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Enclosure compliance? Rely on it!

28 March 2006

Under the RoHS directive, as of 1 July 2006, the use of certain selected hazardous substances in electrical and electronic equipment, including Lead, Cadmium, Mercury, Hexavalent Chromium, Polybrominated Biphenyl (PBB) and Polybrominated Diphenyl Ether (PBDE), will be restricted, with some limited exceptions, writes Steve Gallon. The directive mandates EU member countries to take measures to enforce these requirements, under their respective jurisdictions.

The purpose of the RoHS restriction is in order to both protect human health and the environment by restricting the use of certain hazardous substances in new electrical and electronic equipment, whilst at the same time complementing the Waste Electrical and Electronic Equipment (WEEE) directive, which seeks to eliminate the usage of certain hazardous substances in products; specifically in electrical equipment, that will be treated and recycled at end of their life.

As the deadline approaches, some manufacturers have already withdrawn certain non-compliant enclosure products from the market, but as a buyer of those products, how do you choose?

JUST LOOK FOR THE LABEL?
As it stands, the RoHS Directive does not require that compliant products be labelled with any label. Although some manufacturers are now using RoHS ready labels, the law does not require it and they are being used purely for marketing purposes.

This new directive relies solely on the ‘producer responsibility’ approach to achieve industry compliance. But in order for manufacturers to achieve RoHS compliance, each material contained in each component part, must also be compliant; which in turn means that component suppliers will be required to certify and provide documented support that each component falls below the maximum concentration levels stated in the directive.
The substance limits currently defined are:-

Lead 0.1% by weight in homogenous materials
Mercury 0.1% by weight in homogenous materials
Cadmium 0.01% by weight in homogenous materials
Hexavalent Chromium 0.1% by weight in homogenous materials
Polybrominated Bipheryls (PBB) 0.1% by weight in homogenous materials.
Polybromised Diphenyl Ethers (PBDE) 0.1% by weight in homogenous materials

Homogenous materials in RoHS terms, means a component or material that cannot be mechanically disjointed into different materials by unscrewing, cutting, crushing, grinding, by abrasive processes or similar procedures.
After July 1, 2006 all products on the market, not covered by exemptions will be assumed to meet the requirements of the RoHS Directive, if sold in Europe.

CAREFUL SELECTION
Clearly the prime function of any enclosure is to protect the electric or electronic components housed within it. Engineers must first consider the environment in which the product is to be used in order make careful selections based on the manufacturer’s data. Other considerations such as ingress protection (IP ratings), impact resistance (IK rating), corrosion, thermal protection, UV stabilisation and materials must also be taken into the equation as they impact on the useful longevity of the product.

Once these points have been established, overall costs obviously play their part. It’s a fact that the ultimate reliability of the system you build and supply is often influenced by the initial choice and design of the enclosure, as it is by the components used to build the system itself.

SPECIAL ENCLOSURE REQUIREMENTS
More and more these days, manufacturers are being asked to produce customised products to meet new end user requirements for instance the inclusion of windows, DIN rail mounted MCBs, switches, push buttons or calibration devises, membrane key-pads and displays requiring pre-drilled holes, cut-outs and sub-assembly mounting devices.

EMC shielding is also a necessity in certain environments as electromagnetic protection is needed to protect delicate components from interference from neighbouring devices.
Panel and System Builders are constantly building more and more complex systems in response to their customer’s wishes, which in turn has inspired enclosure manufacturers to produce a wider choice of flexible and innovative enclosure solutions. But remember, whatever your particular requirement, all bespoke enclosures started as a standard box.

Steve Gallon is managing director of Fibox Ltd.


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