Pascal,
I am sure Werner will "jump in" on this one but let me be the first.
There are serious issues concerning the dwell time during testing of Pb
free solder joints.
Because the creep rate is much slower for these type of
solders the dwell time must be increased. The increase should match the
"worst case" conditons
expected in the field. Generally the dwell times should be increased to
30 minutes which allows
release of the accumulated strains.
The Swiss Federal Institute for Material Testing and Research has a very
informative 6 page report about this issue in .pdf format.
Do not try to save money by reducing test times.
It can result in some very nasty fleld problems.
David A. Douthit
Manager
LoCan LLC
Pascal Guiheneuf wrote:
>Hello,
>
>We are trying to set up a test plan for qualifying a lead-free complex board
>(many BGA, 300x400mm2, 2mm thick, TSOP, press-fit connector, etc...)
>processed with a SAC solder cream, Immersion Silver for the board finishing.
>The last proposal focus on a thermal cycling, Tmin=0°C, Tmax=100°C,
>Tdwell=10mn, total cycle time=40mn. We think, by comparison to other results
>found through many papers, that 3000 cycles should be large enough with some
>intermediate ICT tests at 500, 1000, 1500, 2000, 2500. Is anybody aware of
>the Acceleration Factor for such an accelerated test in order to predict the
>life of the board.
>
>2004 was a good year for the semi-emperical studies about this subject, but
>I couldn't fin a crystal clear paper.
>
>Thanks for your help,
>
>Happy new year 2005,
>
>Pascal Guihéneuf
>Nortel Wireless
>UMTS NPI/LCM
>GSM/UMTS Environmentally-Friendly Core Team Leader
>ESN 574-5382 or 33.1.69.55.53.82 (phone)
>ESN 754-2704 or 33.6.64.04.27.04 (mobile)
>
>
>
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