BGA package details

Hi,I am planning to use the NET+50 in the BGA package. I’m concerned about the long term reliability because of different material expansion temperature coefficients of the pcb and the BGA package. * Can I use FR4 for the pcb? * Where can I get information about the BGA package (materials, die size, …)? * Are there any recommendations from NetSilicon regarding the implementation of the BGA package in the design (footprint, pcb material, soldering details, underfilling, …)? Regards Tommy