With the advent of No Clean fluxes and solder pastes, the need for cleaning electronics assemblies disappeared. Or so some would have you think. But while the masses switched, ahem, en masse, to No Cleans, often in hopes of eliminating what was widely seen as a non-value added step from the assembly process, a not-so-funny thing happened: Field failures and legislation. The influx of No Clean coupled with better process control drove the use of cleaning to general consensus of 5% of all boards, mostly for high-reliability application such as military, certain telecommunications, and aerospace. But the broad switch to Pb-free solders, prompted in large part by the RoHS Directive, and more densely packed boards that effectively turn even trace residues from aesthetic nuisances into potential hazards, has brought about a renaissance for cleaning advocates. And to a degree, suppliers of cleaning materials are, well, cleaning up.