Issue link: https://iconnect007.uberflip.com/i/699765
22 SMT Magazine • July 2016 cil. The coupons were then exposed the tem- perature profile similar to that shown in Figure 3 below using a OmniFlo 7 oven in N2 (600- 800ppm O2). Results and Discussion Log SIR results for solder paste A and solder paste B measured on the leads around the small QFP on the IPC-B-52 coupons are depicted in Figures 4 and 5 respectively. Figure 6 shows the mean Log SIR values for all six patterns mea- sured for both solder pastes. As can be seen from the 7-day test, paste A has a consistent SIR read- ing of three orders of magnitude greater than paste B. Paste B is a marginal fail if 100MΩ is used as the pass/fail standard. Figure 7 compares the results for ionic con- tamination measured on the IC part of the B-52 test vehicles with solder paste A and B. Contrary to the SIR readings, the test coupons processed with solder paste A exhibit an ionic contami- nation level that were three times larger than solder paste B. The discrepancy is a result of the easy extraction of benign ionics in the alcohol/ water mixture from solder paste A, and insol- uble contributors to reduced surface insula- tion in solder paste B. A detailed analysis of the chemical nature of the ionic residues was not DIVERGENCE IN TEST RESULTS USING IPC STANDARD SIR AND IONIC CONTAMINATION MEASUREMENTS Figure 4: IPC-B-52 SIR test results of paste A at small QFP leads. Figure 5: IPC-B-52 SIR test results of paste B at small QFP leads. Figure 6: Mean B52-SIR all patterns paste A and paste B. Figure 7: Box plots of ionic contamination measurements of the IC part of B-52 test vehicles processed with solder pastes A and B.