Development of novel ultrasonic transducers for microelectronics packaging

Transcription

1 journal of materials processing technology 209 (2009) journal homepage: Development of novel ultrasonic transducers for microelectronics packaging Fujun Wang a,, Xingyu Zhao a, Dawei Zhang a, Yimin Wu b a School of Mechanical Engineering, Tianjin University, Tianjin , China b School of Mechanical Engineering, Hebei University of Technology, Tianjin , China article info abstract Article history: Received 2 October 2007 Received in revised form 25 February 2008 Accepted 24 March 2008 Keywords: Ultrasonic transducers Dynamic simulation Optimization design Impedance analysis Laser Doppler measurement Novel high-frequency ultrasonic transducers have been developed in order to provide faster, more repeatable and stronger microelectronics bonding technology, and fine-pitch packaging can be accomplished by these transducers. The analytical model of the transducer system is established on the basis of electromechanical equivalent circuitry theory, vibration theory and wave theory, which lays the foundation for determining the initial topological information of the ultrasonic transducer. By use of finite element method (FEM), the dynamic characteristics of components are investigated. The resonance frequency, vibration displacement nodes and rule of ultrasonic energy transmission are acquired by making modal and harmonic analysis. Through optimum design by considering the piezoelectric effect, the dimensions of ultrasonic transducer have been gained finally. The prototyped transducer is tested through the impedance analyzer and laser Doppler vibrometer, which proves remarkable resemblance with the theory and FEM. The experimental results also show that there are no undesirable vibration modes around the working frequency, thus it becomes convenient for the vibration control Elsevier B.V. All rights reserved. 1. Introduction In semiconductor manufacturing, there are two main electrical interconnection technologies: thermosonic wire bonding and thermosonic flip-chip bonding. Wire bonding constructs electrical connections between the pad of die and the lead of leadframe using fine gold or other metal with diameter ranging from 25 m to65 m, and it is still the dominant form of interconnection technology (Shah et al., 1988; Liu et al., 2004). With the trend in shrinking integrated circuit (IC) dimensions and reducing assembly cycle time, the thermosonic flip-chip bonding has been highly advocated in the past few years, and it achieves connections between the chip and the substrate using bumps of electrically conducting material. The flip-chip bonding technology has received considerable attention from both researchers and manufacturers. During thermosonic bonding process, heat, pressure and ultrasonic energy are applied simultaneously (Lee et al., 2005; Marumo et al., 2006). The ultrasonic transducer converts electrical energy into acoustic energy and transmits energy to bonding interface, whose vibration characteristics have a great effect on bonding quality (Chiu et al., 2003; Chu et al., 2003). The transducer is usually driven by the output of an ultrasonic generator with phase locked-loop. The longitudinal vibration obtained from the piezoelectric converter is transmitted and amplified by the concentrator (Xu et al., 2004; Li and Zhang, 2006). A flange is used for mounting the transducer on the bonder, and it should be put at the position node of the transducer to avoid energy loss. The bonding tool is set up at the tip of the concentrator, and the transducer touches the IC or leadframe by Corresponding author. address: wangfujun2000@yahoo.com.cn (F. Wang) /$ see front matter 2008 Elsevier B.V. All rights reserved. doi: /j.jmatprotec

2 1292 journal of materials processing technology 209 (2009) Fig. 1 The structure of ultrasonic transducer for thermosonic bonding. the tool. Fig. 1 shows the structure of ultrasonic transducer without bonding tool. Many researchers are concerned about the advantages of high-frequency bonding over low-frequency bonding, and have conducted several experiments to prove their views. Charles et al. (2002) have presented data on a systematic study of wire bonding using two essentially equivalent ball bonders (one bonding at 60 khz and the other at 100 khz). Pang et al. (2004) has investigated the influence of different frequencies to process windows for thermosonic flip-chip application. Chylak et al. (2004) have studied the effect of bonding frequency on bonding quality by minimizing and equalizing the other factors affecting bond qualities. Their research shows that it can increase shear strength, reduce bonding temperature and shorten bonding time compared with traditional 60 khz bonding, and the finer-pitch bonding can also be achieved because the displacement amplitude becomes smaller at higher frequency vibration. Sherrit et al. (1999) studied the modeling of horns for ultrasonic applications by electromechanical equivalent method. Amin et al. (1995) analyzed the acoustic horns for ultrasonic machining by FEM with computer aided. An approach to design ultrasonic transducers for wedge bonder is put forward based on the principles of modularity and iterations by Parrini (2001), however, he does not effectively introduce how to obtain the initial model of transducers and the optimization design of the transducer. 136 khz ultrasonic transducers using 1 3 piezocomposites are presented by Or et al. (2006), and he researched ultrasonic transducer by FEA software without considering the piezoelectric effect. Due to 1 3 piezocomposites, the transducer exhibits low intrinsic mode coupling and mechanical quality factor, while it is much more difficult to make 1 3 piezocomposites with good quality than PZT (Or et al., 1998; Or and Chan, 2001). This paper deals with the optimization design and experiment test of high-frequency ultrasonic transducer. The analytical model of the transducer system is established based on electromechanical equivalent circuitry theory, vibration theory and wave theory. In order to increase the amplitude of the transducer, the two-step concentrator is adopted. With the help of the analytical model, the initial topological model of transducer can be calculated. The dynamic characteristics of components are investigated by taking account of piezoelectric effect, and the model is optimized by modal and harmonic analysis using ANSYS software. The manufactured transducer is tested through the impedance analyzer and laser Doppler vibrometer, and the experiment results indicate there are no vibration mode couplings around the working frequency. The developed transducer can fulfill finer pitch packaging. 2. The analytical model of the ultrasonic transducer 2.1. Electromechanical equivalent circuitry of the ultrasonic transducer The electromechanical equivalent method is an effective way to deal with ultrasonic transducer design, and it becomes more convenient by using the similarity between mechanical vibration and electrical resonance. In detail, the mechanical force is equal to voltage, and the vibration velocity is equal to current, meanwhile, the mass, rigidity and damp are equal to inductance, capacitance and resistance respectively. The electromechanical equivalent circuitry of ultrasonic transducer can be gained by separating the piezoelectric material into an electrical port and two acoustic ports through using of an ideal electromechanical transformer, which is illustrated in Fig. 2. The front slab, piezoelectric ring stack, back slab and ultrasonic concentrator are connected mechanically in series, and the transducer system has been treated as a linear system. Z is defined as the impedance related to the size, material and resonance frequency of the components, Z 1p and Z 2p are the equivalent impedances of piezoelectric ceramic stack, Z 11, Z 12 and Z 13 are the equivalent impedances of back slab, Z 21, Z 22 and Z 23 are the equivalent impedances of front slab, Z 31, Z 32 and Z 33 are the equivalent impendence of the exponential Fig. 2 The electromechanical equivalent circuitry of ultrasonic transducer.

3 journal of materials processing technology 209 (2009) The position of the node can be determined by ( ) x 0 = l arctg ln S 1 /S 2 (5) Fig. 3 The structure diagram of exponential concentrator. The bonding tool can be modeled as a dual extension beam clamped by the concentrator. According to the theory of Timoshenko beam, the flexural wave equation of the bonding tool can be represented as (Long et al., 2006) ( EI(y) 4 Z y 4 + S(y) 2 Z y 2 I(y) 1 + E ) 4 Z G y 2 t I(y) 4 Z G y 4 = 0 (6) section in the first-step concentrator, Z 41, Z 42 and Z 43 are the equivalent impedances of the column section in the first-step concentrator, Z 51, Z 52 and Z 53 are the equivalent impedances of the second-step concentrator, Z fl and Z bl are the radiant impedances of the transducer in the front and back directions, p is the number of the PZT, C 0 is the one dimension cut-off capacity of the piezoelectric ceramic, n is the electronmechanical conversion coefficient of the piezoelectric ceramic, and V is the voltage applied to the transducer Vibration and wave theories Supposing that a bar is made of uniform and isotropic material, the stress distribution on multi-section can be regarded as even. Thus the one-dimension longitudinal vibration equation of thin bar with variable cross-section can be expressed by 2 x S(x) S(x) x x + k2 = 0 (1) = 1 (A sin Kx + B cos Kx) (2) S(x) where is the function of particle displacement, x is the coordinate in the longitudinal direction, k is the wave number, S(x) is the area of cross-section, A, B are variables depending on the initial conditions of the system, and K is a variable depending on k, S and x. Fig. 3 depicts the structure of exponential concentrator. As is shown in Fig. 3, the area of the cross-section located at the origin is defined as S 1, the vibration amplitude as 1, the force as F 1, and area located at x = l as S 2, the vibration amplitude as 2, the force as F 2, and l is the length of the concentrator. The function of area varies with x can be written as S = S 1 e 2ˇx, where ˇ = ln(s 1 /S 2 ) 1/2 /l. Submitting the function of area into Eq. (1), the frequency equation of exponential concentrator is shown as follows sin( k 2 ˇ2 l) = 0 (3) The vibration magnification factor of the concentrator can be calculated by = S 1 S 2 (4) where Z (y, t) is the flexural displacement, S (y) is the area of the bonding tool, I (y) is the area moment of inertia, is the density, E is the Young s modulus, G is the shear modulus, and is a constant which depends on geometry of the bonding tool. Based on the above theories, the initial model of 100 khz ultrasonic transducer for microelectronic packaging has been determined. The transducer system is composed of the piezoelectric converter and ultrasonic concentrator with two exponential geometry horns whose lengths are both half of the wavelength. To increase the vibration amplitude of the transducer, a two-step ultrasonic concentrator is utilized. The column is used to smooth the first and second-step exponential horn. The ultrasonic vibration is generated by the four pieces of PZT4, and these piezoelectric ceramics are preloaded by a bolt. In order to decrease the error caused by assembly, the front lab and the concentrator are taken as a whole. The back slab and the bolt are made of stainless steel to reduce the amount of energy loss, and the other components of the ultrasonic transducer are made of titanium alloy. The entire length of the transducer is one and a half wavelength, and the tip amplitude of the ultrasonic transducer becomes bigger by the amplification of the concentrator. This model contains the initial topological information of the transducer, which will be optimized by finite element analysis. 3. Dynamic analysis and optimization design of ultrasonic transducer The transducer system is decomposed into piezoelectric converter and ultrasonic concentrator. FEM is adopted in dynamic analysis and optimization design of the transducer, because it is especially suitable for the analysis of complicated threedimension models with isotropic or anisotropic material. The resonant frequencies, vibration mode shapes, the corresponding displacement and some other important information can all be calculated through FEM simulation, meanwhile, the optimization design of piezoelectric converter and ultrasonic concentrator can also be realized by ANSYS software The dynamic characteristics of single piezoelectric ceramic The operating principle of ultrasonic transducer is based on the converse piezoelectric effect of piezoelectric ceramic,

4 1294 journal of materials processing technology 209 (2009) which can be expressed by the following piezoelectric equations {T} =[c]{s} [e]{e} (7) {D} =[e] T [S] + [ ]{E} (8) where {T} is the stress vector, {D} is the electric flux density vector, {S} is the stain vector, {E} is the electric field vector, [c] is the elasticity matrix, [e] is the piezoelectric stress matrix, and [ε] is the dielectric permittivity matrix at constant strain. To accurately study the dynamic characteristics of the ultrasonic transducer, piezoelectric element solid5 is used to define piezoelectric ceramics. The piezoelectric property of piezoelectric ceramics could be defined through [ε] (relative), [e] and [c]. The parameters of PZT4 are shown as follows = e = (C/m 2 ) c = (N/m 2 ) The FEA of piezoelectric material depends on the following coupled finite element matrix equation [ ]{ } [ {ü} + { V} ]{ [[K z ] T ] [K] d [M] [0] [0] [0] + [ [K] [K] z [C] [0] [0] [0] } { {u} {V} = ]{ } { u} { V} } {F} {L} where [M] is the mass, [C] is the damping, [K] is the stiffness, [K d ] is the dielectric conductivity, [K z ] is the piezoelectric coupling matrix, {u} is the nodal displacements, {V} is the nodal electrical potential, {F} is the vector of forces, and {L} is the vector of charges. The vibration modes of the PZT4 can be identified into three categories: the axial, radial and wall-thickness vibrations. Fig. 4(a) shows the equivalent admittance plotted as a function of frequency, the corresponding vibration frequencies are marked on the figure. Frequencies by the impedance analyzer test are marked in Fig. 4(b). Table 1 summarizes the results of FEM and impedance test, which illustrates that FEM simulation results basically match with the test results. It can happen that there are more electrical resonances by impedance test than FEM simulation, which is because the FEM model is approximation of the actual body, and some non-linear and stochastic factors have been neglected during the modeling process. (9) Fig. 4 The dynamic characteristics of single PZT4 by FEM and experiment test Design and optimization of piezoelectric converter The piezoelectric converter is composed of the front slab, piezoelectric ring stack and back slab which are pre-loaded assembled by a bolt. In order to exactly simulate the converter, the pre-load element prets179 is defined, and 35 MPa pressure is applied to the piezoelectric stack. In addition, by taking the length of front slab and back slab in axial direction as the variables and the vibration frequency as the objective function, the optimization model of the converter has been figured out. The axial vibration frequencies lie at khz and khz within the frequency of 200 khz, and the color deformations of piezoelectric converter are separately depicted in Fig. 5(a) and (b). It can be judged that the ultrasonic energy is transferred Table1 Thevibration frequency comparisons between FEM and experimental results Mode number FEM (khz) Impedance test (khz) Relative difference (%)

5 journal of materials processing technology 209 (2009) Fig. 5 The deformation of the piezoelectric converter vibrating in the longitudinal direction. equally at the frequency of khz, while the ultrasonic energy transmission is not so uniform at the frequency of khz Optimization design of two-step ultrasonic concentrator Due to so many variables of the ultrasonic concentrator, it becomes a more complicated task to make an optimization design. In allusion to this problem, the classification of the factors that affect the dynamic characteristics of the concentrator is essential. Here the factors can be divided into the following cases: the material of the concentrator, the shape of the concentrator outline, the shape of concentrator crosssection and the dimensions of every component in the axial and radial directions. Thus the four cases can be researched separately Different materials of the concentrator The material of concentrator has great influence to its characteristics, and it can also affect the design of entire bonding devices. During this process, the design of one half wavelength concentrator has been operated, and the dynamic characteristics of the concentrator made of titanium alloy, aluminum alloy or steel are studied respectively. The diameter of the maximum cross-section is 12 mm, and the diameter of minimum cross-section is 6 mm. Fig. 6 displays the results of concentrator made of titanium alloy. In order to find out the difference of the characteristics among the three kinds of concentrators, several indices of concentrator are compared with each other, and the results are summarized in Tables 2 4. Here l 1 is the axial length, is the magnification factor of vibration velocity, f is the vibration frequency and X 0 is the distance between the position node and the maximal cross-section. It can be concluded that titanium alloy concentrator has larger magnification factor than the concentrators made of aluminum alloy and steel. Fig. 6 The equivalent displacement amplitude varies as a function of axial length. Table2 Theanalysis results of concentrator made of titanium alloy Parameters l 1 (mm) f (khz) X 0 (mm) Analytical model FEA Relative difference (%) Table3 Theanalysis results of concentrator made of aluminum alloy Parameters l 1 (mm) f (khz) X 0 (mm) Analytical model FEA Relative difference (%)

6 1296 journal of materials processing technology 209 (2009) Table4 Theanalysis results of concentrator made of steel Parameters l 1 (mm) f (khz) X 0 (mm) Analytical model FEA Relative difference (%) Table5 Theindices of concentrators with different outlines Parameters f (khz) (10 15 Pa) Conical outline Exponential outline Stepped outline Different shapes of the concentrator outline The one half wavelength concentrators with conical, exponential and stepped outline are conceived, and the finite element models have been established, which are plotted in Fig. 7. The structure element solid95 has been adopted and the sweep meshing is utilized to keep the outline of the concentrator. The material is defined as titanium alloy. The magnification factor and the stress distribution of the concentrators are investigated, and results by FEA are shown in Table 5. Here is the equivalent relative stress. It is evi- dent that the magnification factor of the stepped horn is the greatest, while the stress is also the highest. The one stepped concentrator with abrupt change of the cross-section is not suitable for bonding technology because the bonder usually works with high velocity and acceleration. Thus thoughts are directed towards designing an outline that lies close to stepped outline whilst avoiding the abrupt change of the cross-section. The two-step exponential concentrator is adopted, and the exponential section is used as the transient connection. Fig. 8 illustrates the stress distribution of the concentrators. Fig. 7 The finite element models of concentrators with different outlines. Fig. 8 The stress distribution of the concentrators with different outlines.

7 journal of materials processing technology 209 (2009) Fig. 9 The models of concentrators with circle and rectangle cross-sections Different shapes of the concentrator cross-section The concentrators with circle and rectangular cross-section are researched, and the models of these concentrators are shown in Fig. 9. Here A 1 and A 2 are the areas of the maximum cross-section and minimum cross-section respectively, and l is the length of the concentrator. The entire length of each concentrator is half of one wavelength, and in order to make a comparison between these concentrators, it is ensured that the concentrators possess the same area at the end surfaces and they all have exponential outline. The simulation results by FEA are shown in Table 6. It can be concluded that the magnification factor of the circular concentrator is much higher than the rectangular one Different axial and radial dimensions of the concentrator components Based on the above comparisons by classification, a concentrator composed of two-step exponential horns with circle cross-section is adopted. By using the titanium alloy as the horn material, acoustic electric translation index can be improved and the mass can be reduced. Through ANSYS Parametric Design Language (APDL), the optimization design of the concentrator has been carried out, and the optimization design of the first and second-step horns is operated respectively. The optimization results are separately illustrated in Figs. 10 and 11. Here l 2 is the axial length of the first step exponential section, l 3 is the axial length of the first step column section, l 4 is the axial length of the second-step exponential section and d 1 is the diameter of the second-step horn s Fig. 10 The optimization result of the first step horn. maximum cross-section. Due to axisymmetric structure of the concentrator, the plane model is established in ANSYS to reduce the time of calculation and improve the accuracy. By taking l 2, l 3, l 4 and d 1 as the variables, the vibration frequency as the objective function, the optimization model of the concentrator is worked out finally. By connection of the first and second horns, the two-step concentrator has been obtained. Modal analysis results show that it vibrates in longitudinal direction at the frequency of khz, and the concentrator has two displacement nodes which have zero displacement during the entire vibration process. The entire length of concentrator is one wavelength, and the magnification factor can reach up to Analysis of transducer without flange The piezoelectric converter and ultrasonic concentrator have been designed and optimized until now. A particular problem is to analyze the transducer vibration characteristics, and to exactly find the displacement node where the flange can be designed and fixed. Because of the axisymmetric structure of the transducer without flange, the plane model of the transducer is set up, the element plane13 is utilized to simulate PZT4 and plane42 is for the other material. There are three longitudinal vibration modes from 1 khz to 110 khz, and the Table6 Theindices of concentrators with different cross-sections by FEA Parameters A 1 (mm 2 ) A 2 (mm 2 ) f (khz) l (mm) Circle cross-section Rectangle cross-section Fig. 11 The optimization result of the second-step horn.

8 1298 journal of materials processing technology 209 (2009) Fig. 12 The finite element model of transducer without flange. profiles of exponential horns amplifies the vibration amplitude, making the displacement amplitude at the tip of the transducer is suitable for bonding technology. As is shown in Fig. 14, the vibration amplitude at the tip of single piezoelectric ceramic (No. 1), the ceramic stack (No. 2), the front slab (No. 3) and the concentrator (No. 4) can separately reach up to m, m, m and m at the frequency of 99.3 khz Analysis of the transducer with the bonding tool Fig. 13 The ultrasonic energy transmission of the ultrasonic transducer. corresponding frequencies are 39.5 khz, 67.0 khz and 99.1 khz. Based on the deformed diagram and data of the transducer, the displacement node in the longitudinal direction has been determined at the frequency of 99.1 khz. The finite element model of transducer without flange is displayed in Fig. 12. During bonding process, it is important to achieve a robust result within the defined operating window. The characteristics of the bonding tool have great influence on the performance of the transducer system. The design of bonding tool is based on Eq. (6), and the finite element model of the transducer system with bonding tool is depicted in Fig. 15(a). Through defining path along y direction, the vibration displacement amplitude of the bonding tool has been gained, which is illustrated in Fig. 15(b). Here l 6 is the length of the bonding tool. This figure shows that the displacement at the tip of the transducer can amplified by the bonding tool, and the magnification factor is about Dynamic characteristics of constrained transducer with flange It is well known that the transducer is sensitive in respect to the clamping. In order to achieve mechanical decoupling between the transducer and other bonding devices, the displacement node should be accurately calculated. Now the transducer is fixed on bonding devices at the longitudinal node, which is realized by applying corresponding initial conditions in the hole of the flange in ANSYS. 35 MPa pressure is applied to the transducer at the same time. Simulation results indicate that the transducer vibrates in longitudinal direction at the frequency of 39.2 khz, 67.4 khz and 99.3 khz. The transducer and other bonding devices are mechanically decoupled at the frequency of 99.3 khz. The transmission of ultrasonic energy in the longitudinal direction has been plotted in Fig. 13. Here l 5 is the entire axial length of the transducer. The longitudinal vibration is obtained from the piezoelectric ceramics, and the concentrator composed of two Fig. 14 The displacement amplitude at different longitudinal positions.

9 journal of materials processing technology 209 (2009) Fig. 15 The finite element model and the simulation result of transducer with bonding tool. 4. Experimental test of the ultrasonic transducer 4.1. Impedance test of the transducer Fig. 16 depicts the high frequency transducers manufactured by numerical control (NC) machine. The transducer with twostep exponential concentrator, the transducer with two-step conical concentrator and the transducer with one-step conical concentrator are all fabricated. In order to reduce the error caused by assembly, the front slab and the concentrator are made together. The impedance tests of the ultrasonic transducers are carried out through impedance analyzer. Fig. 17 shows the impedance of exponential transducer varies with the frequency between 1 khz and 110 khz. There are four major longitudinal vibration frequencies, and 99.7 khz is the desired frequency, which is calculated by FEA as 99.3 khz, the relative difference is just 0.40%, thus the accuracy of the FEM in predicting the vibration frequency is impressive. The figure also illustrates that the modes of the trans- Fig. 17 The impedance test results of the exponential ultrasonic transducer. Fig. 16 The picture of the ultrasonic transducers manufactured by NC machine. ducer around 99.7 khz are very few, which minimizes the effect of mechanical vibration modes couplings on the dynamic characteristics of the high-frequency ultrasonic transducer.

10 1300 journal of materials processing technology 209 (2009) Fig. 18 The tip amplitude of exponential transducer in longitudinal direction. Fig. 19 The tip amplitude of exponential transducer in radial direction Laser Doppler measure of the exponential transducer The displacement amplitude generated by ultrasonic transducer is generally less than 5 m. Due to the shape of the transducer and the small vibration amplitude, these motions are not easily probed by commonly used proximity sensors. Non-contact laser Doppler measure is operated to acquire the vibration amplitude because of the advantages of the laser interferometry measure. The information such as the vibration frequencies, the velocity and the displacement amplitude can be achieved with this method The vibration amplitude of exponential transducer in longitudinal direction The tip vibration amplitudes of the transducer in longitudinal direction by laser Doppler measure from 10 khz to 110 khz are depicted in Fig. 18. The amplitude at the tip of the transducer in the longitudinal direction can reach 1.01 m at the frequency of 99.5 khz when applying voltage U =10sinωt to the piezoelectric ceramics. The longitudinal vibration frequencies by laser Doppler measurements are 40.1 khz, 64.2 khz, 86.3 khz and 99.5 khz, which is in good agreement with the results by impedance test. The displacements calculated by FEM basically match with the results by laser Doppler measurements. It can conclude that the FEM simulations exhibit remarkably high predictive potential for the optimization of the high-frequency ultrasonic transducers The vibration amplitude of exponential transducer in radial direction The tip amplitude of the exponential transducer in radial direction is measured and the results are summarized in Fig. 19. It is evident that the vibration amplitude in radial direction is 82 nm at the frequency of 99.5 khz, and this is much smaller than the longitudinal one, which indicates there is little coupling between radial and longitudinal vibration The vibration amplitude of exponential transducer at different frequencies and applied voltage The dynamic characteristics of the exponential transducer are researched, and the tip amplitudes of the transducer as the frequency and the applied voltage are shown in Fig. 20. Judging from the figure, we know that when the applied voltage to the ceramics varies in a certain range, the vibration amplitude increases with it to some degree, when the voltage reach to some range, the vibration amplitude remains constant. When applying voltage U =10sinωt to the ceramics, the tip vibration amplitude at the frequency of 64.5 khz and 99.5 khz is 1.5 m and 1.01 m respectively. Fig. 20 The tip amplitude of exponential transducer varies as the frequency and the applied voltage.

11 journal of materials processing technology 209 (2009) Conclusions references Based on the traditional theories such as electromechanical equivalent circuitry theory, vibration theory and wave theory, the analytical model of the transducer system is established, which lays the foundation for determining the initial topological information of the ultrasonic transducer. The dynamic characteristics of components are investigated by using FEM. The resonance frequency, vibration displacement nodes and rule of ultrasonic energy transmission are acquired by making modal and harmonic analysis. The results by FEM are compared with the results by analytical method, which shows there are little differences between these two methods. Through optimization design using ANSYS APDL, the optimal model of ultrasonic transducer has been achieved finally. A novel high-frequency ultrasonic transducer for microelectronics packaging has been designed, and the transducer is fabricated. The transducer used PZT4 as the driver, the steel for back slab, and the other parts are made of titanium alloy. In order to improve the magnification factor of the concentrator, the two-step structure with exponential outline is utilized. Through the impedance analyzer and laser Doppler vibrometer, the dynamic characteristics of the fabricated transducer are further researched. The experimental results indicate that there are no undesirable vibration modes around the working frequency, and there is little vibration coupling between longitudinal and radial direction, which will facilitate for the design of the ultrasonic generator with phase lock-loop. A general procedure for design and optimization of high-frequency ultrasonic transducer for microelectronics packaging is presented in this paper. By use of vibration and wave theories, FEM, Impedance analysis and Laser Doppler measure, the design and optimization of the transducer have been realized. This method not only can overcome the difficulty in establishing the exact mathematical model of transducer with irregular shapes by analytical method, but also can solve the difficulty in determining the initial dimensions of the transducer solely depending on FEM. Through FEM, the transducer is optimized, and it is the development of traditional theory for designing transducer. The general procedure is also applicable to design transducers for other ultrasonic manufacturing equipments. However, it has some limitations in dealing with the ultrasonic transducer system with large friction. Acknowledgments This research is supported by the National Natural Science Foundation of China (Grant No , No ) and Tianjin Science and Technology Commission Project (Grant No. 05YFGPGX06000). Special thanks are given to the members of Professor X.T. Hu, Dr. L.Y. Xu and their associates at the State Key Laboratory of Precision Measuring Technology and Instruments. With their help, the laser Doppler measurements have been carried out well. Amin, S.G., Ahmed, M.H.M., Youssef, H.A., Computer-aided design of acoustic horns for ultrasonic machining using finite-element analysis. J. Mater. Process. Technol. 55, Charles, J.H.K., Mach, K.J., Lehtonen, S.J., Francomacaro, A.S., Deboy, J.S., Wire bonding at higher ultrasonic frequencies: reliability and process implications. Microelectron. Reliab. 43 (1), Chiu, S.S., Chan, H.L.W., Or, S.W., Cheung, Y.M., Liu, P.C.K., Effect of electrode pattern on the outputs of piezosensors for wire bonding process control. Mater. Sci. Eng. B-Solid 99 (1), Chu, P.W.P., Chong, C.P., Chan, H.L.W., Ng, K.N.W., Liu, P.C.K., Placement of piezoelectric ceramic sensors in ultrasonic wire-bonding transducers. Microelectron. Eng. 66, Chylak, B., Qin, I.W., Eder, J., Achieve optimal wire bonding performance through ultrasonic system improvement. In: Proceedings of Semicon Singapore 2004, Singapore, pp Lee, J., Kim, J.H., Yoo, C.D., Thermosonic bonding of lead-free solder with metal bump for flip-chip bonding. J. Electron. Mater. 34 (1), Li, X., Zhang, D.Y., Ultrasonic elliptical vibration transducer driven by single actuator and its application in precision cutting. J. Mater. Process. Technol. 180, Liu, Y., Irving, S., Luk, T., Thermosonic wire bonding process simulation and bond pad over active stress analysis. In: Proceedings of IEEE Electronic Components and Technology Conference ECTC2004, Las Vegas, USA, pp Long, Z.L., Han, L., Wu, Y.X., Zhong, J., Effect of bonding pressure on transducer propagation in thermosonic flip chip bonding. In: Proceedings of Conference on High Density Microsystem Design and Packaging and Component Failure Analysis HDP 06, Shanghai, China, pp Marumo, Y., Saiki, H., Nishitake, H., Uemura, T., Yotsumoto, T., Deformation analysis of Au wire bonding. J. Mater. Process. Technol. 177, Or, S.W., Chan, H.L.W., Mode coupling in lead zirconate titanate/epoxy 1 3 piezocomposite rings. J. Appl. Phys. 90 (8), Or, S.W., Chan, H.L.W., Liu, P.C.K., Piezocomposite ultrasonic transducer for high-frequency wire bonding of microelectronics devices. Sensor Actuat. A-Phys. A133, Or, S.W., Chan, H.L.W., Lo, V.C., Yuen, C.W., Dynamics of an ultrasonic transducer used for wire bonding. IEEE T. Ultrason. Ferr. 45 (6), Pang, C.C.H., Hung, K.Y., Sham, M.L., High frequency thermosonic flip chip bonding for gold to gold interconnection. In: Proceedings of IEEE Electronic Components and Technology Conference ECTC2004, Las Vegas, USA, pp Parrini, L., Advanced process characterization for 125 khz wire bonder ultrasonic transducers. IEEE T. Compon. Pack. T. 48 (6), Shah, G.N., Levine, L.R., Patel, D.I., Advances in wire bonding technology for high lead count, high-density devices. IEEE T. Compon. Hybr. 11 (3), Sherrit, S., Dolgin, B.P., Bar-Cohen, Y., Pal, D., Kroh, J., Peterson, T., Modeling of horns for sonic/ultrasonic applications. In: Proceedings of IEEE Ultrasonic Symposium, NV, USA, pp Xu, C.H., Chan, H.L.W., Ng, W.Y., Cheung, K.Y.M., Liu, P.C.K., Characteristics of bonds produced by full ceramic and composite ultrasonic transducers. Solid State Electron. 48,