Detailed guidance for RoHS (lead-free) compliance from Arcom

The RoHS (Restriction on the use of certain Hazardous Substances – Directive 2002/95/EC) Regulations ban the putting on the EU market of new Electrical and Electronic Equipment (EEE) containing more than the permitted levels of lead, cadmium, mercury, hexavent chromium and both polybrominated biphenyl (PBB) and polybrominated diphenyl ether (PBDE) flame retardants from July 1 2006. There are a number of exempted applications for these substances.

There are a number of exempted applications for these substances (and the list for requested exemptions is also growing rapidly as July approaches).

The Directive uses the term ‘homogeneous material’ to define the weight limits. The RoHS Guidance documents use the following definition of homogeneous:

29. The term ‘homogeneous’ is understood as "of uniform composition throughout", so examples of "homogeneous materials" would be individual types of plastics, ceramics, glass, metals, alloys, paper, board, resins and coatings.

30. The term ‘mechanically disjointed’ means that the materials can, in principle, be separated by mechanical actions such as unscrewing, cutting, crushing, grinding and abrasive processes.

31. Using these interpretations, a plastic cover (for example) would be a ‘homogeneous material’ if it consisted exclusively of one type of plastic that was not coated with or had attached to it (or inside it) any other kinds of materials. In this case, the maximum concentration values of the RoHS Regulations would apply to the plastic.

32. On the other hand, an electric cable that consisted of metal wires surrounded by non-metallic insulation materials would be an example of something that is not ‘homogeneous material’ because mechanical processes could separate the different materials. In this case the maximum concentration values of the RoHS Regulations would apply to each of the separated materials individually.

33. A semi-conductor package (as a final example) would contain many homogeneous materials, which include the plastic moulding material, the tinelectroplating coatings on the lead frame, the lead frame alloy and the gold-bonding wires.

What this means is that for a complete system, instrument or machine consisting of several circuit boards, wiring looms, displays, etc, every single individual solder joint, integrated circuit and mechanical item must be RoHS compliant. If you build a machine which weighs 100Kg, every last individual ‘homogenous’ item (even if it weighs a fraction of a gram) must be RoHS compliant to claim compliance for the complete product!

The Department of Trade and Industry (DTI) in the UK has played a major part in the development and implementation of the RoHS Directive. The DTI web site also includes the latest (November 2005) guidance notes for the RoHS Directive (includes the RoHS decision tree). This is a useful document.
RoHS_Guidance_November05_Final.pdf