On Jul 25, 1:29 pm, Joe Chisolm wrote:
On Tue, 24 Jul 2007 23:42:47 +0100, Eeyore wrote:
The debate about lead free solders seem to be nearly as politically
charged as that about anthropogenic global warming and a casualty seems to
be useful data.

I've read plenty of comments to the effect that lead-free is less reliable
in the long term (vibration seems to be a key weakness AIUI - maybe also
thermal cycling) which presumably explains the exemptions for certain
categories, yet I've also seen some studies that claim it can out-perform
lead containing solders.

Is there any real hard and fast information out there that one can rely on
?

The main issue for lead free in military and aerospace electronics is
tin whiskers. Tin solder will
grow conductive whiskers that even penetrate conformal coatings. In
low power circuit,
the whisker will short something out. In a high power circuit, it
might burn up like a fuse,
but if it happens in a satellite (no atmospheric pressure) the little
whisker will cause
a plasma arc capable of passing huge amounts of current.

We in the defense electonics industry fight with this issue every day
and the information
is very confusing. Parts turn lead free midstream in production and
seems impossible to
keep tack of it. Every company is dealing with it differently. We stay
away from certain
finishes like bright tin and look at the spacing of components and
coatings on our boards.
This can mitigate some of the reliability risks of lead free.

If high-rel is of upmost importance, we struggle to find tin-lead
parts.