Reasonably activated flux for PCBs - what is Kester 951? Other activated fluxes?

[dmderev]

Hello,
I am looking for a flux to solder PCB connectors from China. They usually are nickel plated or even have some golden color, but they are not taking solder well when used with traditional RMA solder paste. They are instantly soldered with white plumber's flux paste (probably with ZnCl), but I am not sure its residuals will not corrode plated holes inside.

I used a liquid flux marked as "Kester 951" - it worked OK but I cannot find any traces of it on Kester web side. I am wondering what it contained. There is a mention of Kester 2235 but it is sold in gallons only.  Any ideas how to make flux in small q-ty?

And I also would best need a paste form - but more active than RMA. Any advice on that and also if it needs cleaning?

Thanks!

[tooki]

I have no idea why you couldn’t find 951 on Kester’s website. I typed “Kester 951” into Google and got this:
https://www.kester.com/products/product/951-soldering-flux

It’s also linked if you go to kester.com, click “electronic assembly”, then “liquid solder flux”, and then select the “all” tab.

It’s not an RMA flux, it’s an ORL0 no-clean flux.


I have encountered those unsolderable Chinese “gold” headers. I threw them out and got different ones.


Why don’t you browse a website like Digi-key and look at the flux options? They’ll have the datasheets linked, which tell you whether cleaning is required. Beware that with external fluxes (liquids/pastes), no-clean fluxes are only guaranteed safe if they’ve been heated to soldering temperature. Excess flux that has run around the board and been either in sufficiently heated (or not at all) may still be active and able to cause corrosion.