Experimental investigation on laser shock micro hydraulic bulging of copper foil

Abstract

In this study, a novel micro-forming process called laser shock micro hydraulic bulging was proposed to fabricate micro feature on copper foil. In this process, liquid medium water was used as a soft punch, rubber layer with thickness of 200 μm was used to squeeze liquid medium, and laser shock wave was used as driving force. Forming depth, surface quality, thickness thinning ratio, and cross section micro hardness were investigated under different laser energies. Experimental results showed that the forming depth and surface roughness increased with the laser energy. However, the surface roughness increased slightly with the increase of laser energy, and no thermal response area was found at forming area. Maximum thickness thinning occurred at the fillet when laser energies were 565, 835 and 1200 mJ, while fracture occurred at the bottom area (not the apex) when the laser energy increased to 1380 mJ. Hardness test indicated that, when the material was in cold-rolled, the hardness along the cross-section of the formed area showed an irregular trend. When the material was changed with copper foil annealed at 450 °C, the hardness improved remarkably.