A hybrid pin-fin micro heat pipe heat sink consists of a plurality of heat pipes secured to a base. The heat pipes have a generally hollow cross-section which transitions from a first cross-sectional shape (e.g., circular) to a second cross-sectional shape (e.g., triangular). A heat transfer medium (e.g., saturated steam) is sealed within the heat pipes. Cooling plates may be disposed over the base with the heat pipes in physical contact with and passing through the cooling plates. The method of manufacturing the heat pipes consists of passing a heat transfer medium through a pipe section having a first cross-sectional shape while transitioning to a second cross-sectional shape (e.g., by way of a rolling die press), then crimping the ends closed to seal the heat transfer medium therein.