Non darkening Flux?

[tony359]

Hi all,

I was watching a video from NorthWest Repair (The guy there is just doing such incredible repairs) and while he was fixing a bunch of pads on a GPU PCB, I saw this



I've been trying to fix some broken traces on a PS3 CPU for a while but one major issue I'm seeing with my AMTECH flux is that it gets tacky and dark very quickly and then it's a pain to remove and replace.
In the video Tony (I think it's his name) seems to suggest that I am just using the wrong flux?

Any thoughts or ideas?

Full video is here: https://www.youtube.com/watch?v=XYHeetEZcSg

Thank you!

[stj]

hmmm....

flux gets dark either because your burning it or because it's picking up crap off the board.
maybe tell us your temps?

also different fluxes have different content.
oldschool fluxes have Rosin (pine sap) in them and look a bit brown to begin with.
synthetics dont, and some are blends - like Stannol HS10 which is synthetic with added rosin.

why did i mention that?
because Rosin doesnt get along well with the elevated temperatures needed for working with lead-free solders

[tony359]

My iron is usually around 360. With tiny tips I might increase the temp as there is very little thermal mass at the tip.

[stj]

sounds o.k. - i solder at 350 and dont burn the flux

[tony359]

It doesn't burn, it gets a bit too thick and darkens a bit - the guy of the video is a sort of wizard, I don't know how he can do what he does so I take that suggestion seriously! From his (and others) videos I see that their flux stays much more fluid and clear than mine.

[diif]

Genuine Amtech flux ? Which one ?

[tony359]

Amtech 559

[FZG]

I heard about fake Amtech 559 on several occasions. I have a syringe of 559 as well and I am not sure if it is actually genuine since it was rather cheap but it does what it is supposed to do and it does not get dark at 350°C soldering temperature.

[tony359]

I got it on Ebay from someone who claims to be the UK distributor - they showed an AMTECH business card and I believe Amtech shows their name on their website.

[harp]

Long time ago, I have idea to make some clear stuff for special purpose, and your thread is boosting me up.

Here is my video about that, maybe you find some intrest in it, it have semi-english subtitles also, just click CC button.

https://m.youtube.com/watch?v=xCuPTHsScpA
Making clear, non darkening, high temp resistant DIY flux

For these who dont like DIY solution, and love commercial stuff, in this video is mentioned information of this clear flux from first post...

https://m.youtube.com/watch?v=b0yNcSWz0gw

So you can now chose

[tony359]

I've noticed that Tony is mentioning the Stirri flux - I could try and give it a go but I also have the Amtech (original, not the chinese copycat) and that doesn't really work, at least as I'd expect.

I'm checking the Stirri LT-HF-TF product page and it says

Stirri LtºHF-TF is a world's first low-temperature halogen-free soldering tacky paste flux with optical tracer glowing in UV for instant visual QC inspection

Low-temperature soldering tacky paste flux for soldering Tin/Bismuth (Sn/Bi) alloys

Contains QC-Aid™ optical tracer for instant visual contamination inspection. QC-Aid - Everyone can QC.

LT-HF-TF specialty no-clean halogen-free low-temp soldering tacky past – STIRRI® Aerospace & Defense Grade OEM

I admire Tony's work, he's just a wizard. I value his opinion but this feels like the wrong product for soldering regular solder? It's supposed to be used with low-melt solder. Unless its "low temperature" makes it perfect for the tiny soldering where there is not much heat being used?

[CapLeaker]

That looks like you a burnt the flux by not having enough of on it, not the right soldering tip, low quality solder wick, too much heat and or a low wattage iron. And that is the exact result you get. Looks like you did all right to a certain point (cleanup). You may have forgotten to clean the old flux between the take off and the cleanup. Having the right tools and procedure = success. And some parts you just can’t cheap out.

[Aliencomputres]

Kingbo RMA-218,ChipQuik SMD291,NC191

[stj]

that stirri link - i wouldnt touch that stuff.
i cant see anything about the usable temperature range.
if you dont know when a fux will burn, you dont want to be using it.

[Aliencomputres]

that stirri link - i wouldnt touch that stuff.
i cant see anything about the usable temperature range.
if you dont know when a fux will burn, you dont want to be using it.

Google is your friend

[tony359]

Kingbo RMA-218,[B]

I've used the Kingbo 218 for a while. At some point the product changed and became much worse with a horrible "chemical" smell.

I did some research and.. well, I cannot find a "Kingbo" manufacturer. So it looks like it's a random name and every seller is sticking whatever they want in those tubes! So "Kingbo-218" is like Aliexpress "Amtech 559" - it might be good but it depends on the seller and not the product.

About the Stirri, I cannot find that info on the datasheet - but Aliencomputres recommends the Kingbo which simply does not exist so...

https://cdn.shopify.com/s/files/1/06...f?v=1721712131

At the time of writing, the "Kingbo" sold by the seller "Riesba" on Aliexpress is not bad. It smells ok-ish and works much better than the average fake "Amtech". I do have genuine Amtech as well so I know how flux should work

[stj]

Google is your friend

google is nobody's friend.

if i'm trying to sell you something i dont tell you to fucking "google" it.
it's supposed to be listed in the specifications instead of all the other verbal diaria on that page.