What is the surface finish on the PCB? If it is HA
Joe,
What is the surface finish on the PCB? If it is HASL there is a reason
for the contamination.
Regards,
George
George M. Wenger
Andrew Wireless Solutions
Senior Principal FMA/Reliability Engineer
40 Technology Drive, Warren, NJ 07059
(908) 546-4531 (Office) (732) 309-8964 (cell)
[log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Kane, Joseph E (US
SSA)
Sent: Thursday, May 07, 2009 9:13 AM
To: [log in to unmask]
Subject: [TN] PB Surface Contamination
A cleaned bare PB is exposed to bake or reflow, and comes out with
measurable ionic contamination. The board is dirtier at the surface
after
a heat excursion.
The contamination isn't coming from the oven, handling, or anything
external.
Heat causes something to move from the inside of the board to the
outside.
We haven't done any ion chromatography or other testing yet to
run this down, but has anyone heard of or experienced anything similar?
In our normal process, we clean everything multiple times, but if the
contaminant builds up under solder mask, or in other areas that are
difficult to clean, we could have SIR or corrosion problems around fine
surface features or in high voltage areas.
And if this ionic contamination doesn't just move up to the surface,
but is somehow moving around inside the board, could it collect in
some places and lead to CAF or other problems?
Joe Kane
BAE Systems
Johnson City, NY
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