In all likelihood, you may not be leaving flux on the board rather you may be leaving saponifier on the board. Improper rinsing is a leading cause of cleaning related board failures.
The problem with some inline cleaning systems (especially old ones) is that they lack proper rinsing. The final rinse manifold (the last water that comes into contact with the board) is normally powered by incoming water pressure as opposed to a pump. The �sprinkle� of final rinse water may not be enough to displace dirtier pre-rinse water. The only thing worse than leaving flux on a board is leaving saponifier on a board. Saponifiers are much more ionic than flux and therefore are much more conductive. Additionally, a saponifier may continue to �attack� a board after the cleaning process if not thoroughly removed. The fact that you have enough leakage that can �light an L.E.D.� leads me to believe that there is much more than flux on the board.
If it is truly flux residue then consider how a saponifier works. The process of saponification works when two things occur:
1. Contact between flux and saponifier. 2. Exchange of energy (heat, pressure) that forces the chemical reaction that transforms rosin flux into rosin soap.
If your old Hollis lacks the ability to produce the energy required to convert the flux to soap then there will be flux residue on the board.
Check the following:
1. Wash pump pressure (what is the HP rating and PSI?).
2. Clogged nozzles.
3. Is the wash solution loaded (spent)?
4. Is wash solution at correct concentration? Use titration test to determine proper percentage.
5. How�s your reflow profile? Too hot may burn flux on the board and not allow proper removal.
6. What wash temperature are you running? 150F � 160F works best for saponifiers (this is a problem with many polypropylene machines).
You may also want to try a different wash chemical. New wash chemicals utilize a saponifier / aqueous-solvent combination. They rely less on saponification and generally work better on �weaker� machines.
Chemicals I would recommend are:
PCB-Wash (ours) http://www.aqueoustech.com Vigon A200 (Zestron) http://www.zestron.com Kyzen 5020 (Kyzen) http://www.kyzen.com
If nothing is wrong (defective) with your old Hollis and profiles are in order and better chemicals do not solve the problem then you may want to consider purchasing a new cleaning system.
Mike Konrad www.aqueoustech.com konrad@aqueoustech.com
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