Werner,
Every SJ by itself, like every other component on the board, whether
electrical or mechanical, is limited time object, and its time
expectancy is defined by MTTF - mean time to fail.
To avoid referring to every SJ by itself, the MTTF of the SJs are
included in the MTTF of the electronic components.
When a component fails, the assembly may be repaired. The assembly life
expectancy measure is the mean time between failures - MTBF, which is
the reciprocal of the sum of the reciprocals of the MTTF of the
components. Hence, if the MTTF of the components decreases
significantly, the assembly MTBF will decrease as well.
Hence, if the MTTF of the SJs is significantly differs between leaded
and non-leaded soldering, it affects the components MTTF. This is the
basis to my question.
Regards
Ofer Cohen
Manager
Quality Assurance, Reliability and Production Technologies
Seabridge Ltd. - A Siemens Company
Siemens COM FN A SB
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Wednesday, November 16, 2005 00:07
To: [log in to unmask]
Subject: Re: [LF] Reliability prediction of LF soldering
Hi Ofer,
Solder joint creep-fatigue is a wear-out damage mechanism and as such
has not a constant failure rate. thus, the concept of MTBF does not make
sense for solder joints, LF or not.
Regards,
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, Cell: 386-316-5904
E-mail: [log in to unmask], Website: www.engelmaier.com
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