Hi Ryan,

Higher activity does not necessarily mean that the residues after soldering are more corrosive. 
So if you are really confident that all these pastes meet your reliablity criteria I would choose the paste with the best wetting properties. Futher I would feel much more confident with an extensive report of i.e. Trace-labs, than with a glossy brochure with nothing more than the words "pass".

Kind regards

Daan Terstegge
SMT Centre
Signaal Communications
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Personal website: http://surf.to/smtinfo

>>> Ryan Grant <[log in to unmask]> 03/21 4:32 pm >>>
Hi Technetters;
        I'm evaluating some no clean solder paste, and I need some advice.
I have reflown samples on some OSP coated coupons.  Before and after
measurements have given me a relative scale of which pastes wet better than
others. That is what I like to see.  Except that these are no cleans.  Which
means, better wetting on OSP = higher activity.
        The number of different board types and materials involved are so
numerous, I can't practically send a proper representative of production
boards out for SIR testing on my own.  (We are a CEM).
        All of these paste have passed BellCore and IPC SIR requirements.
All product is class II.  So can I accept the best wetting paste,  should I
go with the least wetting paste, or go middle line?
        What is your opinion of the most practical way of balancing the
processing window of wetting Vs reliability?

Thanks for you help

Ryan Grant
MCMS Process Development

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