Archive for June, 2009

Sample Preparation for ROHS/WEEE Directive Analysis

Tuesday, June 9th, 2009

ROHS/WEEE directives require that product components of electrical equipment imported into a number of countries, notably the European Common Market, contain less than 1000ppm of Bromine, Br, Chromium, Cr, Lead, Pb, Mercury, Hg, and less than 100ppm of Cadmium, Cd. Direct-reader, hand-held X-Ray Fluorescence, XRF, instruments have become the choice for quick, efficient screening of products for these elements.

For these analyses the handheld XRF instrument is simply pressed against the surface of the product. The XRF technique only “sees” the very thin, top layer of the sample. Further, the XRF technique is very dependent on calibration with a matrix matched reference material prior to the analysis.

The purpose of this study is to determine if this method is applicable for the directive. This study examines the accuracy and reproducibility of XRF analysis of various electrical components both as received (heterogeneous) and when ground and blended (homogeneous).

For one investigation three circular samples were cut from populated circuit boards and the front and back sides of the samples were analyzed by XRF. The samples were then cut into small pieces and copper parts were removed followed by cryogenic grinding and pressing at 30 tons onto boric acid substrates prior to XRF analysis. The results are shown below, reported as parts per million:

Chromium

Sample Front Back Pellet
1 0 0 32
2 0 0 1166
3 0 0 0

Bromine

Sample Front Back Pellet
1 7726 8323 7287
2 8853 8853 5504
3 8305 8305 10626

Lead

Sample Front Back Pellet
1 305 128 1903
2 181 485 1654
3 261 525 308

As can be readily seen the analytical results of the heterogeneous and homogeneous samples are very different.

  1. In samples 1 and 2 chromium was not detected prior to grinding but found after grinding. Cr levels in sample 2 were very high.
  2. Lead levels were significantly higher in ground samples 1 and 2.
  3. Bromine exceeded the RHOS/WEEE limits in all cases.
  4. Cadmium and mercury were not detected in any of the samples.

A more complete discussion and results from the analysis of additional types of samples, such as connectors and electrical components, can be found in the applications section of the SPEX SamplePrep website: www.spexcsp.com