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Pb-Free Printed BoardThere are potentially some very serious issues involving printed boards and Pb-free. A brief overview presentation can be found here. The major focus points in regard to board robustness have been:
It is important to note that the risk of these issues influencing the product reliability is highly dependent upon the size of the board and the components. Companies reporting the fewest issues with the transition to Pb-free have been with those products that have small components and relatively thin printed boards (i.e., mobile products). Those companies reporting the biggest issues with printed boards and Pb-free have been those with large components (BGAs with more than 600 I/O) and very large printed boards (thickness > 93 mil; size > 12 x 18). Designs with smaller boards/smaller components are able to successfully reflow Pb-free solder at temperatures around 232 to 235°C. Designs with larger boards/larger components can easily see 250 to 260°C during Pb-free reflow. Because of these high temperatures and other material constraints (such as the need for high speed performance), some OEMs and EMS providers are seriously considering a return to vapor phase reflow soldering. While this is not the forum to discuss the merits and problems with vapor phase reflow, it does minimize the variability in temperatures seen across the product during assembly, potential resulting in a 15 to 25°C drop in maximum temperatures. |