Dual-side heterogeneous diamond deposition on copper enables crack-free films with minimal warpage for thermal management

The integration of diamond films onto copper substrates offers significant potential for thermal management in high-power electronics, leveraging diamond's exceptional thermal conductivity and electrical insulation. However, substantial challenges arise from the significant thermal expansion coefficient (CTE) mismatch, leading to substrate warping and film cracking. This study establishes a critical substrate thickness effect through systematic experiments: Single-side nanocrystalline diamond (NCD) deposited on thin copper substrates (0.5 mm) exhibits severe warping (curvature radius: 55.53 mm) but maintains film integrity, whereas identical deposition on thick copper (1.5 mm) reduces warping (radius: 219.4 mm) yet induces extensive cracking due to amplified compressive stress. To overcome this trade-off, we develop a dual-side heterogeneous deposition strategy: NCD grown at low temperature (700 °C) on one side provides strain accommodation, while subsequent microcrystalline diamond (MCD) deposition on the opposite side achieves stress cancellation. This approach simultaneously resolves both failure modes---increasing the warpage radius to 395.03 mm (an increase of 711 % compared to single-side deposition) while ensuring crack-free integrity in both 5 μm thick deposited films. The underlying mechanisms involve: (1) Gradual stress decay through a gradient interfacial architecture (amorphous carbon layer - nanocrystalline buffer - microcrystalline main layer); (2) Enhanced adhesion via mechanical interlocking induced by substrate pretreatment; (3) Plastic deformation at the interface absorbing residual strain. Thermal testing confirms hot-end temperature reductions of 7.7 °C and 42.2 °C compared to AlN and Al₂O₃, respectively, at 6 W power, validating superior heat dissipation. This work provides an electrically insulating diamond‑copper composite with high thermal conductivity for next-generation thermal management solutions.