Laser welding of highly reflective metal with absorbance-enhanced surface structure fabricated using picosecond laser

• Published in: Applied physics. A, Materials science & processing Vol. 126; no. 7
• Main Authors: Sakai, Tetsuo, Hirono, Masatoshi
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.07.2020; Springer Nature B.V
• Subjects: Applied physics; Blackening; Characterization and Evaluation of Materials; Condensed Matter Physics; Copper; Current State-Of-The-Art in Laser Ablation; Electromagnetic absorption; Finite difference time domain method; Incident light; Infrared lasers; Laser beam welding; Lasers; Machines; Manufacturing; Materials science; Nanoparticles; Nanotechnology; Optical and Electronic Materials; Physics; Physics and Astronomy; Processes; Reflectance; S.I. : Current State-Of-The-Art in Laser Ablation; Surface structure; Surfaces and Interfaces; Thin Films; Time domain analysis; Nano-structure; Femtosecond laser; Picosecond laser; Laser ablation; Copper; Absorbance-enhanced surface structure; Ultrashort pulse laser
• ISSN: 0947-8396; 1432-0630
• DOI: 10.1007/s00339-020-03668-2

We present a method to stably weld a copper at lower laser power by blackening the surface. Since the reflectivity of copper is approximately 97% in the infrared range, a precise and stable processing of copper is difficult even at high power using infrared laser. To decrease the reflectivity, we fabricated light-absorbing nano-structure on copper surface using picosecond laser pulses. The structure consists of aggregations of nano-particles, and is capable of absorbing as much as 80% of incident light. We demonstrated that a copper with this structure can be welded using 70% lower irradiation power than a copper without it. Additionally, we theoretically investigated the light-absorbing nano-structure using 3D finite-difference time-domain (FDTD) method.