Background
In Europe, over 90% of electrical and electronic equipment goes into landfill sites - around 6 million tonnes of waste every year. Hence, in order to prevent hazardous materials from entering landfill sites and to contribute to the protection of human health through environmentally sound recovery and disposal of waste electrical and electronic equipment (WEEE), the European Parliament and the Council of the European Union released the RoHS Directive on January 27, 2003.
The RoHS Directive defines its product scope based on the WEEE Directive and is legislation mandating the elimination of banned substances from electrical and electronic equipment (EEE) throughout the EU by July 1, 2006. It prohibits new EEE from being placed on the market after July 1, 2006 if they contain higher than maximum concentration value (MCV) of lead, cadmium, mercury, hexavalent chromium, polybrominated biphenyl (PBB) and polybrominated diphenyl ether (PBDE). The MCV for cadmium is 0.01 weight percent (100 ppm) and lead, mercury, hexavalent chromium, PBB and PBDE 0.1 weight percent (1000 ppm).

Impact
The six banned substances are restricted in equipment that is within the scope of the RoHS Directive. The scope is eight of ten categories of the WEEE-category 1~7 and 10. The RoHS Directive applies to end products that fall within its scope and it means that all the components and combination of components put together to form sub-assemblies must not contain any of banned substances in levels above the MCV.  As to those who are affected, they will be those who manufacture and sell EEE within the specified categories, sell equipment produced by other suppliers under their own brand, and import (or export) affected equipment into the European market.

Challenges
The RoHS Directive is just a guideline. Different progress and legislation for the rolling plans for RoHS Directive in each member state of the EU, no international standard formed, no qualified and unified verification processes and vendors, no unified standards from customers, different progress of RoHS compliant materials and components from suppliers and etc. will complicate the compliance preparations of both producers, importers and their supply chain.
RoHS compliant products involve participation and cooperation among all related departments in each company such as purchasing, quality control, R&D, product verification, manufacturing, quality assurance, technical support, RMA, product management and etc. How to get a consensus and synchronize the progress of each related department to achieve a corporate goal to create RoHS compliant solutions will be a tough challenge.3. The melting temperature of the most popular lead-free alloy candidates are approximately 30^oC to 40^oC higher than the lead-tin (Pb-Sn) solder. This issue will involve concerns about the reliability of products due to a variety of defects such as thermal fatigue of solder joints, tin whisker from electroplated tin termination coatings, delamination of multi-layer PCBs, damage to plated through holes, damage to heat sensitive components and etc.
The melting temperature of the most popular lead-free alloy candidates are approximately 30^oC to 40 ^oC higher than the lead-tin (Pb-Sn) solder. This issue will involve concerns about the reliability of products due to a variety of defects such as thermal fatigue of solder joints, tin whisker from electroplated tin termination coatings, delamination of multi-layer PCBs, damage to plated through holes, damage to heat sensitive components and etc.

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