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November 2006

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Subject:
From:
"Ingemar Hernefjord (KC/EMW)" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Ingemar Hernefjord (KC/EMW)
Date:
Mon, 6 Nov 2006 09:59:50 +0100
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Agree,
We degold all microwave SMT small outline transistors ("helicopters"),
because we had catastrophic gold embrittlement problems. The solder
joints were so brittle, that the leads lifted from the pad in the temp
cycle tests. We measured as much as 15 micrometers of gold! The
semiconductor manufacturer meant, that it is a problem to have control
on the gold process on such small parts. What nonsense! Anyway, we are
today suspiscious with many gold plated parts and do degolding rather
than getting embrittlement.

I'll send some pictures to Steve, so you can see what can happen.
Horror!


Inge
  

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: den 2 november 2006 23:06
To: [log in to unmask]
Subject: Re: [TN] Gold Embrittlement

Hi Amol,
I you have imersion Au, Au-embrittlement is not a problem because there
is not enough Au. Be careful, however, if your PCBs come from China; I
have seen much thicker Au-layers than are possible with iAu.
Calculating the wt% of Au in a soldert joint is an exercise in futility,
because you have to make the assumption--frequently not warranted--that
the SnAu-IMCs are uniformally distributed.
In cases where you suspect thicker Au [and for the matter Ag; which is
equally as bad as Au in causing SJ-embrittlement] deposits, the safest
course of action is to wash the Au (Ag) off by tipping.

Werner

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