Modulating Surface Chemistry of Al Powders for Elastomeric Composites with Applications in Electronic Cooling

Abstract

are generated, the intervention of thermal management via thermal interface materials (TIM) is much required in order to prolong working life and increase reliability. [2] Elastomeric composites are widely used as thermal interface materials in electronics due to their flexibly deform under an applied load and further exhibit elastic recovery. [3] Among them, silicone pads, available in solid soft matter, provide low component stress, rework simplicity, process flexibility, in-application stability, and efficient thermal conductivity. [4] Silicone pads can be prepared by preform and curing or by dispensing silicone gels that, once dispensed, hold their shape and are ideal for applications where high gap stability is required. [5] Upon cure, the silicone pads provide a soft, thermally conductive material capable of reducing air voids and gaps with the capability to withstand warpage. Therefore, mechanical and thermal properties are important indicators for assessing the performance of silicone pads. The crosslinking and entanglement of polymer chains endow elastomers with good mechanical properties, [6] but the irregular chain arrangement also introduces countless interfacial thermal resistance and hinders the heat transfer. [7] Thermal conductivity of bulk elastomers is normally lower than 0.3 W mK −1 . [8] Hence, fillers with high thermal conductivity are added to the elastomers in order to enhance the heat transfer ability while damaging the mechanical performance. In commercial silicone pads, high content (>80 wt%) of aluminum, alumina, zinc oxide, or their combinations are used to build up thermally conductive networks within the composites. In this case, the optimization of the mechanical performance of elastomeric composites is mainly dependent on silicone matrix and filler-matrix interface. The technical scope for modulation by varying the molecular structure of the silicone matrix is limited. [9] Therefore, modulating the surface chemistry of fillers to ameliorate the interface is the main strategy to solve the challenge. [10] In our previous study, [4c] we have modified Al via silane coupling agents with varied chain lengths and explored the corresponding effect on the overall performance. The results indicated the grafting of dodecyltrimethoxysilane (DTS) led to the strongest interface bonding between Al and silicone matrix. However, the deeper effect of different DTS grafting densities Elastomeric composites are an important class of thermal interface materials as they are shape-adaptive, which can fit uneven interfaces and achieve ideal interfacial heat transfer in electronic cooling. There is often a trade-off between mechanical and thermal performances in highly filled composites. Here, the surface chemistry of Al powders via introducing dodecyltrimethoxysilane (DTS) upon different grafting densities is precisely controlled. The results show that the DTS grafting density of 0.24 molecule nm −2 endows the composites with optimized mechanical properties. The tensile stress, elongation at break, a...