PGA (Pin Grid Array):
PGA packaging has been the most common chip package used until recently. It was used starting with 286 processor in 1980s and is still used today for Pentium processors. PGA chip are inserted into sockets, which are often of a ZIF (zero insertion force) design. A ZIF sockets has a lever to allow for easy installation and removal of the chip. Most Pentium processors use a variation on the regular PGA called staggered pin grid array (SPGA), in which the pins are staggered on the underside of the chip rather than is standard rows and columns. This was done to move the pins closer together and decrease the overall size of the chip when a large number of pins are required
