Jim,

        Problem could be in the plating.  The appearance of copper would not
be suprising if the the supplier had a poor plating process.  If you
can, cross section a row of solder balls and observe the plating
quality.  You might find unacceptable variations in the thickness and
quality of the gold and nickel plating.

Best of Luck,
Craig


> Good Day Technet:
>
> First, a little background...  We're in production using a 228 ceramic BGA for
> a military contract.  The base material of the component is gold plated nickel,
> prior to solder ball attachment.  The gold plating is very thin, around .25
> microns.  We've been experiencing approximately 5% (components, that is, not
> solder joints) open circuits found at in-circuit testing (ICT).  Upon removal
> of the BGA (Air-Vac system) from the board, the specific ball location where
> the open was identified at ICT shows no solder remaining on the component,
> where all other locations has solder remaining.  What does remain is a dull,
> gray, crystalline metallization.
>
> SEM/EDX analysis shows Ni/Sn and Cu/Sn.  It is presumed that the Ni/Sn is the
> intermetallic layer created from the nickel base material and the tin in the
> solder.  What puzzles me is the presence of the copper-tin crystallites.  Since
> there is no copper in the solder or on the component, is it possible that this
> copper has migrated all the way up from the board pad to the component/solder
> interface?
>
> Thanks in advance...
>
> ################################################################
> 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
> ################################################################
>
>
Dr. Craig Hillman
CALCE Electronic Products and Systems Consortium
University of Maryland
College Park, MD  20742
(301)-405-5316
[log in to unmask]

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