I have been reading some E-mail regarding solder balling with 
No-clean and water soluble fluxes recently.  I thought I might be 
able to relay my solution to the solder balling problem in our 
process in case it might help someone.

When we first started using water soluble flux, every board emerged 
from the wave covered in minute solder balls adhered to the mask.  I 
considered these to be a result of excess water remaining in the flux 
at the point of wave contact, vaporizing rapidly, and blowing solder 
all over the mask.  To eliminate the problem, I pre-heated our flux 
removal airknife.  This causes a high temperature jet of air to pass over the 
entire board prior to preheating but after flux application.  The 
heated air reduces the amount of volatiles in the flux such as water and 
eliminates solder balling.  We haven't had a solder ball since.

Thanks
Jason Spera
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