Kester

Manufactures who have looked at VOC-Free fluxes have discovered that VOC-free fluxes are not simply "drop in" replacements for the existing flux chemistries. Because VOC-free fluxes contain water as a solvent difficulties are encountered when soldering boards with these fluxes. The difference between VOC-Free and alcohol based fluxes lies in the characteristics of the solvent (thinner).

As lead-free gains momentum, many engineers are striving to set-up a wave solder process that maintains production yields but also offer reliable assemblies. Much has been written on these topics in the past 5 years. Less confusion does exist today about alloy choices available to replace leaded solders, however many are struggling with their successful implementation. Once the lead-free alloy is selected, a solid understanding of its chemical and physical properties is required to enable reliable soldering.

The problem is not limited only to rosin fluxes and solvent cleaning, but also occurs when water soluble fluxes are used and when either flux type is removed with water. The soldering and cleaning processes involve so many chemicals in the flux, circuit board, components and cleaning agents that a complete understanding of the reactions is very difficult if not impossible. There are white residue problems with water soluble fluxes and many of the causes not related to the flux compositions are the same as for rosin fluxes.