>>20 lbs of lead would still result in a significant cost savings<br /><br />Amusingly enough, lead is an alpha emitter. Modern chip packaging is moving to no-lead solder, for this reason. There is often a design rule requiring that there not be a package ball under an on-chip RAM.<br /><br />By the way, 'soft errors' from radiation events is a big issue for memory chip design, and has become an issue for logic design since we went below 0.13u. There is a metric called 'critical charge', defining the magnitude of charge that will flip the state of a flipflop or RAM cell. It's in the range of 2-10fC these days. RAM arrays within chips are 'wrapped' in error-detection-correction (ECC) logic as a rule. System memory, such as a DRAM system, may have several levels of this. Electronic design would be easier if it weren't for radiation, even at the level of terrestrial consumer electronics.