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Knocking Down the Bone Pile: Tin Whisker Mitigation in Aerospace Applications, Part 3
The Effectiveness of 75% IPA/25% DI Extraction Solution on No-clean Flux Residues
June 13, 2019 | David Lober and Mike Bixenman, DBA, KYZEN; and Marietta Lemieux and Mark McMeen, STIEstimated reading time: 12 minutes
The IC data is interesting but does not have enough of a sample size to draw any firm conclusions. What is clear from the data is that the solubility of all of the WOAs is not linear with IPA concentration for this particular solder flux. It appears that, for the flux studied, there is an optimum IPA concentration, which may be located around 50% IPA 50% DI water. This indicates that the commonly used 75% IPA 25% DI water system may not be optimal.
Further Work
The findings of this study are interesting and warrant further investigation. To better refine the gravimetric data for the WOAs understudy a complimentary solubility determination method will be used. Top contenders for this method are titrations, ultraviolet-visible spectroscopy (UV-VIS), laser solubility determination, or a synthetic method [16 & 17]. These methods have the potential for being much more sensitive than the gravimetric method. The UV-VIS method is currently being explored. In addition to additional experimental work for the solubility of WOA in mixed solvent systems, a theoretical approach using Hansen Solubility Parameters is being undertaken [18]. In addition to improving the data as a function of IPA concentration, the temperature dependence of the solubility is of critical importance.
The IC work is being continued as well. Currently, additional IC samples are being run at Laboratory B. This work will be updated and expanded to additional fluxes. The specific flux used is suspected to be a substantial factor in the amount of extractable WOA ions.
References
1. Lee, N.-C. “Reflow Soldering Processes and Troubleshooting: SMT, BGA, CSP, and Flip-Chip Technologies,” Lee, N.-C. B. T.-R. S. P., (Ed.) Newnes, 2002.
2. Sigma-Aldrich. “Abietic acid,” https://www.sigmaaldrich.com/catalog/product/sial/00010?lang=en®ion=US.
3. Nyren, V.; Back, E. “The Ionization Constant, Solubility Product, and Solubility of Abietic and Dehydroabietic Acid,” Förlagsföreningen Acta Chemica Scandinavica, 12, pp. 1516–1520, 1958.
4. Lide, D. R. CRC Handbook of Chemistry and Physics, CRC Press, 2005.
5. Armarego, W. L. F.; Chai, C. L. L. Purification of Laboratory Chemicals: Sixth Edition; Armarego, W. L. F., Chai, C. L. L. B. T.-P. of L. C. (Eds.), Butterworth-Heinemann, 2009.
6. IPC-TM-650 2.3.28 Ionic Analysis of Circuit Boards, Ion Chromatography Method. IPC 2004.
7. Zhou, Y.; Turbini, L. J.; Ramjattan, D.; Christian, B.; Pritzker, M. “Characterizing Corrosion Effects of Weak Organic Acids Using a Modified Bono Test,” Journal of Electronic Materials, 42 (12), pp. 3609–3619, 2013.
8. Verdingovas, V.; Jellesen, M. S.; Ambat, R. “Solder Flux Residues and Humidity-Related Failures in Electronics: Relative Effects of Weak Organic Acids Used in No-Clean Flux Systems,” Journal of Electronic Materials, 44 (4), pp. 1116–1127, 2015.
9. ResearchGate. “Evaluating the Efficacy of a Group of Nontraditional Plasticizers on the Glass Transition Temperature of Ethyl Cellulose Polymer,” https://www.researchgate.net/Example-of-dicarboxylic-acids_tbl1_47413566.
10. Lehman, J. W. Operational Organic Chemistry: First Edition, Prentice-Hall, 2002.
11. Harris, D. C. Quantitative Chemical Analysis: Seventh Edition, W. H. Freeman and Company, 2007.
12. Nong, W.; Chen, X.; Wang, L.; Liang, J.; Wang, H.; Huang, Y.; Tong, Z. “Measurement and Correlation of Solubility of Abietic Acid in Ethanol + Water Mixtures,” Journal of Chemical Thermodynamics, 68, pp. 199–204, 2014.
13. Nong, W.; Chen, X.; Wang, L.; Liang, J.; Wang, H.; Long, L.; Huang, Y.; Tong, Z. “Measurement and Correlation of Solid-Liquid Equilibrium for Abietic Acid + Alcohol Systems at Atmospheric Pressure,” Fluid Phase Equilibria, 367, pp. 74–78, 2014.
14. Royal Society of Chemistry. “The Merck Index Online,” 2013.
15. National Center for Biotechnology Information. “Succinic Acid CID=1110,” https://pubchem.ncbi.nlm.nih.gov/compound/1110.
16. Jouyban, A.; A. Fakhree, M. A. “Experimental and Computational Methods Pertaining to Drug Solubility, Toxicity, and Drug Testing,” InTech, 2012.
17. Yi, Y.; Hatziavramidis, D.; Myerson, A. S.; Waldo, M.; Beylin, V. G.; Mustakis, J. “Development of a Small-Scale Automated Solubility Measurement Apparatus,” Industrial & Chemical Engineering Research, 44 (15), pp. 5427–5433, 2005.
18. Hansen, C. M. Hansen Solubility Parameters: A User’s Handbook: Second Edition, CRC Press, 2007.
Editor's Note: This technical paper was originally published in the proceedings of SMTA International, 2018.
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