You asked two questions, Figuratively:
Q1 - Are all LF solder fluxes created equal?  
A1 - No. See other answers

Q2 - What happens to residues in actual life or life testing?
A2 - To answer this even in the most general terms you would need to be more
specific about the type of flux you are looking at. For example, rosin based
fluxes can effloresce with damp heat to give what looks like a corrosion
product. However if heated the "growth" can melt and revert back to normal
appearance. A cosmetic in other words. Alternatively some other flux types
could start a nice little corrosion cell which will self perpetuate as long
as there is a supply of damp and oxygen and that would be a concern.
This is, as you can see, a long way round to avoid saying ... it depends...

 
Best Wishes
 
 
 
Mike

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Victor Hernandez
Sent: Friday, April 24, 2015 8:31 PM
To: [log in to unmask]
Subject: [TN] LF Solder flux

Fellow TechNetters:

   Are all LF solder fluxes created equal?   I often see m/b with more flux
residue, dry-crusty-yellowish, accumulated around the solder joint.  Yet
others are almost free of flux residue.   I do see that either solder form a
glassy halo around the solder joint at the solder mask surface.   What are
the Pros & Cons.   The solder flux residue is more pronounced on Filed
return assemblies or those which have been subject to reliability testing,
HALT, HASS, S&V & T/C

Victor,


______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________



______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________