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December 2017 • SMT Magazine 47 THE EFFECT OF AREA SHAPE AND AREA RATIO ON SOLDER PASTE PRINTING PERFORMANCE represents an area ratio, starting in Row A with AR of 0.45 and ending with AR of 0.65 in Row E. Each column in these tables represents different aperture shapes. Column 1 always has the shape of a circle, Column 7 is a square and Column 13 is the form of a diamond. Column 14 contains special types of structures that will not be dis- cussed in this paper. Columns 2-6 and 8-12 are paired with the same dimensions and they only differ in their orientation towards the squeegee. Columns 2-6 face with the small side the squee- gee (i.e., north-south orientation), whereby col- umns 8-12 face the squeegee with the long side of the rectangle (east-west orientation). Figure 2 illustrates the aperture design pattern across a row to show differences between the respective column groups of apertures. The stencils used were made of stainless steel foil with laser cut apertures and produced for attachment in a Vector Guard (VG260) mas- ter frame system. A stencil nano-coating was not applied to any of these stencils. Figure 2: Column groups and aperture labels. Table 1: Aperture dimensions, 80 µm stencil. Table 2: Aperture dimensions, 100 µm stencil. Table 3: Aperture dimensions, 120 µm stencil.