JIM ENNIS wrote:
> 
>      This question has come up again.  What are the adverse affects of gold
> plated terminations on SMT components?
>      We have been seeing a number of new sample components with gold
> terminations, and to date, have disqualified  them based on gold
> embrittlement. .  Many of the vendors reps say that this issue is new to
> them and that they sell these parts all over with no questions/problems.  Is
> this still an issue?  If so, why are these vendors supplying parts,
> especially taped/reeled parts, with gold on them?  Tinning these would be
> expensive and hardly practical.
>      Is there a spec/study/whatever that shows the maximum deposition of
> gold before it becomes a problem?
> 
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Jim, you have to calculate the % of gold in the solder joint. If the 
amount of gold is less than 2%, it may be acceptable from embrittlement 
view point. This data is based on large volume joint studies.

If the component is wave soldered, some of the gold will leach into 
solder pot. It  all depends upon wave solder parameters like dwell time 
over wave. For wave solder process gold < = to 30 microinches is ok. More 
than that remains in the joint and forms gold-tin intermetallic.

For SM solder joints, it is a different story. All gold remains in the 
joint and solder volume is small. Another point consider is whether the 
gold is completely dissolved or not. Run a crossection of the joint to 
see if there is gold still on the lead. Gold continue to react with tin 
at use temperatures.
-- 
Pratap Singh
Tel./Fax: 512-255-6820
e-mail: [log in to unmask]

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