Low Temperature and Small Deformation Bonding by Control of Loading Profile

Study on Single Point TAB Bonding Process (Report 2)

Abstract

Bonding under the conditions of low temperature and low loading is required so that an IC chip won't be damaged while being bonded for an inner lead bonding between an electrode terminal on an IC chip and an outer lead terminal. For the thermosonic bonding used in the single point TAB technology, the deformation behavior of the bonding material and the working of the ultrasonic vibration are very significant. An applied load that is one of the bonding parameters in the single point TAB process had influence on the deformation behavior and the working of the ultrasonic vibration. In this report, a correlation between the bonding parameters and the bondability is discussed, and it is pointed out that the control of the loading profile is important for attaining the low temperature and small deformation bonding. The bonding process in the thermosonic bonding is divided to the initial contact process dominated by the material plastic deformation and the adhesion process dominated by the plastic flow at the interface between a gold bump and TAB lead. In the initial contact process, the minimum loadingg force exists to obtain the contact between bonded materials, and the other hands, in the latter adhesion process, the contribution of the ultrasonic energy into the interface becomes larger under the lower loading force. Furthermore, it is clarified that the bonding part with a smaller deformation and a higher strength is obtained by setting the higher value of the initial load and the lower value of the working load in a single point TAB process.