Weak Organic Acids and Surface Insulation Resistance

Weak organic acids (WOAs) are commonly used as activators in no‐clean fluxes. Surface insulation resistance (SIR) was determined as a function of WOA type and residue level through three temperature/humidity test environments. Acidic residue levels were determined after wave solder processing, and after exposure to each of the three test environments. With each of the WOAs studied, the greater the residue level, the lower the SIR. Chemical structure and physical property differences of the WOAs are discussed in the context of differences in SIR observed. WOA volatilisation is found to occur with all four WOAs when exposed to the highest test temperature (85°C). This work shows that testing WOA‐containing solder fluxes at 85°C may not be useful or appropriate.