Overview
IEC 62951-3:2018 specifies a standardized method for evaluating thin film transistor (TFT) characteristics on flexible substrates under bulging. The standard covers test-piece preparation, measurement of dimensions, storage prior to testing, test apparatus and procedure, data analysis and reporting. It applies to TFTs fabricated on flexible substrates such as PET, polyimide (PI), elastomers and other flexible materials where a uniformly distributed pressure (bulging) is used to apply stress.
Key technical topics and requirements
- Scope and purpose: Measure electromechanical behavior of TFTs when a flexible substrate is deformed by uniform pressure (bulge test), enabling comparison and repeatable characterization.
- Test-piece preparation: TFTs must be fabricated to avoid cracks, flaws or delamination; devices should be placed in the central region of the test piece where strain is uniform.
- Dimensional measurement: Accurate measurement of substrate and thin-film thicknesses and dimensions is required because these values feed into mechanical and electrical analysis. The standard recommends that thin-film thickness be smaller than substrate thickness and that substrate material be in‑plane isotropic to achieve equibiaxial stress.
- Storage and handling: Control storage environment to prevent oxidation or surface deterioration prior to testing; damaged specimens (not present immediately after fabrication) should not be tested.
- Test apparatus: Uses a pressure chamber with a defined open window to apply uniformly distributed pressure. Multiple equipment types are referenced (e.g., absorption-type, bulging-type with heating). Lead wires must be attached to source, drain and gate pads for electrical measurement.
- Test procedure and data analysis: Perform bulge testing at specified temperatures, collect mechanical (pressure–deflection/strain) and electrical (DC characteristics) data, and extract TFT parameters (for example, mobility and subthreshold slope) as part of evaluation.
- Reporting: Test report shall include specimen dimensions, test conditions, apparatus description, measurement data and analysis results.
Practical applications and users
IEC 62951-3 is useful for:
- Semiconductor manufacturers developing flexible and stretchable electronics (flexible displays, wearable sensors).
- R&D labs and universities researching electromechanical performance of flexible TFTs.
- Qualification and test laboratories performing comparative or compliance testing of flexible devices and materials.
- Materials and process engineers assessing substrate choices (PET, PI, elastomers) and fabrication effects on device reliability.
By standardizing bulge-based electromechanical test methods, this IEC part helps ensure repeatability and comparability of TFT performance under biaxial strain conditions.
Related standards
- IEC 62047-17 - Bulge test method for measuring mechanical properties of thin films (referenced normative).
- IEC 60747-8 - Field-effect transistors (referenced for transistor terminology and electrical test methods).
Keywords: IEC 62951-3, thin film transistor, TFT, flexible substrates, bulging test, bulge test, PET, polyimide, elastomer, electromechanical properties, pressure chamber, test procedure.
Open preview (PDF)Semiconductor devices - Flexible and stretchable semiconductor devices - Part 3: Evaluation of thin film transistor characteristics on flexible substrates under bulging
