AWS WHC-3.08:2008

Ultrasonic Welding
Scope : Ultrasonic welding (USW) is a solid-state welding process that produces a weld by the local application of high-frequency vibratory energy as the workpieces are held together under pressure.1, 2 The vibratory energy creates a relative transverse motion between the two surfaces, disperses interface oxides and contaminants from the interface to achieve metal-to-metal contact, and produces the weld. The advantages of ultrasonic welding, a process originally developed for the welding of metals needed in critical applications, are complimentary to many of the requirements of joining plastic materials; thus the process is widely used in the welding of plastics. Because of the fundamental differences in the welding of metals and plastics, the scope of this chapter is limited to the ultrasonic welding of metals. Ultrasonic welding is used for applications involving similar and dissimilar metallic joints. It is used to produce lap joints between metal sheets or foils, between wires or ribbons and flat surfaces, between parallel wires, and for joining other types of assemblies that can be supported on an anvil. The process is used as a production tool in the automotive, residential and commercial appliance, refrigeration, air conditioning, and other manufacturing industries. It is used for producing batteries and electrical contacts, fabricating small motor armatures, manufacturing aluminum foil, and joining aluminum components. Ultrasonic welding is used in the automotive and aerospace industries as a structural joining method. The process is uniquely useful for encapsulating materials such as explosives, pyrotechnics and reactive chemicals that require hermetic sealing but cannot withstand high-temperature joining processes. It is widely used in the semiconductor and microelectronics industries. This chapter covers the fundamentals of ultrasonic welding and describes the equipment and operating techniques used in production. A separate section on ultrasonic microwelding is presented. Other topics are welding variables and procedures, weld quality, and applications. A section on the economics of ultrasonic welding is included. Safe practices specific to ultrasonic welding are discussed, and references are supplied for general information on safety in welding.