Repairing corrosion damage to PCBs

I'll tell you how I would call it. I have boards made, and they wash them with water for a short period, then they blow dry them. They set out and dry. If it was soaked in water for a few day's, I think that would spell real trouble. These boards didn't work anyway, so they had to be baked after the short washings. Water might very well get sucked into the layers and take a long time to dry unless baked. Other solvents may very well start to dissolve stuff.

greg

Thus spake GregS:

This is a *long* term project. I'll be letting the boards sit in the sun for days at a time (inside). Any soaking they get will be followed by more than sufficient drying times.

Thanks,

DaveC wrote in news: snipped-for-privacy@news.readfreenews.net:

Some components will wick up chemicals and not work properly,or fail later,and the board itself may develop leakage,and any residue will attract and keep dirt.

I've had 20+ yrs of cleaning electronics at Tektronix.

DaveC wrote in news: snipped-for-privacy@news.readfreenews.net:

IMO,that is insufficient drying. At Tek,we put boards or complete instruments in a drying oven at 120-140 degF for *at least 3 days*,and the oven had a negative pressure to draw out moisture.(exhaust fan) You don't want to go higher than 140,or plastics may soften and warp(like TEK cam drums for switches)

You would do better putting the boards inside your car and leaving it in the sun. The car's interior reaches 140degF.

On Wed, 26 Apr 2006 14:57:54 -0700, DaveC wrote as underneath my scribble :

Youll just do whatever you think, so why bother asking out for any advice in the first place! Your choices dont show much sense. Good luck with it. Charlie+

Unless the board has delaminated, the interior layers are darn near hermetically sealed in the laminating process. It is very unlikely that anything like coffee could penetrate a properly-built board. But, it sure can play hob with the outer layers, especially when the power is on. Connectors are also easy for liquids to wick into. I'd disconnect all the connectors, and some may be the flex-cable type that just presses a flex-print cable against the board, and clean anything there that needs cleaning. If glop got into the hard drive (usually under the keyboard!) that will likely be toast. The fans (if any) may have been glopped up, causing the delayed failure. Just tear it apart (it isn't working any more, anyway) and look for obvious problems. Gentle cleaning with alcohol and an old toothbrush, followed by a day of open-air drying should fix most fixable problems. Conductive glop getting between fine connections can pop chips, so it may not be salvageable. But, worth a try.

Jon

Thus spake Charlie+:

I ask questions here to gather information. I learn. I try to benefit from others' experience and (sometimes) mistakes. This "gauntlet" of possibilities "aims" my decision.

But in the end, of course, the decision is mine. And that choice will be different from yours.

You just proved his point, Dave. Why ask him if you admit from the start that in the end your choices will be different from his...

I work for a very large computer company. At one time, we spec'ed our components and PC boards to withstand a cycle in a dishwasher with Calgonite detergent.

Soaking a PC assembly will (like the poster mentioned) cause other components to absorb water. Bad thing. Aluminum electrolytics would likely take it the worst. PC boards are washed typically with deionized water then run through an "air knife" on a conveyor, then hot air dried during the manufacturing process.

The problem you'll likely run in to is the keyboard membrane switches having contact problems but hey, what you have doesn't work so whadaya got to lose?

I'd opt for a dishwasher cycle (including dry) then placing the board in a warm area for a while to evaporate any other moisture trapped. Problem is each button on the keyboard has a separate switch with a silicon rubber "spring" and each will likely need to be removed.and replaced. Not fun at all.

b.

wrote in news:10f7d$446a4b03$cc1d9013$ snipped-for-privacy@news.flashnewsgroups.com:

Often the rubber "springs" are all one piece of rubber.