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60 SMT Magazine • April 2014 The results indicated that the silicon did not delaminate. Delamination is easy to see in the test as shown in the following images. The following profile was used. However, if the solder paste is a low/no resi- due nitrogen reflow solder paste delamination does not occur. The photographs in Figures 8–13 identify the hard flux issue with delamination of a hard- er urethane coating. Conformal coatings are not hermetic with all the materials tested having varying degrees of moisture vapor transmission. In this case, whereas moisture enters the coating, the softer residue solder paste absorbs the moisture and creates a "pressure cooker" of corrosion and electrical failures (Figure 15). Pictured in Figure 14 are SIR test results showing the beginnings of dendrites. These were run in 85°C/85Rh. SIR testing was also run at 40°C and 90 Rh. This test showed less failures figure 6: Paste 16 (low/no residue) pre-T shock. figure 4: Pre-shock. figure 7: Paste 16 post-T shock/no defects. figure 5: Paste 55 Post-T shock delamination. figure 3: Profile. CONFOrMal COaTiNG OvEr NO-ClEaN FlUX continues fEATurE