Cleaning Assembled PCB's - Page 1
Forum section: electronics / general

author: rfe1
author_rank: Contributor
timestamp: May 31, 2025, 12:36:08 pm
content: HelloAt the moment I clean my assembled PCB's manually, which is quite time consuming and it's not that easy to remove all flux residue, especially when there are a lot THT components on the board.I don't want to use ultrasonic cleaning as there are fragile parts on the PCB that might be damaged by ultrasonic cleaning.I think the washing machines from PBT Works look promising, but as I can't find a price anywhere I assume those machines cost 10k upwards.I found out that you can relatively cheap buy a used laboratory washing machine (for example Miele G7883) , on the first look these machines should be able to mimic the washing process of a dedicated PCB washing machine.Does anybody use such a machine to wash assembled PCB's or has an idea which kind of machine you could get cheap?Thanks in advance

author: eugene
author_rank: Frequent Contributor
timestamp: May 31, 2025, 03:58:55 pm
content: Quote from: rfe1 on May 31, 2025, 12:36:08 pmWhat kind of flux do you use? Some water-wash fluxes are easier to clean than others. I use Kester 2331-ZX (with any solder from the Kester 331 line) and find that it can be cleaned with just a strong flow of hot water, though a soft brush will speed things up.

author: Rat_Patrol
author_rank: Frequent Contributor
timestamp: May 31, 2025, 09:56:37 pm
content: Yup, I would go with a water wash flux and a good saponifier additive to make your life easier.

author: jpanhalt
author_rank: Super Contributor
timestamp: May 31, 2025, 10:39:45 pm
content: Kester 5768 is an all purpose flux remover. It works great in an ultrasonic, but soaking will probably accomplished much the same over a longer period.https://www.kester.com/products/product/5768-cleanerZEP heavy duty acrylic floor stripper has about the same formula. I use it diluted 1 part ZEP to 3 parts total with DI. Works great with only about 1 minute in an ultrasonic.

author: uer166
author_rank: Super Contributor
timestamp: May 31, 2025, 11:41:18 pm
content: A household dishwasher is almost the same as a commercial cleaner. Just use the correct detergent (e.g. Alconox), and it'll work.

author: rfe1
author_rank: Contributor
timestamp: June 02, 2025, 03:40:09 am
content: Would a household dishwasher use a lot of cleaning agent?Also I don't think I can drain the wastewater untreated.Also wouldn't it be neccesary to use DI water instead of tap water?

author: kate
author_rank: Newbie
timestamp: June 02, 2025, 09:13:26 am
content: I'm a  in China. You can use the dry ice cleaning machine for PCBA. [Remaining spam removed by moderator].

author: ajb
author_rank: Super Contributor
timestamp: June 02, 2025, 05:19:28 pm
content: Quote from: uer166 on May 31, 2025, 11:41:18 pmI have seen at least one PCB Assembler who did exactly that -- just a couple of domestic dishwashers and some shop-made drying racks with fans on top.Quote from: rfe1 on June 02, 2025, 03:40:09 amIME, dishwashers use however much detergent you put into them for each cycle, versus the rinse aid which is added to a reservoir and dosed automatically. I don't think you would want to use the rinse aid though.From memory, the assembler I mentioned had a water treatment setup, but it was just basic filtration/conditioning, nut a full DI system. Tap water is probably fine as long as the mineral content is low enough.What you can do with the waste water I'm sure depends on what solder/flux you're using, the volume of waste water generate, and your local regulations. But all of this is technically the same whether you're doing the cleaning by hand or with a machine.

author: jpanhalt
author_rank: Super Contributor
timestamp: June 02, 2025, 07:08:42 pm
content: @rfe1One big difference between the Kester/floor stripper and Alconox is ionic content. Here's what Alconox contains (source = SDS):Hazard-determining components of labeling:Tetrasodium PyrophosphateSodium tripolyphosphateSodium Alkylbenzene SulfonateThe Kester remover contains only a little ethanol amine. If you use a dishwasher or even manual, can you be sure retained Alconox under parts is well rinsed?

author: Doctorandus_P
author_rank: Super Contributor
timestamp: June 03, 2025, 02:35:49 pm
content: I once had a talk with a small company that refurbished second hand electronic equipment and sell it again.They disassembled the equipment, put all the parts (including the PCB) in a household dishwasher, assembled it again and sometimes did small repairs.I don't know what regular (dishwasher) soap does with your PCB's. In general, the "no clean" fluxes can't be cleaned, but any water soluble flux would get cleaned very well.There is no problem with dunking a whole PC in water, as long as you dry it thoroughly before you apply power. Especially area's under IC's may take some time to dry completely. But just as with ultrasonics. some parts may get damaged by too much water.

author: jpanhalt
author_rank: Super Contributor
timestamp: June 03, 2025, 05:04:29 pm
content: Years ago, I read the history of no-clean fluxes. Early on, many were just ordinary rosin flux diluted or less of it. Today, I could find nothing that said they can't be cleaned. The term only means they don't need to be cleaned in most situations.As for regular dishwashing detergents, Cascade is popular and is/was so highly alkaline that it etched glass and ceramics. I suspect it would remove flux, and it might also etch solder.

author: Accu-Sembly
author_rank: Contributor
timestamp: June 04, 2025, 05:52:38 pm
content: A lifetime ago we used a household dishwasher as well. It's definitely doable and can be a budget friendly option. Nowadays we have very expensive machinery that you put dirty boards in and they come out pristine. In fact, we have clients that will bring some of their own in house boards by just for us to wash.

author: jpanhalt
author_rank: Super Contributor
timestamp: June 04, 2025, 08:01:47 pm
content: One impetus to no clean flux was a problem with using halogenated hydrocarbons for cleaning and hazardous waste. Kester 5768 is 90& water as is the diluted equivalent mentioned in post #4. The principal active ingredient is 2-butoxyethanol (aka butyl Cellosolve and other synonyms) + a small amount of ethanolamine . That is extremely common in household cleaners and butyl Cellosolve has a characteristic odor. That is, you can shop by smell instead of SDS sheets.As for how it works, I was skeptical. I used to use absolute ethanol + about 20% or so acetone. My first test was amazing. The board was the cleanest I had seen. Water did not stick to it because of the solder resist. It was shiny. Since then, I have only used the water-based formula for whole boards. If I make a small modification, I revert back to absolute ethanol.The Kester formula is simple and has probably been replicated or replaced with chemically equivalent agents to establish "uniqueness" many times. Unlike highly alkaline dish detergents, it does not etch solder or anything shiny. Too long in an ultrasonic may remove some of the gold from ENIG finishes. I started with 2 minutes and am now down to just 1 minute in an ultrasonic cleaner.