Here is the simple truth: any hand-soldered area on a circuit board must be cleaned to ensure reliable performance. Even no-clean fluxes. Fluxes work because they contain halites (also called activators). These lower the surface tension of the melted solder to improve the wetting of the surfaces. However, activators are salts and salts attack metals, so they must be removed to stop them from attacking the PCB and causing performance problems.
No cleans need to be cleaned
Today, most no-clean chemistries encapsulate the flux activators inside microscopic protective bubbles created during reflow. Benchtop cleaning destroys those bubbles, releasing the halites. This causes corrosion, intermittent failures and dendrite growth. In some instances, no-clean solder pastes and fluxes don’t need to be cleaned after automated soldering because the temperature control generally is perfect. But hand-soldering is far less precise. Near the hot tip of the soldering iron the encapsulation will occur while millimeters farther away it will not.
Four steps of cleaning
So, cleaning hand-soldered circuit boards is essential, even with no-clean fluxes. Proper cleaning requires four steps: wet, scrub, rinse and dry. Think about washing the dishes in your kitchen. First, you wet the residues with water. Grabbing a sponge, you scrub the surface vigorously. Next you rinse the plate thoroughly, removing the last residues. Then you dry the plate with a towel.
If you can’t rinse, you can’t clean
There are four steps to cleaning, but the most important one is rinsing. If you can’t rinse, you can’t clean. When using brush cleaning methods, be mindful to rinse the contaminants off the PCB, otherwise you’ll most likely just redistribute the flux residue back onto the board. To ensure thorough cleaning, use a controlled dispensing system, like the TriggerGrip to thoroughly wet, scrub and rinse, ensuring optimal PCB performance.