Design of Cu/Zr Alloy Interface for Enhanced Thermal Fatigue Performance in Electronic Packaging

This study addresses a critical limitation in direct bonded copper (DBC) materials used in power electronics by introducing a copper-zirconium (Cu/Zr) alloy interposing layer at the copper-ceramic interface. This novel design aims to mitigate mechanical stress induced by mismatched material properties, such as the coefficient of thermal expansion (CTE) and elastic modulus, during thermal cycling. The key findings of this study are (1) thermal fatigue improvement: Test samples with the Cu/Zr interface layer (Cu-Cu/Zr-AlN) three times enhanced thermal fatigue resistance, surviving 30 thermal cycles from -55 to 300 °C before delamination, while standard DBC substrates without the Cu/Zr layer failed after just 10 cycles, indicating a performance improvement with the Cu/Zr alloy, (2) durability projections: Based on the Coffin-Manson model, if the upper temperature is capped at 150 °C, the Cu-Cu/Zr-AlN substrates are projected to survive approximately 1372 cycles, underscoring their potential for long-term reliability, and (3) stress mitigation: The Cu/Zr alloy layer bridges the CTE disparity between copper and ceramic, reducing mechanical stress and improving structural integrity across a broad temperature range (-55 to 300 °C). This study reveals, incorporating the Cu/Zr interposing layer between Cu and AlN substrates significantly enhances the operational lifespan and reliability, making them well-suited for high-temperature and high-stress environments in advanced power electronics. This innovation demonstrates the feasibility of improving thermal fatigue performance while maintaining mechanical integrity, representing a substantial advancement over conventional DBC materials.