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58 SMT Magazine • April 2017 tion is defined as any solid or liquid substance found on or around a trace where there was once flux. The full set of results is summarized in Table 3. The rosin-based and RMA fluxes were fully cleaned (100%) in both classic vapor degreas- ing solvents and in the advanced solvent for- mulas. No-clean fluxes cleaned in classic vapor degreasing solvents resulted in only 10% clean- ing and formed white ionic residues. Solvents A and B fared better on the no-clean formula- tions; most of the solder pastes could be entire- ly removed by at least one of the formulations. A visual cleaning comparison of the Classic Sol- vent and Solvents A and B can be seen in Ta- ble 4. The Indium 8.9HF1 and Indium SMQ92- J were the most difficult for both of the solvent formulations to remove. Visual comparisons of Indium SMQ92-J can be seen in Table 5. Solvent A was able to clean seven out of 10 fluxes to 100% flux removal and Solvent B was able to clean six out of 10 fluxes to 100% flux removal. The lead-free, no-clean formula- tions were the most difficult to clean, though all formulations had at least 50% of the flux re- moved during the cleaning cycle. The SIR test- ing showed favor to the advanced solvent for- mulations; all of the boards that were cleaned in Solvents A and B passed SIR testing, while some of the un-cleaned fluxes suffered failures. This verifies that even though cleaning was not 100% successful on some of the boards, the res- idues were not altered in a way that caused elec- trochemical migration when exposed to heat and humidity. Conclusion New flux and solder formulations with bet- ter safety profiles and processing efficiency hold an importance in modern electronics assem- VAPOR DEGREASING CHEMISTRIES Table 3: Flux Cleaning Results. Table 4: Visual Cleaning Comparison 1. Table 5: Visual Cleaning Comparison 2.