Design And Performance Research Of High-frequency Ultrasonic Transducer With Double-branch Composite Structure

With the continuous development of IC chips towards high integration,miniaturization,and fine pitch,higher and higher requirements have been putting forward for the movement flexibility,bonding efficiency,and vibration amplitude output characteristics of the ultrasonic transducers used in the thermosonic bonding.Under this case,the single-branch-based structure of the transducer gradually changes into a kind of multi-branch-based composite structure.So,this subject proposed a double-branch composite structure for the high-frequency piezoelectric ultrasonic transducer design,in which a newly proposed flexible-hinge-based mounting clamp was also used.Then the structural parameters of the newly developed ultrasonic transducer were dynamically optimized,as well as its dynamic behavior characteristic and the relevant laws.The main contents are shown as follows:(1)A new type of double-branch-based ultrasonic transducer was proposed in which one branch adopted a two-step conical horn stucture and the other a step-cone structure.The front and rear working ends can output different amplitudes,simultaneously.It effectively use the ultrasonic energy transmitted to the back slab of the transducer.The electromechanical equivalent circuit and the four-terminal network method were combined to established the equivalent impedance model of the piezoelectric vibrator and horn of the double-branch-based composite structure transducer,and then the initial dimensions of each part of the transducer were obtained through modular design.(2)The finite element analysis(FEA)and sensitivity analysis methods were comprehensively used to explore the influences laws of the several key geometric parameters on the vibration modal distributions.Based on the perturbation method,the structural parameters were optimized,and then the optimal values of the key parameters of the double-branch-based transducer were determined.The separation of non-operating modes was completed to avoid triggering the non-resonance during excitation.A flexible hinge-based clamp combined the traditional flange and the compliant mechanism was proposed to weaken the influence of the disturbing torque of the clamping frame on the vibration performance of the transducer.The finite element method was used to analyze the influence of the hinge size on the resonance characteristics of the transducer,to determine the hinge size range,and then to establish the flexibility equation of the hinge.The PSO(particle swarm optimization)algorithm was used to optimize the flexibility of the hinge parameters.Finally,the overall model of the transducer was built up,and the finite element analysis was performed to verify the accuracy of the method.(3)Based on the BVD equivalent circuit in the piezoelectric ceramic resonance state,the current dynamic response model of the transducer was established,and the main parameters that affect the dynamic response performance of the transducer was analyzed.Based on Lab VIEW,the transducer power drive and information acquisition system was constructed.The influence of different initial conditions on the dynamic response performance of the transducer was investigated.Then,the percentage peak overshoot and settling time were extracted from the exciting response signal and viewed as two basic morphological feature parameters to characterize the response performance,innovatively.To regulate the exciting response performance actively and get the desired ultrasonic energy delivery efficiency,a new method based on RBF(radial basis function)neural network was developed and it could predict the resonant frequency and the settling time accurately when the excitation condition of the transducer was changed.Test results manifest the newly proposed method is feasible and efficient.(4)An experimental platform for the performance testing of the double-branch-based transducer was built to test the dynamic synthesis characteristics of the transducer under simple and complex conditions.The output amplitude when a single group of piezoelectric vibrators was excited and two groups of piezoelectric vibrators were simultaneously excited was analyzed,and the two groups of piezoelectric crystal stacks A and B are under resonant and non-resonant excitation respectively.Explore the relationship between the vibration trajectory and the excitation mode at the working end of the double-branch-based transducer.Finally,the perfect dynamic optimization design and dynamic response performance research method of the double-branch-based transducer in this study is established.