Fellow,

        I am trying to look for possible causes for a solder ball problem on
the wave process. These boards are practically a Swiss cheese, unmasked 25
mils via holes all over the place, under QFPs, SOIC and everything else,
which limits the wave process window. These assemblies don't have SMT on the
bottom, wave is used only for TH. We've done everything, checking of flux
specific gravity, changed the flux, verified the profile, made sure the flux
get activated...Our process uses a foam fluxer and WS flux. What could
possibly cause solder balls on the top side? the defect rate is aprox. 2-5
boards with solder balls every 20 boards. Any Ideas?

        Any comments would be appreciated


Jorge Rodriguez
Process Engineer
Varian Electronics Manufacturing
615 South River Drive
Tempe, AZ 85281
Phone: (480) 968-6790 X 4258
Fax: (480) 829-4000
E-mail: [log in to unmask]

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