Study Of A Process To Improve The Strength Of Thermo-Sonic Ball Solder Joint

Thermo-sonic ball wire bonding has a large market share at the current chip-pins package.The bonding strength of solder joints at both ends of wire is the important indicators to protect the connection of chip and external electrical. As far as the state of the art, the real bonding area of 1 st ball solder point is usually a long elliptical shape. There is no connection in the center district, it is known as'donut'phenomenon. If the unconnected area on craft could be eliminated, it could greatly improve the bonding strength of 1st ball solder point and improve the reliability and stability of entire chip package.This paper describes the microelectronic manufacturing process of IC packaging technology, highlighting the wire bonding technology, process and development process, lay the foundation for the process researching of improving the strength of ultrasonic ball bonding.In order to improve the bonding strength of solder ball, it is need to clarify the mechanism of bonding. The current interpretation of "donut" phenomenon is mainly based on the mechanism of micro-slip based on elastic theoretical hypothesis. However in bonding process, an significant plastic deformation of FAB (free air ball) is created by the ultrasonic engergy and bonding pressure energy. The contradiction between the FAB's flexibility and plasticity of bonding is not clear so farDue to the high speed (vibration frequency=100Khz), small displacement (few microns) and short time-consuming (tens of microseconds) in ball bonding process, it is not easy to study the dynamic process by experiment. With the rapid development of computer technology, numerical simulation has become a well research method to the bonding process. At present, some researchers have used Finite Element Method to simulate the stress distribution of FAB in bonding process, but they all used the fixed bonding force. There is few research on the slip in the bonding contact interface in ultrasonic vibration process. In this paper nonlinear elastic and elasto-plastic static analysis of FAB in ultrasonic vibration process is carried out by finite element method with ANSYS. We study the evolution way of compressive stress distribution of FAB and sliding area in the contact interface under elastic and elasto-plastic deform.As in the actual ultrasonic ball bonding process, the bond force and ultrasonic tangential force will be unstable because of being susceptible to interference from a variety of factors, must be a very complex feedback control can be allowed to remain them at the value set by the user, the control of displacement is easier than that of force and energy. According to the results of the analysis, combination of micro-slip theory, we propose a new bonding process control that can improve the bonding strength of 1st ball solder point effectively.