The ornamental design for a thermally-efficient heat sink for electronic devices, substantially as shown.
FIG. 1 is a perspective view of a thermally-efficient heat sink for
electronic devices showing my new design;
FIG. 2 is a front elevational view of the same heat sink, the rear
elevational view being the same;
FIG. 3 is a side elevational view thereof, looking toward the right side of
the heat sink as it is shown in FIG. 1, the side elevational view thereof
looking toward the left side of the heat sink as it is shown in FIG. 1
being the same;