Hi John -

I can answer questions 3/4: SERA can detect solder mask residue on a surface BUT
SERA can't tell what the contamination is! The SERA test method determines the 
amount of oxide quantity and type by conducting an oxide reduction. If there is 
some kind of contamination on the surface to be tested that interferes with the 
oxide reduction then the SERA data plot is impacted. I have used the SERA test 
method to help screen a series of boards where there was soldermask 
contamination in the thru holes. Yes, I could have conducted an FTIR or a visual
examination but the SERA data took me a total of 5 minutes per board and 
resulted in a quantitative data plot for documentation. Did SERA give me a 
accurate chemical analysis of the residue - Nope - but it was an effective tool 
for the task. Hope this helps. Give me a call if you have additional questions 
(319-295-1615).


Dave Hillman
Rockwell Collins
[log in to unmask]


______________________________ Reply Separator _________________________________
Subject: FAB: Soldermask Residue - SERA
Author:  [log in to unmask] at ccmgw1
Date:    7/23/97 4:05 PM


     Address,
     
     I've found the recent discussions on Soldermask Residue interesting.  
     I've been faced with a similar problem and have investigated for 
     several weeks. After re-reading everyone's commments with information 
     I have, there are some discrepancies.  Would someone elaborate on 
     these items.  Again everyone has their method for each process, so 
     I'll leave names out.
     
     Which is correct items 1 or 2?
     
     1. Someone noted: Acid cleaners (pH 1 or micro-etchants; ph <1) would  
        remove some residual soldermask residues from the copper lands.
     
     2. OTHER:  Acid cleaners render soldermask residues insoluable, 
        in-turn "locking-in" soldermask onto the copper.  Alkalines are    
        recommended.
     
     My past experiences have been with item 2.
     
     Which is correct items 3 or 4?
     
     3. SERA testing can not detect chemical residues (i.e. soldermask      
        residue).
     
     4. SERA testing will detect chemical residues off a copper land.
     
     Please advise.  Thank you.
     
     John Gulley
     
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