A heat sink, provides a heat transfer pathway to remove heat from the rear face of a printhead substrate. The heat sink is located between the printhead substrate and the printer carriage. The heat sink may, in one embodiment, be biased to float substantially normal to the rear face of a printhead substrate using a biasing device, such as one or more springs, or a one or more spring clips. The springs, which are compressed, tend to urge the face of the heat sink against the back face of the printhead, forming an interface between the two faces. Additional force can be provided by a carriage arm, as its radius acts as a moment arm to assist in pressing the two faces together. A low thermal heat conductivity contact resistance and an improved thermal resistance to heat dissipation between the printhead substrate and the heat sink are provided by the high pressure interface resulting from the use of the springs and the radius of the carriage arm. An additional layer of heat conductive material can be provided at the interface of the heat sink and the printhead substrate. This can reduce the ability of air pockets to form between the heat sink and the printhead substrate. The additional layer is a fabric or thermal grease material which is effective to fill rough areas of surface on either the printhead substrate or the heat sink contact areas.