Dick,
What type of soldering flux are you using -- low solids, water soluble or 
rosin-based?  What is your present
cleaning process?  Have the boards as received gone through HASL or are they 
bare copper preserved?
Call me if you wish to discuss.
Laura Turbini
Georgia Tech
(404)894-9073
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>From: Dick Pond
>To: TechNet
>Subject: Flux Residue After Wave Cleaning
>Date: Friday, February 16, 1996 12:18PM
>
>We're experiencing increased flux residues after wave solder cleaning.  The
>flux residue is causing false failures at bed of nails testing, is visible
>in larger quantities, and measures higher on bulk ionic contamination 
tests.
>Our experiments found two primary problem contributors.  Both 1)one 
specific
>wave soldering flux and 2)some lots of circuit boards must be present.
>The wave flux is a low solids, no-clean(yes, we are water cleaning).
>The boards are FR-4 with liquid photoimageable solder mask, mixed surface
>mount & thru hole, and with routing & holes.
>Both the flux and the board fabricator have been used successfully for 
years.
>The ionic contamination levels range up to 25 times higher(0.1 ug vs 3 ug
>equivalent NaCl) on recent controlled experiments and 100 times higher than
>on past process performance.
>A band-aid fix has been to add saponifier to our hot water wash.
>What's the mechanism of why some board lots have much higher flux residues
>after wave cleaning compared to other board lots in a long established
>process?
>Any advice would be appreciated.
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