With the electronic packaging towards the rapid development of lead free process, the related research on the portable electronic devices subject to impact load is emphasized urgently. At present, the failure modes of fracturing in IMC layer and fracturing on IMC/solder boundary are mostly encountered due to drop test and cyclic bending test respectively. The purpose of this work is to use 3D numerical analysis software ANSYS/LS_DYNA, that were found to be a suitable numerical model for further analyzing the impact fracture of lead-free solder. The relationship between simulation and ball impact test system was compared and the effects of variable parameters on solder balls subjected to impact loading was investigated. Also, the transient deformation and fracturing of solder joints subjected to the impact load were studied numerically and experimentally. Then, the transient response and the failure modes of the solder joint due to impact load were predicted by varied strain rate tests. From the numerical results, the strain rate mechanical properties of solder joint due to high can be effectively obtained. The difference of IMC strength caused three kinds of failure modes of the solder ball, however the failure mode of fracturing in IMC and a party of solder requires a model to simulate with more refined meshes. Different velocities affected the numerical results significantly. The higher the velocity of impact test applied, the lower the impact loading received. That is mainly attributed to the material parameters adopted of a solder ball is strongly dependent on the strain rate considered. Also, it is found that the impact test in reality does not result in a shear-dominant failure mode. While using dynamic simulation instead of the experiment, the damage process of solder joint can be observed. That provides a good reference and contrast for the experimental work in the future.

Abstract This thesis is mainly aimed to the study the basic physical properties of different flux, and the combination with semiconductor packaging of 0.6mm Sn96.5/Ag3.0/Cu0.5 (SAC305) big solder ball, and 0.3mm Sn98.5/Ag1.0/Cu0.5 (SAC105) small solder ball. Big solder ball was proceeded with shear stress test, pull ball test, and tray drop test. However small solder ball was proceeded with shear stress test, pull ball test, zone shear solder balls test and board level drop test. After experiments, samples of different flux, the effect of solder strength and mechanical properties were received and discussed. And failure modes were observed by high-power microscope, SEM and OM. The experimental result shows that the flux doesn¡¦t have direct relationship with the point of welding strong and weak, the point of welding strong and weak is determined by the metal¡¦s characteristics. However, the less of residual flux is, the higher the solder balls shearing force as well as pulling force are. As for the more of residual more of flux, after aged processing, some solder balls have the phenomenon of missing from the IMC layer. And the difference of the residual flux will affect the various failure modes of zone shear solder balls. From board level drop test, the majority of failure modes is pad peeling at the corner of test board side for all test flux, and the remaining failure modes exhibit solder fractured and IMC layer broken. Therefore, the judgement of the residual flux is a very important key factor for the semiconductor packaging. It doesn¡¦t have the direct correlation with the reliability of final products. Keywords: Lead Free, Solder Ball, Flux, Semiconductor Packaging, Tests.

The effect of residual stress on the post-weld-shift (PWS) of a fiber-solder-ferrule (FSF) under a cyclic thermal load is investigated in this thesis. By using the finite element software MENTAT and MARC, the stress distribution in this model of coupled thermal-elastoplasticity is adopted to solve. The temperature dependent material properties are employed to calculate the residual stresses and the thermal stresses of the solder in the solidification process. The PWS of a fiber and the stress distribution of a solder under different temperature cycles are also investigated in this study. The PWS calculated with and without considering residual stresses are compared with the measured data in this study. Results indicated that the effects of residual stresses introduced in the solder solidification can not be ignored. The temperature dependent material properties, i.e., the melting temperature , Young¡¦s Modulus, coefficient of thermal expansion (CTE) and yield strength at high temperature may affect the residual stress distribution and the PWS of the FSF significantly.

This study aims to investigate the thermal fatigue life of the solder ball.Generally, the fatigue of the solder ball results from thermal cyclic loading in different thermal expansion coefficiency of the material in the IC package. To analyze the equivalent stress and the equivalent strain distributions of the solder ball under loading, an analysis software ANSYS was adopted in this study. To stimulate viscoplastic (creep and plastic) property of the solder ball, the Anand model was adopted. From the modified Coffin-Manson equation and the viscoplastic strain range, the fatigue life of the solder ball was obtained finally. The causes of the fatigue life of the solder ball in this study were attributed to many factors, such as the solider ball¡¦s geometry, substrate thickness, different material properties, change of pad diameter, etc. Finally, the researcher found the increasing solder joint reliability methods and supplied the improving solder joint data for the design engineer.

With ever-increasing demands for high-speed data transmission and device capacity to handle various telecommunication data links, the high reliability of these transmission devices is expected for uninterrupted service. A typical optical communication system consists of transmitters in which laser diodes convert electrical signals into light signals, optical fibers with a few pumps transmitting and maintaining these light signals over long distances, and receivers in which photodiodes convert the light signals back into an electronic form. The efficiency of optoelectronic devices in a communication system, which include transmitters and receivers, plays the most important role in determining the quality and the bandwidth of a communication system. For transmitters, the efficiency is defined as the ratio of the light entering the optical fiber to the light generated by the laser diode. Therefore, the optical fiber should be aligned as precisely as possible with the laser diode to ensure the high efficiency. For high performance optoelectronic devices, box-type packages including the dual-in-line package (DIP) and butterfly package with fiber-solder-ferrule (FSF) are widely used. An optical fiber with a metallized end is soldered inside a ferrule tube to form the FSF. The FSF is joined on a u-channel mount in front of laser diode by laser welding. No matter where the fiber locates in the ferrule tube, the place for maximum coupling power can be dynamically measured and then the FSF is fixed. But, researches have shown that the redistribution of residual stress and the stress relaxation of creep phenomenon within the solder will push the fiber shift to the geometrical center of the ferrule and the shift reduces the coupling efficiency of laser module after temperature cycle testing. The efficiency is worse when the initial fiber eccentric offset increased. An optimum approach for reduction of the fiber alignment shift in laser module is to solder the fiber near to the center of the ferrule. A method for automating the FSF packaging process has been developed to fix the fiber within less than 20um of the center of the ferrule. This method makes use of CCD cameras as position sensors to locate the fiber, and compensates all the major sources of inaccuracy resulting from a typical CCD-based packaging system. The accuracy of the fiber position is highly improved from 80um by traditional packaging process to 20um shown in the experiments. Further work is underway to better the accuracy by compensating the minor sources of inaccuracy.

Thesis--Auburn University, 2009. / Abstract. Vita. Includes bibliographic references (p.80-97).

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Ume, I. Charles; Committee Member: Kalaitzidou, Kyriaki; Committee Member: Mayor, J. Rhett. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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