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78 SMT007 MAGAZINE I MAY 2024 ple type is averaged with the other three to four units in the test at each temperature. With eas- ily over 1,000 warpage measurements through- out the test, this makes the data quantity feasi- ble to analyze. Figures 10 to 15 show average coplanarity over temperature for all six sample types respectively. e different moisture con- ditions are shown as four different series on the graphs. Some "W " shape patterns can be seen in the graphs. is is a result of looking at the data without any sign association. Each of the 89 dif- ferent samples used in the study went through a transition between positive and negative at some point during the reflow profile. e transition point varies a bit between the differ- ent samples but is more oen in the 150–200°C range on both heat and cool sides of the profile. For the smaller samples, this trend is harder to visualize due to the lower warpage levels of the sample. Looking closer at the individual sam- ple plots on the 40 mm samples at MSL4, all Figure 10: Average coplanarity over temp, 10 x 11 mm. Figure 13: Average coplanarity over temp, 20 x 15 mm. Figure 11: Average coplanarity over temp, 11 x 12 mm. Figure 14: Average coplanarity over temp, 27 x 27 mm. Figure 12: Average coplanarity over temp, 14 x 14 mm. Figure 15: Average coplanarity over temp, 40 x 40 mm.