According to one source the re-definition has been deliberately introduced following pressure from certain European component makers. It will allow them to continue to supply tin-lead-plated components providing PCBs have less than 0.1 per cent total when finished.
At issue is the interpretation of a new sentence which could allow components with tin-lead plated legs to be used in assemblies after the mid-2006 Restriction of Hazardous Substances (RoHS) Directive deadline.
Without the additional sentence, which re-defines the meaning of the phrase ‘homogeneous materials’, the amount of lead in materials used to construct a component is restricted to 0.1 per cent. With the re-definition, the 0.1 per cent limit may been seen to apply to whole assemblies, or ‘units’ as the definition calls them. A unit could not be as big as a whole computer, as a computer can be taken apart, a European Commission civil servant told Electronics Weekly, it could be a circuit board.
Low concentrations of lead in otherwise Pb-free joints have been shown to cause joint cracking during and post production.
The proposed definition of the maximum allowable banned substance concentration is based on that from the already-functioning End of Life Vehicles (ELV) directive: A maximum concentration value of 0.1 per cent by weight in homogeneous materials for lead, mercury, hexavalent chromium, polybrominated biphenyls and polybrominated diphenyl ethers and of 0.01 per cent weight in homogeneous materials for cadmium shall be tolerated. Homogeneous material means a unit that can not be mechanically disjointed in single materials.
Depending on interpretation, the sentence re-defining ‘homogeneous materials’ – which is not included in the ELV Directive – could allow Sn/Pb-plated components to be used. Without it Sn/Pb plated components are banned.
Investigations by EW suggest the Commission has yet to understand the significance of the re-definition. All [at the meeting] were quite positive [about the wording], including those from the member states, said one civil servant.
This is not the case according to information received by Electronics Weekly, with one EU member state official saying that he was flabbergasted.
