IC chips liquid proof (sealed)? - Page 1
Forum section: electronics / beginners

author: [Chrille]
author_rank: Contributor
timestamp: October 20, 2022, 09:14:59 pm
content: I want to clean some old PCB's that I've got and I want them to be as clean as possible. Previously I have cleaned some other boards using IPA (sprayed on the board) and a brush and the rinsed it away with some more IPA or distilled water and let it dry.But I was wondering if it would be OK to submerge boards in IPA or distilled water and let it sit in the cleaning liquid for some time to be able to get them really clean or as a final rinsing step.I know the board itself can handle it. But how about the populated IC chips, capacitors, trim pots etc? Are the IC's sealed so that water or IPA will not enter inside the chips casing (usually DIP style chips)?

author: james_s
author_rank: Super Contributor
timestamp: October 20, 2022, 09:26:53 pm
content: It works fine. I've washed lots of boards by running them through a dishwasher, or smaller ones in an ultrasonic cleaner.

author: MikeK
author_rank: Super Contributor
timestamp: October 20, 2022, 09:30:49 pm
content: PCB dishwasher:

author: jpanhalt
author_rank: Super Contributor
timestamp: October 20, 2022, 09:30:59 pm
content: t's been reported that even reputable manufacturers like Tektronix used a standard dishwasher for cleaning boards. Unfortunately, I didn't save the citation.

author: james_s
author_rank: Super Contributor
timestamp: October 20, 2022, 09:40:14 pm
content: There's no reason it wouldn't work, nothing special about a dishwasher, it just circulates warm cleaning fluid around with a pump and follows with a rinse. The key is to watch what you put in there as a cleaner. A normal dose of regular dish detergent is fairly caustic although a pinch of it will usually work ok.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: October 20, 2022, 10:23:54 pm
content: In general this works. In one project I worked on we did find that a large FPGA package we were using had a vent plugged with some grease like material. This was more than twenty years ago and I don't remember the part number, exact package type or even the vendor involved, but it didn't survive this type of wash cycle.Also if you are planning on subsequent rework of the boards or if any of the ICs are pushed hard and run very hot I would be wary of "popcorning".

author: DavidAlfa
author_rank: Super Contributor
timestamp: October 20, 2022, 10:30:03 pm
content: As long as you use deionized distilled water and don't soak the boards overnight to avoid moisture ingress, won't be really a problem for encapsulated devices like ics, caps or resistors, but could be for electromechanical devices, we had a lot of issues with -supposedly- sealed relays, in the end the only reasonable way was to add a post-washing fabrication step and solder them by hand.I never felt ok watching all those tactile switches being washed, but I guess they will fail long after the warranty is goneMy company was a bit hacky about this, used normal tap water for the first "bulk" wash, removing all flush from the wave soldering oven and other hand-placed parts, then made a final rinse in distilled water and right away into the over for drying.

author: rdl
author_rank: Super Contributor
timestamp: October 22, 2022, 05:47:06 pm
content: Quote from: jpanhalt on October 20, 2022, 09:30:59 pmI thought I had uploaded the .pdf here, but I guess not and I can't find it now. Here is a link though. They basically just hosed them down. This was many years ago though, best to keep that in mind.https://www.radiomuseum.org/forum/tektronix_washing_your_instrument.html

author: Terry Bites
author_rank: Super Contributor
timestamp: October 23, 2022, 02:07:31 pm
content: Read dis.www.epsprogramming.com/blog/what-is-component-baking

author: CaptDon
author_rank: Super Contributor
timestamp: October 23, 2022, 03:07:01 pm
content: We had a bad experience with an 8 pin DIP device called a dual PVI. There are two individual LED's driving two photo-voltaic devices. When you drive the LED's (with a good amount of current) you get a voltage output from the PV side which is electrically isolated from the driving side. We used these to drive power MOSFET's. The devices where in a white package and were not sealed well. Apparently the manufacturer spec sheet notes that they are not well sealed and should be conformally coated!!! It seems moisture entered the devices during processing and remained trapped by the conformal coating. We started having many many field failures and after sending a large sample of the bad parts back to the O.E.M. they sighted moisture ingress as the reason for failure. We had a lot of burned boards returned from the field, the PVI's output slowly became weaker and the power MOSFET's were no longer in saturation...A really bad thing in a circuit designed to pull down 10 amps through a load from a 74 volt circuit!!!