Is the copper pad that doesn't coat with solder on the bottom or top of the
board during the HASL operation? I'm not sure but my guess is that they may
be bottom side features. If they are bottom side features I might be able
to give you an explanation
Regards,
George
George M. Wenger DMTS
(609)-639-2769 Office (609)-639-3210 Lab
Bell Laboraties Princeton, Engineering Research Center
Supply Network Solutions FMA/AQA/RCA Lab
Po Box 900, Princeton, NJ 085424-0900
Route 569 Carter Rd., Hopewell, NJ 08525
-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Thursday, August 03, 2000 7:37 AM
To: [log in to unmask]
Subject: [TN] Copper Pads After HASL
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.
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