Direct deflection radius measurement of flexible PET substrates by using an optical interferometry

Area of Science:

• Materials Science
• Optical Metrology
• Mechanical Engineering

Background:

• Residual stress in flexible electronics impacts device performance and reliability.
• Accurate measurement of substrate deflection radius is crucial for residual stress estimation.
• Current methods for determining deflection radius are indirect and lack precision.

Purpose of the Study:

• To develop and validate a direct measurement methodology for the deflection radius of polyethylene terephthalate (PET) substrates.
• To enhance the precision of deflection radius measurements for flexible electronic applications.
• To provide a reliable tool for residual stress analysis in flexible electronics.

Main Methods:

• Established a Twyman-Green optical interferometer setup.
• Utilized phase-shifting technology to enhance measurement resolution.
• Prepared five PET substrates with known deflection radii for calibration and verification.

Main Results:

• Successfully demonstrated a direct measurement methodology for PET substrate deflection radius.
• Achieved high measurement precision with an error variance below 3.5%.
• Validated the effectiveness of the optical interferometer and phase-shifting technique.

Conclusions:

• The proposed optical interferometry method provides a direct and precise way to measure deflection radius.
• This technique is vital for accurate residual stress estimations in flexible electronics.
• The methodology offers a significant improvement over existing indirect methods.