ABSTRACT
12-inch wafer has replaced traditional 8-inch wafer with the advantage of lower cost and higher productivity. In this thesis, the research object is the spraying equipment of new process brought by the change of wafer size. The new equipment plays the role of protecting the solder joints on wafer from silicon pollution by spraying a layer of flux on the surface of the wafer. In actual production, there is little method to improve productivity of the new equipment. The research optimized the praying process separately from wafer cycle time and lot-lot set-up time, and the overall optimization were tested by ZYGO’ CP300 film measuring equipment.
Firstly, based on productivity model and a large amount of production data,sensitivity analysis was applied to find out the two key factors that affect the productivity most, which are wafer cycle time and lot-lot set-up time.Secondly, wafer cycle time was optimized based on a flux thickness model by optimizing the model parameters. The results of the optimization were tested by statistical software JMP and productivity was improved by 4.47% through the optimization of wafer cycle time.
Thirdly, lot-lot set-up time was optimized by reducing the waiting time of equipment’s test, the purpose of which is to test whether the current flux thickness in process of spraying is in the weight standards. Waiting time is set to enable the flux in the equipment being full evaporation to ensure the relatively stable flux weight. The waiting time was optimized based on the three flux evaporation models that built in three different environments. The optimization results were tested by JMP software and productivity was improved by7.75 % through the optimization of lot-lot set-up time.Finally, experiments were designed to test the total optimizations by measuring the flux thickness directly using ZYGO’ CP300 film measuring equipment for double check.
The result of test showed that the above two optimizations were able to meet quality requirement of the flux thickness.Through the optimization of the wafer cycle time and the lot-lot set-up time, the productivity was improved by 12.22%. Currently, the research results have been applied successfully in an assembly and test factory.
Keywords: Spraying process, productivity optimization, uniform design, thickness model, evaporation model
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