I am most grateful to all responding generously with information.

This particular response by Dave Hillman triggered some questions which have
been brewing in the back of my mind.  I have been wondering about the
reliability tests being conducted on Pb-free alloys using the currently the
thermal cycle testing established for Pb-containing alloys and the paper
presented at ECTC in May 2002 by Gunter Grossmann, Giovanni Nicoletti, Ursin
Soler from the Swiss Federal Institute for Materials Testing and Research
EMPA, entitled "Results of Comparative Reliability Tests on Lead-free Solder
Alloys".  In it they conclude that "the deformation behaviour of the
materials must be taken into account for tests designed to estimate
reliability of solder joints."  When they changed the dwell times from what
is currently used, to compensate so that all alloys encounter the same
strain, their measurement of the crack length showed that Pb-free alloys
degrade faster than SnPb36Ag2.  I have since been wondering how best to
reconcile the data and tests being done. Comments? Discussion?

Elsa Kam-Lum

-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Thursday, August 29, 2002 1:39 PM
To: [log in to unmask]; [log in to unmask]
Subject: Re: [LF] Sn/10Pb plated components and SnAgCu solder paste



Hi folks! I hesitate to even put this response together as my opinion is
going to bump into some of the other responses experiences but here goes. I
have been cataloging and reviewing a number of Pb contamination
papers/investigations as part of my participation in the JGPP (Joint Group
on Pollution Prevention) efforts to understand the impact of Pb
contamination. The JGPP is in the nearing the completion of a testing
matrix designed to look at the reliability aspects of PbFree and Pb
contamination of High Performance Class 3 electronics assemblies. When
looking at the lump sum of the papers/investigation I have pulled together,
the general trend is that a Pb contaminated solder joint has better
reliability than a Pb only solder joint but is less reliable than a PbFree
solder joint (as measured by thermal cycle testing). Paul Vianco (Sandia)
did a very organized/calculated study using known levels of contamination
which produced similar results. There are also a large number of Pb
contamination studies in progress - one of interest may be the work going
on at Celestica - those folks may be reporting at the upcoming APEX
conference. Also the upcoming SMI conference in Chicago will be devoting a
paper session to the topic. In my opinion the industry is producing data to
understand the whys/whats/whens Pb contamination will impact solder joint
reliability. The impact of Pb contamination is going to be very critical to
many folks - many current Sn/Pb containing assembly have use lives of 20
plus years (and more if you happen to be a B52 aircraft!).  Hope this helps
and good luck.

Dave Hillman
Rockwell Collins
[log in to unmask]




"Kam-Lum, Elsa" <[log in to unmask]>@ipc.org> on 08/28/2002 04:41:13
PM

Please respond to "(Leadfree Electronics Assembly Forum)"
       <[log in to unmask]>; Please respond to "Kam-Lum, Elsa"
       <[log in to unmask]>

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


To:    [log in to unmask]
cc:

Subject:    [LF] Sn/10Pb plated components and SnAgCu solder paste


Dear All:

Anyone has tests results or information on what is the impact of using
components plated with 300-1000 microinches Sn/10Pb with Sn/4Ag/0.5-1Cu
solder paste?  How much Pb before properties and performance of the
Sn/Ag/Cu
solder is detrimentally affected?  Any issues with solderability?  Joint
strength? Reliability?  Any information on this subject is much
appreciated.

Elsa Kam-Lum
Allegro MicroSystems Inc.

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