Thermally Induced Creep and Viscoelastic Behavior of Copper Micropillar Arrays

ABSTRACT Copper micropillar arrays integrated in microchannel structures promise superior heat dissipation, yet their long‐term reliability can be limited by creep deformation under thermomechanical constraints. Here, we fabricate Cu micropillar arrays (∼50 µm in diameter and ∼300 µm in height) via electrodeposition within through‐glass vias (TGVs) and elucidate how heat treatment tailors creep, viscoelastic response, and deformation mechanisms. Nanoindentation creep combined with EBSD and TEM reveals the transition: 200°C promotes grain‐boundary‐mediated deformation with the largest creep displacement (101 nm) and the smallest activation volume (0.64 nm ³ ), whereas 300°C increases dislocation density and produces dislocation pile‐ups/networks that pin grain boundaries, reducing creep displacement to 42 nm, raising the stress exponent to 3.76, and the activation volume recovers to 1.49 nm ³ . Viscoelasticity is quantified with a generalized Kelvin model and retardation spectrum analysis, which shows suppressed relaxation activity after 300°C treatment. Thermal tests on arrays with varying pitch indicate that 70 µm spacing yields the most pronounced monitored‐surface temperature rise (46.5°C) under identical heating, implying enhanced effective heat transport through the micropillar network. These results establish a microstructure–mechanism–property framework to guide the design of Cu micropillar arrays that balance manufacturability, creep reliability, and thermal performance for microscale liquid‐cooling.