A pure copper is widely applied for various products such as a motor, a coil, an electrode and heat sink because of its high electric and thermal conductivity. Recently, for improving through put of these products, demand for a high-quality copper welding has been increasing. Although a fiber laser and a disk laser, which has only 10 % absorption rate for copper at wavelength of 1 um, have employed for copper welding, it is difficult for copper plate to weld without pores. Thus, we paid attention to a blue diode laser which has 60% absorption rate for copper. In our previous study, a bead on plate welding for copper plate was performed with 200W blue diode laser, which recorded highest intensity in the world. As the results, the penetration welding for copper plate at the thickness of 0.3 mm was achieved without spatter and pores. As the thickness increased, however, the output power or input energy was insufficient even with the 200W blue diode laser. In this study, we developed hybrid laser welding system with the blue diode laser and the single mode fiber laser to realize a deep penetration welding for copper.

200 W class blue diode laser and the 1 kW class single mode fiber laser was employed in this study. These lasers were combined on the same axis by a dichroic mirror and focused lasers were irradiated to the copper plate at the thickness of 1 mm by a focal lens. Beam spot diameter at focal point of the lasers were set at spot diameter of 60 μm for the fiber laser and 200 μm for the blue diode laser. As the results, the high-quality bead without pores and vacancies was formed on the pure copper substrate.