Residual Stress Image Inspections Based on Bending Testing for Flexible Transparent Conducting Substrates by Single-Direction Common-Path Image Interferometry

This paper proposes a method for automatic inspection of residual stress images based on bending testing for flexible transparent conducting substrates. A flexible characteristics inspection system with single-direction common-path image interferometry is utilized to inspect residual stress images automatically during the bending testing operation. Accordingly, a 5 × 5 cm
²
residual stress image of a 203-μm line pattern on a conducting Indium tin oxide (ITO) film deposited on Polyethylene terephthalate (PET) substrate with up to 11000 bending cycles is inspected and analyzed. The relationship between the residual stresses and resistance characteristics of the 203-μm line pattern on the ITO-deposited-on-PET substrate based on bending testing is also analyzed. It was found that the change results of the residual stress can predict the resistance characteristics of the ITO-deposited-on-PET substrate sufficiently. Therefore, the inspection results of residual stress images depicted on flexible electronics may help designers and manufacturers to develop products and ensure quality control, respectively, in a manufacturing process.