Copper Nanowire‐Filled Soft Elastomer Composites for Applications as Thermal Interface Materials

Abstract

Efficient heat dissipation is a critical requirement for sustained performance and failure prevention of microelectronic components. Thermal interface materials are used to fill the voids at the solid interface between the device and the heat sink to create a thermally conducting pathway for heat dissipation. This work reports flexible elastomer composite embedded copper nanowires with high aspect ratios (2500–5000), leading to a thermal percolation network at very low volume filler loading fractions of ≈0.009Φ. In order to achieve a high thermal conductivity at ultralow filler fractions, the copper nanowires are freeze‐casted into a monolithic sponge, to create an interconnected network. The composites formed by subsequently embedding the nanowire sponge in elastomer matrix exhibit a thermal conductivity of 3.1 ± 0.2 W mK−1, a 19‐fold enhancement over the pristine matrix, in a temperature range between 20 and 80 °C. The effect of thermal contact resistance at nanowire junctions is substantially reduced by in situ microwave welding of the nanowires. The use of Ecoflex, an ultrasoft silicone elastomer as the matrix, along with very low filler loadings of copper nanowire networks, keeps the elastic modulus <250 kPa, retaining the high compliance of the composites.

Thermal Transport in 3D Nanostructures

“…), EcoFlex (EF, 10, ref. ), epoxy‐terminated dimethylsiloxane (ETDS, 11, ref. ), polyether ether ketone (PEEK, 12, ref …”

“…The heat transfer can be further enhanced by reducing the filler/filler resistance. For instance, through microwave radiation treatment, the thermal conductivity of the EcoFlex (a platinum‐catalyzed addition‐type silicone elastomer) composite with 1.8 vol% Cu NWs can be significantly improved from 0.78 to 3.1 W m −1 K −1 . It is worthy to mention that besides NWs, other metallic multiscale fillers have also been used to enhance the thermal transport in polymer composites.…”

3D Thermally Cross‐Linked Graphene Aerogel–Enhanced Silicone Rubber Elastomer as Thermal Interface Material

“…and fillers with high thermal conductivity (TC) . Traditional fillers include inorganic powders (AlN, BN, Al 2 O 3 , SiC, ZnO), metal particles (Al, Cu, Ag), and carbon materials (graphite, expanded graphite, etc.) .…”

Enhanced Thermal Conductivity and Balanced Mechanical Performance of PP/BN Composites with 1 vol% Finely Dispersed MWCNTs Assisted by OBC

“…However, the thermal conductivities of most polymers are too low to fulfill industrial requirements in electric or electronic systems (1–30 W m −1 K −1 ) . The introduction of highly thermally conductive fillers including graphite, multiwall carbon nanotubes (MWCNTs), or metal/inorganic nanowires into polymer matrixes is a common strategy to fabricate thermally conductive polymer composites. Among these fillers, MWCNTs, a kind of highly thermally conductive 1D material, have attracted much attention due to their high specific surface area, and extremely high thermal conductivity of about 2000–6000 W m −1 K −1 .…”

“…However, the high thermal conductivities of these fillers can hardly be transferred to polymer composites owing to that too many factors influence the thermal conductivity of polymer–filler composites. The rigid interface of the solid surfaces between polymer and fillers is not microscopically flat, thus creating air gaps and voids and resulting in great thermal resistance . The dispersion state of the fillers is another important factor influencing the thermal conductivity of polymer composites .…”