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摘要

"Implementing Robust Bead Probe Test Processes into Standard Pb-Free Assembly" Authors: John McMahon P.Eng, Tom Blaszczyk and Peter Barber; Abstract: Increasing system integration and component densities continue to significantly reduce the opportunity to access nets using standard test points. Over time the size of test points has been drastically reduced (as small as 0.5mm in diameter), but current product design parameters have created space and access limitations that remove even the option for these test points. Many high-speed signal lines have now been restricted to innerlayers only. Where surface traces are still available for access, bead probe technology is an option that reduces test point space requirements, as well as their effects on high-speed nets, and distributes mechanical loading away from BGA footprints, enabling test access and reducing the risk of mechanical defects associated with the concentration of ICT spring forces under BGA devices.