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62 SMT Magazine • July 2015 BENEFITS OF SOlDERING WITH VACuuM PROFIlES, PART 2 greater extent, partitioning of a large ground pad can have a positive effect on wet paste print characteristics and wet paste print stability (e.g., scooping etc.), which may lead to better results. Nor can any single vacuum pressure value be specified, which always yields best possible re- sults. Depending on the wet paste layer thick- ness, the selected solder paste and the stencil aperture, results of less than 2% void content can be attained with vacuum pressure values ranging from 10 to 100 mbar. SMT ArtiCle figure 4: comparison of stencil geometry, stencil type and soldering process. Helmut Oettl is head of application and product management for rehm Thermal Systems.