Good soldering flux?

[shapirus]

Whatever gauge of the needle I use, within reason, or a conical syringe tip, it keeps blocking. I really hate that.

There are a couple of solutions for that : ) (I use the same stuff, 8341).
Solution 1: Use a metal tube nozzle, quite wide (I'm using 1.5 mm hole), and when it's near a hot air tool (i.e. just gently warmed) it will auto-unclog : )
Solution 2: When using a fine flexible plastic nozzle, I use a wire (e.g. through-hole resistor, or any bare wire), poke it around in the end a bit and then it egresses in a fine thin line (if that's what you want, ideal for small SMDs).

Photo shows the metal nozzle I use. Also shows a couple of other fluxes which I've not used yet, but hope to try out sometime.

Yeah. There are workarounds. Unclogging the hole with a piece of wire (solder wire!) is what I do. The thing is, I want to be able to just use the damn flux without any workarounds, and that's where it fails.

[forrestc]

You did not mention it cost more than gold

Only if you buy it direct from indium.

$37.50 for 30ml (big) syringe:

https://www.testequity.com/product/881SO202-FLUXOT-84283-30ml?gad_source=1&gclid=EAIaIQobChMIqvnno-mJhwMVwh6tBh1Yhgx_EAYYASABEgJVwvD_BwE

Or $27.12 after eevblog discount at tequipment:
https://www.tequipment.net/Indium/FLUXOT-84283-25-GRAM-SYR/Flux/

I usually use a coupler to transfer it into another (smaller) syringe and then keep the big tube in the fridge with the solder paste. 

Still not dirt cheap, but not $150 either.

Plus, there are two formulations.   TACflux-020B and TACflux-020B-RC.   The RC is (for whatever reason) rated for a 6 month shelf life. and the non-rc is 12 months. 

[Postal2]

I recommend:

[tooki]

Thanks it makes sense. I will give it a try in my ultrasonic cleaner with IPA and heater on ... I need to buy a gallon of 99% IPA somewhere... (fun fact if you google "IPA gallon" only beer shows up).

Do not do this!!

It’s not safe to fill a regular ultrasonic cleaner with flammable solvent. And it’s expensive.

Instead, fill the machine with water. Then place into the water a smaller container of solvent with the dirty item. The container can be open (like a tray or beaker) or a plastic bag. Plastic bags are a great way to massively reduce your solvent consumption, since you can put in your board and then just enough solvent that when zipped closed, the board is submerged. Seal a bit of air into the bag; this will keep the open end of the bag floating at the surface.

[Smokey]

Ethanol eh?  How about $20 per gallon? 
https://www.totalwine.com/p/1825175-1


Two for the boards..... one for me...