Ultrasonic conundrum - Page 1
Forum section: electronics / beginners

author: palindrome
author_rank: Contributor
timestamp: May 08, 2023, 09:47:12 am
content: Hi!I am using the no clean flux etc in my product, but the boards just look ugly and sticky, so I thought it's time to invest in an ultrasonic cleaner.I have two issues. A year or so ago I bought a small professional ultrasonic cleaner to dip my toes and see how it will work.I bought a specialised flux cleaning product and dissolved it in deionised water as per instructions. The boards cleaned extremely well. I was doing that in my living room as I couldn't (and still can't) afford to rent a proper workshop. So in the evening I developed a very sore throat and high temperature and I had such symptoms of cold for over a week.I am not sure if this was a result of the chemicals used in poorly ventilated living room or I genuinely caught cold and it was just a coincidence. I have not repeated the experiment, but there is probably only way to find out.That being said, is it something that can be done in a living room? I don't use iso alcohol or anything like that.Also if I was going to rent a workshop, how would I approach the topic of ultrasonic cleaning with the landlord?I am sorry if these are stupid questions.The second issue I have is that one of the boards I want to clean contains switches. I can imagine that the cleaning solution will get inside the already soldered switches and so how would I get it out? Dry with hairdryer? The manual for the cleaning product suggest rinsing the board with deionised water after cleaning. I have no idea how to do it with the switches.Do you have any suggestions?Thank you for your time!

author: Terry Bites
author_rank: Super Contributor
timestamp: May 08, 2023, 11:14:17 am
content: Search for MSDS plus the name of your cleaning product. eg UltroPCB+MSDS. Always Read The Fluxing Manual.Your US cleaner may form aerosols of the flux ripping mix. You dont want to breath it in.Attached are the the MSDS or SDS for fluxoff and UltroPCB.You can see the symtoms include "May give off gas, vapor or dust that is very irritating or corrosive to the respiratorysystem."

author: JustMeHere
author_rank: Frequent Contributor
timestamp: May 08, 2023, 11:25:19 am
content: Flux cleaner and a tooth brush works well for me. The cleaner evaporates quickly.

author: jpanhalt
author_rank: Super Contributor
timestamp: May 08, 2023, 12:20:33 pm
content: If you were using a water-diluted flux remover, such as those made by Kester, the SDS is a good guide to toxicity and precautions.* The Kester cleaner has the same class of chemicals as ZEP acrylic floor stripper. I use the ZEP product (diluted 1:3) and it does a great job in an ultrasonic.I also worry about devices, such as switches, that are not sealed. In my latest project, I hand soldered them after assembling and cleaning the rest of the board. I then spot cleaned around them with a non-water based cleaner (ethanol + acetone). The water-based cleaners can be used for spot cleaning too, but the solvent-based cleaner is faster. The difference is evaporation. On the main board, it is virtually dry once removed from the ultrasonic and rinsed with water. The solder resist in hydrophobic. But, water and cellosolves (the chemical class in Kester) evaporate slowly if retained in a switch.As for your symptoms, one can't say what they were due to without much more information. Viral infections can occur year around. Moreover, some people, particularly those with asthma, may be quite sensitive to chemicals in unpredictable ways.*Unfortunately, SDS sheets are usually over cautious about side effects, because it they leave a rare one out, and someone experiences it, the manufacturer may be held liable by omission.

author: palindrome
author_rank: Contributor
timestamp: May 08, 2023, 02:35:51 pm
content: Thank you for your responses so far.Someone gave me advice to try a flux cleaner like MG 4140 and pour a thin layer (so the PCB is not completely submerged - fluid will not go into switches) onto a tray then bathe the PCB in it for a bit and then use a soft bristle toothbrush to brush flux and residue away.So I am going to try that.

author: EPAIII
author_rank: Super Contributor
timestamp: May 09, 2023, 06:17:14 am
content: As for the effects on your health, read the available information on the products you use and, if necessary, consult with your doctor or health care professional.On the question about switches that are already on the PCBs, I can address that from direct experience. I made the mistake of washing down a PCB with a flux remover after some repair work once. As advertised, the flux was dissolved by the remover and then taken inside the switches on the board where it coated the contacts and prevented their operation. After the panic subsided, I had to use about two spray cans of flux remover to wash out those switches: spray, drip dry, test and spray, drip dry, test and spray, drip dry, test. Over and over again I blasted the switches and let them drain into a trash can. Finally the flux was washed out and the switches worked again. Hard learned lesson!Since then when I need to wash down any PCB that has any electro-mechanical parts like switches, relays, connectors, pots, etc.; I make very, very sure that the cleaner does NOT get to those parts in the first place. These parts are often near the edges of a board so this can be done by either holding the board with that edge UP or by not immersing that edge/those components in the ultrasonic bath. And letting it drip dry with that edge or part of the board still up. Some boards may require two or more cleanings at different angles to get all areas free of flux. Also in really problematic cases where these parts are all over the board, dams can be formed around the switches or relays with suitable materials. But TEST those materials with the flux remover before using them on the board. I once used a styrofoam cup to soak a dirty part in a solvent. When I came back to the bench I found a cup with no bottom and a puddle of solvent on the bench top with my part in the middle. Wouldn't want that to happen on a PCB.Another technique that I use is to spray only a small area where the flux remains after repair work and using a tooth brush to scrub that area. Then blotting the cleaner off the board before it drys. This prevents leaving the flux behind. It can be repeated as needed.The basic idea is just keep the switches, relays, connectors, pots, and other electro-mechanical parts DRY.

author: rdtsc
author_rank: Newbie
timestamp: May 09, 2023, 01:25:42 pm
content: If assembling these in-house, suggest leaving off all mechanical actuating components and components which actively wick-up and conceal liquids (switches, relays, transformers, etc.) Clean the boards, then install these components. Not ideal, but getting these wet can spell disaster. Also suggest using compressed air on washed boards to force water out of crevices. For best results, bake the finished boards at 120F 50C to evaporate all moisture.

author: jmelson
author_rank: Super Contributor
timestamp: May 09, 2023, 03:15:31 pm
content: If your boards NEED to be cleaned (high impedance, high voltage) or you just intend to clean for other reasons. then use water-soluble flux. These DO NEED to be cleaned, or they will cause corrosion, but a quick rinse under running water gets them TOTALLY clean! FIVE seconds of running water is all it takes.Jon

author: CatalinaWOW
author_rank: Super Contributor
timestamp: May 09, 2023, 03:36:05 pm
content: It is very likely that your apartment has an openable window. If so placing your cleaner next to the window with a fan blowing out will dramatically reduce your exposure to the vapors. The outdoor climate may not be optimal, but it beats coughing your lungs out.Dittos on the advice about switches and other components with apertures. This can include some connector styles.

author: TERRA Operative
author_rank: Super Contributor
timestamp: May 09, 2023, 05:16:03 pm
content: Run the ultrasonic cleaner in the kitchen under the rangehood or fan, or in the bathroom with the fan running.Or even better, outside, weather permitting.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: May 10, 2023, 03:10:59 am
content: Quote from: TERRA Operative on May 09, 2023, 05:16:03 pmBe cautious. Not all range hoods vent outdoors. Some merely run the air through a grease filter and return it to the room.

author: EPAIII
author_rank: Super Contributor
timestamp: May 10, 2023, 10:50:14 am
content: The board does NOT need to be submerged for the flux to be washed into switches, etc. Read my post above! Also water soluble does not guarantee that it will not get inside components.YOU need to take measures to prevent the dissolved flux from getting into the parts. YOU, YOURSELF! You can't rely on this or thatmagictype of flux or flux remover. It's the measures that YOU take that prevent this.Quote from: palindrome on May 08, 2023, 02:35:51 pm

author: palindrome
author_rank: Contributor
timestamp: May 10, 2023, 11:22:10 am
content: Quote from: CatalinaWOW on May 09, 2023, 03:36:05 pmI live in a quite deprived area and I am forced to work in my ground floor living room that is facing the street. This means I need to have windows covered and can't really open them too much, so that I don't give burglars scouting the streets any ideas. Unfortunately the Police in my country is not interested fighting this type of crime so I am really paranoid about this.

author: palindrome
author_rank: Contributor
timestamp: May 10, 2023, 11:28:30 am
content: Quote from: jmelson on May 09, 2023, 03:15:31 pmIt's more for cosmetic reasons and there are some customer replaceable parts, so I will expect that customer would be opening the device and the view of flux all over the boards is unpleasant also the smell is not too great. But maybe this is only a problem in my head and a customer wouldn't mind. That being said I've seen comments on forums of companies releasing products in the similar niche complaining about this. I would like my product to be the best possible.