After processing the circuit boards we see a white residue. Could this residue be corrosive? What is this white residue? If all of the no-clean flux is not heat activated could it have a negative effect on the circuit board assembly? In addition, we need to conformal coat the boards.
What may happen if we apply the conformal coating over this white residue? It is extremely likely that this white residue from a no-clean flux is perfectly safe. However, it is suggested that you communicate your findings and concerns to your flux supplier for verification. Questions to ask your supplier: Is the residue from this flux supposed to be white?
If not, what circumstances would cause the residue to be white? If the residues do turn white, does this make the residues any more or less reliable than expected? It is important to note that some fluxes do leave a white residue that is perfectly normal and safe.
However, other factors that cause white residues -- such as partial removal of the residue in an inadequate cleaning process or even over-application and under-heating of the flux -- could be cause for concern in terms of long-term product reliability.
Another potential cause of white residue can occur when fluxes are mixed together in a hand soldering operation, and this is generally safe provided that the hand soldering technique especially the amount of flux applied and the completeness of heating the flux is carefully controlled. However, if the protective matrix around the residue is partially removed by an inadequate cleaning regime, then the activators could be exposed.
This may lead to a corrosion process starting on the circuit board and this process could be accelerated in the presence of heat and power on the boards in service and, or high relative humidity. Not considering these three points could easily lead you to having real problems in the long term. Contact us now to discuss what we can offer you in terms of cleaning fluids from our Surclean range of materials. This website uses cookies so that we can provide you with the best user experience possible.
Cookie information is stored in your browser and performs functions such as recognising you when you return to our website and helping our team to understand which sections of the website you find most interesting and useful. Strictly Necessary Cookies should be enabled at all times so that we can save your preferences for cookie settings.
They are required for certain features on the website and without them, the website would not function correctly. If you disable this cookie, we will not be able to save your preferences. This means that every time you visit this website you will need to enable or disable cookies again. Author: Dr Lee Hitchens So why is no clean flux so difficult to clean? Cleaning no clean flux residues is one of the most complex processes when considering cleaning.
So, what do you do when you want to clean the no clean residues? First, consider the saponification factor. So the key here is to ensure that the saponifier completely dissolves the residues. Assemblers first began cleaning no-clean fluxes due to problems found at in-circuit testing. Residues from early, no-clean pastes were tacky and test pins would not always penetrate through to make good electrical contact with test pads. Further, the residue would build up on pins affecting accuracy, and necessitating maintenance.
Since recent formulations have eliminated this problem, no-clean fluxes are now cleaned. The choice of flux chemistry low or high solids, hard or soft residues, etc. Fluxes containing halides leave more residue, but are easier to clean using mild cleaning agents and short wash times.
Alternatively, halide-free, no-cleans produce less residue, but are more difficult to clean. Moreover, exposing no-clean pastes to excessively high temperatures causes residue to harden and solder joints to become dull due to oxidation. Lead-free, no-clean paste can be difficult to clean.
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