Numerical Simulation Study of Residual Stress in AlN/Cu Brazed Joints

Aluminum Nitride (AlN) ceramics have been considered as the promising material for packaging high-voltage and high-power insulated gate bipolar transistor (IGBT), where copper (Cu) coating is covered on the AlN ceramic to enhance the heat dissipation. However, the wide discrepancies in physical properties between AlN and Cu often enable severe residual stress after brazing. To address this issue, this study utilizes finite element numerical simulations to investigate the effects of loading, cooling rate, and filler alloy thickness on the residual stress in AlN/Cu brazed joints. The results show that the maximum axial stress in the AlN/Cu brazed joint appears on the AlN ceramic edge adjacent to the brazing filler alloy, while the maximum shear stress is on the interface between the AlN ceramic and brazing filler alloy, where is near the outer edge. Both the maximum axial and shear stresses increase with the decrease in loading, and the increase in cooling rate and filler alloy thickness. The stress distribution remains relatively consistent for all investigated conditions. The obtained results can provide the theoretical guidance for the high-reliability packaging of Cu-coated AlN ceramic substrates in high-power IGBTs. © 2024 Cailiao Daobaoshe/ Materials Review. All rights reserved.