Heat sink has fins on the top surface thereof and pin portions on the
bottom surface thereof. Rivets having longitudinal through-hole are
inserted into holes in a retention module. When the heat sink and the
retention module are simultaneously pressed downward, the rivets are
inserted into the corresponding holes formed in a base board. The pin
portions are inserted into the through-holes of the rivets so that the
retention module is locked onto the base board and the heat sink is fixed
and the bottom surface of the heat sink is contacted with an integrated
circuit element, at the same time.
