X-ray fluorescence verifies RoHS compliance

EU politicians have decreed a ban or a limit on certain materials that pollute or harm the environment, generating the new EU regulations, RoHS and WEEE.

It affects lead (Pb), mercury (Hg), hexavalent chromium (Cr VI) and cadmium (Cd) as well as polybrominated biphenyls (PBB) and polybrominated diphenyl ethers (PBE).

After the EU regulations become effective in the UK on 1st July 2006, only 1000ppm of all these materials, and only 100ppm for cadmium will be allowed in virtually all products manufactured or sold in the EU.

Manufacturers of electrical and electronic equipment will find themselves particularly challenged as they will only be able to market those products and components that conform to the required minimum levels of harmful substances.

In particular, printed circuit boards, electronic components and solder connections as well as enclosures and single components made of synthetics, must be measured and tested.

To demonstrate conformity with the EU guideline, manufacturers must continually analyse the materials of these components.

Conducting this analysis using the X-ray fluorescence method has many advantages.

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

Personnel without special knowledge of analysis methods can easily identify specimens that are clear of harmful substances.

Components that are at 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.

The Fischerscope X-ray XAN and XDAL from Fischer Instrumentation (GB) 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 subassemblies and complete PCBs.

The XDAL has a programmable x-y stage so many components can be analysed unattended.

PCBs can be automatically scanned to identify any nonconforming component.

The results are displayed in tabular form with the material concentrations that exceed the permitted limits emphasised in colour (red) on the screen or in the printout.

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 X-ray fluorescence instruments.

Analysis with the Fischer instruments takes between 50 and 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 "reading" the correct concentrations and individual coating thicknesses from the fluorescence spectra of such coating systems are achieved by the complex WinFTM V.6 measurement and control software, together with the high precision measurement electronics.

So even banned material under a benign top layer can be identified.