Hi Werner,
You are absolutely correct. Obviously, reliability issues remain the
greatest concern in the switch to pb-free solders.
However, please note that CASTIN was deemed to be more reliable than
Sn63/Pb37 in -40/125C and -40/85 testing. Of course, our reliability testing
is an ongoing process. I will keep all of you apprised on the results of
these.
I also believe that Mike Fenner and Bob Willis have made excellent points
regarding what we currently take for granted with alloys that we are
"comfortable with".
Best to all,
David Suraski
>
>>
>>-----Original Message-----
>>From: Werner Engelmaier <[log in to unmask]>
>>To: [log in to unmask] <[log in to unmask]>
>>Date: Friday, July 02, 1999 8:08 PM
>>Subject: Re: [LF] "Drop-In" Replacement
>>
>>
>>>In a message dated 7/2/99 14:30:00, [log in to unmask] writes:
>>>>Hi Werner (and everyone!),
>>>>AIM has had a number of accelerated fatigue reliability studies
performed
>>>>on CASTIN:
>>>>The CASTIN alloy has passed the following Accelerated Thermal Fatigue
>>>testing:
>>>>Cycles/Time Temperature
>>>>200 cycles/400 hrs -40°C+125°C
>>>>840 cycles -40°C+85°C
>>>>1000 – 1500 hrs -40°C+125°C
>>>>
>>>>Accelerated Thermal Resistance -50°C+150°C and
>>>-40°C+125°C
>>>>
>>>>CASTIN's fatigue resistance also has been tested according to ASTME 606,
>>>>1Hz triangular waveform oscillated between .15% strain and -.15% strain.
>>>>A minimum of 10,000 cycles was required in order to pass. Following are
>>>>the results demonstrating CASTIN passing the test:
>>>>Fatigue Test # Cycles to Failure
>>>>1 11,194
>>>>2 26,921
>>>>3 24,527
>>>>
>>>>In addition CASTIN has proven to superior in strength to Sn63/Pb37 in
the
>>>>following categories:
>>>>Ultimate Tensile Strength 5.73 vs. 4.92 KSI
>>>>Yield Strength 4.86 vs. 4.38 KSI
>>>>Young’s Modulus 7.42 vs. 4.87 MSI.
>>>>
>>>>Please note that the above testing was performed by independent
>>labaratories,
>>>>including ITRI and a very large North American automotive manufacturer.
>>>>
>>>>I hope that this information is useful. Please feel free to contact me
>>>>with any additional questions or to request a full CASTIN information
>>>booklet.
>>>>David Suraski
>>>>AIM
>>>
>>>Hi David (and, of course, everybody else),
>>>The type of testing performed (described above) is precisely what I was
>>>afraid of the "reliability" statement is based on. Unfortunately, the
>>>'Accelerated Thermal Fatigue Testing' does not tell anybody anything,
>>because
>>>no indication is given how large an expansion mismatch, if any at all,
the
>>>solder joints were subjected to, what kind of cycles (dwell times,
>>>temperature ramps) were performed, and how failure detection was
>monitored.
>>>Typically, unless tests follow IPC-SM-785, they are pretty useless. In
>>>addition, a couple of thousand cycles is inadequate to prove similar
>>>reliability to near eutectic Sn/Pb solders.
>>>ASTM-E 606 with a 1Hz-triangular waveform is useless for solder in
>>electronic
>>>applications, because solder joint failures invaribly are caused by
>>>creep-fatigue. A triangular waveform excludes, by design, any significant
>>>creep deformation.
>>>Having "independent labaratories, including ITRI and a very large North
>>>American automotive manufacturer" perform such tests is not really a
>>>recommendation or cause for comfort. Solder fatigue expertise is not
>>>necessarily found there; a very large North American automotive
>>manufacturer
>>>recently had to recall 2-years worth of SUVs (about $ 100M) because
>>>ofsignificant solder joint failures starting after 3 years in the field.
>>>So, this still leaves us without any confirmed equivalent creep-fatigu
>>>reliability for any lead-free solders.
>>>Also, you did not state at which temperatures and strain rates the
>material
>>>properties were determined; tensile strength, yield strength and modulus
>of
>>>elasticity are all dependent on temperature and strain rate.
>>>
>>>Werner Engelmaier
>>>Engelmaier Associates, L.C.
>>>Electronic Packaging, Interconnection and Reliability Consulting
>>>7 Jasmine Run
>>>Ormond Beach, FL 32174 USA
>>>Phone: 904-437-8747, Fax: 904-437-8737
>>>E-mail: [log in to unmask], Website: www.engelmaier.com
>>>
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>>
>>
>
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