Cleaning smoke affected equipment - Page 1
Forum section: electronics / repair

author: David Aurora
author_rank: Frequent Contributor
timestamp: December 31, 2024, 01:37:08 am
content: This is a pretty new one for me- I just had a pile of gear arrive at the shop that was pulled from a burned building. Most of it looks reasonably good from the outside, a lot of soot but nothing looks soaked or melted. Stinks to high heavens of fire though. Obviously it's all going to need some really deep cleaning and testing, I'll need to check the state of things like caps/wire insulation given how hot things might have gotten around it, etcJust curious if anyone knows if any specific cleaning of boards/components may be necessary for smoke residue or if fairly standard alcohol and scrubbing ought to be enough? Obviously I'll get an idea of what's working once I open things up and start, but I'm just not sure what the residue might be like long term and how effective different cleaning chemicals may be

author: amyk
author_rank: Super Contributor
timestamp: December 31, 2024, 02:48:33 am
content: Hexane or other hydrocarbon solvents should work well, although beware that they will attack many plastics too.

author: coromonadalix
author_rank: Super Contributor
timestamp: December 31, 2024, 03:08:07 am
content: they need to go thru ozone chambers to kill the odors

author: Simmed
author_rank: Frequent Contributor
timestamp: December 31, 2024, 03:33:24 am
content: 1) ultrasonic ?2) dish washer ?3) high pressure air blasting ?manual washing PCB in soap/water + drying it is actually normalbut i have never tried dish washer

author: Sorama
author_rank: Frequent Contributor
timestamp: December 31, 2024, 06:08:41 am
content: Professional cleaning companies use dry ice for this.

author: Coordonnée_chromatique
author_rank: Frequent Contributor
timestamp: December 31, 2024, 08:41:36 am
content: Quote from: Simmed on December 31, 2024, 03:33:24 amFlood all possible porosities with water until it is in contact with the silicon dies and thermally cycle them, it is dumb.

author: jpanhalt
author_rank: Super Contributor
timestamp: December 31, 2024, 09:21:14 am
content: @Sorama,Interesting suggestion. Liquid CO2 is a very good solvent. It was used in the very early days of HPLC using a modified Perkin-Elmer GLC by a professor in our department. It's just a bit complex to use.Soot is oily and petroleum solvents may work. I would consider using a water-based flux remover with butyl cellosolve at about 10% final concentration. A lot of household cleaners have butyl cellosolve in them as an active ingredient. Similar hydroxy ethers may also work in water. If you want to go wild, DOT 3 brake fluid in water might even work. It might also remove component markings and evaporate too slowly. So, that would be good.

author: Coordonnée_chromatique
author_rank: Frequent Contributor
timestamp: December 31, 2024, 10:08:54 am
content: Quote from: jpanhalt on December 31, 2024, 09:21:14 amI've encountered some EE that designs chips and work in a fab, they've told me that some casings are porous and the when the water penetrate them, any thermal cycling is mechanically damaging the die.They are wrong ?

author: David Aurora
author_rank: Frequent Contributor
timestamp: December 31, 2024, 10:45:12 am
content: Thanks guys. I should probably clarify what I'm asking a bit as some of these suggestions sound like either guessing or just super sketchy. I've also now had a chance to open a few items and begin cleaning so I have a clearer idea of what I'm up against now.The great news is that so far I'm not seeing any actual heat damage on things, purely smoke residue. But the shit is absolutely everywhere, like to the point I'm having to pull out every single board/control/switch etc because it's all got black stuff on it/around it/under it. Not even necessarily visible to the naked eye, but basically anywhere I drag a cotton bud it comes off black.So far I'm having good results with a combination of brushing dry/blasting with compressed air to loosen things up to begin with, then isopropyl or a couple different cleaners (Amberclens or regular household multipurpose cleaner) depending on the section in question and materials. I'm basically cleaning things until I can swab them with a cotton bud and it comes off clean, which has been quite an effort but the results are looking good so far.There are a lot of different pieces of expensive equipment with a lot of different materials (everything from regular electronics to plastic, rubber, screen printed panels, tolex, etc) so I feel like this may be the only safe way to do it rather than going ham throwing everything in dishwashers or whatever. The main point of my question though is if anyonehas experiencewith the long term effects of these kinds of cleanups? If you had good results, what did you use? Same question if you didn't have good results. And if that was the case, what kind of issues did you encounter over time (e.g. corrosion, failing pots and switches, etc?)

author: Sorama
author_rank: Frequent Contributor
timestamp: December 31, 2024, 11:27:04 am
content: Dry ice is …dry.No moisture.As a court expert I have seen several specialist companies cleaning important items that suffered from flooding or a fire.It’s amazing what you can do with dry ice wrt waterless cleaning.

author: jpanhalt
author_rank: Super Contributor
timestamp: December 31, 2024, 11:28:27 am
content: Long-term experience removing smoke residue is probably a small niche. Long-term experience using water based flux removers (e.g., Kesters 5768) is a much bigger audience. I have been using a similar formula for only 2 or 3 years as a hobbyist, but the fact that Kester promotes it is evidence it works well. DI or distilled water for rinse is cheap. Kester 5768 was introduced by Kester in 2019 according to Google AI. Is that long-term?A problem with alcohols is that they are poor solvents for inorganic materials, and while absolute versions will dissolve grease and fat, a little water changes that dramatically. Most people do not use absolute IPA or ethanol.

author: Swake
author_rank: Frequent Contributor
timestamp: December 31, 2024, 11:56:41 am
content: Post clean experience:- Measurement instruments (not only electronics, all of it): calibration and certification. I pushed for several certifications with some months in between to rebuild the trust in the equipment, but that didn't fly with the bean-counters.- Calibrate the probes too, verify they remain in spec long term.- Anything that measures with an orifice (things like gas analyzers, pressure probes, pH testers, ) : change the probe, don't clean, it is messed up and you'll never have a reliable measurement anymore, cleaned or not.- Filters: Replace them, also the metal washable types.- Reference speakers: sell them, especially so if they have a bass reflex port or something equivalent.- Most medical gear: trash it, it cannot be trusted anymore. I think that is a rule anyway, but that gear is also used in different (non-human) contexts such as veterinary or in labs.- Anything 'safety': radio wave protection, beam protection, thermal/electric insulation or detection: replace, you don't play with your own health.Optics: I have no idea.On another level: do not trust the insurance company when they state 'it is clean now and good for use'. Have it verifiedindependently.

author: David Aurora
author_rank: Frequent Contributor
timestamp: January 01, 2025, 01:20:53 am
content: So I've done a few spot tests with various cleaners/techniques now and the water based flux cleaner suggestion is actually pretty amazing for getting the sooty residue off, thanks for the tip. I've ended up putting some in a foaming dispenser which makes it easier to get good coverage between components without having to absolutely bathe the boards in it (which in turn makes cleanup of the cleaner itself far easier).Will test more as I go today but so far this is the winner

author: jpanhalt
author_rank: Super Contributor
timestamp: January 01, 2025, 02:13:53 am
content: It's a great solvent mixture. That's why it is so ubiquitous in cleaning products. Rather than buy from Kester, I get the formula-equivalent thing from ZEP as its heavy duty acryic floor stipper. ZEP may not marketed in Australia.It works fine with manual methods. I use an ultrasonic (60 seconds). One can do parts of a board at a time if the whole board won't fit. On my first use, I was amazed during rinse that water didn't stick. Solder resist is also water resist, and when its clean and rinsed, the boards are almost dry. Of course components may be wet and have water underneath them, so I blow that out with air. If retained water is a real problem, I would finish with aqueous alcohol and dry. (Aqueous alcohols mix faster and more freely with water than neat alcohols do.)

author: Simmed
author_rank: Frequent Contributor
timestamp: January 01, 2025, 03:59:51 am
content: looks like i have to try ZEP next time

author: jpanhalt
author_rank: Super Contributor
timestamp: January 01, 2025, 11:53:47 am
content: Here's the US SDS:https://www.weber.edu/WSUImages/Union/chemicals/cleaning/Zep-Heavy-Duty-Floor-Stripper.pdf(attached)There seem to be various versions, and of course, not every component needs to be in the SDS/MSDS. I was a little concerned about the NaOH shown in some and called ZEP technical service. The chemists in that area was not aware it was added. That is, it was listed just in case it was an impurity. In any event, it is not much. He told me Australia was one of the few areas where it is not distributed. I have not confirmed that.I dilute it very approximately 1 part ZEP to three parts total with water. Originally, I used my 40-year old Bransonic ultrasonic for 2 minutes. But found 1 minute works just as well. I have not tried shorter times. I have nothing against the Kester product, except availability locally.