Hi Werner,

The tests had been done with 16 boards for each solder each and
assembled with the same mixed components ranging from 0402, MLCC 1210,
PLCC, and QFP68 (reflow) till SSOP-16, SO-28, VSO40, SOT69, tantal-A
up to tantal-D capacitors, DIL-sockets and large stand-up elctrolytic
capacitors (wave), all  simultanuously tested in dual chamber thermal
shock equipment with 15 minutes at the T-extremes. The inspections had
been done visually and checked, when in doubt, afterwards with SEM on
cross sections. The rejection criteria was 50% solder joint
distortion. The test had been stopped when 50% had been failed on
component level, and a maximum of 2000 cycles.

Of course, the SnPb solder joints at the end has severe plastic
deformation prior to fail, the other solders had less plastic
deformation but deeper cracks along the grain boundaries
(SEM-analysis).

Indeed, one component failed earlier than the other but, the ratio for
each component was about the same.

Peer



2008/2/14, [log in to unmask] <[log in to unmask]>:
> Hi Peer,
> These results, as many others, show that the accelerated test results are
> comarable [Peer, what were the dwell times at the T-extremes?]. However,
> that does not mean that functional relaibility would be of
> equalproportionality. Because SnPb solder creeps much faster, the cyclic
> creep process is more complete and more creep strain has occurred for SnPb
> under identical conditions. However, this is really comparing apples and
> oranges.
> In real product, the cyclic dwell times are typically long enough for
> essentially complete creep at least at the high T for either SnPb or SAC; so
> the slower creep rates for the Pb-free solders do not prodect the SJs.
> However, absent accelerated reliability models for Pb-free solders, the
> accelerated test results cannot be extrapolated to product conditions as
> yet.
>
> Werner
>
>
>
> **************
> The year's hottest artists on the red carpet at the Grammy Awards. Go to AOL
> Music.
> (http://music.aol.com/grammys?NCID=aolcmp00300000002565)

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