I would check the board with HIPOT to see if any leakage may be present.



Jeffrey Bush
Director, Quality Assurance and Technical Support

                          76 Technology Drive - POB 1890
                             Brattleboro, Vermont 05302-1890
                                Tel. 802.257.4571.21 Fax. 802.257.0011
                                    [log in to unmask]
                              http://www.vtcircuits.com	



-----Original Message-----
From: Greg Goodenbury [mailto:[log in to unmask]] 
Sent: Tuesday, March 23, 2004 4:47 PM
To: [log in to unmask]
Subject: [TN] Have you seen this before?


To TechNet Gurus:

 

I have a circuit board that is exhibiting an extremely unusual problem.
It's a basic 4 layer 1 ounce FR4 board with 7 mil traces/spaces.  The
board passed CAD netlist electrical test, checks out fine with an
ohmmeter, and nothing visual shows up with an x-ray.  The board has a
3.3 volt power supply which is about 2 inches away from the FPGA that it
drives.  

 

Somehow, the voltage is being lost between the power supply chip and the
FPGA.  When manually applying 3.3 volts with all components removed, we
are measuring a partial voltage drop (.3 to .7 volts) on some pins of
the FPGA footprint pattern that are NOT supposed to be connected at all.
Being that there are no visible shorts, and the electrical test didn't
detect anything, we can't determine why we are loosing power.  Almost as
if there was some kind of inductance involved, but I can't se where.

 

We're at a loss.  Any ideas would greatly be appreciated.

 

Greg Goodenbury

 

= = = = = = = = = = = = = = = = = = = = = = = = = = = =

Conquest Technology, Inc.          407-359-1919

1500 Town Plaza Ct                   407-359-1918 Fax

Winter Springs, FL 32708-6224   [log in to unmask]

= = = = = = = = = = = = = = = = = = = = = = = = = = = = 

 


---------------------------------------------------
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
-----------------------------------------------------

---------------------------------------------------
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
-----------------------------------------------------