A pillar grid array package (PGA) includes a substrate, a chip disposed on top of the substrate, and a plurality of stud bumps disposed on bottom of the substrate. The stud bumps are formed in an array and each has a flattened top to electrically connect to a printed circuit board, PCB, by an anisotropic conductive paste to achieve a thin package and to avoid substrate warpage problems of a ball grid array (BGA) during high-temperature reflow processes.