"Mike Gilmour" wrote in message
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"Serge Auckland" wrote in message
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"Mike Gilmour" wrote in message
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Regulations and more regulations, it must be difficult for manufacturers
to keep up with it all. The WEEE Waste Electrical and Electronic
Equipment and the RoHS Restriction of Hazardous Substances Directives
that were published by the European Commission in 2003, are due for
implementation by July this year. Amongst a legion of other directives,
lead free solder can only be good thing but the appearance and flow of
the solder joint has changed (even its a better joint). I do miss
that mirror finish and easy flow of leaded solder compared to the newer
duller lead-free variety. Guess it'll be a bit harder to spot dry
joints or time, any opinions.
Whilst soldered joints may not look as nice, lead-free solder has to be a
good thing. I hate to think how many flux fumes I inhaled and lead I
ingested from holding the solder in my teeth when trying to repair an XLR
in an awkward position. No comments about my sanity, I've made them all
myself already.

Isn't it more the case that other people notice whilst you yourself stay
oblivious ;o)

The flux fumes will still be inhaled but without traces of lead (was there
much lead in the fumes?)


There's much less hand-soldering now than there used to be, so hopefully,
there are also much fewer dry joints. Anyone from a manufacturing
environment care to comment?

S.


The new lead-free solder has hugely inferior wetting properties to leaded
solder. As a result, rather more aggressive flux is used. This is somewhat
more acidic than that used previously, so the fumes are considered to be
even more hazardous. Further, the tip temperature of a hand iron needs to be
in the region of 50 deg C hotter than previously. This elevated temperature
causes the flux to boil off more readily than before. Also, the inferior
wetting properties result in the application time of the iron tip to the
joint, to be increased from approx 1.5 seconds to about 4 seconds, to make a
satisfacory joint. Thus, a more aggressive flux, is boiling off more
readily, and for a longer period of time. This is considered to be more
hazardous to health than the previous situation. Colophony ( rosin ) fuming,
is considered to be a serious cause of industrial asthma. It is unlikely
that any lead was ever inhaled as a result of soldering.

As far as how good this stuff is. Since manufacturers have been introducing
it, I have seen a huge increase in production bad joints, in non-traditional
places e.g. on high pin density chip packages. This is partly because of the
inferior wetting, partly because of the totally different melt-flow-reset
profile, which does not encourage capilliary action anything like as well as
the old leaded solder, and partly as a result of the manufacturers trying to
keep the required temperature increase of their flow solder lines, as low as
they can, so as not to cause damage to sensitive LSIs, and even cause
substrate delamination. The problems get even worse with high thermal
inertia components such as power transistors, connectors, heatsinks etc. I
see many items coming through my workshop for repair, suffering from bad
joints in all of these places.

I'm not convinced of the eco validity of this directive with respect to lead
in solder. Less than 1% of the world's mined lead, went into solder. Over
80% goes to car battery manufacture. This is easily dealt with at
end-of-life, by having proper recycling in place. This will not change, as
it has been declared a technology with no viable alternative, so exempted.
In July, the WEEE directive comes into force throughout the EU. All
electronic equipment will then have to undergo a serious level of recycling
at end-of-life, and if the car battery recyclers can deal with the huge
amount of lead that they have to, then I'm sure that the same could be done
for the comparitively tiny amounts, in solder.

If lead-free solder is such a good alternative to the leaded variety, you
might ask yourselves why the American military have flatly refused to use
it, and the avionics and medical equipment industries, have been granted
exemptions from using it ...

Just as an aside, it will still be perfectly legal to use leaded solder
after the directive comes in, for the repair of equipment placed on the
market before the July 1st deadline. This situation will continue for the
forseeable future. It is also generally recommended, that only solder of the
same type as was originally used to make a joint, is used to rework it, as
mixing of different alloys can result in a joint which is potentially
compromised for long term reliability. Some solder manufacturers dispute
this, but I would rather be safe than sorry. Although it will become less
common, leaded solder should remain available for a considerable time.

Arfa