A heat sink assembly is provided for a pluggable module. The heat sink assembly includes a heat sink having a module side and an end surface that intersects the module side. The module side is configured to thermally communicate with the pluggable module. A holder extends from the end surface of the heat sink. A thermal interface material (TIM) layer extends on the module side of the heat sink. The TIM layer is configured to engage the pluggable module. The TIM layer includes an end that is engaged between the end surface and the holder of the heat sink.