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How To Clean a Vintage Circuit Board Assembly?



How To Clean a Vintage Circuit Board Assembly?
A vintage computer board is contaminated with decomposed anti-static foam. The microprocessor and other ICs have a sticky grime on the leads. The Assembly Brothers, Phil Zarrow and Jim Hall, address this situation and share their own suggestions.
Board Talk
Board Talk is presented by Phil Zarrow and Jim Hall of ITM Consulting.
Process Troubleshooting, Failure Analysis, Process Audits, Process Set-up
CEM Selection/Qualification, SMT Training/Seminars, Legal Disputes
Phil Zarrow
Phil Zarrow
With over 35 years experience in PCB assembly, Phil is one of the leading experts in SMT process failure analysis. He has vast experience in SMT equipment, materials and processes.
Jim Hall
Jim Hall
A Lean Six-Sigma Master Blackbelt, Jim has a wealth of knowledge in soldering, thermal technology, equipment and process basics. He is a pioneer in the science of reflow.

Transcript


Phil

And welcome to Board Talk with Phil and Jim, the Assembly Brothers, also known as ITM Consulting. We’re here to help you with your process, assembly, problems, methods, equipment, materials old and new.

Speaking of old Jim, this is a real interesting one we have here from J.W. J.W. writes, I have a vintage computer board that is contaminated with what appears to be decomposed anti-static foam. The board has been in storage for forty years. Hey, who does this remind you of?

The microprocessor and other ICs on this board have a sticky grime on the leads. Due to the rarity and value of the board, I want to preserve it and make sure it will be operational. It has been suggested that 90% isopropyl alcohol soaked on the entire board followed by brushing with a soft toothbrush is recommended. Do you have any other thoughts on how to tackle this problem?

Jim

Time stamp, forty years ago is before no-clean. So, this was either assembled with an RMA or a water-soluble and it was probably cleaned one way or another. The degrading static-foam could be anything. Alcohol might clean it. Alcohol is certainly a safe thing for most products.

The one thing with cleaning in general, Phil, is that if this a completed board. There may be things on the final assembly that were put on after cleaning that aren’t compatible with any cleaning. You really need to determine that.

Open switches, open coil devices and things typically if it is not a no-clean process, they are added as secondary ops, after the entire board is clean. You want to make sure of that. My advice would be to try a little alcohol on a rag or a Q-Tip or something on specifically the contamination that you are looking at on these leads and see if it cleans it. If it does, great.

If there is nothing that can’t be cleaned on there, then alcohol is a safe solution. Alcohol doesn’t clean everything. You may find that the alcohol doesn’t clean this residue that you are seeing supposedly from the decomposed anti-static foam.

In that case, you are going to have to look for a stronger or a different cleaning solution, a solvent or an aqueous material until you find one. Then clean the whole board with that. Again, being conscious of what else is on the board.

Phil

Right, my brother has once again given us wonderful, sage advice. I would say going back forty years ago, as Jim mentioned before the Montreal protocol, I think there is a good chance if it was a computer board this board was built with RMA fluxes and probably originally solvent cleaned and a vapor degreaser. Remember that?

Good old tri-chlore and other great stuff. Freon, yeah. You have to watch out for that tricore attacking that might have been done, as Jim said secondary operations. I think Jim’s advice and the inclination is trying an isopropyl first.

Beyond that, I keep getting these flyers that vinegar does all of these great things. It might make it smell kind of funny. I actually had a board a while back that I dug up from my archives. This thing was probably from the late 60s, maybe even earlier. It had core memory on it.

I wound up cleaning it using a saponifier. I took it over to one of my friendly saponifier suppliers and we ran it through a clean with saponifier. There wasn’t anything from concern from a water-standpoint and secondary ops. Also, I wasn’t going to attempt to make this board operational. That is really very ambitious of you J.W.

You know Jim, thinking about this forty year old board, you realize that this board is probably older than a lot of people listening to us on Board Talk.

Jim

You’re right, Phil.

Phil

We hope we gave some good advice here. We both hope our listeners and readers will chime in with some thoughts too. Beyond that, no matter how old your board is, if it is an old fossil like Jim and I, then whatever you do hope it wasn’t soldered by my brother.

Jim

And I hope it wasn’t soldered by my brother.

Comments

Jim and Phil make a good point in saying that there may be components that may not be compatible with DI water, so IPA is the best bet, and a spot-cleaning technique should be used with a dispenser rather than flooding the board. It is advisable to remove the excess static foam from the board with a separate natural bristle brush first. You can purchase an aerosol can of IPA and a dispenser that has a natural bristle attachment that then could be used to spot clean while using a lint-free wipe to absorb excess IPA. Flooding the board should be avoided, if possible.
Russell Claybrook, MicroCare, LLC
Simplegreen works wonders.
Brian Martel, Madgetech
Parts were put on post cleaning because they could not be cleaned (switches) or they could not take the heat (LCD displays). If there are mixed components then the laborious IPA/tooth brush is the safest start. Provides control of cleaning location and cold cleaning. Labor costs are immaterial at this point given the concern that the PCA is irreplaceable. It is unlikely that a water wash flux was used. Any remnants of pink death would have corroded this device long ago.
Larry Dzaugis, DZA
If this board does not have any components on it that are of concern for aqueous-based cleaners and those same components are robust enough to withstand ultrasonic cleaning, I would certainly recommend that approach. I recently cleaned a number of populated circuit boards for CAT GPS AccuGrade Grade Control Systems using a mildly alkaline-based cleaner in an ultrasonic tank. The boards came out looking new. The customer has now installed this process. Of course, these CAT circuit boards are not vintage nor irreplaceable:-)!!
Wade Rohland, Northern Technologies International Corporation
I've been using either a dishwasher for really soiled boards, or super clean and a paint brush. Run it under hot water and hang over a dehumidifier. Been doing this with vintage arcade and pinball pcbs for years with no Ill effects.
Rich
Hey guys, you’re forgetting the king of pc’s back then, IBM. Their flux of choice in the day was good ole battery acid Lonco 3355-11 or pink death. The good thing is they also washed everything in half mile long water cleaners so I doubt there’d be any residue left from that process.
Ray Chartrand, Chartrain Consulting

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