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Old June 6th 07, 11:08 PM posted to alt.comp.periphs.mainboard.asus,sci.electronics.design,nl.comp.hardware,alt.comp.hardware.pc-homebuilt,alt.comp.periphs.videocards.nvidia
Chris Jones[_2_]
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Default SST replacement chip for Winbond chip (Bios for A8N32-SLI)

Frank McCoy wrote:

In alt.comp.hardware.pc-homebuilt Skybuck
wrote:

What do they mean with:

Lead and Lead-free.

Do they mean the metal ?


Yes. Mostly in solder.
At one time *all* solders were lead/tin based; with 60/40 lead-tin
eutectic solder being the commonest for all electronics.


Is their a health risk during normal operation... like lead particles
in the air or so ?

Not *particles* per-se; but lead fumes. Small, actually, as the lead
doesn't vaporize much at barely liquid temperatures; but not nonexistent
either. The fumes *do* solidify into minute particles though; which are
easily breathed.


I have read many times that below 500 degrees C, the vapour presure of lead
is not high enough to be a hazard. I have not heard any claims that the
fumes from soldering contain hazardous amounts of lead. What IS
potentially hazardous is the fumes from the burning flux that accompanies
soldering. The flux for lead-free soldering supposedly results in more
dangerous fumes because it is a more active flux and the temperature is
higher, but then you weren't supposed to breathe it anyway....


Or is this only of concern during a fire/meltdown ?

Mostly during:
A. Production.
B. Scrapping.
C. Yes, fire/meltdown.

Production these days have mostly switched almost completely to non
tin/lead solders. Scrapping old electronics though is a problem when
they end up in landfills where the lead can leach out over time.


This is the supposed reason for RoHS, which implies that they do not believe
that they will succeed in collecting the waste under the other expensive
scheme that they have introduced (WEEE), or alternatively, they might be
wanting to redefine "burning circuit boards" as "recycling", or perhaps
they recycle them as a "means of filling unwanted holes in the ground".
I'm not sure which it is.


Or is it only of concern when throwing it in the waste basket ?

For the *consumer* mainly the last.
That's just one reason of many that they're beginning to outlaw throwing
electronics devices of any size in the trash. Cadmium and other toxic
metals are now becoming of even more concern than lead these days;
because many/most companies *are* removing lead based solders from their
manufacturing methods.

Another plus for recycling is the *reclaiming* of many valuable metals
such as copper and gold (and yes, lead and cadmium too). Electrolysis
works wonders there.

One thing *hard* to reclaim is the lead in CRT glass, used as a barrier
for the soft radiation emitted. However, luckily, such thick glass
envelopes are declining rapidly in popularity in favor of flat-panel
displays for both TV and computer monitors, that just don't NEED such
thick leaded-glass envelopes any more.


But they still allow you to put hundreds of kilograms of lead on the roof of
your house, in direct contact with rainwater! Somehow it makes the lead on
a non-compliant 0402 component seem insignificant.

Chris