Hi Rick - I didn't look up the IPC-T-50 definition of "flash" but its
definitely not 80-100uinches! Many folks would consider a "flash" thickness
to be less than 10 uinches but with some of the new immersion finishes such
as immersion gold, immersion tin, and immersion silver being in the 2-7
uinch thickness range a "flash" thickness could be considered as only 1-2
uinches (does anyone in TechNet land have a true definition of a "flash"?
Is it in 6012?).  Regardless of the definition of a "flash" thickness you
have an issue with gold embrittlement - take a look back in the TechNet
archives for more information but the brittleness you are experiencing is
most likely a case of the gold/tin intermetallic phase causing solder joint
cracks. Good luck.

Dave Hillman
Rockwell Collins
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Rick Thompson <[log in to unmask]> on 01/28/99 05:48:14 PM

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Subject:  [TN] Gold Flash Spec for PCB?




Hi,

Can someone recommend IPC or other specs that deal with thickness
specifications for gold flash and/or plating on PCBs? Any other sources of
information or recommendations would be appreciated as well.  I have a
customer who needs plated gold for wire bonding but in the interest of
saving money, they've elected to have the entire PCB plated with 80-100
microinches of gold. This is causing us alot of problems with solder joint
quality in terms of brittleness of the joints. I'm trying to offer them
some
alternatives, but am not that familiar with what's considered "standard".
Any insight would be greatly appreciated.

Thanks.


Rick Thompson
Ventura Electronics Assembly
2665A Park Center Dr.
Simi Valley, CA 93065

+1 (805) 584-9858 voice
+1 (805) 584-1529 fax
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