Abstract
One of the authors has investigated a metal-metal joining by using “unusual wetting”, which is the phenomenon where a liquid metal unusually spreads by capillary action, on the porous layer of metal surface formed in oxidation-reduction process. While the oxidation-reduction treatment creates an adequate porous structure for “unusual wetting” throughout, it is not easy to control the area of porosity formation to realize a selective joining because of a difficulty of localized oxidation-reduction treatment. In the present work, we propose the utilization of laser for creating an adequate structure for local “unusual wetting”. The surface fine asperity structure observed on Cu substrate after laser irradiation was named “surface fine crevasse structure”. The wettability of liquid Bi for the above modified surface structure was investigated to confirm “localized unusual wetting” of liquid Bi on “the surface fine crevasse structure” of Cu substrate. In addition, we succeeded in joining two Cu substrates by “unusual wetting” in the surface fine crevasse structure prepared by laser irradiation.
