| Electronics > Beginners |
| isopropanol question |
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| jmelson:
--- Quote from: Lucky-Luka on June 29, 2019, 10:45:55 am ---Hi all I've read that isopropanol is a good choice to clean up the board after the soldering is done. I've tried it with my second ever pcb. The result wasn't satisfying at all. After I brushed some 99.9% isopropanol on the back of the board a sticky white patina formed. I've tried to clean the mess using a polishing cloth. The result is in the picture. I'm not satisfyied at all. What's the problem? Cheers --- End quote --- First, it depends on the flux used. There is no-clean, solvent-clean and water soluble. If you really need to clean the board, then use water soluble flux (WS) and just wash in water, maybe with a little gentle scrubbing with a toothbrush. If you use one of the other fluxes, then it can be difficult. There are flux remover preparations that have a variety of stuff to break down and hold the flux in suspension. One was roughly equal parts of isopropyl, ethanol and ethyl acetate. But, what I do for the non-WS flux is use plenty of alcohol, let it soak in for a minute, then brush with a toothbrush for about one minute, and immediately rinse with lots of water. You will see the alcohol turn white when the water hits it, that is the flux residue dropping out of solution. You need to wash it away as rapidly as you can, before it deposits back onto the board. Depending on the required level of cleanliness, one or two cycles of this process should get the board pretty clean. For ordinary digital boards, I use no-clean flux and don't clean the boards. For critical stuff like high-impedance or high voltage circuits, I use either solvent clean or water soluble. Jon |
| Shock:
--- Quote from: rcbuck on June 30, 2019, 03:21:06 am ---I use a toothbrush and denatured alcohol for the first cleaning stage. I follow up with IPA and a different toothbrush. I then rinse under running cold tap water for about 30 seconds. I have high water pressure here, about 95 PSI. Then immediately dry the board with a hair brush dryer set to high temperature and high blow speed. The boards always end up looking very clean. No signs of damage to the silk screen or solder mask. --- End quote --- Plain tap water is not good for electronics, especially finishing with it. Denatured alcohol contains additives as well. Instead I would dilute pure IPA with deionized water, or if you needed something more aggressive make either an IPA or deionized water solution along with some other electronics safe detergent or more aggressive solvent (this is what manufacturers do). Rinsing with deionized water or IPA (in a ventilated area) from a squirt bottle works well to wash it all off, you can always do a two step rinse. |
| vk6zgo:
You can get a bit too "precious" with cleaning PCBs, especially ones that have already been in service. These often accumulate a layer of dust & other "gunk" over the years, but continue to operate properly. As I now have to buy my own solvent, I have gone to plain old "methylated spirits". People say it leaves "a white residue", but in my experience, that is just dissoved flux that hasn't been wiped away properly. |
| Brumby:
--- Quote from: ptricks on June 29, 2019, 11:01:37 am --- --- Quote from: Lucky-Luka on June 29, 2019, 11:00:03 am ---so what do you use? only a toothbrush? --- End quote --- If you scrub the board with alcohol and brush, then rinse it off with alcohol there should not be any residue, it will just dry clean, no wiping needed. --- End quote --- This is how I do it. I have IPA in a spray bottle which makes for easy application. |
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