BGA Ball Grid Array
Chip package with solder balls on the underside instead of pins around the edge — more contacts in less area.
Standard for CPUs, GPUs, RAM chips, NAND, modem chips. The ball grid allows hundreds (sometimes thousands) of pinouts. Downside: nearly impossible to repair without a rework station — a single bad ball means the whole chip has to come off. The PS3 "yellow light of death" and Xbox 360 "red ring of death" were both BGA faults where solder cracked after temperature cycles.