Heat sink fastening device and thermal module assembly using same

A thermal module assembly, comprising:

• a mount being provided on two opposite outer sides with a protrusion each;
• a heat sink being mounted on the mount and including a base associated with the mount and a radiation fin assembly held on the base;
• the base being provided on two opposite lateral sides with two outward extended flat portions, each of the flat extended portions being provided on a top with a recess, and the recess having a through hole formed on a bottom thereof to extend through the flat extended portion;
• a heat sink fastening device being located on at least one side of the heat sink and including:
• an operating member being located above one of the flat extended portions and including a cylindrical cam portion and a switch portion radially outward extended from an outer surface of the cam portion;
• the cam portion having an upper end and a lower end;
• the upper end being formed into a pair of cam surfaces, each of the cam surfaces having two opposite ends respectively formed with a high-point notch and a low-point notch;
• the cam surfaces being respectively extended from the low-point notch to the high-point notch in an upward slope;
• and the lower end of the cam portion being aligned with the recess on the flat extended portion;
• a mounting ring being mounted in the cam portion and internally defining an axial bore;
• a retaining member being axially extended through the cam portion and having an upper end and a lower end;
• the upper end being provided with at least one pivot hole, and the lower end being downward extended to form a retaining portion, which is provided with at least one engaging hole for engaging with one of the protrusions formed on the mount;
• and the upper end of the retaining member being upward extended through the through hole on the flat extended portion and the axial bore of the mounting ring to the upper end of the cam portion;
• an elastic element being received in the cam portion and located between the mounting ring and the recess of the flat extended portion to fit on around the lower end of the retaining member;
• and
• a pivot shaft being located on the upper end of the cam portion and rotatably received in the at least one pivot hole formed at the upper end of the retaining member;
• and the pivot shaft having a first end portion and a second end portion being separately rested on the pair of cam surfaces;
• and
• wherein the switch portion of the operating member can be horizontally pulled from one position to another position to rotate the cam portion about an axis thereof, so that the cam surfaces are brought to rotate at the same time, causing the first end portion and the second end portion of the pivot shaft to move along the cam surfaces from the high-point notches to the low-point notches or vice versa, which in turn brings the retaining member to move downward or upward in the direction of the axis of the cam portion.