Since the first ultrasonic welding machine for metals was developed and patented in 1960 there have been significant technological advances which now make the process a practical production tool. It is interesting to note that the process patent was first applied for in 1952/53 but "the patent examiner and his supervisor did not believe that solid state welds could be made without the use of heat, filler metal, super glue or the like and requested permission to visit and witness this process themselves"2. Early power supplies employed vacuum tube technology, could not produce high power levels of ultrasonic energy and were inefficient and expensive. Early work was limited to research and development which showed the promise of the process and spurred further technical development. Today, ultrasonic energy in general is a well established tool of industry having applications in nondestructive testing, industrial ultrasonic cleaning, ultrasonic plastic joining and, the subject of this paper, ultrasonic metal welding. Ultrasonic metal welding has much to offer the user including speed, efficiency, excellent weld quality, elimination of consumables, long tool life and the ability to be automated. (See Figure 1.)
Ultrasonic energy is mechanical vibratory energy which operates at frequencies beyond audible sound, or 18,000 Hz (18,000 Hz being the upper threshold of the normal human hearing range). Two basic frequencies are used; 20,000 Hz and 40,000 Hz, depending on the application. Selection is based upon the required power levels, the amplitude of vibration required and the size of the ultrasonic tool to be used. Frequency is important because it directly effects the power available and the tool size. It is easier to generate and control high power levels at the lower frequency. Also, ultrasonic tools are resonant members whose size is inversely proportional to their operating frequency. (See Figure 2.) The generation of ultrasonic energy starts with conversion of conventional 50 or 60 Hz electrical power to 20,000 or 40,000 Hz electrical energy by a solid state power supply. (See Figure 3.)
Since the first ultrasonic welding machine for metals was developed and patented in 1960 there have been significant technological advances which now make the process a practical production tool. It is interesting to note that the process patent was first applied for in 1952/53 but "the patent examiner and his supervisor did not believe that solid state welds could be made without the use of heat, filler metal, super glue or the like and requested permission to visit and witness this process themselves"2. Early power supplies employed vacuum tube technology, could not produce high power levels of ultrasonic energy and were inefficient and expensive. Early work was limited to research and development which showed the promise of the process and spurred further technical development. Today, ultrasonic energy in general is a well established tool of industry having applications in nondestructive testing, industrial ultrasonic cleaning, ultrasonic plastic joining and, the subject of this paper, ultrasonic metal welding. Ultrasonic metal welding has much to offer the user including speed, efficiency, excellent weld quality, elimination of consumables, long tool life and the ability to be automated. (See Figure 1.)
Ultrasonic energy is mechanical vibratory energy which operates at frequencies beyond audible sound, or 18,000 Hz (18,000 Hz being the upper threshold of the normal human hearing range). Two basic frequencies are used; 20,000 Hz and 40,000 Hz, depending on the application. Selection is based upon the required power levels, the amplitude of vibration required and the size of the ultrasonic tool to be used. Frequency is important because it directly effects the power available and the tool size. It is easier to generate and control high power levels at the lower frequency. Also, ultrasonic tools are resonant members whose size is inversely proportional to their operating frequency.
(See Figure 2.) The generation of ultrasonic energy starts with conversion of conventional 50 or 60 Hz electrical power to 20,000 or 40,000 Hz electrical energy by a solid state power supply. (See Figure 3.) 
