Abstract
PCB manufacturers are switching from the use of RMA fluxes in their soldering and rework processes to low residue type (i.e., ‘no‐clean’) fluxes. Unfortunately, successful changeover is not simply a matter of substituting a no‐clean into an existing RMA process. Soldering process parameters must change, necessitating an understanding of the interplay between flux chemistry and heat delivery. Higher temperatures can result in an effective decrease in the concentration of the active fluxing agents. Also, data show a decrease in the inherent wetting force of a no‐clean flux with increasing temperature. These two factors reduce fluxing action below the rate of oxidation occurring at the solder connection and the soldering iron tip. These can lead to incomplete surface cleaning and inefficient heat transfer, resulting in poorly soldered connections. Lower solder joint defect rates are obtained with no‐clean solders and fluxes when soldering temperatures are reduced to a minimum.
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