What are 2-3 best water-cleanable, and isopropyl alcohol-cleanable liquid flux for use on PCBs, available in 1-4 oz. hobbyist quantities in the US? Ideally, it would be sold in a plastic applicator bottle with a dispenser needle (although I know I can buy such bottles with such needles, if need be).
Did a search on this forum and did not see specific brands of liquid flux being mentioned.
Did a search on this forum and did not see specific brands of liquid flux being mentioned.
This type of stuff might be one option:
https://www.amazon.com/SRA-Soldering-Flux-Low-Solids-No-Clean/dp/B008OC0E5M?th=1
IIRC they make pen dispensers for a variety of liquid fluxes. Part of the question might be what kind of solder you are using and what iron temperature (assuming use of an iron, that is). Liquid fluxes I have tried may tolerate less heat than a paste flux. https://www.amazon.com/MG-Chemicals...1411&s=hi&sprefix=paste+flux,tools,190&sr=1-2
https://www.amazon.com/SRA-Soldering-Flux-Low-Solids-No-Clean/dp/B008OC0E5M?th=1
IIRC they make pen dispensers for a variety of liquid fluxes. Part of the question might be what kind of solder you are using and what iron temperature (assuming use of an iron, that is). Liquid fluxes I have tried may tolerate less heat than a paste flux. https://www.amazon.com/MG-Chemicals...1411&s=hi&sprefix=paste+flux,tools,190&sr=1-2
I quite like MG chemicals products. I have a flux pen - MGchemicals 837-P for the work I do but SMT flux is thicker and keeps the components in place. I have some SMT paste incoming but I may also get some thicker flux.
I use a flux pen made by Kester. For SMD reflow I use solder paste applied through a stencil. Place the components and bake in a toaster oven.
Tom
Tom
I use Kester #186 (RMA). I use it whenever I need a little extra flux.
Note that electronics solder already has flux in it so you don't generally need any extra. Solder paste is flux paste with solder balls in it so you definitely don't need extra flux there. I use extra flux in three scenarios:
I wouldn't bother with liquid flux in a bottle. It seems to make a huge mess. Just get a flux pen. I've been using the one I have for 10-15 years now.
I write quite a bit about the different flux types here: https://neurochrome.com/pages/choosing-solder
Tom
Note that electronics solder already has flux in it so you don't generally need any extra. Solder paste is flux paste with solder balls in it so you definitely don't need extra flux there. I use extra flux in three scenarios:
- Fine-pitch SMD (think QFN and TQFP packages) where I need the extra surface tension to prevent solder bridges. I usually tin the pads, clean off the flux, apply fresh flux, place the part, and reflow with a hot air tool.
- The rare solder joint that just doesn't seem to flow correctly.
- When de-soldering a stubborn pin where I need the residual solder to flow well enough to get sucked up by the solder sucker.
I wouldn't bother with liquid flux in a bottle. It seems to make a huge mess. Just get a flux pen. I've been using the one I have for 10-15 years now.
I write quite a bit about the different flux types here: https://neurochrome.com/pages/choosing-solder
Tom
Tom, thank you for your insights. My solder is Ersin 5-core rosin and it works well, but I was planning to use the flux to remove solder off pins, and to install components on old boards (even after cleaning them, they still seem a bit wonky). I will check out your missive on solders.
Where I used to work we had these cleaning tools that looked like a very small wire brush at the end of a dental pick. I wonder if something like that would work for you. It sounds like what you need is an extra abrasive pencil eraser. Speaking of... Back in the day when erasers had one end that was coarse and intended for removing ballpoint pen, I did use that end of an eraser for cleaning up circuit boards before soldering. Like this one:
Tom
Tom
We used to say "typewriter eraser". The round pink wheel ones are long-gone or else now hard as rocks. But there are several brands of stick eraser. These used to be abrasive. Or hunt "ink eraser".
https://en.wikipedia.org/wiki/Typewriter_Eraser,_Scale_X
https://www.amazon.com/Faber-Castell-Faber-Castell-Perfection-Eraser/dp/B00TUFV3XY/
https://www.amazon.com/Charles-Leonard-Pencil-Eraser-80795/dp/B001T8SAB8/
https://www.amazon.com/Sand-Eraser-Ink-Pencil-3pcs/dp/B013ZA7HCU/
Oh I remember those. I never associated them with typewriters, though. The typewriter I had access to had a correction tape with some white stuff on it that you pounded into the paper to cover up your mistakes.
Some googling reveals that one can get the "ink eraser" (the blue part) in one chunk. The pink part can be useful for removing gunk from the gold fingers of RAM sticks, ISA/PCI cards, etc.
Tom
Probably not the same, but there are "scratch brushes" which apparently, if properly picked and used, do not scratch (much?). brass steel nylon fiberglass. Cars, watches, other uses. Breaking oxide ought to be easy. (If you will flux, you don't need to brush the oxide all the way through, only to let the flux get under old/heavy oxide and do its thing.)
https://www.micromark.com/Ultra-Micro-Fiberglass-Brush
https://www.etsy.com/listing/514343229/4-scratch-brush-brass-steel-nylon
https://www.amazon.com/Fiberglass-Scratch-Brush-Pen-applications/dp/B07S3RCTGZ
https://contenti.com/fiberglass-scratch-brush
I have never held one, have no connection, yada yada.
I DIY my own out of amber pine rosin and alcohol.
Works fine and is easy to clean with alcohol and an old toothbrush.
Partly carbonized areas are easy to scratch away.
Works fine and is easy to clean with alcohol and an old toothbrush.
Partly carbonized areas are easy to scratch away.
Aha! Thank you for the search term! They're not identical to what we had at work but close. They look to be of higher quality than what we had... But those are what I had in mind. The fibreglass ones should be good for cleaning smooth surfaces. Just don't breathe the fibreglass dust.
That could be. I haven't noticed any degradation in the performance of the flux in my flux pen. Just keep it capped when you don't use it so it doesn't dry out. As far as I know the biggest issue with flux in bottles is that the solvent evaporates and leaves you with useless goo. The flux pen has a seal that prevents this from happening.
Solder paste does expire after a while. As far as I know that's just the solvent evaporating from the flux. That leaves you with a chunk of solder balls held together by dry flux. That's not particularly useful for soldering but maybe for a paperweight. 🙂 That's why I buy solder paste in small amounts and store it in the fridge.
That said, I use the flux pen and solder paste for prototypes. I leave the mass production to those who do that sort of stuff every day for a living.
Tom
Works really well on model railway track and Scalextric/slot car track too. Used one meant for rail track for years. Like this: https://www.ebay.co.uk/p/2254417568
Probably "it depends". Rosin is tough. I've seen some funky old bow-rosin in violin cases. Wasn't a bug in amber (petrified rosin) the start of Jurassic Park?
But good (at least commercial) electronic flux is doped with activators and buffers for better action. (The ads say.)
Flux-core solder I bought in the 1970s still works fine; lead+tin is a good seal. Also a can of acid-flux (not for fine wires!!) of similar age works fine. My land is all pine/spruce trees and sap-streaks stay sticky for years (I have not tried soldering with raw pine sap, yet). But as Tom says, solvents evaporate. And why would they tell you what to juice it up with if they can just put a short date on the jar and tell you to buy fresh every few months?
Radio Shack sold a retractable fiberglass brush, and I bought one decades ago. It got worn out: I used the brush for all kinds of things: cleaning flashlight bulbs and contacts, batteries and their contacts, etc. I think that Small Parts also carried them, but then Amazon bought them and put them out of business. Small Parts was the best for getting all kinds of unusual tools and parts (well, unusual to layperson like me).