![]() The medium flows slightly after printing to reduce visible mesh marks left in the print. In this process, the mesh aperture on the screen is pulled away from the printed surface behind the squeegee, leaving behind the ink that was once inside the mesh aperture. Initially, the squeegee blade presses the medium into the open apertures of the image, and then removes the excess as it passes through each aperture. While the squeegee moves across the screen, the mesh of the screen comes in contact with the board, allowing the medium to roll onto the PCB. The starting position of a screen printerĪs shown in the figure, the screen is positioned just above the board, and the medium (ink) lies in front of a flexible squeegee. The emulsion is usually applied on both sides of the mesh, and a defined thickness is built upon the underside (the side that contacts the board). A stencil of the required image is created by applying a photosensitive emulsion to the mesh. The screen printing process involves a screen formed by stretching a mesh of fine polyester or stainless steel wires over a rigid frame to serve as an image carrier.
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