The Optimized Design And Vibration Characteristics Of The High-frequency Piezoelectric Ultrasonic Transducer Of The Flexible Clamping Mechanism

Piezoelectric ultrasonic transducers are the particularly important components of thermosnonic bonding for the microelectronics,determining the reliability,quality and efficiency of the bonding interconnection.With the ever-developing of the integrated circuits(ICs)towards multi-lead,fine pitch,and high density,higher bonding quality,accuracy and efficiency are required.In this context,thermosonic bonding with high frequency(HF)ultrasonic energy has received extensive attention.However,practical applications show that the ultrasonic energy transmission efficiency of HF transducers can be affected by many factors,and there are still many problems that need to be settled.To improve the ultrasonic energy transfer efficiency and tip vibration amplitude output of HF transducer,a new type of HF ultrasonic transducer with the flexible mounting clamp was designed and a complete and systemic optimization design method was established.An experimental system was specially developed to test the performance of the newly proposed HF ultrasonic transducer.The main research contents are as follows:(1)Based on the electro-mechanical equivalent theory and block-based design method,an equivalent four-terminal networks for the piezoelectric driver and ultrasonic horn of the HF ultrasonic transducer was established,then,the frequency equation of the transducer was derived,and the initial geometric parameters of the transducer were calculated.(2)Based on the ANSYS finite element analysis(FEA)platform and the structural sensitivity analysis theory,the gemoetric parameters of the HF ultrasonic transducer were perturbed and the structural sensitivity coefficients under different modes were determined.The resonant mode and non-resonant mode of the HF transducer were separated successfully through structural parameters optimization,avoiding the occurrence of modal concentrated.Then,the dynamics optimization design for the HF transducer was realized and the optimal geometries of the transducer were received.(3)When combining the flexible hinge with the traditional mounting clamp of the ultrasonic transducer,a new kind of flexible clamping mechanism was designed which could realize the motion decoupling between the ultrasonic horn and the fixing bracket in the bonding machine,reducing the negative influence of the fixing bracket on the tip vibration amplitude output of the transducer.Three kinds of flexible mounting clamps were proposed,involving beam hinge-based mounting clamp,circular hinge-based mounting clamp and elliptical hinge-based mounting clamp.The results of analytic calculation and FEA show that the vibration amplitude outputs of the HF transducers are closely related to the decoupling potentials of the mounting clamps.Finally,a new method based on fuzzy logical technology was established to achieve the optimal structural parameters of the flexible mounting clamps,and the beam hinge-based mounting clamp and the circular hinge-based mounting clamp were viewed as examples to test the newly proposed method.(4)A series of the HF transducers with different flexible mounting clamps were fabricated by NC machine.An experimental system was built up to investigate the dynamics and elecrtrical characteristics of the HF transducers,based on which,the feasibility and effectiveness of the new proposed methods for optimization design of the transducer was also tested.Thus,a new method to enhance the vibration amplitude output of the HF ultrasonic transducer was developed.The correlations between the assembly preload force,properties of the exciting signal(voltage amplitude and frequency)and dynamics and electrical characteristics of the HF transducers were studied deeply,which can lay a vital foundation for the dynamic control of the HF ultrasonic transducer in the future.(5)The newly proposed methods,which can realize the dynamics optimization design of the HF ultrasonic transducer with flexible mounting clamp,was used to design a new type of HF transducer.This kind of HF transducer possesses a series composite structure and it can realize double-end ultrasonic energy transfer and multi-amplitude output.It also can operates at dual-resonance.A series of the test experiments were then performed after the HF transducer was manufactured.All these jobs are conductive to the carry out the design of the transducers with complex and multi-drop ultrasonic wave transfer structure(complex structure),as well as the research about its applications in the thermosonic bonding.In the meanwhile,the jobs also can provide the theories and technologies for the HF ultrasonic transducers in other applications.