Defects in aluminum thin films deposited on pet substrate and their formation mechanism

Defects in aluminum films deposited on PET substrate by a vacuum web coater were investigated to clarify their formation mechanisms. The defects detected by optical transmission equipment were taken from a plastic web, and then observed with optical and scanning electron microscopes (SEM). Subsequently, the shapes were classified into four types: teardrop, splashing, scattered dots and round. However, the features of the microstructure were classified as follows: Clear boundary line without filmsUnclear boundary line with transparent filmsUnclear boundary line with transparent films and residual particles at the center and thermally damaged and penetrated. It has been suggested that the defect formation mechanisms are as follows: (a) splashing of molten aluminum droplets, (b) oxidation of aluminum due to oxygen-containing substances such as water and oil and (c) oxidation of aluminum due to the adhesion of polymer lint