cleaning lead-free HASL board before soldering

[1sciguy]

I have some boards that were manufactured with lead free HASL last year and I find that they don't readily flow when I'm soldering with fluxed Kester SN96.5 lead free solder.  It takes about 1.5 seconds to wick the pad even though the through-hole pin flows right away.  If I clean the pad with a pencil eraser prior to soldering, it wicks in about 1/2 second.  So clearly the boards are in need of a cleaning before I sit down to solder them.  Is there a liquid bath meant for pre-cleaning?  I am switching all future boards to immersion gold plating, but looking to use up my old boards.  I've read about 99% isopropyl, but wondering if there is something more aggressive.

Thanks,

John

[Mangozac]

I don't think IPA will work for removing oxidisation (if, as I suspect, that's what has occurred). How many boards do you have to do - it sounds like the pencil eraser method might be the quickest solution? Although I'm sure there would be some kind of chemical available for this process.

It's important to keep unused PCBs sealed up in their packets with silica gel until you're ready to use them.

[phil from seattle]

This might work - https://rbpchemical.com/product/hasl-precleaner-sl/  I have no knowledge or experience with it though.

[OwO]

thin layer of flux + hot plate should do it.

[Ian.M]

Scrub them with a green panscourer?