CLEANING SURFACE-MOUNTED ASSEMBLIES.

Tough problems in cleaning surface-mounted components are considered. Usually square or rectangular in shape, these devices are often supported only a few mils off a board surface. The space between package underside and board can offer a haven to contamination from the soldering process. The trick here is to ensure that the cleaning solution penetrates under components and is strong enough to remove residues without damaging the assembly. It is shown that cleaning becomes harder as the size of component increases. Approaches used by six manufacturers to removing ionic (polar), organic (non-polar) and particle contaminations are presented and several points are made. The choice of cleaning agents and their selection are also considered.