Intel announced that they now produce lead-free flip chip solder joints in their 45 nm technology. You will recall that flip chip solder joints are exempt from RoHS for lead (Annex 7. — Lead in high melting temperature type solders (i.e. tin-lead solder alloys containing more than 85 % lead)). Successes like this will lead to these types of exemptions being rescinded in a few years, I think. A photo of the standard leaded flip chip joint versus the new no lead joint is shown above. Note the copper bump and SAC alloy structure in the new lead-free soldr joint.
I wouldn't be surprised if these new lead free flip chip joints have some performance advantages over the old tin-lead joints as well. Remember that the old flip chip solder joints are about 90% lead and 10% tin (90/10). The copper in the bump, which is a much better conductor of heat (about 5 times that of 90/10) and electricity (about 10 times that of 90/10) and SAC solder (about 50% better than 90/10 in both conductivities) result in a much better thermal and electrical conductive joint. Given the tremendous heat dissipation requirements for Intel microprocessors, the better thermal conductivity is likely a real benefit. I wouldn't even be surprised if the increased electrical conductivity has a measurable positive effect.
Congratulations to Intel and good news to our industry.