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Old 05-18-2019, 01:03 PM   #1
Dannyx's Avatar
Join Date: Aug 2016
City & State: Constanta
My Country: Romania
Line Voltage: 230VAC 50Hz
I'm a: Hardcore Geek
Posts: 2,846
Unhappy Does flux expire ?? Flux discussion.

Good day folks. Today I managed yet again to fail to fix a laptop board, which is actually beyond the point of this discussion, but it got me thinking about the flux I tried using: does flux expire or go bad in any way over time ? Stupid question, I know...

I've never been happy with any of the flux(es ?) I've used so far: whether at home or at my former shop, they all "vanish" pretty quickly once I start heating the part, leaving the area "dry", with nothing for the part to float in...this makes aligning QFNs an absolute misery and I hate it ! It seems to happen more with hot air rather than the iron...

I worked on this particular board at home, where I had a syringe of Amtech RMA-223-UV flux that's easily 10 years old, so I decided to use that because I had nothing better on hand. I think I bought it when I was in friggin' highschool It had turned a dark-brown color over the years from the original yellow of most fluxes, but I tried it anyway. It came out of the syringe alright and even seemed to flow nicely, but suffered from the same issue: as soon as I used my hot air nozzle, instead of the part flowing in place, the flux vanished but the chip just stood a big middle finger >_>

Ironically, the flux Louis Rossmann uses is also Amtech, though a different kind, and his seems to stay liquid no matter how much he heats it up, which makes me think mine is either not the right kind or it's gone bad...

Then there's Kingbo...the guy at work who does reballings uses this stuff...don't know how good it would be for "manual" soldering...

I'm a noob at micro-soldering but I have to get my feet wet somehow, so I practice with what I have. Not spending 13 dollars on the same flux as Louis because it wouldn't see enough use to make it worth it - it may not sound like a huge amount, but it's a pretty penny to me. Cheers guys.
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