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84 SMT Magazine • March 2014 feaTure Printing Performance Printing tests were performed at 25°C in a DEK Horizon 05 printer using the Efsot Verifica- tion board 1 with a 120 microns laser cut stain- less steel stencil and 250 mm length squeegees. The test board includes a printing pattern test area (horizontal and vertical), 0.4 mm pitch QFN, 0402 and 0201 printing areas (Figure 8). The minimum pressure according to printing speed was determined (Table 5, Figure 9). Paste C requires much more pressure than the other pastes and is not able to stand high printing speeds (Figure 10). The printing quality was assessed mainly on the printing test patterns using criteria accord- ing to Philips Notation 1 : The results are rejected if the smearing result is below or equal to 2 on 0.27 mm opening width and 0.13 mm space width or if the printing result is below or equal to 2 on 0,22/0,18: under stencil cleaning is then required. The details to assess printing quality are explained in Figures 11 and 12. The printing definition and the smearing ability were evaluated for each solder paste at a medium speed of 50 mm/s. The pressure ap- plied is the minimum pressure determined be- fore plus one bar additional. The first board is printed and the quality is visually inspected, then, without any cleaning, a second board is printed, etc., until the criteria are reached. Ta- ble 6 shows the example of pastes C and F. For shorts, paste C reached the criterion after 13 rELIaBILITY aSSESSmENT OF NO-cLEaN aND WaTEr-SOLUBLE SOLDEr PaSTES, ParT 1 contin ues Figure 8: a) efsot verification board and b) detail of printing pattern. figure 9: graph of pressure according to speed. Table 5.