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Testing for compliance heats up
Rob Spiegel -- Design News, March 8, 2006
Not all component suppliers are equally trustworthy, so electronic product manufacturers – and at least one distributor – have taken to testing components to make sure they comply with RoHS. Now companies are discovering that not all testing methods are equal.
Chicago-based distributor, Newark InOne, decided to spot test components it received from suppliers. The company used X-Ray Fluorescence Spectrometry (XRF) technology, a quick and easy testing method. Some XRF testing systems come with a gun that’s similar to a barcode scanner. You point it as the sample, and presto, results.
But those results are not always accurate. “Some companies have a gun and they point it at the component and it will say that bromide is present, so they’re rejecting the component,” says Jeff Shafer, SVP of product at Newark InOne. “But the test cannot identify whether it’s a banned substance.” Some bromides are fine, others are banned by RoHS.
When suppliers began to balk at Newark InOne’s test results, the company turned to a different form of testing, one in which the component is actually broken down. Using the more rigorous test produced results that matched the suppliers’ claims. The process of finding the right testing method wasn’t painless. “We spent thousands of dollars to find out what testing worked,” said Shafer.
In addition to XRF testing, there are a number of what is called “wet” testing, which involves dissolving the component and measuring its contents. One popular choice is Inductively Coupled Plasma – Atomic Emission Spectrometry (ICP-AES), but there are plenty more. These tests take long and are more expensive than the quick XRF testing.
One of the problems with the gun-based XRF testing (which is also called non-destructive because it leaves the component intact) is that it only penetrates the component a few centimeters. If you have a chip that is coated in ceramic, it won’t see through the coating and detect lead. Non-destructive XRF testing works well for scanning surface coatings and solder joints. To get an accurate scan of a hefty component, the part being tested has to be destroyed. Many claim the XRF process works just fine when it scans a ground up component.
Underwriters Laboratories in Northbrook, Ill has developed a series of tests for RoHS compliance. “We developed a test program, not a single test,” says Scott MacLeod, principle chemist at Underwriters Laboratories. “Recently we’ve begun to offer XRF. We also offer traditional destructive elemental analytics for heavy metals, Inductively Coupled Plasma Spectrometry, ICP-AES or OES, and we also use atomic absorption (AA).”
MacLeod notes that some of the controversy over testing methods comes not from problems with the testing instruments but rather problems with preparing samples. “Usually people associate the test with an instrument and the instrument is only part of the test,” said MacLeod. “Any analytical test consists of two parts, the measurement by the instrument and the preparation of the sample, which involves a lot of human touch.” He notes you can have a “$10 million instrument but if you don’t prepare the sample properly, the results are useless.”
A common problem with poorly prepared samples comes from interferences. “If your sample has three different things in it and you’re looking to measure one of them, some instruments are influenced by the other two, which makes measurement difficult,” says MacLeod. He notes that destroying the component before testing often helps to overcome this problem.
