We use a thick film 50 ohm 0603 .2 W resistor on a ceramic substrate
BGA device.  The BGAs are pretested before
PCA assembly.  After placing the BGA on a PCA assembly and reflowing the
PCA a number of the resistors either increase
in resistance or open.  The resistors on the BGA substrate have already
seen a reflow cycle to mount the resistors on the
substrate.  They are on the substrate during underfill cure.

      During BGA removal from the PCA we have discovered that more of the
resistors ( 6 per part) either open or high
resistance.  The BGA in question is used on two completely different
assemblies built by two different PCA houses.  The
BGAs have different date codes.  The only thread we currently have is that
most of the suspect BGA lots (all but one) used
resistors from the same lot.  We are pointing toward some defect with the
resistors.  I have both "good" and bad resistors
from the same lot of parts.Does anyone know where I would send some of the
defect resistors for an independent analysis?

Thank you in advance.

Best Regards,

Mike Forrester

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------