Gradient-Driven Multi-Scale Modeling for Coupled Thermal–Mechanical Optimization of Copper– Diamond Composites in High-Power Electronics Packaging

Copper-diamond composites offer exceptional potential for thermal management in high-power electronics packaging, yet balancing high thermal conductivity with low interfacial stress remains challenging. Here, we present a hybrid strategy that integrates gradient structural design with multi-scale finite-element modeling to optimize both thermal and mechanical performance. First, we establish micro-scale representative volume element (RVE) models to quantify how diamond volume fraction (10~40 vol %) and particle size affect effective thermal conductivity and interface stress under thermo-mechanical coupling. Next, we introduce a multi-layer gradient arrangement, decreasing diamond content by 5 vol % per layer from heat source to substrate, and demonstrate via simulation that this configuration reduces peak interface stress by 45 % relative to a uniform composite, while enhancing thermal conductivity. Finally, embedding the optimized gradient composite into a simplified packaging structure shows a 31 % and 27 % reduction in junction temperature compared to aluminum and copper substrates, respectively, and a 38 % lower peak structural stress. These results validate our multi-scale, gradient-based approach as a scalable framework for designing high-reliability, high-performance thermal substrates in advanced electronic packages.