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This paper presents the results of humidity testing of weak organic acids (WOAs), namely adipic, succinic, glutaric, dl-malic, and palmitic acids, which are commonly used as activators in no-clean solder fluxes. The study was performed under humidity conditions varying from 60% relative humidity (RH) to ∼99%RH at 25°C. The following parameters were used for characterization of WOAs: mass gain due to water adsorption and deliquescence of the WOA (by quartz crystal microbalance), resistivity of the water layer formed on the printed circuit board (by impedance spectroscopy), and leakage current measured using the surface insulation resistance pattern in the potential range from 0 V to 10 V. The combined results indicate the importance of the WOA chemical structure for the water adsorption and therefore conductive water layer formation on the printed circuit board assembly (PCBA). A substantial increase of leakage currents and probability of electrochemical migration was observed at humidity levels above the RH corresponding to the deliquescence point of WOAs present as contaminants on the printed circuit boards. The results suggest that use of solder fluxes with WOAs having higher deliquescence point could improve the reliability of electronics operating under circumstances in which exposure to high humidity is likely to occur.
Original languageEnglish
JournalJournal of Electronic Materials
Volume44
Issue number4
Pages (from-to)1116-1127
ISSN0361-5235
DOIs
StatePublished - 2015
CitationsWeb of Science® Times Cited: No match on DOI

    Research areas

  • corrosion, Flux residue, impedance spectroscopy, leakage current, reliability of electronics, surface insulation resistance, Adsorption, Corrosion, Crystal structure, Leakage currents, Organic acids, Palmitic acid, Printed circuits, Quartz, Spectroscopy, Electrochemical migration, Flux residues, Humidity conditions, Impedance spectroscopy, Printed circuit board assembly, Relative effects, Surface insulation resistances, Weak organic acids, Printed circuit boards
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