Noncuring Graphene Thermal Interface Materials for Advanced Electronics

Abstract

development of next generation of compact and flexible electronics. [1] The increase in computer usage and ever-growing dependence on cloud systems require better methods for dissipating heat away from electronic components. The important ingredients of thermal management are the thermal interface materials (TIMs). Various TIMs interface two uneven solid surfaces where air would be a poor conductor of heat, and aid in heat transfer from one medium into another. Two important classes of TIMs include curing and noncuring composites. Both of them consist of a base, i.e., matrix materials, and thermally conducting fillers. Commonly, the studies of new fillers for the use in TIMs start with the curing epoxybased composites owing to the relative ease of preparation and possibility of comparison with a wide range of other epoxy composites. Recent work on TIMs with carbon fillers have focused on curing composites, which dry to solid. [2][3][4][5][6][7] Curing TIMs are required for many applications, e.g. attachment of microwave devices, but do not cover all thermal management needs. Thermal management of computers requires specifically noncuring TIMs, which are commonly referred to as thermal pastes or thermal greases. They are soft pliable materials, which unlike cured epoxy-based composites, or phase change materials, remain soft once applied. This aids in avoiding crack formations in the bond line due to repeated thermal cycling of two connected materials with different temperature expansion coefficients. Noncuring TIMs also allow for easy reapplication, known as a TIM's reworkability property. Noncuring TIMs are typically cost efficient-an essential requirement for commercial applications. Various applications in electronics, noncuring grease-like (soft) TIMs are preferred. Examples of the applications include but are not limited to cooling of servers in large data centers [8] and personal devices which are the primary targets for these applications. Current commercially available TIMs perform in thermal conductivity range of 0.5-5 Wm −1 K −1 with combination of several fillers at high loading fractions. [9] State-of-the-art and next-generation electronic devices require thermal pastes with bulk thermal conductivity in the range of 20-25 Wm −1 K −1 . [10,11] This study focuses specifically on noncuring TIMs with graphene and few-layer graphene (FLG) fillers.Curing and noncuring TIMs consists of two main components-a polymer or oil material as its base and fillers, Development of next-generation thermal interface materials (TIMs) with high thermal conductivity is important for thermal management and packaging of electronic devices. The synthesis and thermal conductivity measurements of noncuring thermal paste, i.e., grease, based on mineral oil with a mixture of graphene and few-layer graphene flakes as the fillers, is reported. The graphene thermal paste exhibits a distinctive thermal percolation threshold with the thermal conductivity revealing a sublinear dependence on the filler loading. This behavior contrasts wi...

Noncured Graphene Thermal Interface Materials for High-Power Electronics: Minimizing the Thermal Contact Resistance

“…It was also established that few-layer graphene (FLG) maintains high thermal conductivity, similar to bulk graphite owing to its smooth surface and, as a result, insignificant reduction in thermal conductivity due to the phonon—boundary scattering [ 27 , 28 , 29 , 30 ]. A mixture of single-layer graphene and FLG demonstrated the largest enhancement in the thermal conductivity of the TIM composites [ 19 , 20 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 ]. In the context of thermal research and TIMs, we will refer to the processed mixture of graphene and FLG flakes with lateral dimensions in several μm range as graphene fillers .…”

Multifunctional Graphene Composites for Electromagnetic Shielding and Thermal Management at Elevated Temperatures

“…[ 2,3,20,21,24 ] TIMs are applied between two solid surfaces in order to fill the microscopic voids at the interface, and enhance the thermal transport from a heat source to a heat sink. [ 25–27 ] The base materials for TIMs are amorphous polymers, which have low thermal conductivity, typically in the range from 0.2 to 0.5 Wm −1 K −1 . [ 28 ] For this reason, the polymers used as base materials for TIMs are filled with highly thermally conductive fillers to enhance their overall thermal conductivity.…”

A Multiscale Investigation on the Thermal Transport in Polydimethylsiloxane Nanocomposites: Graphene vs. Borophene

“…Graphene exhibits outstanding physical properties, including ultra-high thermal, mechanical and electronic carrier mobility. The high-quality properties of graphene, along with its outstanding flexibility, have made this nanomaterial a highly promising candidate for employment in thermal management systems [ 3 ]. Graphene continues to attract large interest among researchers [ 4 ] due to its electronic structure, which reflects outstanding thermal properties and has a calculated thermal conductivity up to 10 KW m −1 K −1 [ 5 ].…”