3D-programmable streamline guided orientation in composite materials for targeted heat dissipation

Filler-reinforced polymer composites demonstrate pervasive applications due to their strengthened performances, multi-degree tunability, and ease of manufacturing. In thermal management field, polymer composites reinforced with thermally conductive fillers are widely adopted as thermal interface materials (TIMs). However, the three dimensional (3D)-stacked heterogenous integration of electronic devices has posed the problem that high-density heat sources are spatially distributed in the package. This situation puts forward new requirements for TIMs, where efficient heat dissipation channels must be established according to the specific distribution of discrete heat sources. To address this challenge, a 3D printing-assisted streamline orientation (3D-PSO) method was proposed to fabricate composite thermal materials with 3D programmable microstructures and orientations of fillers, which combines the shape-design capability of 3D printing and oriented control ability of fluid. The mechanism of fluid-based filler orientation control along streamlines was revealed by mechanical analysis of fillers in matrix. Thanks to the designed heat dissipation channels, composites showed better thermal and mechanical properties in comparison to random composites. Specifically, the thermal conductivity of 3D mesh-shape polydimethylsiloxane/liquid metal (PDMS/LM) composite was 5.8 times that of random PDMS/LM composite under filler loading of 34.8 vol%. The thermal conductivity enhancement efficiency of 3D mesh-shape PDMS/carbon fibers composite reached 101.05% under filler loading of 5.2 vol%. In the heat dissipation application of 3D-stacked chips, the highest chip temperature with 3D-PSO composite was 42.14 °C lower than that with random composites. This is mainly attributed to the locally aggregated and oriented fillers’ microstructure in fluid channels, which contributes to thermal percolation phenomena. The 3D-PSO method exhibits excellent programmable design capabilities to adopt versatile distributions of heat sources, paving a new way to solve the complicated heat dissipation issue in 3D-stacked chips integration application.