The described embodiment relates generally to the field of ultrasonic bonding. More specifically, an apparatus for bonding a number of wires directly to a metal substrate in a single operation without the use of any kind of adhesive or solder is disclosed. The apparatus is an ultrasonic bonder. The ultrasonic bonder has a horn with a cavity specifically sized for the number of wires to be bonded. The ultrasonic bonder is driven at a frequency that corresponds to a resonant frequency of the wires to be bonded.