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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Subject
[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 μm [100 μin]" 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 μin 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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