Werner,
Good points and I totally agree.I have stayed out of this,but must comment
on a few things.Being a representative of the Aerospace Industry,I feel some
hasty generalizations have been made in this forum.We are not running to
embrace any new technologies,nor are we hiding with our collective heads in
the sand.We are evaluating,testing and qualifying the alternatives to
determine the best strategies for incorporating lead-free materials and
processes into our systems.
Sharing data and knowledge,as well as supporting organizations such as
IPC,will help all of us make the best decisions for the industry as a whole.
Dewey
> -----Original Message-----
> From: Werner Engelmaier [SMTP:[log in to unmask]]
> Sent: Thursday, August 02, 2001 7:49 AM
> To: [log in to unmask]
> Subject: Re: [LF] Eutectic alloys?????
>
> Hi Tetsuo,
> I have no arguments with most of what you wrote, but I need to set the
> record
> straight on 2 of your points, so people do not draw the wrong conclusions.
> [1] You write "the Sn-Ag-Cu system (and the Sn-Cu) system is stronger in
> all
> respects than the Sn-Pb alloys."
> That maybe, and is likely, the case--however strength is not a good
> indicator
> of fatigue resistance.
> [2] You state "the experience with commercial products that have been in
> the
> field for nearly two years seems to confirm that. This is particularly
> the
> case in regard to thermal fatigue, possibly the main cause of failure in
> electronic circuitry, where the lead-free alloys have a much longer life."
> There have not been good data, following IPC-SM-785 testing guidelines,
> published, that really characterize the creep-fatigue life of of lead-free
> solders; without such data nobady can make any statements as to the
> inferiority, equaity, or superiority of any of these alloys. To
> annectotally
> refer to '2 years of commercial products in the field' is totally
> meaningless; 2 years of cheap [read throw-away] consumer products does not
> prove anything, one way or the other. It may be more impressive under the
> hood of an automobile, but even that is meaningless because of a total
> lack
> of definition of the actual loading conditions on the solder joints.
>
> So as far as I am concerned, the jury is still out as to the reliability
> of
> lead-free solders.
>
> Werner Engelmaier
> Engelmaier Associates, L.C.
> Electronic Packaging, Interconnection and Reliability Consulting
> 7 Jasmine Run
> Ormond Beach, FL 32174 USA
> Phone: 386-437-8747, Fax: 386-437-8737
> E-mail: [log in to unmask], Website: www.engelmaier.com
>
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