Abstract:
To design multi-stage inspection plans in a printed circuit board (PCB) factory for reducing total cost of quality because total cost of quality of a case study factory is substantial. The author develops the cost model based on the concept of Cost of Quality (CoQ). The developed cost model consists of inspection cost, cost of lot rejection, and cost of lot acceptance. These costs depend on sampling parameters, which are sample size and acceptance number, in each of the inspection steps. The inspection plans considered in this research are based on the widely-used ANSI/ASQC Z1.4 standard single and double sampling plans. The developed cost model is then used to select the values of sample size and acceptance number at each inspection step in order to minimize the total cost of quality with the constraints that the average outgoing quality (AOQ) of finished product is not allowed to increase when compared with the previous sampling plans (IPC-6012B). It is found that the selected parameter values of the single sampling plan based on the proposed cost-based model provide lower total cost of quality compared with the cost of the double sampling plan. Even though the single sampling plan introduces higher inspection cost than that of the double sampling plan, it has much lower failure cost. In addition, the cost-based single and double sampling plans provide 4.48% and 4.14% cost saving respectively when compared with the previous sampling plan. Moreover, the values of the average outgoing quality obtained from both proposed plans are better than that of the previous plan.