Hi Christina -- The paper entitled 'Effect Of Au On The Reliability Of
Fine Pitch Surface Mount Solder Joints" from the 1991 SMI Proceedings may
provide some helpful information. I can Fax a copy if you'd like.

Dan Babcock
Sr. Engineer
Maxtor Corp
[log in to unmask]

>Subject: Brittle Solder Joints
>
>Hello,
>
>I am looking for some information either from experience or papers on
>what causes brittle solder joints.  We have immersion gold over nickel
>and use eutectic solder paste. Board material is high-temp FR4.   I
>would like to know:
>
>1.  How many heat cycles a solder joint will tolerate without becoming
>brittle.  Is there a temp that a solder joint becomes brittle and the
>crystalline structure changes (as in steel tempering)?
>2.  What would be the definition of a heat cycle (would it be reaching
>183 C or something else)?
>3.  What is a safe temp to have boards at  during a stress testing..
>
>any information or a contact to find information would be greatly
>appreciated.
>Thanks in advance for your help,
>
>Christina Piasky ([log in to unmask])
>Sequent Computer Systems

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