The factors determining the quality of surface mount technology (SMT) solder joints are numerous, and complex. The exploration of these factors, and how they may affect the reliability and quality of the joints can only be achieved through continuous research. In this project, essential areas of SMT joints were selected for study and analysis, with the intention of providing additional design and process guidelines for the production of quality SMT joints. In the infrared reflow process, one of the common defect phenomena is the occurrence of tombstoning; that is after soldering only one end of the component is soldered while the other is lifted up, assuming a position like a tombstone. The initiation of tombstoning during reflow was analysed based on the forces acting on the component. A model was developed to predict the initiation of this phenomenon. The model shows that, under vibration-free conditions, the surface tension of the molten solder is the source of the force causing the initiation of tombstoning. The contact angle, which varies with the length of the printed circuit board solder land, has a significant effect on the value of the surface tension acting as a force pulling upward on the component. The model further shows that tombstoning initiation is due to the combined effects of the surface tension; the weight of the component; the dimensions of the component; the length of the solder underneath the component; and the length of the solder protruding from the end of the component. Selected components were used as examples for predicting the conditions of initiation, and these conditions were further substantiated by a series of experiments. Another area of study was a method which directly pulled the components off printed circuit boards and this was used as a means for testing the bond quality of surface mount technology leadless chip solder joints. Components D7243, CC1206, RC1206, RC121O, and CC1 812 were selected for this study. It was found that the ultimate tensile force which breaks a component off the printed circuit board has the potential to be used as a parameter for measuring the quality of the solder joint. The effect of solder thickness on the strength of a joint has also been investigated. The shape of joints soldered by two methods, wave soldering and infrared reflow, were compared. Joints at the two ends of a component produced by infrared reflow were found more uniform than the ones produced by wave soldering. A recommendation is made here for the wave soldering approach in achieving uniform solder joints. The effects of solder shape on the joint strength were further investigated by finite element analysis. A convex joint was found marginally more robust than a concave joint. Two aspects of the internal structure of SMT solder joints were investigated, void content and copper/tin intermetallic compounds. The voiding conditions of wave-soldered and infrared reflow joints were compared. No voids were found in all specimens that were produced by wave soldering. However, there were always voids inside joints produced by infrared reflow. Microhardness tests indicated that the hardness of compounds at the copper/solder interface of infrared reflowed joints is lower than that in the wave-soldered joints. It is considered that the lower hardness of the interfacial region of the infrared reflowed joints is due to the presence of voids. Scanning electron microscopy was used to study the formation of copper/tin intermetallic compounds for joints produced by infrared reflow. The results show that Cu 6 Sn5 was the only compound with a detectable thickness. Other compounds such as Cu3 Sn, were virtually not found at all. Aging of the joints at 100°C, shows that both the Cu 6Sn5 and the overall interfacial thickness grew with time. One of the important areas which had been overlooked previously and was studied in some details was the effects of solder paste exposure on the quality of solder paste. The characteristic changes of solder paste due to exposure were investigated in three areas, weight loss, tackiness, and rheology. The evaporation of low boiling point solvents was considered as the main contribution to the loss in the weight of the solder paste. The weight loss against exposure time was found to follow an exponential behaviour. A method was designed to evaluate the tackiness changes of solder paste due to exposure. It was found that the decay of tackiness against exposure time can be expressed by a power law. It is recommended that solder paste manufacturers should provide the necessary characteristic constants so as to enable the characteristics to be calculated after a specific exposure. The rheological changes of the solder paste as a result of exposure were also investigated. The implication on the printability of the solder paste due to these changes was studied and discussed.

In order to make company work efficiently, managers often divide an enterprise into several functions or departments, such as sales, marketing, human resource, finance and manufacture. However, in this structure, managers would fail to see the wood for the trees. Because each department manager has to be responsible for his own performance, which may easily leads these managers to make decisions that are fit for their department instead of the whole company. Therefore, it¡¦s impossible for companies to make an optimized decision in a dynamic environment. As we enlarge space and time, we can find out that decisions may influence one by another, and the feedback of each decision has a long time delay which makes the manager try to see the wood for the trees even harder. For one manager who tries to show up his performance in a short time will leave the side effect which caused by time delay to other people. What even worse is they can¡¦t predict how much side effect is behind. In this research, we used system dynamics and systems thinking to develop our system dynamics model for the case study. And we developed a MFS(management flight simulator) as a learning tool. Students who manipulate this MFS can enrich their ability to see the wood for the trees. In this case study, we choose a factory which provide electronic product assemble services as a research object. The company was established since AD 1989 until now. After first five years hard working time, it started to grow up stably by keeping changing the product and service. In this industry, success is relied on product quality, price, service and delivery time. Only by making the optimized decision in this competition market can gain better performance. This thesis simulated the case company surface mount technology plant from 1995 to 2006 for 12 years. Students can make different decisions to obtain different equity and capital equipment to evaluate their performance. By different result, simulators can reconsider the structure which is behind the game and their own mental models. After learning from this virtual world, players will find out that their own mental models influencing the final result. From the result and experience, one simulator can accumulate their know-how for the next game. After experiencing this double loop learning process, player will finally learn how to make the best decisions by systems thinking for the real world. Keywords : System Dynamics¡BSystems Thinking¡BDynamic Complexity¡BEnterprise Modeling¡BManagement Flight Simulator¡BSurface Mount Technology(SMT)¡BElectronic Manufacturing Services(EMS)