Downhole electronics assemblies including a modular carrier including a top rail and a bottom rail, the top and bottom rails each including a pair of longitudinally extending sides and the top rail providing one or more ribs that extend between the longitudinally extending sides of the top rail. A circuit board is positionable between the top and bottom rails and has a top side and a bottom side and one or more electronic components mounted on at least one of the top and bottom sides. One or more damping pads interpose the circuit board and a host downhole tool such that contact between the circuit board and the host downhole tool is prevented.