Design And Optimization Research Of Bidirectional Vibration Ultrasonic Transducer For Wire Bonding

Wire bonding is a simple,low cost and multiple packaging technology that plays a key role in pin packaging.Ultrasonic transducer is the core mechanical structure of wire bonding process,and the overall packaging quality is determined by energy transfer processing and its dynamics characteristics.One-dimensional longitudinal is common loading mode in chip bonding transducer currently.This mode might cause insufficient bonding surface,which not only leads to decrease bonding strength,but also affect the reliability and service life of the bonding point.In this paper,the whole ring and half ring piezoelectric ceramic plates are separately excited to generate a combinatorial ultrasonic vibration of axial longitudinal vibration and horizontal bending vibration,instead of the traditional single axial vibration.Therefore,a piezoelectric transducer with longitudinal and bending ultrasonic energy loading mode is studied in wire bonding process.This transducer can increase the conversion efficiency of ultrasonic energy and improve the quality of packaging.The main research contents are as follows:Based on the theory of ultrasonic one-dimensional longitudinal vibration,the overall equivalent circuit of longitudinal vibration is constructed with the equivalent dynamics and electrical model of the transducer,and the structural dimensions of the longitudinal vibration of the transducer are derived in this dissertation.According to the electrical impedance mathematical model of the longitudinal vibration structure of the transducer,the impedance characteristics of the longitudinal vibration of the transducer is calculated in MATLAB.The design method of longitudinal and bending vibration structures of the bidirectional transducer and the finite element analysis software are applied to determine the assembly position of the semi-circular bending vibration ceramic sheet in the transducer and the initial mechanical dimensions of the transducer.The resonance frequencies and modal of the longitudinal and bending modes of the transducer are simulated by ANSYS modal analysis.The influence of the size parameters of each part of the transducer on the resonant frequency is obtained by the frequency sensitivity method,and the optimization of the structure and dimensions are studied in this dissertation.The degeneration of longitudinal and bending vibration modes is realized,and the position of the installation ring is coincided with the position of the longitudinal and bending resonance nodes of the transducer.Harmonic response analysis is applied to obtain the amplitude variation curves of the transducer output in different directions with different operating frequencies,and it is verified that the pitch vibration in the other direction has limited effect on the longitudinal vibration and bending vibration of the bidirectional transducer.The impedance characteristics of the prototype are tested by an Impedance Analyzer,and the test results are basically consistent with the results of finite element simulation analysis.The Ultrasonic Tester,Laser Doppler Vibrometer,Signal Amplifier and other instruments are used to construct the vibration test platform of the bidirectional transducer,and the longitudinal and bending vibration curves is obtained.The amplitude of the transducer under different driving voltages is tested,and it is found that the amplitudes of longitudinal vibration and bending vibration show an approximately linear upward trend with the increase of driving voltage.A comparison test of the bonding effect of the two-way transducer are carried out.It is proved that the bonding quality of the two-way transducer is better than the traditional one-dimensional bonding quality according to the test solder joint morphology,bonding surface and other factors.The research and structural design of the bidirectional transducer are innovative significance for the improvement of the wire bonding process.