Can Age and Storage Affect Performance of No-Clean Flux Residue?
Solder paste flux chemistry, storage temperature, and age seem to have a subtle impact on SIR performance of the flux residue.
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Authored By:
Eric Bastow
Indium Corporation
Clinton, New York
Summary
This paper uses J-STD-004B SIR (Surface Insulation Resistance) testing to examine this question. Two commercially available SAC305, Type 4, no-clean solder pastes - one with a ROL0 and the other with a ROL1 J-STD-004B classification -were subjected to two different storage conditions (room temperature and refrigeration) and aged for varying lengths of time. After aging, the solder pastes were printed and reflowed using the same common reflow profile and then submitted to SIR testing to see what, if any, difference could be detected in their SIR performances. The reason for testing both a ROL0 and a ROL1 was to see if differences in chemistry could have an impact on how a solder paste ages relative to SIR performance.
Conclusions
In closing, we can see that solder paste flux chemistry, storage temperature, and age seem to have a subtle impact on SIR performance of the flux residue. The performance differences that may exist are not enough to threaten an SIR failure as defined by IPC J-STD-004. Nevertheless, those applications that are especially sensitive to current leakage may want to take these factors into consideration when selecting and storing a no-clean solder paste.
Initially Published in the IPC Proceedings
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