In a message dated 8/21/98 2:44:24 PM Pacific Daylight Time, [log in to unmask]
writes:

<<  Just one note, all reflowed solder joints have dull or gray-looking
appearance.  That's normal.  Gold diffuses into melting solder causing dull or
gray-looking solder joints. >>

Hi Mike!

     Matthew gives you good advice about your apertures. About his comment of
the solder joints looking dull and grainy on gold boards, I got a tip for you
to make em' look better, use a 2% silver solder with them (62/36/2). It lowers
the melting temp a little...I think liquidous is 179 C. vs. 183 C. with a
63/37, and that ain't all that different, it's still eutectic, and it
shouldn't cost much different (if you get charged anything different at all)
from a regular ol' 63/37.

     I worked at a memory company a couple of years ago where we had quite a
few gold boards and that's what we used and our vendor charged us the same
price...I'm not a metallurgist, so I can't tell you PRECISELY why the joints
look better with a 2% silver, but they do, I'm not pulling your leg either...

      I do remember reading something quite a while back that there was a
mistaken belief floating around that if you used silver in your solder that it
would prevent the leeching of the gold into the joints during
reflow...something about the silver in the solder being a noble metal like
gold is, raises the percentage of noble metal in the solder joint which
reduces the leeching of the gold. We all know now that's not true, but I'm
thinking maybe where that belief may have gotten started was difference in the
solder joint appearance...someone may have thought back then that the addition
of silver really did stop the gold leeching.

-Steve Gregory-

################################################################
TechNet E-Mail Forum 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's web site (http://www.ipc.org) "On-Line Services" section for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################

################################################################
TechNet E-Mail Forum 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's web site (http://www.ipc.org) "On-Line Services" section for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################