The Free On-line Dictionary of Computing (30 December 2018):

Pin Grid Array

    (PGA) A style of integrated circuit socket or
   pin-out with pins laid out on a square or rectangular grid
   with a separation of 0.1 inch in each direction.  The pins
   near the centre of the array are often missing.

   PGA is often used on motherboards for processors, e.g.
   Socket 6 and Socket 8.

   PPGA is "plastic PGA" (as opposed to ceramic?).

   See also SPGA.

   (2000-03-09)