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Date: | Wed, 15 Aug 2012 21:23:44 -0500 |
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Hi Graham - the 100 uinch value is applicable to PTH technology solder
joints, the limit for SMT technology solder joints is much lower. The
issue is gold embrittlement which isn't just driven by the gold thickness,
you also need to take into account the volume of solder for the joint and
the time/temperature parameters - aka do you give the gold sufficient time
to diffuse throughout the solder volume. The IPC JSTD-001 Handbook and the
IPC-820 Handbook both have some good information on gold thickness/gold
embrittlement topic. Good Luck.
Dave Hillman
Rockwell Collins
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Graham Collins <[log in to unmask]>
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[TN] gold removal question - to remove or not?
Hello Technet
I'm in the midst of a debate about gold removal. Our policy on component
leads is to double dip tin all gold. J-STD-001 says I do not have to do
it if there is less than "2.54 ìm [100 ìin]" of gold, but is it realistic
to operate on that basis? For example, looking at an Airborne brand
connector I find the spec sheet says that there will be 50 ìin gold,
minimum. Which is not totally helpful as it does not tell me maximum. I'm
assuming given the price of gold that they aren't looking to put a lot
more than the minimum on, but how controllable is the process? Could we
check the thickness once and assume we are safe?
(and as you can tell from my phrasing I'm of the more conservative camp on
this one, still dipping the parts until proven wrong)
regards,
Graham Collins
Halifax Production Engineering
(902) 873-2000 ext. 6215
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