Preliminary Experiment Study On In-situ XRF Technique Applied In RoHS Certification

RoHS restriction (the Restriction of the use of certain hazardous substances in electrical and electronic equipment) restricts that electric production and its components exported to European requirements should be limited to the six components: Pb, Hg, Cd, Cr6+, PBBs, PBDEs and other harmful substances. In recent years this restriction has been widely used in some industry area such as electric and equipment, quality detect and environment protection and so on. In various detect means, the portable XRF technique, which has been widely used in RoHS detect, environment survey and commerce detect, provides a method with fast, low cost and non-destructive character to achieve the in-situ filter, examine and control the content of nocuousness elements. This technology has a great practicality value in production as a fast analysis tool. From a practically application point of view in this paper, after investigating and analyzing the new process of RoHS restriction, we use the IED-2000P energy dispersive X-ray fluorescence instrument to analyze Br, Hg, Pb, Cr and Cd elements in mixed preparation of powder samples, pressed sample piece, and real article in normal life. The purpose is to validate the practicality and effectiveness of XRF technique in electrical equipment field based on RoHS restriction.Some restrictions by law of radioisotope in application and storage have been considered, and it is not conducive to use in common production industry, so a low power X-ray tube as a radioactive source was employed in X-ray fluorescence instrument to make practice research as well as enlarge its practicality. Both theory and practice are proved that it is effective to improve the exited efficiency of Cr characteristic X-ray by using W target, and by using Ag target can improve that of Pb,Hg,Br, but not effective to Cd element, While the Kαseries characteristic peak of Cd are submerged by Ag's Kβpeak, so to adopt Ag can achieve a useful content measure of Cd element. In this paper, the prepared powder samples, pressed sample piece, and real articles are excited by low power X-ray tube to search the best status in different measuring samples.In the condition that using low-power X-ray tube to excite sample and measure the quantity, we can obtain,after performing a lot of test, the optimum measurement geometrical arrangement of the the tube of X-ray fluorescence equipment, detector and sample as following:to keep the sample stationary, we set the angle between X-ray tube and sample asα=57°, the angle between probe and sample asβ=63.5°, the distance between tube output window and sample as a=11mm, and distance between probe window and sample center as b=12mm. The diameter of Pb-collimator is 1mm. For the element whose absorption limit is smaller than Ag target, the high excite efficiency can be get by adjusting the voltage of X-ray tube to the value that is 1.5 times larger than the absorption limit of element to be measured.In accordance with the high-risk areas existed with harmful substances, samples with different matrix have been prepared. For powder samples and their pressed sample slice, standard curve method was used to carry XRF practice and establish the standard curve of Cr, Pb, Hg, Br, Cd in different matrix material based on least-square method. Then reference standard and relative error to estimate the eligible of samples has been obtained, and the application efficiency of XRF technique in RoHS standard has been validated.Considering the large interspaces in powder sample particle and uneven surface, and in order to make a close result to the actual situation, boric acid flanger-substrate technology widely used in national has been adopted in this paper. We chose part of powder samples and use press instrument to make sample slice, by research computing to assure the saturation. Comparing the measurement result and discussing the effect of uneven effect.By using X-ray tube to excite sample and analyzing the test data, we can offer the reference for practically application about it. The average error of Cr and Br is 16.20% and 12.39%,respectively, in the Cr,Br powder sample of the polyethylene body; Hg and Br is 20.54% and 17.47%, respectively, in the Hg,Br powder sample of the polyethylene body; Cr and Hg is 8.77% and 36.09%, respectively, in the Cr,Hg powder sample of the silicon dioxide body; Pb and Br is 37.74% and 37.61%, respectively, in the Pb,Br powder sample of the stannum body; Br is 5.33% and Cd can't be get in the Br,Cd powder sample of the calcium carbonate body; Cr and Pb is15.27% and 27.51% ,respectively, in the Cr,Pb powder sample of the copper body; Pb and Br is 9.15% and 10.53%, respectively, in the Pb,Br slice sample of the stannum body; Hg and Br is 12.61% and 7.08%, respectively, in the Hg,Br slice sample of the polyethylene body; Br is 4.28% in the Br,Cd slice sample of the calcium carbonate body.In this paper, more representative of the electrical and electronic products or components in normal life are selected for physical measurement, and for the goal may contain elements to adjust measurement conditions to obtain measure spectrum of different physical samples. After analyzing of the spectrum, the peak of goal elements should be determined, and relative content analyze can be taken based on the similar matrix matter sample plate recognized as the standard to determine whether the toxic matter over standard or not. For the surface of some physical matter is uneven and the standard selected is not norm, so we can not guarantee that the result is reliable, but it is a good practice to explore the practical application.In addition, the asymmetry of samples can deeply effect the result especially in the tube measure, because of the particularity of tube exciting device, large influence to count was brought by asymmetry samples. So, one should purchase some other countries standards to decrease the error caused by these reasons. The excited source of X-ray tube sends seriate spectrum which can effect the analysis of energy dispersive X-ray fluorescence, so filter or the second target was adopted to improve the peak-to-background ratio and accuracy.Finally, the conclusion based on the whole graduate research practice issues and cooperation analysis of experiment result was obtained, and that is, it is feasible and reliable to carry the work of filter detect based on RoHS restriction by using portable X-ray fluorescence analysis instrument, and it has the characteristic of portable and rapid.