X-Ray Fluorescence (XRF) is probably the best screening method available for green compliance. XRF is fast and accurate. It provides analytical results to identify and quantify elements present in a sample. The method easily identifies the 5 banned elements, Cd, Cr VI, Hg, Pb, and Br (in PBB and PBDE). Innov-X Systems makes XRF even easier to use by adding portability and intelligent software.
The Innov-X portable XRF analyzer is about the size and shape of a large cordless drill. The base of the handle is broad and flat, serving as a well-balanced stand for the unit. It has a rugged, blue plastic housing with a metal snout covering the working end of the miniature X-Ray tube and PIN diode detector. On top, an HP iPaq computer plugs into the unit for control and results. The entire analyzer weighs 4.5 pounds and is very easy to handle due to the excellent balance. It has a battery life of 4-8 hours depending on usage.
Analysis speed can be very quick. You can get results in as little as 10 seconds. The quality of those results depends on the sample content. With short exposure times, the lighter elements have much higher uncertainty levels. Common and heavy metals show up clearly and accurately with short scans. However, the best way to increase accuracy is to increase scan time. The longer you hold the trigger in, the better the results. 30-second scans produce quite good results for most of the middle to heavy elements. A 1-minute scan does a good job on almost all ordinary samples. For the absolute best results, a 3-minute scan is needed. Going beyond 3 minutes is of little or no value. For qualitative detection, sub-minute scans are probably adequate. For quantitative analysis, stick with longer scans.
As I said earlier, XRF is perfect for compliance screening. The procedure is simple. Take a reading of the sample with the XRF unit. If banned materials are not detected, then the sample is free of them. The parts can be cleared as compliant. If banned materials are detected, then you begin your non-compliance process. This could include contacting the supplier to determine the problem, sampling stock and possibly purging it, sending the part out for detailed chemical analysis, and halting production.
Using the Innov-X analyzer is quite easy. At startup, the system requires an initial calibration cycle of 45 seconds with a calibration strip clipped onto the working end. After that, the analyzer is ready to go. With a few taps on the iPaq, you choose the analysis method, then point and shoot. Indicator lights on the top and back end of the unit tell you when it is ready and when it is actively emitting X-Rays. For large samples, you just press the end of the unit against the item and pull the trigger. For smaller samples, clear plastic tape is a great way to hold the sample in place over the analyzer window.
I particularly enjoyed using the Innov-X analyzer to look for Pb and other metals in plastic parts. PVC is especially troubling. I have encountered wiring manufacturers claiming that their wires and cables are RoHS compliant, though they still use PVC insulation. The Innov-X revealed 4% Pb in the PVC insulation of several wire samples. This is right in the middle of the 2% to 6% range for Pb stabilizers that were once used in almost all PVC. Clearly, you have reason to be concerned about PVC in your purchased parts. XRF is the quickest and most cost-effective way to scan for such hidden risks.
I really liked using the Innov-X portable XRF analyzer. It is a simple, powerful and very useful tool. The analysis software identifies elements automatically, and gives you the option of examining the raw spectral curves to check it. After you see a few K and L orbital peak pairs, you will quickly get the hang of qualifying the results from an unknown sample.
For RoHS screening, Innov-X recommends a combination of the Soils and Alloy modules. If you plan to use XRF at Incoming Inspection, you will probably want to get the optional desktop stand, which makes screening very convenient and more efficient. The X-Ray tube has a 2-year warranty and an expected life of 3 to 4 years under normal usage. Tube replacement cost is about $2.5K. The average cost of an analyzer is about $32K, and leasing plans are also offered.
Note 1 - 2005-06-25 - After I first published this article I learned that the above statement is true, but is not the entire story. Radio-isotopes do indeed require considerable paperwork upon purchase and when transported. X-Ray tubes enjoy greater freedom with varying restrictions. Two states regulate all X-Ray sources, including portable XRF units using miniature X-Ray tubes. Colorado requires registration and inspection of the unit when purchased and annually thereafter. In between inspections, there are no restrictions on travel. As with most regulations, things change over time. Be sure to quiz all sales reps on the regulatory requirements for your locale before purchase. Back to article