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 and 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.