Mr. Bergmann,
   I am very much interested in knowing more about the subject matter :
Black Pad ".
Please send me or direct me to an appropriate site to find out additional
information.

victor,

-----Original Message-----
From: Fritz Bergmann [mailto:[log in to unmask]]
Sent: Tuesday, August 13, 2002 8:42 AM
To: [log in to unmask]
Subject: [TN] Black Pad problems ???


We have developed an automatic inline screening system for the detection of
the "Black Pad" phenomenon on electroless Ni/Au printed circuit boards:
THESSY BP (thermal screening system for Black Pad).

Composite coatings of electroless nickel-phosphorous and immersion gold
(ENIG) have become established as preferred solderable surface finishes for
high reliability applications involving complex PCB designs. Over the last
three years, more and more interconnection failures occurred after final
assembly of the PCB's due to a poorly formed joint at the solder/nickel
interface. When the suspect joint is stressed, the connection is easily
broken, leaving an open circuit. In other cases, the pads are dewetting
during the soldering process. The dewetted pads are discolored black, which
lead to the nomenclature "Black Pad".
Investigations on Black Pad show that it is caused by a corrosive interlayer
between the gold and nickel layer. It is an insidious problem, since this
interlayer is covered by gold and therefore, it has been not able until now
to detect Black Pad by non-destructive methods. The symptoms of Black Pad
only occur after soldering which causes high costs.

THESSY BP is based on thermographic measurements on a PCB whichever before
shipping or assembling. It works automatically as an inline system which is
able to sort out "infected" PCB's. The prototype setup yielded a detection
rate of 95%.
For further information, please contact Fritz Bergmann.
--
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