Welding of Fine Metal Particles by Using a Tungsten Needle and Measurement of the Strength of the Joints

Abstract

Gold particles several tens of micrometers in size were welded onto a gold substrate. High voltages of 4 kV or more were applied to a tungsten needle in contact with the particle on the substrate at a very low contact pressure. The particle was welded to the substrate in an instant with sparks. The needle was then retracted to 20 !m above the particle and a high voltage of about 2kV was applied to the needle. An electric discharge between the needle and the substrate enveloped the particle, and the joint was strengthened. The joint strength was measured, and the fractured surface was examined by scanning electron microscopy and scanning laser microscopy. The mechanism of joint strengthening is discussed. It is clear that an inert gas flow during the electric discharge is necessary to strengthen the joints.