Is NC flux supposed to leave a lot of sticky residue? - Page 1
Forum section: electronics / general

author: Axk
author_rank: Regular Contributor
timestamp: March 02, 2019, 07:18:45 pm
content: The label on the syringe (not the original syringe on the photo below) says "FluxPlus Solder Flux, Rosin 7019074 6-412-A"The datasheet says it should leave no more than 2.5% of residue.am I not heating it long enough for most of the thing to evaporate or is it counterfeit?Leave a lot of sticky residue which I would expect with rosin, but then why do they say it only leaves 2.5% of residue?

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: March 02, 2019, 07:37:44 pm
content: No-clean does not mean there is no residue, but that the residue does not lead to problems if left on the board after soldering. However, this is not true in all cases. There arescientific paperson no-clean fluxes and several conclusions can be drawn from the findings.1: No-clean can help with cost-effectiveness without leading to problems2: Under certain conditions, no-clean flux left on the board leads to problems (i.e. higher temperatures)3: No-clean flux is harder to wash of the board than eg. aqueous clean fluxConcerning the amount of residue left on your board: Since you did not show how much flux you used during the soldering process, it can not be judge if this is a lot of residue or rather typical.Personally I like the use of flux the can easily be removed with an ultra sound cleaner bath.

author: HalFET
author_rank: Frequent Contributor
timestamp: March 02, 2019, 07:42:49 pm
content: Based on the residue, I would say you attempted to use Louis Rossman levels of flux. A rinse with alcohol or a dedicated flux remover would probably be a good idea at this point.

author: helius
author_rank: Super Contributor
timestamp: March 02, 2019, 07:52:27 pm
content: No-clean fluxes are not all the same, but it is often the case that the residues are hard to clean using alcohol alone. They tend to be on the hard and glossy end as opposed to soft and sticky. Alcohol+naphtha type cleaners do better on these residues.

author: stj
author_rank: Super Contributor
timestamp: March 04, 2019, 06:06:11 am
content: so much flux, yet the soldering on the voltage regulator looks like shit!

author: Axk
author_rank: Regular Contributor
timestamp: March 04, 2019, 12:57:50 pm
content: The voltage regulator was soldered in the "old times" when I didn't have this flux

author: Siwastaja
author_rank: Super Contributor
timestamp: March 04, 2019, 01:41:00 pm
content: Quote from: stj on March 04, 2019, 06:06:11 amToo little heat.Flux is great, but a bit overrated. Often what you arereallylacking, is heat, and you can't replace it with flux. Big enough tip, really, for good thermal transfer.

author: KL27x
author_rank: Super Contributor
timestamp: March 05, 2019, 06:05:12 am
content: If your residue is still sticky, it's probably not fully evaporated. Once it is fully dried, the average rosin flux will be completely non-sticky at room temperature, and it will shatter if you press on it with a scribe. If you're gonna clean it, its easier to do it before it is fully dried. If you're going to leave it on there, then more heat will help to dry it out faster. Rosin residue is not visually attractive, but it is largely inert. I usually leave it alone, unless I am going to apply a conformal coat.If you open an old cathode tube television, chances are pretty good you'll find tons of brown rosin flux residue all over cheap phenolic resin single-sided boards. Those televisions lasted forever.Some distributors try to make a distinction between rosin flux and NC. In actuality, I find "NC" doesn't mean much. It can mean low solids with minimal resin/rosin, or it can mean a high solids that is NC because the residue is inert. The general idea is that you don't have to clean it. But just because the residue is ugly doesn't mean you have to clean it. The manufacturers or said televisions used rosin flux and didn't clean it. By today's standards, that might qualify as a no clean flux. But it's hard to say what "no clean" means, because it's an industry term that means w/e the industry wants it to mean and is subject to change or evolution.

author: electromotive
author_rank: Regular Contributor
timestamp: March 05, 2019, 05:22:17 pm
content: The red label (90%) rubbing alcohol and a cotton swab work great for removing flux residue.