1Kanagawa University, Yokohama, Kanagawa, Japan
2Asahi EMS Co Ltd, Yokohama, Kanagawa, Japan
Ultrasonic welding can weld same and different metal specimens directly using ultrasonic vibration. The welding area is limited within very thin layer and possible to weld different metal specimens which have different melting temperature such as aluminum, copper difficult to weld by usual methods. Welding conditions are changed by frequency, dimensions of specimen and especially vibration locus. High frequency linear vibration systems up to 1 MHz are designed for metal welding. Complex vibration welding systems with elliptical to circular loci are proposed and the systems are using (1) multiple transducers integrated with a circular disk and (2) longitudinal-torsional vibration converters with diagonal slits driven by a longitudinal vibration source. For plastic welding, high frequency linear vibration systems up to 180 kHz avoiding radial vibration resonance of the system. Maximum vibration velocity for 180 kHz system obtained is over 5 m/s (peak-to-zero value). Frequency characteristics of 0.1-mm-diameter aluminum and 1.0-mm-thick copper plate specimens using welding systems of 40 to 800 kHz are shown in Fig. 1. Required vibrations at 15 kHz to 27 kHz for usual specimens are also shown in circular areas. Required vibration amplitude for metal welding decreases as frequency becomes higher, and welding conditions are improved significantly. Using complex vibration of circular locus, required vibration amplitude decreases significantly as shown in Fig.2. Fig. 3 shows the frequency characteristics of plastic welding in the range of 27 kHz to 180 kHz. For large specimens, two-vibration-system and butt welding methods are effective. Using complex vibration, required vibration amplitude decreases significantly, and large and uniform weld strength are obtained independent of vibration direction, and multiple and seam welding become possible. For large specimens, two-vibration-system and butt welding methods are effective. Metal specimens were joined directly without any oxide, mutual diffusion and any different structures. For plastic welding, required vibration velocity and amplitude become smaller as vibration frequency is higher due to larger vibration absorption of plastic materials. The welding method using fundamental and higher resonance frequencies was proposed and shown very effective.