Manufacturing considerations when implementing VOC-free flux technology

Pockets of gas, or voids, trapped in the solder interface between discrete power management devices and circuit assemblies are, unfortunately, excellent insulators, or barriers to thermal conductivity. This resistance to heat flow reduces the electrical efficiency of these devices, reducing battery life and expected functional lifetime of electronic assemblies.

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.

This paper will discuss commonly experienced defects associated with NoClean surface mount processes and propose methods to solve these issues. Much of the discussion can be applied to any surface mount process (i.e. water soluble, RMA, or No-Clean), but some are directly associated with No-Clean processes.