Subject: | |
From: | |
Reply To: | TechNet E-Mail Forum. |
Date: | Thu, 24 Sep 1998 16:06:44 +0200 |
Content-Type: | text/plain |
Parts/Attachments: |
|
|
A source for research in the matter is 'ASM Corrosion Handbook Nr 13',
1,000 pages or more. Also 'Electronic Packaging and Corrosion' by Morris
E. Nicholson (ISBN 0-87170-291-6). You will find something there, I'm
sure. / Ingemar Hernefjord
Ericsson Microwave Systems
--------------------------------------------------------------------
> I need help tracing the possible root causes for a circuit failure
from
> the field. Does anyone have any experience with open circuit traces
due
> to a silver sulfide corrosion concentrated at the juncture tin-lead
> solder joints and silver thick films? We are seeing this only on
joints
> that are low voltage potential. There is silver sulfide corrosion at
> other randomn areas, but the heavy corrosion is primarily at just a
few
> points where the solder and silver meet. Under the microscope, it
looks
> like a black worm crawling along the interface between the solder
joint
> & the silver thick film. We pot the circuit board in silicone gel to
> protect the circuit from moisture. So far, we haven't traced the
source
> of sulfur to any material that we use to make or to package the
circuit
> board.
> The packaging does not contain cardboard, so sulfur from the packaging
> is out. We meticulously clean the board after reflow soldering the
> printed solder paste, so flux is out. Is it possible that we are
getting
> sulfur gas from the enviroment? The environment is automotive,
> underhood. Is it possible that there is a galvanic action that is
> concentrating the corrosion to just a few solder joints?
> Thank you all for your time.
>
> ################################################################
> 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
################################################################
|
|
|