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88 SMT007 MAGAZINE I SEPTEMBER 2020 from 30°C to 300°C. A baseline DSC study of the only activator was carried out to discover whether the activator undergoes any heat change during this thermal ramp. Representa- tive DSC thermograms are shown in Figure 7. DSC results reveal endothermic peaks for only the activator runs corresponding to the melting point of the activators. Additional exothermic and endothermic peaks are observed for oxide- activator mixtures. These additional peaks we believe are resulting from the reaction between activators and copper oxides. A closer look at the thermogram also reveals activator ACT1 reacts with cupric oxide just after it melts around 140°C, while the other, ACT3, reacts with cuprous oxide at a similar temperature after melting at 100°C. ACT3 also showed a smaller reaction exotherm around 220°C with cupric oxide. This indicates each of the activators reacts with a particular oxide at a particular temperature range. Thus, a multi- component activator package, where different constituents will react with different oxides at different temperature ranges, will be efficient to remove all the oxide from OSP coating. Wetting of Solder on OSP Now, with the knowledge on the flux ingredi- ents required to remove thermally treated OSP, we wanted to evaluate their efficiency to wet solder. A few activators and solvents selected from the aforementioned studies were short- listed, as shown in Table 1. A wetting evalua- tion was carried out on ENTEK Plus HT coated OC-3 coupons using Malcomtech SWB-S2 wet- ting balance tester fitted with SAC305 solder bath. Wetting data were collected on both as-coated and 2x Pb-free reflowed coupons Figure 7: Representative DSC thermogram of activator copper oxide mixtures.