Statistical Quality Control Of The Notebook Li-ion Battery Pack Projection Weld

Information, energy and environment are the main topics which are concerned by human society in 21st century, Li-ion battery, as the newest secondary battery, plays the key role for these three topics. Now, the Li-ion battery is applied widely in various fields due to high working voltage, high energy rate, long cycle life, little self discharge, no memory effect, no pollution. Especially in the information field, as one of main components to realized the notebook PC portability, the Li-ion battery pack performance becomes the main aspect of note PC which is concerned by user. But now, due to the working voltage of a single Li-ion battery is only about 3.6V~3.7V, it can't supply the power for the notebook PC directly. Usually, series-parallel Li-ion batteries shall be connected by welding, then become battery pack to realize its function, So the weld quality impacts the performance of battery pack.Sony, as a pioneer company who realizes the Li-ion battery mass production. Is still a leader of designing and manufacturing in this field due to its advanced technology. First, This thesis introduce briefly the history, principle, characteristic and development future of Li-ion battery; then describe the assembly process of the notebook PC battery pack. After discussing on the quality cost of battery pack production. It is concluded that the key process affecting the quality of Li-ion battery pack is projection weld. Thus, how to improve the weld quality by the traditional statistical quality control technique is discussed and researched in this thesis as below:Firstly, after analysis the main factor which influences the quality of projection weld. Applying designing of orthogonal experiment to find the better set condition for the projection weld.Second, studying to apply the statistical process control chart to realized the weld process quality control for the weld intensity. On the basis of it, through discussing the relationship between the statistical process control status and process capacity, researching the appropriate upper or lower monitor limit range of the weld current. Then the innovative conclusion of the"μ±4σ"limit is put forward.Lastly, analyzing the related economic benefit.This research shows that it is effective in improving the weld quality and reducing the failure cost in the weld process of the notebook PC Li-ion battery pack by applying the traditional statistical quality control technique and tools, and also shows the great economic benefit is gained after this subject implementation. Therefore, it is meaning and valuable research on how to apply the traditional statistical principle and tools in engineering practice. Some of conclusions or exploration in this thesis can be used for good reference as the basis for decision-making and quality improvement in the company or relative industry field.