In one embodiment, an infrared (IR) sensor module includes an IR sensor assembly, including a substrate, a microbolometer array disposed on an upper surface of the substrate; and a cap disposed on the upper surface of the substrate and hermetically enclosing the microbolometer array. A base is disposed below the substrate, and a heat spreader having a generally planar portion is interposed between a lower surface of the substrate and an upper surface of the base. In some embodiments, the heat spreader can include a material having an anisotropic thermal conductivity, e.g., graphite.