Manufacturers are facing a huge headache once the EU’s RoHS and WEEE Directives take effect to demonstrate that their products conform with the regulations. Ray Scruby of Fischer Instrumentation looks at a practical strategy to prove conformity

The clamour from this impending environmental legislation has been getting greater over the past few months and unless you had the good fortune to spend the whole of the summer on a beach it has been difficult to avoid.

Its introduction has been a little confused, with delay after delay and exemptions still not clear, but one thing is now certain; the regulations become compulsory in July 2006.

Confusion over the implementation of the legislation has done little to dispel the natural reaction to try to ignore it and hope that component suppliers will solve all the problems for us. As components now originate from virtually anywhere in the world, it may be a little naive to trust in the good nature of all of the middlemen.

Element mapping: Lead (Pb) distribution after an automated scan

Our EU politicians have decreed this ban, or a limit, on certain materials that pollute or harm the environment, generating the EU wide regulations, RoHS and WEEE and the existing ELV. Manufacturers of electrical and electronic equipment will find themselves particularly challenged as even one lead containing component will contaminate an entire solder bath.

The complete list of affected substances is lead, mercury, hexavalent chromium (Cr VI) and cadmium as well as polybrominated biphenyls (PBB) and polybrominated diphenyl ethers (PBE). After the EU regulations become effective in the UK on 1 July 2006, only 1000 ppm (parts per million) of all these materials, and only 100ppm for cadmium, will be allowed in virtually all products manufactured or sold in the EU.

There are exceptions for medical and the military (who incidentally face critical problems of ensuring that lead is used on their assemblies - just imagine tin whiskers growing quietly in some ICBM silo) and there are other areas still under discussion or requiring clarification.

This, of course, has a significant impact on manufacturers of electrical and electronic equipment, as they will only be able to market those products and components that conform to the required minimum levels of harmful substances. In particular, PCBs, electronic components and solder connections as well as enclosures and single components made of synthetics, must be measured and tested. The onus is on manufacturers to demonstrate conformity - and continuing conformity with the EU regulations. The cost of a recall if a failure were identified would, for most, be catastrophic.

A complete analysis may involve the destruction of the article and effectively turning it into an electronic soup. This is time consuming and also expensive.

It is possible, however, to get a quick and accurate screening of components and assemblies using X-ray fluorescence. This has several advantages, taking only a few seconds, being non-destructive and also automated if many similar components need testing.

The X-ray fluorescence method is especially economical for screening the components as a first step of the inspection process.

Personnel without special knowledge of analysis methods can easily identify specimens that are clear of harmful substances. Components that are near the critical borderline or above can then be analysed quantitatively or rejected. The supplier can then be required to provide a detailed analysis or replacement parts.

Energy Dispersive XRF analysers automate the analysis procedure.

The instruments are fully enclosed and can be operated with basic skill levels in factory, laboratory or even office environments with minimal safety requirements. No prior preparation of the sample is required before measurement, so no damage is done to the component. The measurement chamber is large enough to take sub-assemblies and complete PCBs.

Some instruments have a programmable XY stage so many components can be analysed unattended. PCBs can be automatically scanned to identify any non-conforming component. The results are displayed in tabular form with the material concentrations that exceed the permitted limits emphasised in colour on the screen or in the printout.

Overlay spectrum shows a clear peak for the banned substance cadmium

The accurate analysis of chromium and bromine in the components significantly simplifies the otherwise difficult detection of Cr (VI), PBB and PBE concentrations.

If the amounts of chromium and bromine are below the permitted quotas, then the same holds true for Cr (VI) or PBB and PBE. Therefore, other time and cost-intensive analysis methods can be avoided by the use of these X-ray fluorescence instruments. Analysis takes between 50 to 200 seconds, depending on the dimensions of the components to be measured.

The detection limit of lead, mercury and bromine is below 10ppm, for cadmium and chromium below 20ppm. As the instruments use a range of collimators, very small specimens, or areas on specimens, can be measured and analysed, using a video camera for precise positioning. This allows, for example, the analysis of lead and cadmium in narrow PCB tracks and the smallest soldering pads.

A particular strength of these instruments is their capability for analysis of complex coatings.

In practical applications, it is often necessary to examine electronic components comprising several layers of differing alloys. The extremely difficult challenges of determining the correct composition of each individual layer from the fluorescence spectra of such coating systems are achieved by the measurement and control software. Thus a banned material under a benign top layer can be identified.

The X-ray fluorescence method, combined with the fast, easy automation process of spectrometers results in a dependable and economic verification of the conformity of components for electrical and electronic equipment for RoHS and WEEE.

Ray Scruby is managing director of Fischer Instrumentation

www.fischergb.co.uk

See also: Electronics Weekly's WEEE Directive and UK WEEE regulations, a roundup of content related to the WEEE Directive.