Electronics > Beginners
Isopropanol vs Ethanol for Flux cleaning
plazma:
Depending where you live you may find pure IPA sold as anti-freeze agent for diesel engines or truck air brakes. I bought 1 liter bottle for 4€ in Finland.
KL27x:
I use 95% ethanol. There is no PCB component/plastic that I have encountered which is noticeably degraded or dissolve in short exposure to ACTEONE, let alone ethanol. Housings are a different story. But even here, I have never encountered any problem with ethanol.
The benefits of ethanol, to me:
1. smell is much less noticeable/objectionable to me
2. 95% will STAY 95%. Isopropyl will slowly absorb water from the air that you let into the container; it stabilizes at 91%
3. Hardware store sells it in big tin containers which are a convenient size/shape to sit on a shelf along with all my other solvents and finishes which I conveniently buy at the same store.
Bitrex, smitrex.
I don't really care if there's a little trace of bitrex in there. If it wasn't soluble in the 5% water, it would just settle to the bottom of the container and wouldn't serve it's purpose, no? The 5% water also has to dissolve the ionic contamination from the board you're cleaning. Or the ethanol has to at least suspend it while you brush it off.
If you just leave the ethanol to dry on the board, of course the bitrex will remain on the board. Along with all the flux residue you were trying to clean off.
Pure isopropyl would be useful for final rinse, if you needed it. For basic cleaning, it doesn't matter if there's a trace of something else in there. It will still get the board much cleaner than it was before. There will be plenty more contamination in the bathwater just from the smelly guy sitting in the tub.
MrAl:
Hi,
I use isopropyl usually 70 percent. Seems good enough and easy to get at almost any store.
Have to watch out though as some places are selling 50 percent now, and i would not use that stuff. 90 percent yes even better.
I use 70 percent for other general cleaning too though so i always have it on hand.
Ian.M:
I've used denatured Ethanol and Isopropanol (IPA). 95% denatured Ethanol is great for getting the crud off really dirty boards - wave soldered or reflowed with no defluxing then used in a poorly ventilated room by chain-smokers till a crust of gooey cigarette tar has built up on every surface.
However, before using denatured Ethanol on anything sensitive, its advisable to evaporate about a ml to dryness on a watchglass (or similar concave glass surface) using warm air or other gentle heat source, and note if there is any objectionable residue*. Also observe the last of the liquid closely as it evaporates to see if it is oily. On sensitive high impedance circuits its only the first stage of a cleaning process and needs to be followed by an aqueous phase to remove ionic contamination and then by a good technical grade of 95% (or purer) IPA to quickly remove the residual water from the aqueous cleaning phase + any detergent residue. The board can then be dried with no risk of iron component leads and other parts rusting, or heat damage due to prolonged and excessive drying temperatures.
On less sensitive circuits, you can probably skip the aqueous cleaning phase unless a water soluble flux was used, or objectionable streaking was left after drying. Blotting off as much denatured Ethanol as possible followed by an IPA rinse (without drying in between) is usually adequate.
As IPA forms an azeotrope with water, (87.7% IPA by weight), and absorbs moisture from the air, if you ever need to use it for rapid water removal, you need drier IPA than that, so that traces of moisture aren't left behind as it evaporates. Keep all bulk IPA containers tightly stoppered, and only dispense enough for a few days use.
* If you are intending to use denatured Ethanol as a single cleaning stage, you will probably want to test the conductivity of the residue if there was any apparent. Add a drop of deionised water and see if the residue is water soluble then compare conductivity with a control drop of the deionised water, taking care to use clean electrodes and immerse them the same distance with the same separation.
ogden:
I've used Kontakt PCC bottle which mostly is IPA + some Ethanol & Methanol. Brush is very, very important part of this "tool". Such bottle is always ready to use, too. For surface mount boards additional "air duster" bottle (which indeed is not "canned air" but butane+propane) will be useful as well. It does two things - blows away mix of flux+cleaner from tight places and helps to dry board. Slower evaporation of IPA is very helpful here - you have time to grab duster before it is too late.
Take those images in product webpage with grain of salt - you don't have to spill cleaning fluid all over the PCB or table. Just wetting brush is enough. At the end of the job - spray into brush again and clean it with paper towel/tissue, that's it. After trying such cleaner - you will never use cotton swabs on PCB again :)
http://www.kontaktchemie.com/koc/KOCproductdetail.csp?division=&product=KONTAKT%20PCC&ilang=all&plang=all
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version