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72 SMT007 MAGAZINE I JULY 2019 ity at 200 cycle intervals for the following four components (Figure 31): • 1196 PBGA, 35x35 mm, 1.0-mm pitch, SAC 305 (u309) • 196 PBGA, 15x15 mm, 1.0-mm pitch SAC 305 (u1) • 64 CBGA, 9x9 mm, 0.8-mm pitch, SAC 305 (u300) • 2512 thin-film ceramic zero-ohm resistors (R350) As of the time of this writing, we had reached 4,200 cycles with very few failures on any components other than the (expected) 2512 thin-film ceramic zero-ohm Resistors. Paste D boards were not assembled at the same time as the other pasteboards, so it had only com- pleted 1,000 temperature cycles as of the time of this article without any failures (Figure 32). As expected in Figure 33, the low-tempera- ture (bismuth-containing) alloys slightly out- performed the control Material A during this relatively low strain rate testing. Environmental Impact and Potential Cost Savings With a greater than 50-degree peak temper- ature delta and a lower-temperature profile overall, it should be clear that the energy con- Figure 31: The test vehicle arrangement and the locations of the four monitored components. Figure 32: Temperature cycle chamber characterization response (0–100°C, 10-minute ramps and dwells). Figure 33: Weibull failure plots for the three materials (Pastes A, B, and C) on the 2512 capacitors.

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