In an attempt to minimize the ecological impact of the increasing amounts of “e-waste” generated as electronic devices reach the end of their lifespan, the European Union passed the Restriction on Harmful Substances (RoHS) directive. This directive is an edict prohibiting the use of a handful of different materials in any electronic devices manufactured after a certain date (with some exceptions allowed for some applications like medical devices). As a manufacturer, ensuring that your supply chain is RoHS compliant is vital; not only would accidental inclusion of non-RoHS parts bring the final product out of compliance, but may have adverse reliability effects as well.
The primary tools for RoHS auditing are chemical analysis methods. Some of the restricted materials – lead, mercury, cadmium, and chromium – are elemental in nature, and can easily be identified with elemental analysis tools like energy dispersive spectroscopy (EDS) or x-ray fluorescence (XRF). Depending on the size and shape of the device to be analyzed, this analysis can even be performed in-situ, with no destructive sample preparation necessary.
The other substances restricted by RoHS are molecular in nature, and require more sophisticated techniques for identification. Polybrominated biphenyls and polybrominated diphenyl ethers (PBBs and PBDEs, respectively) are both proscribed from use by the RoHS directive due to their relatively severe ecological and medical impact; however, they cannot be reliably identified with elemental analysis techniques, since there are relatively innocuous compounds containing bromine that are not banned from use. Instead, a technique that analyzes the molecule as a whole, like Fourier transform infrared spectroscopy (FTIR) must be used, often requiring destructive preparation of the sample.
Energy Dispersive Spectrograph of a lead-free solder. The EDS can detect constituent elements of a material down to 0.1%.
Active or passive components, printed circuit boards or printed circuit assemblies, are all candidates for RoHS auditing. Even simple electronics building blocks like connectors, thermoplastics, or other raw materials should be checked to ensure compliance to RoHS restrictions.
- Screening samples purchased from a third-party vendor
- Certifying new assemblies