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44 SMT007 MAGAZINE I MARCH 2018 Print Test Preparation The list of resources used to complete the M0201 print testing is supplied in Table 4. We decided to implement a printing process that included the most advanced and enhanced setup to create the best possible opportunity to print well. The printing machine used was a modern, well maintained, fully automatic, option loaded, state of the art model. Three key options on this machine that were used include automatic height adjusting edge snugging clamps, dedi- cated vacuum tooling, and ultrasonic squee- gee technology. The virtues of these options have been previously reported [13, 14] . Type 5 fine powder solder paste material is recom- mended for miniature device printing was used exclusively. As previously described, one laser cut stencil was treated with a polymer nano-coating, otherwise the two stencils are identical. The printing procedure consisted of using fixed process parameters of conservative, but practical levels that should accommodate mass printing tempo. To view the natural degrada- tion of the printing process the automatic under stencil wiping process was disabled. Each print test run consisted of two warm- up prints on blank boards, followed by ten consecutive test prints that were subsequently measured by advanced SPI equipment. Table 5 denotes the experiment variable list and run order. Three categories of PCB include printing on the bare Cu backside of the board, large pad sorted boards, and small pad sorted boards. The stencil aperture is considered to have the best gasketing opportunity for print- ing on the bare Cu side, while having the worst gasketing opportunity printing on the small pads. The first three print tests involved the three different board types and were all printed using the nano-coated stencil. The remaining three print tests repeated the same process, except using the un-coated stencil. Print Test 7 was added to validate the results from Test 4. Results The data from the complete printing experiment outlined in Table 5 is consolidated into a single interaction plot compar- ing mean paste volume transfer efficiency results in Figure 13. The values in Table 6 report the specific data plotted. Data labels 4 and 7 (Figure 13) identify repeat Test 4 and Test 7 results. The plotted point in-between indicates the average of the two test conditions. Test 4 and 7 results are more alike to one another for the 50mm thick step stencil apertures due to a more favorable area ratio permitting easier paste transfer compared to the full 80mm thick stencil aper- tures. The red horizontal dashed Table 4: Experiment tools, materials, and settings. Table 5: Experiment variables, run order.