperature, requiring more advanced measurement techniques.
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Test Apparatus and Measurement Techniques
For substrates, single-wavelength optical probing suffices, while thin films require dual-wavelength probing to compensate for non-linearities and thickness-related variations. The apparatus includes laser sources, optical setups for reflectance measurement, and calibration procedures.
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Testing Procedures
The standard specifies procedures for measuring thermoreflectance signals during bending or uniaxial stretching of flexible semiconductor materials. It defines how to calibrate signals, perform optical measurements, and document thermal parameters such as local and average temperatures, initial and final temperature states, and thermal time constants.
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Data Reporting
Test results include reflectance values as functions of temperature, thermal response curves, and calculated thermal time constants. Documentation supports reproducibility and comparison across devices and materials.
Applications
IEC 62951-5:2019 applies to the following practical use cases:
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Flexible Electronic Devices
Evaluation of thermal behavior in flexible semiconductors used in wearable electronics, foldable displays, and bendable sensors.
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Stretchable Semiconductor Devices
Characterizing thermal performance in devices designed for uniaxial stretching or complex deformation during operation.
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Thin-Film Flexible Materials
Optimizing and validating thin-film materials for use in advanced semiconductor applications including flexible photovoltaics and bio-integrated electronics.
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Thermal Management in Emerging Technologies
Providing essential data to improve heat dissipation and reliability of flexible electronic systems under mechanical stress.
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Product Development and Quality Assurance
Enabling manufacturers and researchers to standardize thermal testing, ensuring product safety and performance consistency.
Related Standards
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IEC 62951 Series
Part of a broader series covering flexible and stretchable semiconductor devices, providing complementary guidelines on material properties and testing methods.
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IEC 60050-845
Electrotechnical vocabulary standard related to definitions of reflectance and optical properties, referenced for terminology consistency.
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ISO/IEC Directives, Part 2
Governs the drafting and formatting principles for IEC and ISO standards, ensuring clarity and harmonization across documentation.
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Other Optical and Thermal Measurement Standards
Related guidelines on non-contact temperature measurement and semiconductor device characterization provide foundational methods supporting thermoreflectance techniques.
Keywords: IEC 62951-5, thermoreflectance, flexible semiconductor devices, stretchable semiconductors, thermal characteristics, optical thermometry, test method, non-contact temperature measurement, thin-film materials, substrate materials, thermal time constant, flexible electronics, standardization, semiconductor testing
Open preview (PDF)Semiconductor devices - Flexible and stretchable semiconductor devices - Part 5: Test method for thermal characteristics of flexible materials
