Issue link: https://iconnect007.uberflip.com/i/699765
July 2016 • SMT Magazine 45 which at 85%RH took a platen temperature of 36.5°C. Hence with this experimental arrange- ment the ambient temperature and humidity and the platen temperature are all indepen- dently controlled, and the impact of these fac- tors can be assessed independently. It is also pertinent to note that the platen temperature at which condensation occurs closely agrees with the dew points given in Table 1. An indication that an even level of conden- sation is achieved is shown in Figure 5. Here features of the water film can be seen across the entire surface and crossing the track and gap without hindrance. Assessing Conformal Coating Performance In this study the same test vehicle was used as described above, but manufactured with 1 and 3-oz copper, corresponding to track heights of approximately 35 and 105µm. The test vehi- cle is shown in Figure 6. The applied coatings in- cluded one of the new super hydrophobic nano coatings, two types of acrylic, and two types of polyurethane. The first acrylic was also tested after a double spray process, and both polyure- thanes were tested in a thick form. Cross sec- tions of the coatings are shown in Figure 7, the copper thickness is approximately 35 µm, from which the coating thickness can be gauged. Both polyurethanes can be seen to amply cover the track, whereas the acrylic coatings are just managing to do this, and it is not clear whether the nano coating has covered the track. CONDENSATION TESTING—A NEW APPROACH Figure 5: Uniform condensation across the SIR pattern. Figure 6: SIR test coupon used for coating studies. Figure 7: Coating coverage on the 1oz copper tracks of the SIR patterns. Figure 8: SIR testing of conformal coated boards.