"Now that the flip-chip bump solder points that used to contain lead have been replaced with a copper column and lead-free solder the processors are more environmentally friendly, but this does come at a cost. The melting point of lead-tin is 183C, whereas the melting point of lead-free solders is greater than 220C. This means increased stress on the flip-chip package and more power consumption since the convection ovens need their baking temperatures increased. To manage the increased stress and survive the higher process temperatures, Intel reengineered many parts of the processor..."
Article Title: Intel Beats AMD to Lead-Free Processors
Article URL: http://legitreviews.com/article/582/1/