Issue link: https://iconnect007.uberflip.com/i/911509
74 SMT Magazine • December 2017 The laser uses more energy to plunge into the middle of the aperture and less energy to provide a clean cut around the perimeter shown in Figure 4 from previous studies 1-3 . Topography of Aperture Walls The roughness measurement was performed on the aperture walls of a test coupon for each stencil. The coupons were cut in half where in- dicated in Figures 5a and 5b, and four apertures were measured for each coupon. The topogra- phy comparison of A1 and C11 single aperture show a dramatic difference in roughness. Additionally, stencil C11 showed signifi- cant bottom side slag shown in Figures 6a and b, measuring over 30 microns high. This would raise the stencil off the board surface and like- ly would lead to excessive paste deposit volume caused by poor gasketing and allowing paste Table 3: Visual assessment of stencil apertures after 6th print. Representative photos are shown in Appendix I. Figure 3: Square apertures with radiused corners. Figure 4: Typical cutting path of a laser beam. EVALUATION OF STENCIL TECHNOLOGY FOR MINIATURIZATION Figure 5a: Aperture topography of coupon A1. Figure 5b: Aperture topography of coupon C11.