Russell McMahon wrote:

> Real world failure picture
> 
>         http://nepp.nasa.gov/whisker/photos/pom/2004april.htm

It seems that your original question was more about dendrites than about
whiskers? 

>From that link above: "A "Whisker" generally has the shape of a very thin,
single filament or hair-like protrusion that emerges outward (z-axis) from
a surface.  "Dendrites", on the other hand, form in fern-like or
snowflake-like patterns growing along a surface (x-y plane) rather than
outward from it."


Regarding the "they should have known better" argument, here is an
interesting quote from this same page: "In fact, many manufacturers have
been offering pure tin plated components as a standard commercial (and in
some cases high reliability) product for years while others are exploring
pure tin alternatives for the very first time.  Many electronics
manufacturers have never heard of the phenomenon of tin whiskers and
therefore, may not consider the risks of tin whisker growth during the
validation of new plating systems."

This doesn't sound as if a regulatory agency that works closely with
manufacturers would have necessarily known about this. 

They further say: "NASA GSFC is aware of several instances where the
procurement specification required "No Pure Tin", but the product supplied
was later determined to be pure tin." Are you sure you haven't been using
components with pure tin plating for years and don't know about it? :)

Gerhard

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