Open package form-stable phase change microspheres with low thermal contact resistance for the thermal management of electronic devices

Thermal contact resistance (TCR) is a key factor that affects the rapid heat transfer process based on thermal interface materials (TIMs). Phase change TIMs have the property of thermally induced solid–liquid phase change, which is an advantage to improve the contact state and reduce TCR. However, the contradiction between form-stable and wettability must be solved during the application of phase change TIMs. In this work, a flexible, form-stable and low TCR phase change TIMs of graphene/acrylic polymer foamed microspheres/polyethylene glycol (G/APM/PEG) has been successfully prepared by "open package". APM is light and the surface are covered with micropores, which can be adsorbed a large amount of liquid phase PEG to prevent leakage and retain good wettability. Furthermore, the thermal properties of G/APM/PEG were systematically studied. The TCR results between "open package" method and "closed package" method were compared. The critical thickness value in all measure conditions were calculated. The thermal conductivity of G/APM/PEG filled with graphene (4 wt%) is 230% higher than that of APM/PEG. The TCR of G/APM/PEG is 0.5~0.9 K∙cm2/W at 65 °C (40 Psi), which is far lower than that of TIMs from "closed package" (3.5~5.3 K∙cm2/W). This is because the G/APM/PEG from "open package" exposes part of the surface of PEG to air, greatly improving the contact state. In addition, the maximum critical thickness is about 0.3 mm for all G/APM/PEG under different measure conditions. It confirms that the TCR is relatively small in all measure conditions and the thermal conductivity resistance is dominant.