Cleaning PCBs without damaging solder masks can be a bit tricky. After finishing a board, you might find yourself staring at flux and grime. Before you reach for just any solvent, consider how to clean those PCBs without lifting masks or fading labels. What are your go-to safe cleaners, brushes, and techniques?
Back when I started as an engineer, TCE was the goto cleaning fluid. A year later, my employer was one of several local companies found guilty of polluting the local groundwater. They would dump barrels of TCE, spent etchant, and other nasty stuff out in "evaporation ponds" in the back lot, but plenty seeped into the ground. It was accepted practice in the '40s, but by the '70s people knew better, and the judge agreed--they should have stopped the practice long before the court told them they had to.
After they agreed to install scrubbers at valley wells and operate them for the next 25 years, the only acceptable solvent was 91% isopropyl alcohol. Operators used an acid brush with the bristles trimmed to about a 1/4 inch length. It takes a little scrubbing, but it works. Sop up the sticky liquid that results with a piece of cotton gauze. You can also blow off the wet board with compressed air, but this is also a good way to generate static, so you may need a "nozzle static eliminator" if you work with sensitive parts, as nearly everything seems to be today. Google it.
There are no-clean fluxes, but these are noxious whereas the old fashioned rosin solder, if you happen to breathe the fumes, won't send you into an immediate coughing fit. But, maybe that's a warning where rosin doesn't give you one when it should.
Since I brought it up, many communities offer no-cost hazardous waste disposal to their residents. Please don't pour any of the solvents you use in your hobby down the drain.
