P
Phil Allison
Guest
Hi to all,
Been doing a little digging on the apparent banning of CdS cells as a result
of the EU's infamous "RoHS Directive" and came across a nice example of how
INSANE the whole RoHS business really is.
The case involves semiconductor maker Vishay Semiconductor (Austria) and
high voltage, glass encapsulated diodes.
Background:
--------------
Glass used in electronic components is ALLOWED to have lead in it -
normally as PbO ( lead oxide). The face plates of CRT tubes being the main
example, where the lead helps stop X-rays being emitted.
The use of tin-lead solder has been banned as is Pb in the plating used on
component leads - so most component leads are now plated with pure tin
rather than tin-lead alloys.
The maximum percentage of Pb allowed in any such coating is 0.01% (or
1000ppm ) by weight.
The problem Vishay found:
------------------------------
The glass used to make high voltage diodes contains a small percentage of
PbO - it lowers the melting temp, improves the flow of the material and
eliminates defects like included bubbles.
But when an engineer at Vishay checked the plating on the connecting leads
of finished diodes, he found that some of the Pb had leached out from the
glass and contaminated the pure tin coating under and adjacent to the glass
bead. Lab tests revealed that the percentage of Pb in the coating was around
0.3% in these areas - ie 30 times the limit !!!
Horrors !!!!!
The parts do *NOT * comply with the RoHS Directive !!!!
The amount of Pb that leached out of the glass bead was utterly miniscule -
something like 5 to 10 *micrograms* per diode (see my note at end).
Vishay even tried using non-leaded glass of various types make the same
diodes, but without success.
Eventually Vishay gave up experimenting and filed an application for an
exemption from the RoHs directive - no simple task and not that often
successful.
The bureaucrats who pontificate on these things suggested Vishay try using
Nickel or Gold to plate the diode leads and see if the Pb still leaked out.
It did.
Eventually, the exemption was granted:
See #37 in this list -
http://www.rohs.gov.uk/Docs/Exemptions%20without%20link%20backs/RoHS%20Exemptions%20-%20Lead%20(2).pdf
An interesting comparison:
------------------------------
In the example just given, the issue involved about 10 micrograms of Pb per
diode.
Takes 100 million such diodes to reach 1kg of Pb
- that's a LOT of diodes, right !!
During WW2 something like 10 billion rifle calibre bullets were expended all
over Europe - not to mention WW1 or all the other countless previous wars.
The total number must be several times more.
Nearly all of these bullets are lying in the ground somewhere, while others
landed in the lakes and oceans that surround Europe. Each of bullet
contained about 10 to 12 grams of Pb.
So, spread all over the European landscape are billions of these lumps of
Pb.
The total weight of which is circa 250,000 tonnes.
I wonder if we will soon see the creation of an RoHS bullet.
Only socially responsible to have safe bullets.
...... Phil
Been doing a little digging on the apparent banning of CdS cells as a result
of the EU's infamous "RoHS Directive" and came across a nice example of how
INSANE the whole RoHS business really is.
The case involves semiconductor maker Vishay Semiconductor (Austria) and
high voltage, glass encapsulated diodes.
Background:
--------------
Glass used in electronic components is ALLOWED to have lead in it -
normally as PbO ( lead oxide). The face plates of CRT tubes being the main
example, where the lead helps stop X-rays being emitted.
The use of tin-lead solder has been banned as is Pb in the plating used on
component leads - so most component leads are now plated with pure tin
rather than tin-lead alloys.
The maximum percentage of Pb allowed in any such coating is 0.01% (or
1000ppm ) by weight.
The problem Vishay found:
------------------------------
The glass used to make high voltage diodes contains a small percentage of
PbO - it lowers the melting temp, improves the flow of the material and
eliminates defects like included bubbles.
But when an engineer at Vishay checked the plating on the connecting leads
of finished diodes, he found that some of the Pb had leached out from the
glass and contaminated the pure tin coating under and adjacent to the glass
bead. Lab tests revealed that the percentage of Pb in the coating was around
0.3% in these areas - ie 30 times the limit !!!
Horrors !!!!!
The parts do *NOT * comply with the RoHS Directive !!!!
The amount of Pb that leached out of the glass bead was utterly miniscule -
something like 5 to 10 *micrograms* per diode (see my note at end).
Vishay even tried using non-leaded glass of various types make the same
diodes, but without success.
Eventually Vishay gave up experimenting and filed an application for an
exemption from the RoHs directive - no simple task and not that often
successful.
The bureaucrats who pontificate on these things suggested Vishay try using
Nickel or Gold to plate the diode leads and see if the Pb still leaked out.
It did.
Eventually, the exemption was granted:
See #37 in this list -
http://www.rohs.gov.uk/Docs/Exemptions%20without%20link%20backs/RoHS%20Exemptions%20-%20Lead%20(2).pdf
An interesting comparison:
------------------------------
In the example just given, the issue involved about 10 micrograms of Pb per
diode.
Takes 100 million such diodes to reach 1kg of Pb
- that's a LOT of diodes, right !!
During WW2 something like 10 billion rifle calibre bullets were expended all
over Europe - not to mention WW1 or all the other countless previous wars.
The total number must be several times more.
Nearly all of these bullets are lying in the ground somewhere, while others
landed in the lakes and oceans that surround Europe. Each of bullet
contained about 10 to 12 grams of Pb.
So, spread all over the European landscape are billions of these lumps of
Pb.
The total weight of which is circa 250,000 tonnes.
I wonder if we will soon see the creation of an RoHS bullet.
Only socially responsible to have safe bullets.
...... Phil