Method of bonding wires

A method of bonding wires between a semiconductor die and a substrate on which the die is mounted comprising:

• providing an ultrasonic transducer comprising an ultrasonic energy generation device, an ultrasonic vibration amplifying device coupled at one end to the ultrasonic wave generation device, a bonding tool coupled to the opposite end of the ultrasonic vibration amplifying device, and a mounting structure located between the ends of the ultrasonic vibration amplifying device;
• identifying a first and a second ultrasonic frequency of vibration of the energy generation device at which the vibration amplitude is:
• (i) substantially zero at an energy generation plane, the energy generation plane being perpendicular to a longitudinal axis extending between the ultrasonic generation device and the bonding tool and the energy generation plane intersecting the ultrasonic generation device,
• (ii) substantially zero at a mounting plane, the mounting plane being perpendicular to the longitudinal axis and being coincident with a mounting contact point between the mounting structure and a wire bonding machine on which the transducer is mounted, and
• (iii) non-zero at a bonding plane, the bonding plane being perpendicular to the longitudinal axis and intersecting the bonding tool;
• and
• performing a first wire bond by operating the ultrasonic transducer at the first ultrasonic frequency and performing a second wire bond by operating the ultrasonic transducer at the second ultrasonic frequency, the second ultrasonic frequency being different from the first ultrasonic frequency.