The explosion of SMT and highly-density packages has resulted in more complex and higher density board designs in order to incorporate more features into products while reducing overall package size. This has, in tum, created major challenges for the surface mount manufacturing process, particularly in solder screen printing, component placement, and reflow soldering. Investigation into these areas will contribute to our understanding of the origin of post reflow defects in surface mount assembly and improvement in product quality. The thesis particularly explores empirically the relationship between screen printed paste deposit, the final joint geometry and the fluxing behaviour within the reflowing solder. The thesis also demonstrates the effect of modified screen printing parameters and the lead geometry.

The fatigue-induced solder joint failure of surface mounted electronic devices has become one of the most critical reliability issues in electronic packaging industry. Prediction of the shape of solder joints has drawn special attention to the related development and engineering applications. Numerous solder joint models, based on energy minimization principle and analytical methods, have been proposed and developed. The methods are extensively utilized to the shape design of solder joint. However, it is important to find a suitable method to real applications. Herein, a series of experiments with different geometric parameters of SAC405 solder joints were carried out and the results were compared with the prediction by Surface Evolver Program. The changes of geometric shape with respect to different parameters of solder joint were also discussed. The influence of the geometric parameters, such as volume of solder joint, package weight, solder surface tension, and gravity force to the shape of solder joint were investigated. Two experiments with SAC405 solder balls were carried out. One is to observe the different reflowed geometry shape of solder balls with various volumes, and another is to observe the different reflowed geometry shape of solder balls with various loadings on them. The results show that the models made by Surface Evolver program are very similar to the real shapes observed by experiments, and the differences are between -3% ~ 6.5%. Thus, the results show that the predicted shapes are satisfactorily suitable. Finally, the predicted models by Surface Evolver program were also put into the ANSYS program, and preceded the fatigue life prediction due to thermal cycling tests. The comparison of the effect on fatigue life with respect to different geometry shapes is illustrated. The results show the shape of solder ball due to high loadings is better than that in thermal cycling tests.

In this thesis, the response of solder balls under high-speed impact was investigated. Five solder compositions, such as Sn/4.0Ag/0.5Cu,Sn/3.5Ag/0.75Cu,Sn/1.0Ag/1.0Cu, Sn/3.0Ag/0.5Cu and Sn/2.6Ag/0.6Cu with two pad surface finishes and ball impact test system were used to implement four kinds of experiments including different impact speeds, different hammers, different reflow times and different aging time in room temperature after reflow. From experiments, the variations of solder strength and mechanical properties were received and discussed. At the same time, failure modes and variations of solder structure after reflow were observed by using SEM and X-ray EDS. The experimental results show that maximum impact force on solder joints increases with the increasing of impact speed when it reaches a critical value. The impact force of Sn/2.6Ag/0.6Cu with Ni/Au pad finish is the maximum among all the solder compositions at varied impact speeds. Maximum impact force on solder joints will decrease with the increasing of mass of hammer. The strength of solder ball were reduced significantly after reflow, however, it makes no difference for solder strength to reflow twice. It was found that maximum impact force and impact energy of solder joints didn¡¦t change a lot, but the ductility and stiffness of them varied unstably under the condition of room temperature for seven days after reflow.

The purpose of thesis is to study the transient analysis of structural responses of solder joints under high-Speed impact. By using the experimental and simulation analysis. The experimental work can be divided into six parts, such as different impact speeds, different solder¡¦s components, different pad finishing, different UBM and Runner, and different thickness of PBO. From experiments, the variations of solder joint strength and mechanical properties were received and discussed and the failure mode. The empirical results show that maximum impact force on solder joints decreases as the impact speed increasing. The solder joint strength becomes stronger with the solder adopting elements of Ni and Co. The strength of solder ball was reduced significantly after a reflow. The intermetallic compound strength reduces with solder ball adopting high content of Ag. In impact test, the resistance of UBM of TiAl is better than that of TiAlTi. The runner adopted with the element Pd can improve the IMC reliablility to reduce Mode I failure. However, the PBO thickness has little influence on IMC strength. From the numerical results, in the consideration of strain rate on solder joint the mechanical properties of solder joint could be effectively investigated. According to the different IMC strength there will produce three failure modes of solder ball and the impact force becomes higher as the IMC strength setting higher. If the lower yield stress is considered in lower IMC strength, the impact force is not the highest of all, but the time duration is the highest of all.

The main aim of this paper is to study for the warpage and von Mises stress of PBGA package caused by the variations of mechanical properties of materials in IR-reflow process. At first, taking advantage of the package symmetry only one quarter of the package was modeled by MSC. Marc. The influence of heat transfer was considered by comparing the results of Coupled mechanical-heat transfer analysis and Mechanical analysis. In the second part, the coefficient of thermal expansions and elastic modulus of molding compound and substrate are selected as the four control factors, and the influence of the four control factors to the warpage and von Mises stress were observed. At last, emperical formulas to predicted warpage and von Mises stress values were obtained.

Este estudo sobre imigração internacional em São Paulo do fim do século XIX e início do século XX aborda o refluxo dos migrantes pela reemigração e pelo retorno. Apresenta o fenômeno com a perspectiva do movimento imigratório internacional, como parte importante de um movimento maior e mais dinâmico, e não apenas como reflexo das condições econômicas e sociais locais. Analisa o perfil dos imigrantes em refluxo a partir das listas de bordo de saída do porto de Santos em 1908 e dos relatórios oficiais entre 1890 - 1920. As fontes permitiram identificar o destino, a nacionalidade, os vínculos familiares, a idade, o sexo e a religião dos envolvidos. Essas características foram interpretadas e relacionadas com os condicionantes econômicos e demográficos, bem como com os padrões definidos pela historiografia da imigração. / This study about international immigration in São Paulo at the end of 19th century and the begining of 20th century has the purpose to approach the migrants reflow from remigration and from return. It shows the mentioned phenomenon with the international immigration movement perspective, as an important feature from a higher and dynamic movement and not only as a reflex of economic and social conditions from this place. The analysis was made based on the immigrants\'s profile in reflow, from the schedule on departures boarding lists from Santos in 1908 and the official reports from 1890 to 1920. The source allows to identify the destination, the nationality, the family laces, the ages, sex and the religions from these people. These characteristics were interpreted and linked to the economic and demographic conditionants, as well as the definite patterns from immigration history.

Este estudo sobre imigração internacional em São Paulo do fim do século XIX e início do século XX aborda o refluxo dos migrantes pela reemigração e pelo retorno. Apresenta o fenômeno com a perspectiva do movimento imigratório internacional, como parte importante de um movimento maior e mais dinâmico, e não apenas como reflexo das condições econômicas e sociais locais. Analisa o perfil dos imigrantes em refluxo a partir das listas de bordo de saída do porto de Santos em 1908 e dos relatórios oficiais entre 1890 - 1920. As fontes permitiram identificar o destino, a nacionalidade, os vínculos familiares, a idade, o sexo e a religião dos envolvidos. Essas características foram interpretadas e relacionadas com os condicionantes econômicos e demográficos, bem como com os padrões definidos pela historiografia da imigração. / This study about international immigration in São Paulo at the end of 19th century and the begining of 20th century has the purpose to approach the migrants reflow from remigration and from return. It shows the mentioned phenomenon with the international immigration movement perspective, as an important feature from a higher and dynamic movement and not only as a reflex of economic and social conditions from this place. The analysis was made based on the immigrants\'s profile in reflow, from the schedule on departures boarding lists from Santos in 1908 and the official reports from 1890 to 1920. The source allows to identify the destination, the nationality, the family laces, the ages, sex and the religions from these people. These characteristics were interpreted and linked to the economic and demographic conditionants, as well as the definite patterns from immigration history.

Hybrid pixel detectors are widely used in many fields, including military, environment, industry and medical treatment. When integrating such a detector, a vertical connection technique called flip-chip bonding is almost the only way to realize the high-density interconnection between each pixel detector to the read-out chip. Such bonding can offer high-density I/O and a short interconnect distance, which can make the resulting device show excellent performance. Electro deposition is a promising approach to enable a low cost and high yield bump bonding process, compared with conventional sputtering or evaporation which is currently utilized for small-scale production. Due to that, Indium bumping process using electroplating is selected, as a result of which indium bump arrays with a pitch of 220 μm and a diameter of 30 μm have been fabricated using a standard silicon wafer processing. UBM (under bump metallization) for indium bumping was Ti/Ni (300 Å/ 2000 Å). It helps to increase adhesion between the wafer and the bumps and also serves as an excellent diffusion barrier both at room temperature and at 200°C. The indium is electroplated, using an indium sulfamate plating bath, and then formed into bumps through a reflow process. The reflow is made on a 200°C hot plate with a continuous flow of nitrogen over the wafer. During the reflow the indium is melted and forms into bumps due to surface tension. All the corresponding procedural processing steps and results are incorporated in this paper.

This research details the development of a novel process for four commercially available no-flow fluxing underfills for use with flip chip on FR4 substrates. The daisy chain test die was used such that two point resistance measurements could be used to determine the integrity of the solder interconnects post reflow. The impact of the underfill dispensing pattern on underfill void formation is determined in a full factorial dispense DOE that includes two factors: pattern and speed. Evaluation metrics include underfill material voiding and fillet shape. The impact of the placement process is determined in a second full factorial DOE involving three factors at two levels each: dispense pattern, placement force, and dwell time. Metrics include interconnect yield and underfill voiding. The results of these DOEs are used to select an optimal placement process for each material to be used for the remaining reflow experiments. The process developed is a novel approach to no-flow processing; the material is dispensed to the side of the bond site and allowed to flow under the chip after placement by capillary action during the early stages of reflow. This development allows for void free assemblies using no-flow materials. Reflow parameters are investigated using a parametric approach. The following parameters are varied at 2 levels individually off a baseline profile: Peak Temperature, Time > 183 oC, Peak Ramp Rate, Soak Time, and Soak Temperature. A ranking was developed for each material based on the observable metrics: interconnect yield, underfill material voiding, two point resistance, and a grain area fraction term. The results were used to select an optimal assembly process for each material. Test boards were assembled in replicates of 30 according to the optimal process for each material, and AATC -40 to 125 oC thermal cycling test was performed. The MTTF for these assemblies has exceeded 3000 cycles; the void free process successfully avoids premature failure due to solder extrusion into voids. Further process development work has demonstrated that the process is scalable to larger area array die and other edge dispense patterns have also been demonstrated to result in void free assemblies.

In July 2006, the legislation of RoHS(The Restriction of the use of the Hazardous Substances in Electrical and Electronic Equipment) is fully implemented in EU. Although the major industries have response and preparedness for lead-free products, but they have no complete solution for using lead-free solder paste to replacing tin-lead solder paste. Therefore, two major issues arose in the surface mount process which are the cost increasing and the reliability decreasing of electronic products caused by higher reflow temperature. In addition to these two issue, surface mount of LED is also faced with the problem of attenuating of light intensity of LED due to the increasing of reflow temperature. After years, the companies of solder paste product and surface mount technology accumulate a lot of processing experience and they have certain yield on reflow process of LED. In order to keep competitiveness and market share, the know-how is treated as confidential. By working with about 10 professional surface mount manufacturers, it is interesting to note that solder paste and oven temperature curve used by each manufacturer are not actually the same. By adopting the experiences of cooperation with several professional surface mount manufacturers through experiments, the purpose of this thesis is to find the optimal reflow process parameters such that the light intensity loss of the LED caused by lead-free reflow process can be reduced as much as possible. By using Taguchi method and the executed experiments , the optimal parameter-combination have found efficiently from the four parameters: the peak of reflow temperature, the peak temperature of residence time, the brand of solder and the pre-baking time of LED. The results showed that the peak reflow temperature has the greatest influence among the selected four parameters and the following is the peak temperature residence time. The light intensity loss can be reduced up to 4-9% by adopting the obtained optimal parameters.