In a message dated 98-03-11 14:24:24 EST, you write:

>
>  I was told recently of a printed circuit card assembly that, when the
>  assembly is powered up in the morning, the board runs, but that by the
>  afternoon, it fails.  Next day, same board, same results.  The engineer
>  thinks this problem is due to a "flux short".  Is this possible?
>

Yes, it is possible.  Can you give some idea as to the flux technology you are
using (water soluble, RMA, no-cleans) and the processing (cleaning).  What is
the failure mechanism?  Excessive electrical leakage?

Many fluxes have hygroscopic elements, which if not fully removed from the
board through heat volatilization or cleaning, will attract moisture.  If you
have halide residues present, you can get a weak electrolytic solution (on a
microscopic scale) which leads to excessive leakage.  If the failure mechanism
goes away when you put the assembly into a dry oven or in an area of very low
humidity, then flux residues may be the problem.  But, the other responders
have also given good possible sources of the problem as well.

Doug Pauls
Technical Director
CSL

################################################################
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 web site (http://jefry.ipc.org/forum.htm) for additional information.
For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311
################################################################