What's the carrier fluid used in gel like fluxes? - Page 1
Forum section: electronics / general

author: e100
author_rank: Frequent Contributor
timestamp: October 05, 2023, 04:25:46 pm
content: The safety data sheets don't say presumably it isn't regarded as a hazardous ingredient.I bought some (probably fake) NC-559-ASM flux from Aliexpress which works surprisingly well.The gel sort of behaves like a silicone grease, definitely not water soluble, washes away OK using alcohol.Is simply wiping this off considered 'good enough' or do you really need to remove all traces otherwise bad things will happen in the future?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 05, 2023, 06:33:14 pm
content: Have seen polyethylene glycol (unknown MW) and petroleum jelly listed before. You'd have to play around to see which ones are actually compatible with rosin and other additives (soluble, useful for purposes).Tim

author: jpanhalt
author_rank: Super Contributor
timestamp: October 05, 2023, 07:54:24 pm
content: If you are asking about ordinary paste rosin flux, it is usually rosin + paraffin + petrolatum (petroleum jelly) + other stuff. There are lots of gelling agents for petroleum-based things. Search "petroleum gelling agents." Many, maybe most are non-hazardous, so its anyone's guess.

author: David Hess
author_rank: Super Contributor
timestamp: October 06, 2023, 12:49:19 am
content: I think part of it could be glycerine, and then maybe add some methyl cellulose powder?

author: thm_w
author_rank: Super Contributor
timestamp: October 06, 2023, 10:09:27 pm
content: Quote from: e100 on October 05, 2023, 04:25:46 pmIts 100% certain, not probably. I prefer it as well, it seems to leave very little residue, probably just less active ingredients in it?Wiping off with alcohol is fine, you don't need to remove all traces of it. Sometimes I'll just leave it as is. If you are soldering BGA's its not like you can clean under the BGA anyway unless you ultrasonic the board.You can see SDGs test here:

author: luudee
author_rank: Frequent Contributor
timestamp: October 07, 2023, 04:34:06 pm
content: Some flux I bought a few months ago ... I was saving the picture for the right moment, lolCheers,rudi

author: Kleinstein
author_rank: Super Contributor
timestamp: October 08, 2023, 07:30:01 am
content: Quote from: David Hess on October 06, 2023, 12:49:19 amGlycerine would be for a water soluble easy to clean flux. Actually just pure glycreine can work as a flux that is super easy to clean (well soluble in water and alcohol), but it should be removed as it attracts water and thus may cause leakage and may promote corrosion.A paraffin part could explain a hard to remove part in the flux residue. The good thing it should be not harmful - more like protecting in a non clean flux.

author: David Hess
author_rank: Super Contributor
timestamp: October 08, 2023, 12:22:47 pm
content: I do not think it is available anymore, but Kester had a paste version of their 44 flux and Grainger has the MSDS:https://complyplus.grainger.com/grainger/msds.asp?sheetid=28788598050-09-7 ROSIN 25-50%57-11-4 STEARIC ACID, PURE 10-25%65-85-0 BENZOIC ACID 2.5-10%107-21-1 ETHANEDIOL 2.5-10%Ethanediol is ethylene glycol. Stearic acid is a waxy fatty acid. Maybe the benzoic acid is being used as a preservative?

author: tooki
author_rank: Super Contributor
timestamp: October 08, 2023, 01:32:37 pm
content: Quote from: e100 on October 05, 2023, 04:25:46 pmThe question in the title and this question are fairly unrelated, and it’s this question that really matters.The answer depends entirely on what soldering process you use. No-clean fluxes have two key temperatures: one which activates the flux, and another, higher one which neutralizes it again.If the flux is not heated hot enough to neutralize it, the residues may be corrosive.(More accurately, it’s my understanding that it’s the activators that are actually neutralized. Rosin itself returns to an inactive state by cooling alone.)In practice, this means that if the flux is used in a reflow oven (where the entire board reaches soldering temperatures), then the residues are safe. But if it is used for hand soldering with an iron or hot air, then you cannot be certain the flux reached a high enough temperature. (In particular, the excess that melts and runs off early on, getting into and under nearby components.) In these cases, I would clean thoroughly.Also, I tested a bunch of different fluxes, liquid, gel, and paste, including numerous no-clean ones, and practically all were corrosive if left on for extended periods, even totally unheated. The partially warmed flux that wicked into stranded wire, for example, produced corrosion in most cases.Flux residues from no-clean or rosin solder wire are not a problem, since they’re melted right into the joint and definitely reach adequate temperatures.

author: thm_w
author_rank: Super Contributor
timestamp: October 13, 2023, 12:19:19 am
content: Quote from: tooki on October 08, 2023, 01:32:37 pmI've tested the clone flux unheated for a few days on bare copper and there is no sign of corrosion. Tried again after heating the flux to 150C, nothing. What this paper saw was corrosion only when humidity reached a certain point:https://www.sciencedirect.com/science/article/abs/pii/S002627142100161XSo that makes sense, current RH here is super low.QuoteThe true no-clean flux?:https://www.circuitinsight.com/programs/54672.html

author: tooki
author_rank: Super Contributor
timestamp: October 13, 2023, 11:18:54 am
content: Quote from: thm_w on October 13, 2023, 12:19:19 amA few days isnothing. Check in after a month or two.Yes, humidity will interact with some fluxes and accelerate it. But long-term, a LOT of no-clean fluxes are corrosive if not fully heated.

author: thm_w
author_rank: Super Contributor
timestamp: October 13, 2023, 08:55:53 pm
content: I agree, I've seen many old boards with localized corrosion and signs of flux. I'll leave this board for a month+ and see if anything shows up.

author: tooki
author_rank: Super Contributor
timestamp: October 14, 2023, 09:59:54 am
content: Quote from: David Hess on October 08, 2023, 12:22:47 pmPaste fluxes and tacky/gel fluxes are very different.