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July 2016 • SMT Magazine 49 CONDENSATION TESTING—A NEW APPROACH Figure 10: Condensing conditions with the 1oz copper tracks with the nano and polyurethane coatings. the copper track and in particular, whether the corners are coated. The results from the con- densation testing of these coated boards are pre- sented in Figure 12. The results in Figure 12 show that the two polyurethane coatings behave in a very similar mode as shown in Figure 10. The nano coat- ing results are not shown here as they also per- formed similarly to before. However, now the two acrylic results are different, with the single coated acrylic showing a large drop in SIR, in- dicating that the corners of the tracks are not covered. Supporting this conclusion, the image in Figure 13 shows corrosion at the track edge, and with corrosion products forming across the top of the coating between the anode and cath- ode. The acrylic-1 results show the SIR drop- ping to 106Ω from the first condensation event, with the behavior remaining broadly consistent through the following condensation cycles. With the double coated acrylic the SIR results are not as bad, but SIR values are dropping be- low 108Ω, and with a trend of decreasing SIR with each condensation cycle. The 1oz copper SIR pattern boards the results in Figure 9 do not show any difference between the single and double coated boards, but with the 3-oz copper SIR pattern boards the results do show a clear difference, and furthermore the acrylic coating Figure 11: Coating coverage on the 3oz copper tracks of the SIR patterns.