Patent ID: 7641431

Claim:
A fastening device securing a heat sink to an electronic device mounted on a printed circuit board, the printed circuit board defining a plurality of apertures, the heat sink being disposed on an upper side of the printed circuit board and defining a plurality of fixing through holes corresponding to the apertures of the printed circuit board, respectively, the fastening device comprising: a back plate disposed on a lower side of the printed circuit board, the back plate extending a plurality of nuts upwardly corresponding to the apertures of the printed circuit board and the fixing through holes of the heat sink, respectively; and a plurality of fasteners each comprising: a shaft comprising a head at one end thereof, an engaging section at an opposite end thereof, a connecting section between the head and the engaging section, and a tray extending above the engaging section and below the connecting section, the tray having a taper outer surface with a large, upper diameter and a small, lower diameter; a spring being set around the connecting section between the head and the tray of the shaft; and a gasket being set around the connecting section of the shaft, and retained between the spring and the tray of the shaft, the gasket comprising a lower, annular sidewall, the lower, annular sidewall having an internal diameter larger than the large, upper diameter of the tray and adapted for engaging in the heat sink with the engaging section extending below the heat sink; wherein when the fastening device assembles the heat sink to the printed circuit board, the engaging section of the shaft of each of the fasteners sequentially extends through a corresponding one of the fixing through holes of the heat sink and a corresponding one of the apertures of the printed circuit board and engages in a corresponding one of the nuts of the back plate.