What tacky flux should I stick to?

[Alphaprot]

Sorry for the bad pun in the headline, I simply couldn't resist...

tl;dr What no clean lead-free tacky flux do you use / can recommend for hot air rework of the usual suspects (QFP, QFN, SOIC, small BGAs etc. pp.)?

While I'm awaiting delivery of a AOYUE (the unpronouncable brand) hot air rework station, I already started looking for a tacky flux. Despite Louis Rossmann being one of my YouTube subscriptions, I do not wanna run straight towards his praised AMTECH flux. Currently I'm using EDSYN FL 22 R for normal soldering of THT, but from its dark color it appears to have quite a lot rosin in it. Might not be what you want to get sucked under your ICs by capillary effect, where it will be pretty impossible to clean it (I do not own an ultrasonic cleaner), even if it's supposed to be "no-clean". It is 1.1.2 according to ISO 9454-1 (= Rosin with halides), so you want to clean that off..

After watching this video from Steve Gardner https://youtu.be/iKDAmY9Rdag, I wasn't that much wiser than before (although I didn't know that liquid flux evaporates thaaaat fast, this is why I wanna go for tacky/paste flux). Some of the Banggood stuff he tested had severe flux spitting when it liquified, you don't really want that. Another big problem with many of those cheap fluxes is, that you know near to nothing about the level of corrosive residues they leave behind. Problem with the AMTECH stuff: most of it is not genuine, but a cheap knockoff. I would not say that makes it a bad choise - it simply makes it a more unpredictable choise in terms of what to expect.

Syringes of 5-10 CCM should be fine for my "hobby needs".

I spent almost a whole day looking through different offers now (wasted would be a more appropriate expression), so I'm now turning to you and would kindly ask about some recommendations.

Kind regards from Germany - and stay save!

[deadlylover]

The Chip Quik SMD291 is okay and is more readily available from reputable dealers than the Amtech outside of the US.

edit: ehhh it's conductive even when non activated, check comments below for more details, I probably wouldn't recommend it knowing this.

[OwO]

There are NC-559-ASM clones, most of which work very well and is hard to tell from the original. The usual caveats apply; avoid ebay and carefully vet vendors on aliexpress. Get one that doesn't claim to be genuine amtech; you will have less chance of getting "fake" nonperforming flux.

For example this is the one I'm using:

[Shock]

Look up the major brands at your local electronics distributor. Then visit the manufacturers websites and find something that fits your requirements. Check if they have a reflow profile, datasheet and read the msds for safety. Use fume extraction and do some of your own performance and conductivity testing as shown in the below video (he is using an insulation tester now).

Flux is bad enough as it is without buying some random counterfeit shit from china, ebay or amazon. Good luck breathing in fragranced drain cleaner.

[SiliconWizard]

The Chip Quik SMD291 is okay and is more readily available from reputable dealers than the Amtech outside of the US.

Also recommend that. Has served me well.

[eliocor]

+1 for Chip Quick SMD291 !

[Shock]

Since you use Chipquik SMD291 try and reproduce the test in this video, it may be counterfeit flux being used as the label appears backwards and marked differently. Chipquik is stated as non conductive, would be interesting to see if your flux is conductive and how residue acts under heat and humidity etc.

While the stuff in this video wets well (and undoubtedly the real product does) it would also be good to know how badly the genuine product smokes and spits. It has a good in and out of fridge shelf life of 24 months and says in the datasheet REL0 which is meant to be resin based and halide free. It also says in the datasheet it's synthetic no-clean (aka clean later) and in the msds the main ingredient is modified rosin.

[eliocor]

The conductivity test is absolutely nonsense: it should be done AFTER the flux has been activated ; it is also true that I _always_ wash my boards with IPA.
 
BTW, I only buy such peculiar materials from reputable sources: DigiKey or RS.
 
 P.S.: sorry, but my knowledge of Russian is nihil, so maybe the maker of the video tells something which can explain his tests!

[Shock]

Of course afterwards and even multiple reflow profiles. I don't see the harm in making comparisons to when it was freshly applied as long as you don't jump to conclusions on the results too early.

[SantaClaw]

On the topic of flux, banggood seems to have an issue with pricing for this decent "amtech" flux, you can get 4 tubes for 7,23$

https://www.banggood.com/2pcs-AMTECH-NC-559-ASM-PCB-BGA-Reballing-Solder-Flux-Paste-10CC-p-960102.html

Feel free to delete if not relevant.

[wraper]

The Chip Quik SMD291 is okay and is more readily available from reputable dealers than the Amtech outside of the US.

Worst tacky flux I ever tried. Worse than fake Amtech from ebay. Purchased 2 syringes from digikey, now don't know what to do with this crap. Short working time, solders like crap, a lot of foaming, a lot of ugly residues. Also it's conductive in non activated state. So not suitable for soldering with soldering iron as it won't ensure full activation.

[wraper]

I suggest Alpha OM-338. Stellar soldering performance, long work time, non conductive even before activation and relatively inexpensive compared with other branded fluxes.

[wraper]

The conductivity test is absolutely nonsense: it should be done AFTER the flux has been activated ;

Except it does matter a lot because you won't get it to fully activate in many cases, particularly when doing rework.

it is also true that I _always_ wash my boards with IPA.

And it won't get it out from beneath SMT components.

[deadlylover]

Since you use Chipquik SMD291 try and reproduce the test in this video, it may be counterfeit flux being used as the label appears backwards and marked differently. Chipquik is stated as non conductive, would be interesting to see if your flux is conductive and how residue acts under heat and humidity etc.

My tube from RS seems to test at about 7-10MOhms just dotting it on the bench, what a piece of crap. Will have to look into other options when I run out.

[wraper]

My tube from RS seems to test at about 7-10MOhms just dotting it on the bench, what a piece of crap. Will have to look into other options when I run out.

Just be aware that most Amtech fluxes are conductive as well. IME white creamy fluxes (synthetic) usually are non conductive. Those which are clear/ semi clear usually are conductive.

[I wanted a rude username]

There are NC-559-ASM clones, most of which work very well and is hard to tell from the original. The usual caveats apply; avoid ebay and carefully vet vendors on aliexpress. Get one that doesn't claim to be genuine amtech; you will have less chance of getting "fake" nonperforming flux.

The Hanwuyou one you use is scarce on AliExpress in 100 g tubs, but cheap on Taobao. Thanks for the tip!

[Shock]

It's cheap and someone else uses it, must be safe!

[Alphaprot]

I suggest Alpha OM-338. Stellar soldering performance, long work time, non conductive even before activation and relatively inexpensive compared with other branded fluxes.

I just looked that up because I haven't heard of the Alpha brand before. It turns out that this is a solder paste ^^ But well - technically it does contain no-clean flux for lead-free 
Thank you anyway.

Thank you for your valuable recommendations, folks, much appreciated
According to my little research, here is an incomplete list of what no-clean tacky flux brand (NOT distiguishing between use-case lead-free/lead/both) is supplied by what distributor:

TME: AMTECH, ALPHA
Mouser: Chemtronics, Chip Quik
Farnell: Chemtronics, Chip Quik, CIF, EDSYN, MG Chemicals (but rather narrow product range/line-up)
Digikey: Chemtronics, Chip Quik, Kester, Multicore, SRA Soldering Products
RS-Components: Chip Quik, Circuitworks, ERSA, MBO, STANNOL
ARROW: MG Chemicals (rather narrow product range - one syringe)

[wraper]

I suggest Alpha OM-338. Stellar soldering performance, long work time, non conductive even before activation and relatively inexpensive compared with other branded fluxes.

I just looked that up because I haven't heard of the Alpha brand before. It turns out that this is a solder paste ^^ But well - technically it does contain no-clean flux for lead-free 
Thank you anyway.

It's flux, not solder paste. https://www.tme.eu/en/details/topnik-gel-bga/fluxes/alpha/om-338/
OM-338 PT is solder paste.

Datasheet: http://www.marox.sk/images/produkty/tavidla/om338.pdf

[Alphaprot]

Thanks for the clarification, my bad @wraper

Added ALPHA then in my little list..