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The following application of Taguchi Methods was related to us by Professor Dennis Kehoe during the 'Regional Symposium on Quality and Automation' organized by the School of Industrial Technology, Universiti Sains Malaysia, in May 2000.
Viasystems, a manufacturer of multi-player printed circuit boards (PCB) and custom-designed backpanel assemblies, had been asked by its major customer, Cisco to produce a 20-layer PBC with a circuit track width of 4 mils. The board would be known as the 'Hydra Board' and would be priced at around RM2000. Cisco is currently the world's leading manufacturer of information network products.
In order to demonstrate to Cisco its capability to meet Cisco's requirements, Viasystem developed a six-stage cycle known as the 'Process Qualification Lifecycle' as shown in Table 4. DOE, in particular, Taguchi Methods, was employed at stage IV in order to demonstrate that Cisco's requirements could be met even when the process is operated at its 'window' i.e. at the extreme ends of the process specifications. The experiments consisted mainly of 4 runs (i.e. Taguchi's L 4 orthogonal array) and 8 runs (i.e. Taguchi's L 8 orthogonal array) and took approximately 4months to complete. Over five thousand boards were used for the experiments.
Uncontrollable variables (i.e. variables the are difficult or expensive to control under actual manufacturing conditions such as humidity, dust, product variants, etc.) were incorporated into the experiments in order to determine their effect on the performance of the process (ways of minimizing the effect of such variables can be then generated on the basis of such information). The experiments produced 'benchmark' data that could be used for further process improvements. In April 2000, on the basis of the data generated by the experiments and the other stages of the lifecycle, Cisco awarded Viasystems the contract for the Hydra Boards.
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