标题: 制程能力指标Cpk估计方法之比较
A Comparison of Methods for Estimating Process Capability Index Cpk
作者: 赖柏先
Bao-Shien Lai
彭文理
W.L. Pearn
工业工程与管理学系
关键字: 制程能力指标;覆盖率;信赖下界;process capability index;coverage rate;lower confidence bound
公开日期: 2006
摘要: 制程能力指标Cpk被视为高科技制造产业中用来衡量制程或产品品质最普遍的指标之一。主要解决多重工制造产业之制程能力量测与评估等问题并进行处理与分析,进而提升产品品质以达超低不良率之品质要求。对于制程能力之量测与评估,指标Cpk提供了制程良率的信赖下界之重要讯息,因此被业界广泛应用且被认为是一个可信度极高的尺度标准。为了正确地估计与准确地推论制程能力指标Cpk,许多文献分别以传统频率学派与贝氏方法等观点,进行制程能力之分析与推论。对业者而言,信赖下界可以提供最低之制程能力的重要资讯,对于品质工程师在监控制程与评估制程之绩效,可提供制程或产品之品质保证,以提高顾客满意度之服务水准。另外,样本大小之决定对于能否掌握品质特性之关键亦是另一个需要探讨的主题,相对来说,在在影响到资料收集过程中成本之提升。本篇论文主要的目的是以传统频率学派与贝氏方法等观点来比较Cpk之信赖下界,并且略述其优点与缺点,以及点出适用的情况与重要发现。并从实务的观点出发,同时考虑信赖下界之绩效,我们以各样本下推荐适用的信赖下界得以准确地估计与推论制程能力指标Cpk。最后,我们以一个现实生活中晶圆电阻器制程的例子作结。
Process capability index Cpk has been the most popular one used in the manufacturing industry dealing with problems of measuring reproduction capability of processes to enhance product development with very low fraction of defectives (in Parts Per Million; PPM). The index Cpk provides a lower bound on the process yield, a widely recognized criterion for measuring process capability. To properly estimate and accurately infer of the capability index, numerous methods of the Frequentist and the Bayesian perspectives are proposed. In the manufacturing industry, lower confidence bound estimates the minimum process capability providing pivotal information to quality engineers on monitoring the process and assessing process performance for quality assurance. The sample size determination on key quality characteristics is also an important subject directly related to the cost of data gathered procedure. The main objective of this paper is to compare and contrast the lower confidence bounds on Cpk using two approaches, Frequentist and Bayesian approaches, and to outline correspondent advantages and disadvantages of the methods and the keynotes of the applicable discoveries. From practical point of view, we tabulate the accurate and proper lower bound for given n based on the consideration of the performance of lower confidence bounds as sample size n in the fulfillment of capability assessment. A real-world example taken from a MELF resistor manufacturing process is investigated to illustrate the applicability of the proposed approach.
URI: http://140.113.39.130/cdrfb3/record/nctu/#GT009333547
http://hdl.handle.net/11536/79508
显示于类别:Thesis