A semiconductor device assembly can include a first die package comprising a bottom side; a top side; and lateral sides extending between the top and bottom sides. The assembly can include an encapsulant material encapsulating the first die package. In some embodiments, the assembly includes a cooling cavity in the encapsulant material. The cooling cavity can have a first opening; a second opening; and an elongate channel extending from the first opening to the second opening. In some embodiments, the elongate channel surrounds at least two of the lateral sides of the first die package. In some embodiments, the elongate channel is configured to accommodate a cooling fluid.