Achieving isotropic thermal properties in graphite flake/Cu composites through the radial structural design of reinforcement

Conventional graphite flakes (GFs)/Cu composites suffer from severe anisotropy in terms of their thermal conductivity (TC) and coefficient of thermal expansion (CTE) between the in-plane and through-plane directions, which as thermal management materials (TMMs) play crucial roles in the overall heat dissipation performance of electronic components. To address this issue, a radial structural design for the reinforcement phase of GFs was developed. In this study, conventional stacked structured GFs/Cu composites and newly designed radial structured GFs/Cu composites were prepared by electroless plating of Cu on the surface of GFs followed by fast hot-pressing technology. The GFs content was varied from 30 to 70 vol%. The spatial orientation of the GFs was determined via X-ray computed tomography. For the radial structured GFs/Cu composites, the CTE were 11.52 and 14.42 ppm K⁻¹ in the in-plane direction through-plane direction when the GFs content was 50 vol%, and the TC reached maximum values of 681 and 590 W m⁻¹ K⁻¹ in the in-plane direction and through-plane direction when the GFs content was 50 vol%. The TC in the through-plane direction was nine times greater than that of the stacked structured GFs/Cu composites (65 W m⁻¹ K⁻¹) at the same GFs content, demonstrating overall isotropy. Although radial structured GFs/Cu composites have more defects that can affect their thermal properties due to process factors, they have better heat dissipation abilities in practical applications; this indicates their great potential as a new generation of TMMs.