Effect of stencil wall aperture on solder paste release via stencil printing

Abstract

Solder paste printing is a process by which the correct amount of solder paste is applied to the printed circuit board via a stencil. The solder release from the stencil printing process very much depends on the type of solder paste and stencil conditions such as the shape of the aperture, size, and thickness of the stencil. This paper investigates the stencil condition in particular the stencil wall aperture and its relationship to the solder release ability. In this work, two types of stencil wall openings A and B were used, which differ in a different ways of cutting to achieve the wall aperture. The cutting process produced different surface roughness of the wall aperture of the stencil. Stencil printing was performed to print the solder paste onto the PCB pad. The release of solder paste was observed by solder paste inspection (SPI) and analyzed qualitatively and quantitatively. The results show that stencil B gives a better solder compared to stencil A. This is due to the smoother wall aperture compared to stencil A which has a roughened wall aperture. This shows that the performance of stencil printing in terms of solder printing quality is highly dependent on the surface roughness of the stencil aperture. Stencil quality is important as it affects the performance of solder paste printing, and this process is mainly carried out in the electronics industry. Therefore, understanding stencil conditions is important for electronic technology that uses solder printing.