Re: Lead Solder

"Steve Richardson" <oldnoccer@xxxxxxxxxxxxxx> wrote in message
news:5tadnW6BlYIp2efZRVny1g@xxxxxxxxx
Component failures in ciritical systems are always an issue, and systems
should be designed so that dire consequenes are infrequent (by fail-safe,
redundancy, voting, more intelligence in testing signal quality, etc) -

It should be but isn't, unless there is regulation to enforce it such as in
the aviation industry, other industries are governed by market forces which
usually won't pay for anything like that. The generator industry is a case
in point, even though they may be providing backup power for something as
critical as a hospital no one will pay for true reliability.

Surely the key factor is the mean time before failure (MTBF) for
components,
often declared by manufacturers.

It's a while since I did MTBF calculations for the military and aerospace
sectors but back then we could rarely get figures from manufacturers and
I've no reason to believe they are any more forthcoming now. We had to use
the figures from MIL Handbook 217 which is the bible of reliability
prediction and is notoriously biased against anything new and unproven, I
don't know what the latest issue has to say about lead free but the fact
that the military and aerospace have an exemption probably says it all.

There simply isn't sufficient experience of lead free to be confident of
anything and what evidence has emerged is all bad, there's a well documented
but anonymous story about a very large phone company who tried to go lead
free a couple of years to get some commercial advantage over their
competition but had huge failure rates and was forced to go back to lead.

Information from component distributors is that most companies who are going
lead free have left it very late in the hope of some sort of reprive and are
now having huge problems, you can get to maybe 90% lead free components but
the last 10% is very hard. There are also lots of fake lead free components
on the market and if you have just one lead component on a board and put it
through a wave soldering or selective soldering machine you contaminate the
whole solder bath and have to throw away not only thousands of pounds worth
of solder but also the bath itself as you can't clean it properly. It's
going to be the last nail in the coffin of some UK firms, and for what?,
WEEE is going to force the recycling of the products anyway!.

Greg



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