Does flux go bad in a 'noticable' way? - Page 1
Forum section: electronics / beginners

author: GianS
author_rank: Newbie
timestamp: May 09, 2021, 08:08:24 pm
content: I have this flux that I think is (or has, as some sort of component of) Zinc Chloride, from around 1990. 50 grams costed my father about 3-4€ from a lab that used to repair TVs.Well my questions, as per title, is; this flux still works a charm after 30 years but does it have any bad short comings? Like destroy a board or oxidise something if I forget to clean some of with IPA.(I have my doubts if it's Zinc Chloride or not because most of the stuff on ebay is amber colored instead of trasparent)

author: thinkfat
author_rank: Unknown
timestamp: May 09, 2021, 08:53:55 pm
content: This is an acidic flux. Don't use it for electronics. I just wanted to get that out first. It is probably also hygroscopic. I would not trust it.

author: GianS
author_rank: Newbie
timestamp: May 09, 2021, 09:43:42 pm
content: Quote from: thinkfat on May 09, 2021, 08:53:55 pmWell, I don't know what these terms mean, and a quick Google search is not giving me the needed insights.Is this the type used by welders to join copper stuff sold instead in the electronics market? I have seen this substance in a new form factor with all Chinese writing on it instead of English but they always mention welding and soldering as the same thing so not so much trust on them...https://www.prokits.com.tw/Product/8S005/Looking at their website (which I did not find before as searching "pro's kit" on google didn't give to me the website as on of the first results), the shell and name (8S005) is the same from the old age but the substance it's made of appears different nowThere is the datasheet with all its proprieties in the product page but who knows what it's referring to if they've been using the same name for 3 decadesThanks for your response, it works as flux but I understand I should be buying something up to standards.

author: MathWizard
author_rank: Super Contributor
timestamp: May 10, 2021, 10:16:30 am
content: Yeah the Zinc Chloride stuff is not good for PCB's, it will eat away at the PCB over time.The 1st OP said it's hygroscopic meaning it absorbs moisture, so after 30yr's ........it will probably be still just fine for soldering pipes, but still no good for on PCBs, too hard to clean up.IDK what happens to electronics solder and flux as they age, I used to use my grandfather's rosin-core solder, the style of the tube it was coiled on, and the labeling on it, makes me think it was from the 1950 - 1970, I can't decide. But it still worked fine.But is it leaving nasty residues? IDKThese days I avoid the cheap Ebay types, and get Kester or 'MG Chemicals' brands. Watch out though because they sell a few different types, some really strong that make a mess too, that really should be cleaned after. The MG-Chem 1 I use, "RA rosin", that spits a lot of conductive sludge on stuff, so even on Through hole stuff I've had shorts, even after reasonable cleaning( but I guess not)

author: exe
author_rank: Unknown
timestamp: May 10, 2021, 11:43:11 am
content: The answer is written right on the lid inbigred letters.

author: madires
author_rank: Super Contributor
timestamp: May 10, 2021, 12:56:56 pm
content: You can make you own flux for soldering electronics by dissolving colophony in IPA. The old style flux tins are good for decades, while the modern jelly type flux comes with a "best before" date.

author: exe
author_rank: Unknown
timestamp: May 11, 2021, 07:52:29 am
content: I'd suggest just buy flux like rf800 (less concentrated) or tk83 (more concentrated). Those are rosin-based and seemed to me quite good. They are not very active, but also non-conductive and non-corrosive. Those are not the best fluxes, but I found them suitable for my projects.If making own flux, I found mixing colophony with ethanol rather than IPA gives it better smell. Although, frankly, performance-wise it was poor. I attribute that to the lack of activators.Be careful with "no clean" fluxes. It can mean... pretty much anything. So, it's always a safe bet to clean (and dry) the board after soldering.