A downhole tool system includes a tool housing, a chassis located within the tool housing, and an electronics assembly positioned on the chassis within the tool housing. The electronics assembly includes a heat sink comprising an inner surface and an outer surface. The outer surface includes a tapered portion and in is contact with the tool housing. The electronics assembly further includes one or more electronic components mounted onto the heat sink, in which at least a portion of the electronic components is in contact with the inner surface of the heat sink.