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16 SMT Magazine • February 2014 nesses were measured. Their specifications are as follows: • Circular microBGA apertures: 10.8 mil • Square microBGA apertures: 10.8 mil • Rectangular 0201 apertures: 11.8 x 13.8 mil • Foil thickness: 4 mil The apertures were measured on the PCB side with a Microvue automated vision sys- tem; 32 of each aperture size were measured per stencil. Round apertures all measured to within 0.5 mil of their specifi- cation; square or rect- angular ones measured within 0.7 mil of their specification. Foil thick- ness were consistent at 4.0 mil on the SS due to its precision manufac- turing process and aver- aged 3.9–4.0 mil on the electroformed stencils. The average measure- ments are reported in Table 5. The measurements were used to calculate the actual aperture vol- umes and area ratios shown in Table 6. Paste Volume Measurements & Print yields The paste volume information and print yields resulting from the 10-print tests are shown in Tables 7–9. SPI databases were also queried for the mi- croBGAs average positional offset in X and Y. The results are shown in Table 10. analysis experiment #1: effect of Cutting Parameters and Nanocoating 1) Print Yields Print yields are determined by the automatic solder paste inspection system. All 9472 depos- FINe-TuNING THe STeNCIL MaNuFaCTurING PrOCeSS continues FEATUrE Table 5: Average aperture mea- surements. Table 6: Aperture volumes and area ratios for test stencils.