基于多点报警准则的高质量过程缺陷率控制图

Defective Rate Control Chart for High Yield Process Based on Multi-dot Alarm Rules

为了提高用于高质量过程监控的累积计点值控制图的监控效率，提出了一类采用多点报警准则的高质量过程缺陷率控制图设计，并给出了计算这类改进型控制图的平均运行长度的马尔科夫链方法。为了验证该设计方法的改进效果，分析比较了采用多点报警规则的3种累积计点值控制图（报警规则为连续两点出界、连续三点中有两点出界、连续三点出界）与报警规则不改变的（报警规则为有一个点出界）累积计点值控制图的监控效率。比较结果表明：在受控状态下平均运行长度都为370的情况下，多点报警的累积计点值控制图的失控状态下的平均运行长度分别较报警规则不变的控制图的平均运行长度减小了约44％、40％、63％，控制图发现缺陷率增大的效率明显改善。得出结论：这种多点报警的累积计点值控制图发现缺陷率增大的速度提高40％～60％。

A kind of defective rate control chart for high yield process based on multi-dot alarm rules is proposed to improve the detecting efficiency of cumulative quantity control charts. A Markov chain method is used to calculate average run length of these charts. To illustrate the improved efficiency, the perform- ances of three multi-dot alarm rule charts are compared with normal alarm rule chart. The results show that, when the average run length in control for the four charts reaches 370, the average run length out of control of three multi-dot alarm rule charts decreases respectively by nearly 44% , 40% and 63% of the unchanged alarm rule chart. The efficiency of detecting the increase of defective rate is improved signifi- cantly. The design method proposed can increase the speed of control chart to detect rate raise of high yield processes in 40% - 60%.