[SI-LIST] Re: PCB Leakage Currents

This sounds like contamination on the board. Finger prints, poorly cleaned
boards after soldering or contamination in the board's manufacturing process
could all lead to leakage currents.

Try washing and rinsing the board thoroughly and retest. Also check some
un-stuffed boards to see if there is any leakage on those.

Tom Dagostino
Teraspeed Labs
13610 SW Harness Lane
Beaverton, OR 97008
503-430-1065
http://www.teraspeed.com
tom@xxxxxxxxxxxxx

Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
401-284-1827

Teraspeed is the registered service mark of
Teraspeed Consulting Group LLC

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of
Christopher.Jakubiec@xxxxxxxxxxxx
Sent: Wednesday, April 20, 2005 8:56 AM
To: si-list@xxxxxxxxxxxxx
Cc: Christopher.Jakubiec@xxxxxxxxxxxx
Subject: [SI-LIST] PCB Leakage Currents


All,

I am currently working with a PCB DUT board that interfaces to an ATE
(tester).  I am using this board along with a single socket to measure
power MOSFET DC characteristics.  The PCB is a simple 4 layer board that
routes the force/sense resources of the tester to the MOSFET socket.  I
currently do not know the exact layer stackup of the board since I
merely created the schematic, and the layout was done elsewhere.  I do
know that there are a set of force and sense traces on the board for 5
individual tester resources.  1 resource connects to the gate, 3
resources to the drain, & 1 resource to the source(source is also tied
to ground).  There are also some digital traces on the board that bring
digital power for the EEPROM and the relays, and these have tantalum and
electrolytic capacitors included.  Everything on the board, analog and
digital are using 1 single point ground.

My problem is when I am trying to measure off-state leakage from drain
to source of the MOSFET (Vgs =3D 0V, Vds =3D 55V), I measure >200nA of
current before I even put the device in the socket.  When I repeat the
measurement with a blank PCB board I measure 20nA, so I don't believe
that it is coming from the tester or cables.  The tester resource that I
am using for the measurement has accuracy & resolution <100pA.  Any
ideas of where this 200nA leakage current may be coming from?

Thanks,

Chris
Infineon Technologies
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