Dear sir,
        Please do not wipe the paste if your paste is NC because the paste will
plug into the via hole and hard to clean after that. Please try following
steps as I am performing.
        1. Wash the paste off the board with hot water manually.
        2. Send to ultrasonic cleaner with 10-15% of Alpha metal Loncoterge 520,
40-50 degree C, 15 minute. Another is Alpha Metal SC-10 but it has strong
smell.
        3. Send it through water cleaner M/C.
        4. Before use Inspect that board under microscope 10X.

        Please noted if your board is double side assembly and one side has the
SOIC install over the via hole, please assembly the SOIC side is the 2nd
side. The most importance is reduction the misprinted PCB, take care the
screen process.

With best regards,
Noppadol S.


At 11:46 28/7/98 -0400, you wrote:
>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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