Strategy for achieving high sintering and mechanical response performance of nano-Cu/two-dimensional material composite via nanoscale surface-defect-induced longitudinal diffusion

Abstract

High thermal conductivity two-dimensional nanosheets have been proven to enhance the thermal performance of nano metal die-attach materials. Due to the weak affinity between metal nanoparticles and nanosheets, the improvement of mechanical properties of die-attach materials is greatly limited. In this paper, we proposed a strategy of introducing nanoscale surface defects on the surface of two-dimensional nanosheets to induce longitudinal sintering of nanoparticles, achieving ultra-high sintering and mechanical properties of nano-Cu based composite. Using two-dimensional BN nanosheets as an illustrative example, we conducted molecular dynamics (MD) simulations to reveal the influence of surface defects on induction effect. Furthermore, we examined how the location, arrangement mode, geometric size, and shape of surface defects contribute to enhancing the mechanical performance of composites. Our findings indicate that surface defects that are aligned can inhibit the alternating deformation of BN nanosheets between high and low states, and mitigate damage to the crystal structure of composite by decreasing material interactions. Sintering neck that penetrates the surface defects holds a pivotal position in bolstering the mechanical attributes of composites. By adjusting the longitudinal interconnection and minimizing the interactive squeezing effect, an increase in surface defect induction points can achieve ultra-high mechanical properties of composites. Altering the geometric dimensions of surface defects can adjust the underlying competitive relationships between constraints and gap wrinkles in the deformation of BN nanosheets. In addition, surface defects consistent with the sintering neck morphology can achieve the best mechanical properties of the composite. This work provided an effective method for designing and optimizing high thermal conductivity and high-strength nano-Cu based die-attach materials.