Hope this is helpful.


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Subject: Re: Flux Residue After Wave Cleaning
Author:  ETIDWELL at DSC-1100
Date:    2/17/96 11:10 AM



     If this were a problem at DSC, the first thing I would do would be to 
     perform some FTIR scans on the joints causing the false failures.  
     This would at least supply you with some generic chemistry as to 
     what's causing the lack of contact.  

     And since I just got back from chromatography school, I would be doing 
     some extract measurements on raw boards and boards after wave solder.  
     Then you would be able to place some identity on the "source" of your 
     problem.  And due to the sensitivity of LC/IC, you could even possibly 
     pull an extract from you Omega Meter and get a distribution of flux 
     residues from this analysis.  It would take some analytical method 
     development, but with the FTIR and LC/IC I feel confident we could nail 
     it down.

     I know this information probably won't help this guy because he 
     probably doesn't have these types of analytical abilities.  It 
     wouldn't suprise me if the PCB fab supplier has changed his HASL flux 
     chemistry/process or the wave solder flux supplier has changed his 
     flux chemistry or produced a contaminated lot of flux.  ???????


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Subject: Flux Residue After Wave Cleaning
Author:  MNEIDER at DSC-1100
Date:    2/16/96 3:21 PM


     Ed this looks like one for an expert like you to respond to 

     mark


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Subject: Flux Residue After Wave Cleaning
Author:  BWOOLDRI at DSC-1100
Date:    2/16/96 1:23 PM


Mark,

Any words of wisdom for this guy?

Bruce


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Subject: Flux Residue After Wave Cleaning
Author:  [log in to unmask] at SMTPLINK 
Date:    2/16/96 11:38 AM


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.