Gold embrittlement in Tin solder joints

[Connectordude]

Since my infancy as a new engineer I have been taught about the gold embrittlement issues related to tin-lead solders, specifically 63/37 alloy. It has been my understandng that the problem is associated with gold percentages above 3% weight and its intermetallic formation with lead. To avoid this issue altogether I have often specified the use of Tin-Silver (Sn96) instead of the Tin-Lead when joining gold plated components, without a pre-tinning process. Recently this approach has come into question and a so called "expert" has said that the issue is the gold forming intermetallics with the tin, not the lead. Now I know that one of the most popular and historically reliable solders used in microelctronic assembly is gold-tin (Au/Sn 80/20). My logic tells me that if gold and tin had a problem with each other there would be no way this solder would stand the test of time, so I am crying Bull... on the so called "expert". Can anyone provide some relavant testimony or insight?

 

[ScottyUK]

If you have questions on the more exotic solder alloys like Sn/Au the tech guys at Indium Corp were (20 years ago - how did that go so fast?) highly knowledgable and fairly free with advice, the more so if it involved one of their products. For the 'common' alloys the equivalent guys at Multicore - which is now part of Henkel, IIRC - were equally knowedgable. Hopefully the acquisition and merger process hasn't diluted the engineering support too much.


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If we learn from our mistakes I'm getting a great education!

 

[zappedagain]

How about this one:

http://www.semlab.com/goldembrittlementofsolderjoints.pdf

 

[Connectordude]

That white paper is pretty well know and I have seen it before, but it just repeats some of the historical bad news about tin-lead solders. Ideally what I am looking for is someone that can comment about the tin-silver solders suspectibility to embrittlement, if any.

 

[ScottyUK]

What did the guys at Indium and Multicore say?


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If we learn from our mistakes I'm getting a great education!

 

[Connectordude]

I sent an email to Indium and got an "oput of office" reply. I plan to contact Multicore later today if I get a chance. I have dealt with the Indium folks before and received good support. Don't know why I didn't think of that one myself. I appreciate your suggestion.

 

[ScottyUK]

If you get a response please post the gist of it here, it will be interesting to hear from the experts and maybe dispel some of the voodoo hoojoo about gold embrittlement. I'm long out of the hybrids business but still take an interest in stuff which used to be my day-to-day life.


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If we learn from our mistakes I'm getting a great education!

 

[mcgyvr]

There is Kester too..