An electronic device with improved heat dissipation properties comprises metallic housing. A base circuit board may be positioned within the housing in a plane parallel to the backside. Multiple connectors for coupling cassettes to the base circuit board may be positioned about the periphery of the base circuit board such that multiple cassettes may be positioned adjacent to each side of the housing. Each cassette includes a printed circuit board with a plurality of heat generating components coupled to the printed circuit board and having a thickness extending towards the side of the housing. The cassette includes a metallic housing with a heat dissipation structure contacting: i) the side of the housing; and ii) each heat generating component. Each of at least two heat generating components have different thicknesses and the heat dissipation structure had different thicknesses between the side of the housing and each heat generating component.