I have no grudge against you Andrew (and I hope you have no grudge against me), but to be pedantic, mixing ammonia with water results in a mix of NH4+ and OH- ions, and it is the latter which results in the mix having a pH exceeding 7.0. (To be more pedantic, there are both H+ and OH- ions present (and in equal numbers) in (non-deionised) pure water, and the consequence of adding NH3 is to result in an imbalance in the number of H+ and OH- ions, with the latter then dominating.)
However I fully agree that if anyone was to follow up with a mildly acid wash, then it would be very prudent to ensure that the boards did not end up in an acidic state afterwards. It would probably be prudent to also have a following wash consisting just of (deionised) water, so that if the consequence of the previous (mildly acidic) wash was to leave the board either very mildly acidic or very mildly alkaline (if the pH of that wash had not been fully "spot on"), then at least the pH of the board in its very final state would still be closer to 7.0 than would otherwise be the case. Regards, Geoff Harland. ----- Original Message ----- From: <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]>; <[email protected]> Sent: Monday, December 18, 2006 11:30 PM Subject: Re: [PEDA] "No-clean" flux leakage, was: (500V power supply) > Since ammonia is basic (pH >7.0), one _technically speaking_ might want > to consider an acidic wash (a dilute solution of white vinegar comes to > mind) prior to final wash with de-ionzed water, in order to neutralize > any active NH3 components still present on the PCB or components. You'd > have to experiment to find the right wash strength to properly > neutralize (and not acidify) the board. > > FYI Both alkali and acidic deposits will react negatively with exposed > metal. > > r, > > aj ____________________________________________________________ You are subscribed to the PEDA discussion forum To Post messages: mailto:[email protected] Unsubscribe and Other Options: http://techservinc.com/mailman/listinfo/peda_techservinc.com Browse or Search Old Archives (2001-2004): http://www.mail-archive.com/[email protected] Browse or Search Current Archives (2004-Current): http://www.mail-archive.com/[email protected]
