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Comparison of HD Mobile & Traditional Handheld XRF for RoHS Applications

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SIGNIFICANCE

RoHS, the Restriction of the use of Hazardous Substances in Electrical and Electronic Equipment Directive (2011/65/EU) requires member states of the EU to adopt and publish the laws, regulations, and administrative provisions necessary to comply with the directive by January 2, 2013. RoHS prohibits electrical and electronic equipment from entering the EU market which contains an excess of the following restricted materials: lead, cadmium, mercury, hexavalent chromium, polybrominated biphenyl (PBB) and polybrominated diphenyl ether (PBDE) flame retardants. The current RoHS limits are 0.1% or 1,000 parts per million (ppm) for all substances except for Cd which has a limit of 0.01% or 100 ppm and these limits apply to all homogeneous parts and materials of the finished product.


THE ADVANTAGES OF HDXRF®

 

Small Spot

Small features and components in electronics, like on finished PCB boards, can be challenging for traditional handheld XRF to analyze.

The standard spot size on most handheld XRF analyzers is 8-12 mm. There is often a “small spot” optimization available on these analyzers which can achieve a spot size of 3 mm. However, this small spot size is achieved by collimating the X-ray source. Collimating drastically reduces the analyzer signal (counts) and thus increases limit of detection (LOD) and decreases precision and accuracy.

Traditional Handheld XRF

HD Mobile

8-12 mm standard spot

3 mm “small spot”

1 mm spot size

~85% loss in counts from standard spot size to small spot size

No loss in counts to achieve small spot

Low Limits of Detection

The DCC optics not only focus the X-ray source to a 1 mm spot size but they also filter the source to a monochromatic excitation beam, effectively removing all background signal originating from the tube source.

The images below illustrate the importance of DCC optics in achieving low limits of detection. The high background signal generated by the tube source makes it difficult to distinguish elemental signal from the background.

Note in the profile of the incident beam after being filtered by a DCC optic, the high background from the X-ray tube source is eliminated which makes even small element peaks much more prominent and easier to quantify. This low limit of detection is especially helpful for measuring Cd at and below concentrations of 100 ppm.

HD Mobile, powered by HDXRF® technology, is a handheld XRF analyzer that has a 1 mm spot size which is achieved without any loss in analytical performance by utilizing patented Doubly Curved Crystal (DCC) optics and NOT by collimation.


Inside HDXRF Doubly Curved Crystal (DCC) optics capture three narrow energy regions of a polychromatic incident beam, eliminate scattering background, and focus the incident beam to a 1 mm spot size.




HDXRF VS. TRADITIONAL HANDHELD XRF DATA COMPARISON

Experiment

A selection of metal reference materials were measured 3-5 times each with both a traditional handheld XRF analyzer and with the HD Mobile handheld analyzer powered by HDXRF®. For the traditional XRF results, small spot size feature was enabled. Analysis time for all measurements was 40 seconds.


Results

The current RoHS limits are 0.1% or 1,000 ppm for all substances except for Cd which has a limit of 0.01% or 100 ppm and these limits apply to all homogeneous parts and materials of the finished product. IEC 111/2/NP further outlines inconclusive regions to be followed when screening by XRF. If concentration of elements fall within an inconclusive region, further testing is recommended.

  • For most matrices, inconclusive region for Pb, Hg, and Cr is 700 ppm < X < 1300 ppm (lower limit shown in above chart by dashed orange line)

  • For most matrices, inconclusive region for Cd is 50 ppm < X < 150 ppm (range shown in above chart by purple dashed line)

Both copper samples have lead values well below inconclusive region and traditional XRF reported Pb at a concentration above the lower limit of this inconclusive region. Additionally Cd result for Copper 17868 was a false positive by traditional XRF and HDXRF LOD result was very close to certified value. For the zinc sample, mercury result is well below inconclusive region and the traditional XRF analyzer LOD reported a result that was well above the inconclusive region (indicative of a false positive result).


CONCLUSION

The data presented above demonstrates a clear advantage of HD Mobile powered by HDXRF technology over traditional handheld XRF especially in copper matrix. HDXRF is able to quickly and accurately quantify total elemental content at and below the RoHS regulatory limits. HDXRF is a fast, non-destructive analytical procedure that can be easily operated in a laboratory, at a warehouse, or at a customs facility.