Experimental Techniques for Static and Dynamic Analysis of Thick Bonding Wires

Abstract

Thick bonding wires are used in modern power modules as connectors between integrated circuits, carrying current from one circuit to another. They experience high values of current, which generates heat through Joule heating and can lead to various failure mechanisms. Typically used wire materials in industry are aluminum (Al), copper (Cu), and intermetallic compounds of Cu-Al. They are broadly used because of their strength, high thermal conductivity, and low resistivity.

This study reports on the influence of thermal loading on the mechanical behaviour of bonding wires. Experimental techniques are developed and introduced in this thesis to analyze quasi-static and dynamic response of bonding wires 300 µm in diameter. First, an experimental technique is developed to measure the quasi-static displacement of bonding wires carrying DC currents. It is then deployed to measure the displacement, as well as peak temperature, of three types of bonding wires, Al, Cu and Aluminum coated Copper (CuCorAl) to study the response under DC current.

Secondly, an experimental technique is established and deployed for modal analysis of bonding wires under thermal loading. Experimental results demonstrate a drop in the natural frequency of bonding wires with increased thermal loads. Moreover, a harmonic analysis technique using thermal excitation is developed and applied to analyze the mode shapes and frequency response of bonding wires.

Furthermore, an analytical model and a finite element model are used to analyze static and dynamic responses of bonding wires. Numerical and experimental results are compared in this thesis.