Hi John,

I certainly agree with you on Item 2. The soldermask is usually an
Acrylate/epoxy blend and after cure is very chemically resistant to almost all
solvents. As developed, acid solutions cause the resist to set and is usually
insoluble. Alkaline solutions will strip the resist if it is uncured.

Regards,

Les Connally
[log in to unmask]

------------------
Original text

From: [log in to unmask], on 7/23/97 3:53 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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