Study Of Ultrasonic Nonlinear Propagation Mechanism At Contat Interface In Bond System

Thermosonic chip bond technology is a potential process in the current chip package area. Ultrasonic bond transducer system is the important part in ultrasonic chip bond process. The nonlinear characteristics of contact interface in ultrasonic bond transducer system are mainly factor of ultrasonic transmission efficiency reduction and chip bond failure. This thesis comes from Research Fund for the Doctoral Program of Higher Education of China, Ultrasonic Propagation Mechanism in Contact Interface of Chip Package Transducer System and Design, No.20060533068 and National Natural Science Foundation of China, Ultrasonic Propagation Mechanism in Contact Interface of Chip Package Transducer System and Low Power Consumption Contact Interface Design, No.50405064. In order to improve the ultrasonic transmission efficiency at the contact interface of ultrasonic transducer and the quality of chip bond and stability of transducer vibration, the thesis study on ultrasonic transmission at the contact interface of the ultrasonic bond transducer. Ultrasonic energy loss, waveform conversion and harmonic variation are studied. The nonlinear vibration fundamental of contact interface is important for the ultrasonic transducer optimize design, manufacture and use.In this paper, the study consists of:Firstly, based on Hertz contact theory and Snell law, the model of ultrasonic propagation through contact interface was studied. The factors of contact interface including:interface roughness, the actual contact area, contact interface stress and interface adhesive. The relation of the factors affecting on ultrasonic propagation was obtained. The nonlinear ultrasonic propagation equation is established, and is solved using reductive perturbation method. The spring-damp-mass model of ultrasonic propagation through contact interface is established, in the light of ultrasonic propagation chracteritics at contact interface.Secondly, ultrasonic propagation through contact interface is simulated using of mechanical dynamics simulation software. It is gained that ultrasonic propagarion varys with the contact interface stress, contact interface stiffness and interface damp. The test is done on ultrasonic bond platform. The contact interface roughness, contact interface stress and interface adhesive are taken account. It is abtained that the waveform distortion and high harmonic generation is relating to contact interface parameters. The relation of the bonding strength and the higher order harmonics of bond tool vibration are obtained.Finally, the equivalent impedance model of ultrasonic transducer's contact interface is established using of mechanical and electrical equivalent model. Based on electromechanical analogy method, the contact interface model is established, which concludes contact interface material, contact interface status parameter. The equivalent impedance model of ultrasonic transducer is gained. The model is proved is validatied by experiment using impedance analysis method. The content of the above research, methods and conclusions have a positive effect on understanding contact transducer interface's nonlinear vibration of ultrasonic transducer. Those are help for analysis and design of chip bonding transducer system. It plays a fundamental significance that improving the manufacture of semiconductor devices. There are some references on other ultrasonic transducer system.