Fellow Technetters,

Occasionally we encounter a phenomenon of copper pads remaining
after HASL.  The copper pad is always a pad that is defined only by
soldermask on a ground plane area. Usually it is square or rectangular and
from
.040" to .080" in dimension. Often small writing in the mask will also remain
copper.
We've checked:
    developer; strength, temp, spray pressures, rinse pressure, rinse temp
    developed the boards faster, slower, pad side up vs. pad side down

We've checked:
pre clean strength, temp, copper removal, tried faster ,slower , two times
etc.
new flux , old flux, spiked flux(HCL), longer solder dwell

Is it possible that this is caused by the geometry of the pad?  It creates a
sort of inground pool with a mask border. Maybe it doesn't rinse or develop
clean or maybe in the leveler it creates a vapor barrier that doesn't allow
the
solder contact with the copper.
That job at the Ice Cream stand is looking better and better!

Any input appreciated.

Thanks

Brett Austin
Nationwide Circuits Inc.

##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in
the body:
To subscribe:   SUBSCRIBE TECHNET <your full name>
To unsubscribe:   SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Keach Sasamori at [log in to unmask] or
847-509-9700 ext.5315
##############################################################