Temperature gradient and shear strength in nanosecond laser welding of silicon carbide and copper

This study investigates the bonding and cracking behavior of SiC-Cu joints during nanosecond laser welding, focusing on the influence of temperature gradients and processing parameters. By combining experiments and simulations, optimal bonding conditions were identified: laser power between 35–45 W and scanning speed of 2–4 mm/s, producing temperature gradients of 22,000–35,000 K/cm. Within this range, crack-free bonding occurred with a width-to-depth ratio ∼0.967, while higher ratios (∼1.014) led to excessive lateral heat spreading, stronger thermal stresses, and consequently higher crack susceptibility. The heat-affected zone (HAZ) was minimized to 10–25 μm, and EDS analysis revealed a Cu–O–Si interfacial layer, mitigating the formation of brittle intermetallic compounds (IMCs). The highest shear bonding strength of 4.5 MPa was achieved at the laser power of 45 W and scanning speed of 3 mm/s, emphasizing the significance of precise parameter optimization. In contrast, at laser powers exceeding 46 W, temperature gradients surpassed 37,000 K/cm, produced severe thermal stresses and interfacial instability, HAZ expansion, and crack formation. These conditions reduced the shear strength to as low as 1 MPa. The research provides critical insights into temperature-gradient management and bonding reliability, supporting the development of robust semiconductor–metal joints for microelectronics, aerospace, and high-performance energy systems.