About a year ago we did some "rule of thumb" thinking on this subject. You
might check the archives.
I think we came up with a number like 15 micro inches with a 5 mil stencil.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dehoyos, Ramon
Sent: Monday, November 06, 2006 8:14 AM
To: [log in to unmask]
Subject: Re: [TN] Gold Embrittlement
Inge:
15 micrometers thickness is almost 600 mils. About 6 times the
"safe" thickness allowed by J-std-001. Have you seen gold embrittlement with
less than 100 mils, or anyone else? It would be interesting to know.
Comment, there is a lot of waste of gold by electroplating instead of using
Immersion.
Regards,
Ramon
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ingemar Hernefjord
(KC/EMW)
Sent: Monday, November 06, 2006 4:00 AM
To: [log in to unmask]
Subject: Re: [TN] Gold Embrittlement
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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