Issue link: https://iconnect007.uberflip.com/i/1137649
38 SMT007 MAGAZINE I JULY 2019 The first five circuit boards from the print- and-pause test were used for reflow perfor- mance and voiding measurement. The next two circuit boards from the print-and-pause test were placed on a counter and left open to the air overnight. They were reflowed the fol- lowing day (after 24 hours) and reflow perfor- mance was measured. Reflow Profile and Performance Reflow was done in a 10-zone convection reflow oven. A linear ramp-to-spike (RTS) type profile was used (Figure 10). The parameters for the profile are summa- rized in Table 5. Wetting, solder balling, and graping were measured for each solder paste. This was done with freshly printed solder paste and again with circuit boards that sat open to the air for 24 hours. Figure 11 shows the wetting pattern on the PR test board. This pattern includes 12 vertical and 12 hori- zontal parallel lines with 15 solder paste bricks printed down each line. The solder paste bricks Figure 9: Print-and-pause test method. Figure 10: Linear ramp to spike (RTS) reflow profile. Table 5: Reflow profile parameters. Figure 11: PR test board wetting pattern before (L) and after reflow (R).