Acronym for the “Restriction of Hazardous Substances” Directive, an agreement among European Union member countries to limit the use of six hazardous substances in electrical and electronic equipment. The directive bans the placing on the EU market of new equipment containing higher than specified levels of lead, cadmium, mercury, hexavalent chromium, polybrominated biphenyl (PBB) and polybrominated diphenyl ether (PBDE) (PBB and PBDE are flame retardants used in some plastics). The RoHS directive (which is not a law) took effect on July 1, 2006. While the directive only covers EU countries, a number of manufacturers of products distributed in the U.S. have begun to implement its standards.
The limits apply to any individual substance that could (theoretically) be separated mechanically – for example, the shielding on a cable or the tinning on a solder joint. For example, a radio comprises a case, screws, washers, a circuit board, speakers, etc. The circuit board comprises a printed circuit board, integrated circuits, resistors, switches etc. A switch comprises a case, a lever, a spring, contacts, pins, etc. Any component that can be identified as a “homogeneous” material must meet the limit. So if the case was made of plastic with 2,300 ppm PBB used as a flame retardant, then the entire radio would fail the requirements of the RoHS directive.