# Queuing theory on semiconductor flow line

 Author: Choi, Kam-yau Title: Queuing theory on semiconductor flow line Degree: M.Sc. Year: 2000 Subject: SemiconductorsSemiconductors -- ManufacturesQueuing theoryHong Kong Polytechnic University -- Dissertations Department: Multi-disciplinary StudiesDept. of Management Pages: vi, 70 leaves : ill. (some col.) ; 30 cm Language: English OneSearch: https://www.lib.polyu.edu.hk/bib/b1553102 URI: http://theses.lib.polyu.edu.hk/handle/200/4084 Abstract: This dissertation studies a semiconductor manufacturing company at Hong Kong, which belongs to an international enterprise. This enterprise has several other similar manufacturing companies at other countries. Based on the updated information, the enterprise still cannot be the market leader at the semiconductor field either on both volume and price. The ultimate objective of this dissertation is to rise up Hong Kong plant's production volume with lower price. To achieve this objective, the tandem queue theory with the idea of a birth-death process is used to develop a mathematical model for the typical production method in this Hong Kong semiconductor manufacturing company. The production is having infinite input of bare lead-frame at random with exponential arrival time and the components such as die, wire and plastic casing are assembled on this lead-frame and then the following processes such as de-flashing, solder plating, visual inspection, electrical testing, cutting, laser marking and packaging are done with exponential service time on the semi-products in order of arrival at each of a number of machines in series. Finite buffers are locating among the machines to prevent belt stop due to line blocking. The developed model shows that the queue length before each machine is independent among the machines and that installing infinite buffer among the machines can make the production line non stop theoretically. Actually, it is impossible to have infinite buffer. A formula is then developed to find a buffer size for each machine which can give same average queue length as infinite buffer with considering the input arrival rate and the service rate of this machine. In comparing the theoretical data using the developed model or formula with the actual data collected from a production line, about buffer size and outputs, it is found that the present buffer size can already act as an infinite buffer for each machine but there are mismatching found in the output. After analyzing, the mismatching is mainly due to the down time for each machine. As it is known that space is precious at Hong Kong so that increase buffer size is the last method, the first thing to do is to decrease the down time of each machine by finding their causes.

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