Divergence in Test Results Using IPC Standard SIR and Ionic Contamination Measurements

Estimated reading time: 6 minutes

Figure 8: Paste A and Paste B SIR per J-STD-004B/IPC-TM-650 Method 2.6.3.7.

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/cm² 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 measured ionic contamination. Thus, the ionic contamination of a PCBA does not predict any reliability 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 reliability if SMT assemblies.

*Co-Authors: M. Holtzer, T. Cucu, M. Liberatore, M. Schmidt, Alpha Assembly Solutions; and S. Moser, L. Henneken, P. Eckold, U. Welzel, R. Fritsch, D. Schlenker, Robert Bosch GmbH.

References

1. Seelig, K. “VOC-Free Flux Study-Not All Weak Organic Acids are the Same,” APEX 2012 Proceedings (2012).

2. Chan, A.S.L., Shankoff, T.A. "A Correlation 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 Assemblies in Today’s Environment” (1991).

5. Tegehall, P-E., “Cleanliness and Reliability,” IVF Research Publication 96846 (1996).

6. Crawford, T., “An In-Depth Look at Ionic Cleanliness Testing,” IPC-TR-583 (1993).

This article appeared in the July 2016 issue of SMT Magazine.

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