The UKs compliance arm has purchased x-ray fluorescence (XRF) equipment to help scan electronic products for RoHS compliance. The move brought jitters to RoHS experts who insist that XRF equipment is inaccurate in determining whether products contain RoHS-banned substances. They say the device even if used properly can give false readings. As an example, XRF equipment will detect lead in the ceramic in capacitors even though lead in that use is exempt. Other RoHS experts, however, claim XRF devices are an appropriate first step in determining RoHS compliance, since the device can quickly give a product a clean bill of health.
While XRF may not be the last word in determining whether electronic products or components contain banned substances, the tool may be a good beginning in compliance monitoring. The European Union (EU) enforcement authorities recognized that XRF is not the last word in accuracy in the May 2006 Enforcement Guideline, says Mark Myles, services director at the Goodbye Chain Group, a Colorado Springs, Colo. firm that helps OEM clients with environmental compliance. The EU authorities recommend that XRF be used as an initial screening device that may be used to indicate the need for further and more high-resolution tests.
Myles notes that the EU enforcement guideline spells out that the XRF is not the final word on compliance. The guideline emphasizes that the limitations for XRF be taken into account, making explicit the fact that XRF cannot distinguish between exempt and non-exempt applications for RoHS substances, or for different types of brominated plastics or different ionic species of chromium, says Myles. The guideline recognizes that detecting banned substances can be very costly and involved to the point of impracticality in an electronic product, which is very complex from a materials standpoint.
The EU will likely pursue a testing process that will have multiple steps. The first using inexpensive, handheld XRF equipment will simply give inspectors some indication as to whether further tests might be necessary. With a brief under a minute test, the XRF device can determine whether a product clearly passes or fails for banned substances, says Myles. This makes it possible to reserve costly and time-consuming laboratory analytics for samples that have produced a borderline XRF result.
Myles points out that any single measurement tool has limitations, but the XRF tool, used as a first-step screening device, is an appropriate measure to take in order to identify questionable products that need more testing while giving an ok to products that are clearly in compliance. Any type of measurement tool has inherent limitations related to resolution, precision and accuracy. XRF is no exception, says Myles. Like other measuring instruments, XRF must be correctly used by trained personnel to give meaningful results. But thus employed, XRF is a valuable compliance assurance tool.