RoHS: Restriction of Hazardous Substances, the European Union Directive 2002/95/EC
Compliance with RoHS/WEEE (Waste Electronic and Electrical Equipment) in electrical and electronic equipment is set at July 2006. The directive restricts the use of certain hazardous substances, in electrical and electronic equipment inluding relays. Lead, Mercury, Cadmium, Hexavelent Chromium, Polybrominated biphenyls (PBBs) and Polybrominated diphenyl ethers(PBDEs) are all subject to restriction. Generally relay manufacturers are replacing lead solder with tin solder, and AgCdO contacts with AgSn02. This will effect switching certain loads and high temperature operation.
Song Chuan relay production was changed during 2004 and 2005 to comply with this EU directive. As solder, plating and contact materials were replaced, each was designated "Green Product". Packaging and marking distinguishes pre-change production from new. The change took place between August 2004 and November 2005.
Various exemptions under the RoHS Directive have been approved since first publication. The list is extensive. Of particular interest is the "Cadmium Exemption" confirmed by the Commission decision on 21st October 2005, reference 2005/747/EC.
Point 8: Cadmium and its compounds in electrical contacts and cadmium plating... e.g. Cadmium oxide in silver/cadmium oxide contacts AgCdO.
This means that relays can be supplied with AgCdO contacts, and be compliant with the RoHS Directive.
This contradicts earlier advice and is based on the switching qualities of AgCdO which cannot be matched by other materials. In some cases performance might otherwise be less than half that offered by this particular compound. If in doubt, or for more detail contact the Relay Company.
These notes are intended as a brief insight into the contact materials used in Relay Company products.
A standard contact material used in many general application relays, the copper and nickel contents give the hardness. Single contact minimum 20V/50mA. Twin contact minimum 10V/20mA. Long contact life, but tends to oxidise at higher temperatures.
More resistant to welding at high loads than hard silver, with high burnout resistance. A good standard contact material. Minimum contact load, 20V/50mA single contact, 10V/20mA twin contact.
Used for high AC loads because it is more resistant to welding at high switching current "peaks". Material erases evenly across the surface. Not recommended for strong DC breaking arcs because of the wear this creates(one side reductions). Minimum contact load 20V/50mA. Note that Cadmium was originally included in the list of materials prohibited under the European RoHS Directive (see above). Following applications for exemption based upon the qualities of AgCdO in electrical contacts, approval for exemption was confirmed by the Commission decision of 21st October 2005. This has led to some confusion, with some products already withdrawn, or contact material replaced with Silver Tin Oxide(AgSn02). From October 2005 AgCdO contacts are exempt from the RoHS Directive, meaning that subject to all other conditions, relays with these contact materials can be RoHS compliant.
The tin oxide makes the material more resistant to welding at high making current peaks. Has a very high burn out resistance when switching high loads. Low degree of material migration under DC loads. Minimum contact load 20V/50mA. Useful where very high inrush currents occur, such as lamp loads including fluorescent. Silver Tin Oxide is frequently chosen as the replacement relay contact material for Silver Cadmium Oxide as the latter is withdrawn.
Similar to Silver Tin Oxide but more resistant to inrush. Minimum contact load 12V/100mA.
More resistant to welding at high loads than hard silver, with high burnout resistance. A good standard contact material. Minimum contact load 20V/50mA single contact, 10V/20mA twin contacts. Used by Kuhnke on some heavier duty relays.
Used for switching low loads > 1mA/100mV. This plating will be removed by friction and erosion after around 1 million switching cycles in "dry circuits". Used in single and twin contact forms (twin contact is particularly useful in dusty enviroments).
Has the same qualities as 10µm Au but is less durable. It is generally used to prevent corrosion / oxidation of relay contacts during storage.
The Relay Company, H.Kuhnke Ltd have made all reasonable efforts to ensure the accuracy of the information shown in this web site. The information provided should not be relied on as legal advice or regarded as a substitute for legal advice. The reader should exercise his own care and judgement before relying on this information in any important matter.
To speak directly to experienced relay professionals please contact.
The Relay Company
H. Kuhnke Ltd
21 Abbey Enterprise Centre
Romsey, Hants, SO51 9AQ
Telephone: +44 (0)1794 514445
Fax: +44 (0)1794 513514