Given that RoHS certification depends solely on the presence or absence of certain materials in a given device, it is only natural that 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. Many manufacturers may adopt one or more of these techniques as an in-line auditing solution, allowing product to be certified as it is received from suppliers rather than after it has been assembled into a final product.
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 the 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.
While RoHS certification can be an expensive and time-consuming burden, it is a worthwhile endeavor for any electronics manufacturer. Not only is it the responsible choice for a global corporate citizen, but it also opens up markets that would otherwise be off-limits due to the RoHS directive. For manufacturers wishing to make the “lead-free leap” and produce compliant products, RoHS certification – performed either internally or by a third party – is the first step in the right direction.