Yes, Steve, I have, in my DIA projector!
It started with sudden interrupts, the light switched on and off, and couldn't find what was wrong, until one day, i dismantled the old machine (antique now, aren't they!) and what did I see? Nothing like I have seen before: the ceramic socket (temp gets high from a 250W halogene globe)has two heavy brass sockets which both enclose the Kovar pins from the bulb. One of the two pins were nearly eaten up, and around the whole area a silver/greenish glimmering 'metal snow'. Beautiful, but not good for the moment of waiting spectaculars. What I did? Put in another lamp, of course. And one day, months afterwards, same thing happened. Now, one of the heavy copper sockets were gone! Nothing left, and one teaspoonful of the metal snow. So, wrong metal combination, high current, high temperature caused all this. After change to copper/zinc-free sockets, no problem any more. The situation is not equal to your, maybe, but probable of same nature. So, keep an eye on the material-current-c!
!
urrent concentration-temperature in your construction.
Contact the ElectroMigration AntiMigration Society's Migration Bureau.
Ingemar Hernefjord
Ericsson Microwave Systems
-----Original Message-----
From: Stephen R. Gregory [mailto:[log in to unmask]]
Sent: den 29 februari 2000 16:34
To: [log in to unmask]
Subject: [TN] Was; Electromigration Now; Electrochemical Migration
Hi ya'll!
After all the replies that were sent to me, I think what I have is
electrochemical migration. I wish I had a microscope where I could take a
picture to show you, but I'll describe things again.
There is a 6-pin header that is hand-soldered on this board. The board failed
due to a short from VCC to Ground. We removed the header to see if we could
spot anything beneath the plastic of the header because we didn't see
anything on the other side of the board. This header location has traces that
run between some of the pins, and what I discovered that is if the mask isn't
perfectly registered, the clearance area around each of the holes for the
header will expose an area on the traces that are running between them.
On one of the boards that I looked at yesterday, I observed a "fern-like"
stucture of copper that appeared to be growing from the anular pad of the
header pins to the exposed area of the trace. I seen this at two places at
the header locations...
I also discovered (to my dismay) that one or two of the operators have just
been hand cleaning after soldering in this header. That since has ceased
(dammit!)...
Again, I just want to ask, has anybody else ever seen actual copper filaments
grow like that? From the replies I got back yesterday, most were telling me
that I should be seeing a black, or maybe greenish mess there, and that it
would be really tough to tell if it was copper. But I swear, it clearly has a
copper color to it..
Thanks again!
-Steve Gregory-
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