Bev,
It's only a tough question if 1). You didn't have a metallurgy course or 2).
you start to get old and forgetful.  I didn't take #1 but I know a lot about
#2.  I think Dave, like the rest of us, is starting to fall into #2.

I think he meant to tell you AuSn4 and AgSn3 not Au4Sn and Ag3Sn

Regards,
George
George M. Wenger, DMTS Bell Laboratories Princeton
Supply Network Solutions
PO Box 900, Princeton NJ 08542-0900
Route 569 Carter Rd., Hopewell, NJ 08525
(609)-639-2769 (Office), 3210 (Lab), 2346 (Fax)
[log in to unmask]


-----Original Message-----
From: David Hillman [mailto:[log in to unmask]]
Sent: Monday, April 23, 2001 12:54 PM
To: [log in to unmask]
Subject: Re: [TN] Embrittlement


Hi Bev! There is a fairly large set of industry data on the solder joint
reliability problems induced by Gold/Tin intermetallic  (Au4Sn) formation
and a smaller data set on the solder joint reliability problems induced by
Silver/Tin intermetallic  (Ag3Sn) formation.  See Klein Wassink's book ISBN
0-901150-24-X. I would expect that if you have both intermetallic species
in a solder joint it just would not be a "good" thing. The use environment
of the assembly would also play a role in just "how much" intermetallic
degradation would be allowable. Tough question - good luck.

Dave Hillman
Rockwell Collins
[log in to unmask]




Bev Christian <[log in to unmask]>@IPC.ORG> on 04/16/2001 08:33:58 AM

Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
      to Bev Christian <[log in to unmask]>

Sent by:  TechNet <[log in to unmask]>


To:   [log in to unmask]
cc:

Subject:  [TN] Embrittlement


Good morning!
Here is a met. question to start off the day.

We know that if we have over 4% gold in a 63/37 tin lead solder joint we
risk gold induced embrittlement because of the production of a  significant
amount of the tin/gold intermetallic.  It is also common practise to use a
slight variation of the eutectic solder with a 62/36/2 Sn/Pb/Ag
composition.
We also know that gold and silver are 100% soluble in each other.  My
question: if the final tin/lead based solder joint composition has a
COMBINED noble metal percentage in the 4% range how bad is that for solder
joint reliability?

regards,
Bev Christian
Research in Motion

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