Dissertation > Industrial Technology > Metallurgy and Metal Craft > Welding, metal cutting and metal bonding > Welding process

Optimizing the Process of Lead-Free Wave Soldering Based on DOE

Author LiHui
Tutor LiMingYu;ShiJianWei
School Harbin Institute of Technology
Course Materials processing
Keywords the lead free wave soldering DOE the optimized process the mathematics model the defects
Type Master's thesis
Year 2008
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Wave soldering is regarded as one of the processes for producing electronic products which is controlled difficultly. When many companies for producing electronic products are on stream by wave soldering, the process of wave soldering is established by the experience from the engineers and the data from the equipment provider. But this method lacks of scientific testing and statistic base, so it is difficult to achieve the high quality in electronic assembly.DOE (design of experiment) is an aggregate for experiments which is based on statistics. It’s a powerful tool for optimizing product and process design, reducing cost, and solving problem. In this paper the method is introduced to optimize the process of lead free wave soldering. Two methods in DOE used to study the process is fractional factorial design (FFD) and respond surface methodology (RSM).Primary research on the process of lead free wave soldering is made by the fractional factorial design. Based on the good weldability of the component and rationalization of pad design, we use the fractional factorial design of 6 factors and 2 levels (2 IV 6-2). In this experiment the flux, preheat temperature, immersion depth, dwell time, the temperature in oven and the angle of conveyor are regarded as experiment factors, and the amount of bridge and cold solder per one printed circuit board (PCB) are regarded as the experiment result. The experiment result shows the main defects in lead free wave soldering are bridge and cold solder, and there are few the defects else. The result also tells that the flux, the dwell time and the angle of conveyor have great impact on the formation of bridge, and they can be controlled so suitably that the amount of the defect will be reduced greatly. Similarly, the flux and dwell time are the most important factors for cold solder. If we offer good control to the process, the amount of the defect reduces sharply. At last, the main 3 factors which affect the quality of wave soldering can be gained, and they are the flux, dwell time and the angle of conveyor.According to the result above, respond surface methodology (RSM) can be used to optimize the process of lead free wave soldering. The flux, dwell time and the angle of conveyor are regarded as our object, and the average amount of the defect in printed circuit board (PCB) are response. From this experiment, the optimized process of lead free wave soldering and the mathematics model about the relationship for the process and the defect can be gained.The equation is solved to find the optimized process of lead free wave soldering which includes the amount of flux is 0.15g or 750μg/in2, preheat temperature is 120℃, immersion depth is 0.8mm, dwell time is 2.3s, temperature in oven is 260°, the angle of conveyor is 6.3°. It is proved by practice that the process mentioned above is used to manufacture to control the defect in 2000PPM.Finally, the academic analysis and discuss are followed by these experiments for the process of lead free wave soldering and the defect, which can offer the materials for the further research on wave soldering.

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