Supplier selection is an important process of purchasing function. The process of selecting the best suppliers involves multiple criteria, both quantitative and qualitative, and alternatives. The decision makers have to make trade-offs between tangible and intangible factor because some of them may be contradictive. The main objective of this thesis is to develop a framework to facilitate this selection process, including determining the best suppliers based on relevant criteria and the order quantity from each selected supplier under volume discount environment. In this thesis, we developed two multi-objective methods to determine the best suppliers and the order quantity for each supplier. The first method first use AHP to determine the weights of criteria, alternatives, and objectives. Then the objective functions are combined into a multi-objective function using the weight of each supplier resulted from AHP. The second method selects suppliers and determines order quantities in a way that the sum of scaled deviation from optimal objective value is minimized. The proposed methods are applied to a supplier selection problem of a case company in the semiconductor testing/packaging industry. The result of the case study indicates the proposed methods are applicable to real-world supplier selection problems.

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