SMT - From the Editor

We're almost at the point where we can celebrate the one-year anniversary of the EU's RoHS Directive going into effect globally. Looking back, it's been a fairly quiet year for lead-free manufacturing, despite overwhelming concerns regarding reliability, compatibility, feasibility, and policing. The calm may be due to the fact that there have been no major documented incidents of companies failing to comply. Lack of stern policing by EU member states has been widely noted. Regardless of being deemed the "Y2K" of the electronics assembly industry, no company has let on to any major issues on the line or through customs.

But don't break out the bubbly just yet — there still are several things that must be resolved for a smooth continuance of the lead-free movement. One area of concern for OEMs and EMS providers, component manufacturers, and distributors is part numbering and tracking. The International Electronics Manufacturing Initiative (iNEMI) noted that its members are breaking it down beyond simply parts numbering, and are calling for the use of unique part numbers for BGA components to distinguish lead-free ball metallurgies other than SAC 305 or SAC 405. This includes low silver, added dopants, and other SAC or non-SAC compositions. iNEMI claims that suppliers are away migrating from conventional SAC 305/405 ball metallurgies — reducing silver content down to 0.3% and adding other metals, such as nickel — to boost product life during mechanical shock, such as drop tests of cell phones and other portable devices.

Metallurgical changes, however, can be further cause for concern. "While variations in alloy metallurgy may improve mechanical shock performance, they can also impact the manufacturing process in a number of ways. Since these changes can affect form, fit, and function of the device, they should be documented by the issuance of a part change notice (PCN) and should be associated with a change in manufacturing part number (MPN)," notes an iNEMI statement. These changes will allow companies to control and optimize the manufacturing process prior to assembly, ensuring repeatable and reliable BGA attachments and minimizing ship holds due to unknown parts.

Jim McElroy, CEO of iNEMI, explains that metallurgical changes with solder balls are inevitable. And these changes will, in turn, create a ripple effect regarding modified reflow profiles and adjustments to the assembly process. It is also believed that low-silver compositions could affect a device's moisture-sensitivity level (MSL) rating. These variations in assembly characteristics and performance among different ball metallurgies necessitate accurate part numbering. But how will additional part numbering changes affect manufactures who have already developed numbering systems in their facilities? Part numbering/tracking may get worse before it gets better. "It's a natural progression," says McElroy. "Lead-free is out there now and people are getting some experience with it, and they're finding some things they don't like. It seems that the alloy list is growing, rather than converging." Presumably, at some point, however, this will converge with fewer choices as companies settle on one favored composition, he adds. Luckily, any detailed inventory tracking system can handle additional numbering requirements, but not without cost. Smaller manufacturers with smaller staff, as well as larger manufacturers with a robust, varied parts inventory, may view this creation of new part numbers as additional work and cost. But when it comes down to overall device reliability, full knowledge of metallurgical properties could save money down the road.

iNEMI members supporting this position include 3M, Agilent Technologies, Alcatel-Lucent, Analogic, Celestica Inc., Delphi Electronics & Safety, Hewlett-Packard (HP), Huawei Technologies Co. Ltd., Intel Corporation, Jabil Circuit Inc., Microsoft Corp., Micro Systems Engineering Inc., Plexus Corp., Sanmina-SCI Corporation, Solectron Corporation, and Tyco Electronics Corporation. The initiative is looking at possibly pulling a project together that will compare different metallurgies with the hopes of getting the list to converge instead of diverge. If that occurs, McElroy noted, iNEMI would bring in other interested parties, including solder suppliers and packaging houses.

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