In this master's thesis is described an approach to solving the challenge of precise positioning of LED diodes within tolerance limits of ± 100 μm with a short-term process capability of 1.66. Achieving such narrow tolerances of placing LED components is possible by introducing new process steps such as gluing, optical verification of the center of the LED component illuminating surface and placing the component with a calculated offset.
The theoretical part introduces the basics of SMT (surface mounted technology) production, theoretical contributions to uncertainty, a description of the technological process for precise placement of LED components, and presentation of quality methods and quality tools.
In the practical part, the Six Sigma DMAIC method approach is described step by step. A real production challenge of narrowing the process spread in placing LED components in the SMT process was addressed. The approach to the challenge was systematic. New knowledge was gained step by step, and the production process was improved with the help of quality tools.
Two DMAIC approaches are described in the master's thesis based on practical examples. For optimizing a new adhesive process in the company, an approach involving the creation of a statistical process model using a Design of Experiments (DOE) experiment was used. The approach proved to be correct, as a useful model for adjusting the desired shape of the adhesive drop was obtained with a small number of repetitions. To achieve a smaller positional uncertainty of the center of the LED illuminating area, the problem was addressed with circles of improvement. Six rounds of improvements were carried out. Important knowledge about the use of devices, design of reference systems, and the influence of tolerances of input materials was gained during the implementation of improvement cycles.
As a result of the collected knowledge, Ishikawa diagrams and process diagrams were created, offering significant value in the case of further use of process technology in new projects. The outcome of optimization and improvement cycles was a stable adhesive process and achieving tolerances in the process of placing the center of the LED illuminating area within tolerances of ± 100 μm with a short-term process capability Cmk: 2.12 and a standard deviation of ±19 μm.
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