Figure 1. Low-resolution scanning electron micrographs of the exfoliated graphite platelets for the production of the thermal interface material.
The moderate-resolution scanning electron micrographs of the exfoliated graphite platelets are illustrated in Figure 2 for the production of the thermal interface material. It is well known that many electronic components, and especially power semiconductor components such as transistors and microprocessors, are more prone to failure or malfunction at high temperatures [57, 58]. Consequently, the ability to dissipate heat often is a limiting factor on the performance of the component. Heat dissipation may be affected by the direct mounting of the electronic component to a thermal dissipation member such as a cold plate or other heat sink or spreader. The dissipation member may be a dedicated, thermally-conductive ceramic or metal plate or finned structure, or simply the chassis or circuit board of the device [59, 60]. However, beyond the normal temperature gradients between the electronic component and the dissipation member, an appreciable temperature gradient is developed as a thermal interfacial impedance or contact resistance at the interface between the bodies [61, 62]. The thermal interface surfaces of the component and heat sink typically are irregular, either on a gross or a microscopic scale [63, 64]. When the interfaces surfaces are mated, pockets or void spaces are developed therebetween in which air may become entrapped. These pockets reduce the overall surface area contact within the interface which, in turn, reduces the heat transfer area and the overall efficiency of the heat transfer through the interface. To improve the heat transfer efficiency through the interface, a thermal interface material may be used to fill the gap between the heat sink and electronic component to fill in any surface irregularities and eliminate air pockets. The thermal interface material may be a pad or other layer of a thermally-conductive, electrically-insulating material. Even in a direct contact, however, the processor and the attach block do not transfer heat efficiently, because the quality of contact between two non-conforming solid surfaces is typically poor. A thermal interface material may therefore be inserted between the processor and the attach block in order to enhance the thermal contact between the two surfaces. Under mechanical pressure, the soft thermal interface material conforms to the microscopic surface contours of the adjacent solid surfaces and increases the microscopic area of contact between the thermal solution surface and the silicon die surface and therefore reduces the temperature drop across this contact. The quality of the contact between the processor and the attach block, or thermal interface material performance, depends on the quality of the thermal conduction through the thermal interface material and the quality of contact between the thermal interface material and the two surfaces. Consequently, a precise material tester capable of providing precise measurements of thermal interface material performance may be useful to improve overall thermal solution designs for notebooks and other devices.