TECHNET Archives

February 2000

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Gabriela Bogdan <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 29 Feb 2000 08:30:50 +0200
Content-Type:
text/plain
Parts/Attachments:
text/plain (69 lines)
Hi, Steve!
Yes, I have seen them, especially on assemblies on which condensation took place, and
on locations which were hand soldered or reworked.
Check the environmental conditions in use. There is an empirical water drop test you
can perform under microscope, I remember we did it once by applying the voltage
difference between the conductors and putting a drop of distilled water on the area .
You can actually see the "tree" growing.
Gaby

"Stephen R. Gregory" wrote:

> Hi All!
>
> I've learned about electromigration, and fortunately have never had a real
> problem with (that I know about anyway). But recently, we've had some boards
> returned to us that have failed for a short from VCC to Ground, usually at
> the same area on the board.
>
> It's beneath a keyed header that is hand soldered on the board. The first
> couple of boards we got back, we couldn't find the problem. But we just got
> back 3 more and I did see something. In trouble shooting we remove the header
> (it's got a plastic body that has the plastic key molded into it) so we can
> see if anything beneath the plastic.
>
> Well, on one board today I think I saw something. There's traces that run
> between the header pins and on one trace, it looked like the mask was not
> adhered to the trace well. Then looking at it under higher magnification,
> there was what appeared to look like these copper fern like structures
> between the trace and the anular pad of the PTH on the laminate.
>
> Will the dendrites be copper colored? All the pictures I've seen they have a
> silvery gray to white appearance...I guess it would depend on which was the
> cathode and which was the Anode in the scheme of things as to what the
> dendrites would look like huh?
>
> Has anybody else ever seen this?
>
> Thanks ya'll!
>
> -Steve Gregory-
>
> ##############################################################
> 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
> ##############################################################

##############################################################
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
##############################################################

ATOM RSS1 RSS2