Circuits Assembly - January 2008 - (Page 43)

escaping (and rescuers from entering) burning areas. In a computer room, a fire in one machine can release acidic fumes that produce catastrophic failures in nearby machines. These combustion-related implications sound horrible, and I’m sure there are plenty of other sound reasons to eliminate halogenated materials. Often, however, it’s the halogenated compounds that permit higher temperature operation and prevent fires in the first place, and elimination or substitution is not a simple process. Just like leaded solder alloys, there are no drop-in replacements for many halogenated products. How do we define halogen-free and halide-free? Both halogens and halides can be found in trace amounts as impurities in many materials. Therefore, upper limits for the presence of these materials have been set by the following organizations: The International Electrochemical Commission defines halogen-free as: • <900 ppm chlorine. • <900 ppm bromine. • <1500 ppm total halogens. IPC defines halide-free as: • <500 ppm of a flux’s solids content, as chloride (fluoride and bromide are adjusted for molecular weight difference and calculated as chloride). How do we test for halogens and halides? Halides can be detected using simple spot tests as described in J-STD004A. They can be quantified using ion chromatography (IC). But halogens themselves are a little more difficult to test for. IC cannot distinguish them unless they are first ionized; the test preparation procedure itself can influence the results. Combustion IC is generally considered a reliable technique that ionizes the halogenated compounds through a combustion process. Another routine analytical technique that can detect halogens (and many other elements) down to the parts-per-billion level is inductively coupled plasma (ICP) spectroscopy. However, neither of these techniques can distinguish between an ionic halide and a non-ionic halogen. To sum up: A halogen is a chemical element found in many electronics components and is the focus of systematic regulatory elimination. In many cases, there are no simple drop-in replacements for halogenated materials. A halide is an ionic compound that contains a halogen and is often used electively in fluxes to improve soldering performance. Halides may also be subject to elimination in the foreseeable future; by definition they are a type of halogen. The use of halides in fluxes is optional, but some difficult solderability situations demand them. And as for halite, well, depending on where you live, that could be a necessity also. I live in New Jersey and right now we’re expecting a snowstorm, so my next task is to check for the presence of halite in my garage. ■ Au. note: I had a lot of help gathering and making sense of all this information. Many thanks to my associates Mitch Holtzer, Mike Murphy, Sanju Arora and Mike Liberatore for their inputs and their patience as I compiled it. Pb-Free Lessons Learned Get your daily dose of PCB industry news and views. Subscribe to PCB UPdate The daily e-mail newsletter ﬁlled with news and resources for PCB design, fab and assembly professionals. Edited by Ronda Faries, former editor of Printed Circuit Design magazine, PCB UPdate does the work for you—ﬁnding and organizing the latest news and articles from Printed Circuit Design & Fab, Circuits Assembly and the World Wide Web into an easy-to-read, one-page e-newsletter Experience the convenience of e-mail news delivery, combined with trusted brands and industry expertise. Subscribe now at www.pcbupdate.com. circuitsassembly.com Circuits Assembly JANUARY 2008 43 http://www.pcbupdate.com http://circuitsassembly.com

Table of Contents Feed for the Digital Edition of Circuits Assembly - January 2008

Circuits Assembly - January 2008 Contents Caveat Lector Industry News Market Watch Talking Heads Focus on Business On the Forefront Screen Printing Better Manufacturing Walking on Water Flux Selection for Lead-Free Wave Soldering An A-to-Z Guide to X-Ray Inspection, Part II Evolution in Action Research Priorities for the Electronics Industry Selective Soldering Process Doctor Pb-Free Lessons Learned Materials World Product Spotlight Ad Index Assembly Insider Technical Abstracts

Circuits Assembly - January 2008

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.