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SMT-July2016

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July 2016 • SMT Magazine 23 performed. The results are a borderline pass for solder paste A with high SIR values and a pass with a wide margin for the samples that used solder paste that failed to consistently main- tain a SIR above 100 MΩ during the constant climate test. Log SIR per J-STD-004C is shown for pastes A and B in Figure 8. In this case, SIR values are 4.5 or- ders of magnitude higher for paste A than paste B. Conclusions These divergent test results emphasize why a ROSE test should be used as a relative test to qualify a process, and to use the baseline SIR/ Ionic contamination measured using the dual purpose test as a benchmark for "future trouble shooting or process improvement efforts." Test coupons with ionic equivalent measurements just below the 1.56 µg/cm 2 NaCl equivalent limit used in ANSI/J-STD-001f were shown to have three orders of magnitude greater surface insulation resistance, but still have 3X mea- sured ionic contamination. Thus, the ionic con- tamination of a PCBA does not predict any reli- ability of the electronic control unit under high temperature and high humidity conditions. It is highly recommended that the 5-22A task group review and amend ANSI/IPC-J-STD-001f to account for the known divergence in SIR and Ionic contamination results on the electrical re- liability if SMT assemblies. SMT *Co-Authors: M. Holtzer, T. Cucu, M. Libera- tore, M. Schmidt, Alpha Assembly Solutions; and S. Moser, L. Henneken, P. Eckold, U. Welzel, R. Frit- sch, D. Schlenker, Robert Bosch GmbH. Note: This article was presented at the technical proceedings of the IPC APEX EXPO 2016. References 1. Seelig, K. "VOC-Free Flux Study-Not All Weak Organic Acids are the Same," APEX 2012 Proceedings. 2. Chan, A.S.L., Shankoff, T.A. "A Correla- tion between Surface Insulation Resistance and Solvent Extract Conductivity Cleanliness Tests," Circuit World, Vol. 14 Iss: 4, pp.23–26 (1988). 3. Mittal, K.L. "Treatise on Clean Surface Technology," Vol. 1, p.81, (1987). 4. Hymes, L. "Cleaning Printed Wiring As- semblies in Today's Environment" (1991). 5. Tegehall, P-E., "Cleanliness and Reliabil- ity," IVF Research Publication 96846 (1996). 6. Crawford, T., "An In-Depth Look at Ionic Cleanliness Testing," IPC-TR-583 (1993). DIVERGENCE IN TEST RESULTS USING IPC STANDARD SIR AND IONIC CONTAMINATION MEASUREMENTS Figure 8: Paste A and Paste B SIR per J-STD-004B/IPC-TM-650 Method 2.6.3.7.

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