Hi Gerald & Ken,
I suppose you think of Dave's report below (Dave's reports are always
masterpieces):
http://www.aciusa.org/leadfree/leadfree_impact_of_reflowing_a_pbfree_sol
der_alloy_using_a_tin-lead_solder_alloy_reflow_profile_on_solder_joint%2
0_integrity.html
The growth of intemetallic platelets or needles near interfaces is
always a bad sign. From classic mechanics, we know that you get tension
build-up or force concentration along such shapes. Furthermore, von
Mises equations give, that you get maximum travers forces close to the
interface ball-pad. These two facts make a high risk for starting
microcracks, which can grow and finally cause an electric failure.
Inge
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Gerald Bogert
Sent: den 15 augusti 2007 00:23
To: [log in to unmask]
Subject: Re: [TN] SAC Soldered With SnPb
August 14, 2007
Good question.
I also need info in this regard for SAC for all type of component
leads/terminations that may be finished with SAC.
Is it better from a reliability standpoint to just live with a SAC
finish for SnPb assembly level soldering, or otherwise re-work the
components to replace the SAC with SnPb?
Are we at the point yet where we can reliably predict equipment life in
the field for SAC alloy as compared to SnPb alloy? I have need seen any
widely accepted industry papers yet that equate accelerated life testing
results to expected product fieldlife using SAC alloy.
On a related issue, for pure tin, I understand that NEMI is not
endorsing it unless there is a nickel under-plate. Just annealing after
plating for pure tin plated parts is not acceptable per NEMI
recommendations.
I believe Dave Hillman of Rockwell published some data regarding
soldering to SAC with SnPb solder.
If you get any info on SAC or pure tin plated leads/terminations, I
would appreciate it if you could forward to me. Thanks. Seems like
when I post a question to Tech-Net, I get very few answers. Could be my
questions are difficult to answer.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bloomquist, Ken
Sent: Tuesday, August 14, 2007 4:51 PM
To: [log in to unmask]
Subject: [TN] SAC Soldered With SnPb
We are a Class 3 manufacturer and are looking at the different lead
finishes that can be soldered successfully with SnPb. One that we are
having a hard time finding information on is SAC lead finish soldered
with SnPb. I know that it's not good practice for BGA's but what about
SMT and through-hole parts?
Thanks in advance,
KennyB
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