In a message dated 05/19/2000 10:48:43 AM Central Daylight Time,
[log in to unmask] writes:
<< TechNetters,
I'm looking at a what seems to me like a good sized piece of 303 stainless
steel, plated with nickel-tin, a standoff about 7 mm in diameter, 6 mm long,
with a wall thickness of about 1 mm. Using a metcal iron, our folks are
having trouble soldering this to a PC board. One of the quality inspectors
says there has not been a problem in the past, with this part, using the
metcal iron. The standoffs have been in stock for 1 year after nickel-tin
plating.
Here are two questions I think of:
(1) Is 1 year beyond the shelf life of nickel-tin plating? Operators think
there is a "coating" on the standoffs that inhibits soldering.
(2) Any ideas about a preferred soldering technique for a part like this?
Thanks for any feedback. All production supervisors are out for the day, so
QA is trying to handle this one...Lou Hart Compunetix >>
Hi Lou!
I suspect that if those parts have been sitting around a year, you've got a
problem. They've probably lost their solderability...unless you use some VERY
active flux! Lonco's "Red Death" comes to mind...check out the paste I did
from the following page:
http://205.181.179.3/TechRev/mfsa/tintin.html
-Steve Gregory-
Tin-Nickel (65% tin - 35% nickel)
Although it can be readily soldered when freshly deposited, it has produced a
wider scatter of solderability test results than any of the alloys previously
discussed, and thus it probably rates as the least solderable of these
alloys. Like bronze, it is not a soluble coating. Fortunately, however, its
solderability can be improved by the application of a thin coating of tin,
gold or solder plate, and the retention of solderability of such coatings is
very good. The best coating for preserving the solderability of tin-nickel is
a "flash" (1.0-1.5 microinches) of gold. This combination of deposited metals
not only produces deposits that solder well and maintain their solderability
for long periods of time, but it also ranks favorably in wear resistance,
appearance and contact resistance with all competitive coatings.
##############################################################
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
##############################################################
|
