Bryon,
I am not sure what you are asking, but I can guarantee you that soldering wires into standard-size (.020" to .060" diameter) cup contacts with a thickness of 1 micron of gold (40 microinches) is going to result in embrittlement if they are not pre-tinned to remove the gold (just the solder cup, not the contact end).
I also have experienced firsthand gold embrittlement issues, and they have included gold-cup contacts. I should say especially gold cup contacts soldered into military-style connectors.
And yes, most engineers would never guess that. Many have tried to prove to me there is no issue by soldering the wires into the cups and following that immediately with some type of pull-test to "prove" the reliability of the contact. Few understand it is a time-variable phenomena. More than once they have come back to me with the fractured solder joints 6 months or a year later and sheepishly admitted "I should have listened to you".
Gold embrittlement is not well understood. Sometimes as little as 1% by volume of gold can lead to embrittlement issues. I know that it is not just the percent of gold, but also the configuration of the solder joint that matters. Larger stranded wire gauges such as 20 AWG wire, after tinning the wire and soldering them into the cups, can impart tremendous stresses on the SJ in the cup when the wires are moved or flexed. It does not take a whole lot of flexure to fracture the SJ from the cup if the cups are not pre-tinned to get the gold out or at least greatly reduce the amount.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bryon Boone
Sent: Thursday, January 13, 2011 1:34 PM
To: [log in to unmask]
Subject: [TN] Gold cup Terminal>Gold removal
Hello TechNet World.
Anyone like to comment, suggest, direction to take, on the requirements of J-STD-001 Class 3 Section 4.5?
It is my understanding and experience that the plating thickness that manufacturers specify on their contacts is a reference to the overall contact, and that the percentage of gold 'inside' the cup varies greatly, hence the double tinning process requirement. Most contact manufacturers specify that their gold plating thickness is around 1.0 µm, which most engineers that have no soldering experience believe gold removal is not required, nor objective evidence is required.
Any info is greatly appreciated.
I have experienced firsthand, gold embrittlement issues in the past when working to MIL-STD-2000
Regards.
Bryon Boone
CIT, Product Engineer III
Carlisle Interconnect Technologies
6801 South 180th Street
Tukwila, WA 98188
Phone: (425)656-5617
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Email: [log in to unmask] <mailto:[log in to unmask]>
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