On-Machine Measurement for Surface Flatness of Transparent and Thin Film in Laser Ablation Process

Abstract

In printed electronics, laser ablation is used to repair defective patterns on transparent, flexible, and thin films, using high-power lasers. The distance between the film surface and laser focus is sensitive to changes as the narrow focus depth of the lens is the range of tens of microns. However, a film fixed on a conductive vacuum chuck (CVC) is always curved, owing to chucking bending; thus, laser focusing must be locally performed before ablation. Therefore, this study proposes a non-contact measurement method for the surface flatness of a transparent and thin film, to compensate for laser defocusing in a large area. The surface flatness was obtained using camera-focus points on the porous surface of the CVC. The focus points were interpolated to achieve a smooth and continuous surface flatness for chucking bending. A laser distance sensor was used to verify the surface flatness from the proposed method. The surface flatness was used to inspect the printed patterns, and to perform laser ablation on the film. The proposed method is advantageous for large-area laser ablation and is expected to become indispensable for repairing machines in printed electronics.

Circular saw flatness on machine measurement using a point laser displacement sensor

“…A number of algorithms have been proposed to compute the value of flatness for data point sets [3]. They can be classified into two categories: least squares evaluation methods and minimum zone methods.…”