Fulton,
       Just a quick note: if caught before part placement, we instruct our
     operators NOT to wipe the boards before cleaning, and this all but
     eliminated the solder balls. If there are parts on, there is not much
     choice.
     We use an alcohol based wash/spray system without ultrasonics (can
     damage multilayers?) Good Luck.
     Jeff Hempton
     United Technologies Electronic Controls


______________________________ Forward Header __________________________________
Subject: [TN] Solder-ball
Author:  Fulton Feng <[log in to unmask]> at Internet
Date:    7/28/98 11:46 AM


Hi, TechNetter
I am wondering anybody out there ever experienced solder ball with mis-print
PCB. The scenario is when we have  mis-printed PCB in solder paste printing
process, we used to wipe off the paste with alcohol from the PCB surface and
send them to aqueous cleaner. What happened is when we looked at the PCB
under microscope, we found all the masking edge and vias  sticked with
solder-balls(Solder paste). The solder paste we used was no-clean
water-soluable paste. The questions are:
*        Is there any difference in between clean and no-clean paste for
cleaning PCB?
*        Has anybody used ultra-sonic cleaner for PCB cleaner?
*       What kind of cleaning agent are your guy using?
*       Any different approach to take care of this solder-ball issue?
Any input is appreciated!

Thanks in advance!

Fulton Feng
Nortel
MPK

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