Yoshihiro Sagisaka

Proposal of Microjoining Method UsingShock Wave Generated by Femtosecond Laser Irradiation

Femtosecond laser is a type of ultrashort-pulse laser. Ultrashort-pulse laser irradiation generates high-pressure plasma and shock waves at the surface of the target. If the target is irradiated in water, the shock waves are enough to deform the target plastically. The authors proposed a new microjoining method using the shock waves accompanied by femtosecond laser irradiation. A thin wire was mounted in a fit bore drilled in a plate, and the laser was focused around the edge of the wire end face. The wire was deformed by shock waves generated by many laser pulses. After the laser irradiation, the deformed wire prevented the release of the plate, as well as the rivet connection. Some model tests were performed to examine forming properties and joining strength. Laser pulse energy, spot diameter and laser spot position influenced the deformed shape and joining strength. In the case of irradiation close to the wire edge, the deformed shape and joining strength varied. They were made stable by transferring the laser spot intermittently.