Quantification of the Energy Flows During Ultrasonic Wire Bonding Under Different Process Parameters

Abstract

Despite of its wide and long-term application for interconnections in the field of microelectronics packaging, a quantitative understanding on the mechanisms of ultrasonic (US) wire bonding is still lacked. In this work, the energy flows from the electrical input energy to the different mechanisms during the US bonding process are quantified based on real-time observations via which the relative motions at the wire/substrate and the wire/tool interfaces can be detected. The relative motions at the two interfaces are proved to be caused by both the continuous plastic deformation and the US vibration. The normal force and US power interdependently affect the relative motion amplitudes. The deduced energy flows show that the energy from the transducer mainly flows to the vibration induced friction at the two interfaces and the microwelds formation, deformation and breakage. Despite of their significance to the process, the other mechanisms receive only little amount of energy. The impacts of the process parameters including normal force, US power and time on the energy flows are quantitatively investigated. A good coupling of the normal force and the US power guides more energy to the formation of microwelds while a long process time would increase the friction induced energy consumption.