Intel is planning to transition its processor to 100 percent lead free with the launching of the 45 nanometer technology series of processors (ex: Penryn processor) most probably by end of this year. The whole process is not simple as it involve huge cost and effort to revalidate the new process technology and it took this Giant chip maker almost six years to get rid of lead element in silicon fabrication.
Besides the huge cost that involved to redesign and revalidate the material as well as characteristics change, the more challenging parts come in when the process technology need to be revised to cater for higher melting point of lead free (alloy that mixes copper, silver, and tin) processor as compared to normal lead/tin processor manufacturing. And sometimes it becomes more complicated when not all components on the boards are lead free. Just imagine that some normal lead components need to survive higher reflow temperatures and yet have to maintain similar reliability standard.
Nevertheless, it does have benefits with the implementation of lead free element besides its environmental friendly. As most of you aware, copper which replaces lead is a better conductive material with lower impedance that will aid in design and proper system functionality. The earliest we can have a full lead free motherboard will be in 2008 once the chipset is ready for transition. This is a continuous effort and hopefully it has set a good example for other manufacturers to follow towards green environment.