A novel laser scattering measurement method to detect tension in the PET film during the roll-to-roll manufacturing process

Polyethylene terephthalate (PET) film is a critical substrate material used in the fabrication of flexible electronic devices through Roll-to-Roll (R2R) manufacturing processes. Due to its elastic and flexible nature, PET film is prone to deformation and wrinkling under creep and temperature rise during motion, particularly when subjected to the rolling action of R2R systems. Such deformation adversely affects manufacturing accuracy and compromises device stability and reliability. To address this issue, a novel on-machine metrology method based on polarized laser scattering (PLS) was proposed to detect the tension state of PET films. Experimental results demonstrated that both tensile stress and surface wrinkling of the PET film can be effectively detected using the proposed PLS approach. The tensile stress level and wrinkle height exhibited exponential correlations with the PLS signal. The minimum detectable stress and wrinkle height were determined to be 6.47 MPa and 8.3 μm, respectively. The work advances the agenda of digital metrology and digital manufacturing processes in demanding environments, especially with the moving substrate such as in the R2R manufacturing.