Spurious Response wrote in message
news
On Wed, 25 Jul 2007 08:42:50 +0100, "N Cook" wrote:

Military , aerospace & medical do have derogation from WEEE and RoSH, but
can anyone nail down precisely why they are exempted.



Absolutely. Lead based solder alloys are ****ing superior, and Tin
based, non-leaded alloys are inferior, and have VERY POOR reliability
numbers.

It is really quite simple math.

A mission critical application REQUIRES a system where one does not
have to expect some lame failure mode to creep in due to the utilization
of a VERY POOR, failure mode prone device interconnection methodology.

The next time I get a year or 2 year old 800 GBP/1500 USD combo in for
repair with loose simple, thermally un-stressed,but vibrationally stressed
components, I will actually measure the extraction force of the obviously
suspect ones and some of the remaining ones, with a spring balance and a
hook of wire. I would never have expected otherwise well-soldered (but
obviously lead-free solder) very basic "components" like soldered wire
links,1/3W resistors,TO92 transistors, to have solder failures after
decades, let alone a couple of years.

Some more relevant background text from
http://www.lboro.ac.uk/research/iemr...202015%20Makin
g%20a%20Visible%20Difference%20EIGT%20Report.pdf
nothing about failure rates in the bullet-points though

"..... The lead-free solder proposal was introduced at short notice by the
EU in
1998 as a revision to the WEEE Directive under Article 175 (environment),
and is the subject of qualified majority voting, so the UK has no power of
veto. The UK was the only member state represented by its industry
ministry, and other member states were represented by environmental
ministries. No rigorous fiche d'impact was undertaken. The proposals take
effect from 1 July 2006.
Subsequently, the Removal of Hazardous Substances (RoHS) provisions,
which deal with other hazardous substances, were made under Article 95
(single market). So interdependent legislation will be introduced under
different agreement arrangements.
Unintended consequences include:
* Increased material and component costs because some PCB material
and some components cannot be used with higher temperature solder;
* Re-certification costs for safety critical products;
* Damage to soldering equipment from electrochemical corrosion,
following use of tin-rich solder in machines previously used with lead-
based solder;
* Increased capital equipment cost as equipment life shortens;
* Increased costs associated with inspection, testing and tracking to
demonstrate compliance;
* Training and retraining costs for staff working with new materials;
* Increased capital and inventory costs as manufacturers keep separate
lines and stocks for defence and exempt products. ....."

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/