制程能力介紹

1、page 1,製程能力介紹,page 2,content,製程能力名詞說(shuō)明 短期製程能力cpk vs 長(zhǎng)期製程能力ppk 6 sigma 教材相關(guān)內(nèi)容講解 範(fàn)例說(shuō)明,page 3,數(shù)據(jù)型態(tài),計(jì)數(shù)型數(shù)據(jù) : 可以數(shù)的數(shù)據(jù) 不良品數(shù) / 良品數(shù) 生產(chǎn)良率 / 合格率 yield(%)/ dppm (計(jì)數(shù)型製程能力) 計(jì)量型數(shù)據(jù) : 設(shè)備/工具量測(cè)數(shù)據(jù) 尺寸/厚度/, 線寬 / 鍍銅厚度 / 產(chǎn)品尺寸 cp / cpk / ca (計(jì)量型製程能力),page 4,page 5,page 6,計(jì)量型製程能力,基本觀念 所謂的製程能力(計(jì)量型數(shù)值)，是指一個(gè)製程在固定的生產(chǎn)因素與穩(wěn)定的管制下(3)所生產(chǎn)

2、產(chǎn)品之品質(zhì)符合客戶需求(客戶規(guī)格)的能力。其中包括兩個(gè)評(píng)價(jià)方向,即精度(cp)與準(zhǔn)度(ca)。,page 7,page 8,製程精確度型態(tài),page 9,製程精確度型態(tài),page 10,製程能力名詞,cp : 精度 precision 標(biāo)準(zhǔn)差 離散趨 ca : 準(zhǔn)度 accuracy 平均數(shù) 集中趨勢(shì) cpk : 製程能力 結(jié)合精度&準(zhǔn)度的指標(biāo),page 11,1. 製程精密度cp cp值在衡量製程之變異寬度與規(guī)格上下限之範(fàn)圍的相差情形，其定義為規(guī)格上下限之間可以容納多少個(gè)3(亦即是6)。 (1) cp的計(jì)算式 (2) cp 又稱為 potential capability，即指製程潛在的最大

3、能力，也就是製程之中心值與規(guī)格之中心值重疊而沒(méi)有偏移時(shí)，亦稱為短期能力(short-term capability) 。當(dāng)製程之中心值與規(guī)格之中心值有偏移時(shí)，製程能力就必須減掉下述的矯正值 ca 。,(t=規(guī)格上限-下限),page 12,(2)等級(jí)判定：cp值愈大，表示品質(zhì)愈佳 (傳統(tǒng)工業(yè)的分級(jí)),0.67=4/6,1.00=6/6,1.33=8/6,1.67=10/6,在電子業(yè),cp均要求要達(dá)到2.0, 即達(dá)到6sigma的水準(zhǔn),page 13,cp值圖示,usl,lsl,lcl,ucl,page 14,2. 製程準(zhǔn)確度ca ca值在衡量製程之實(shí)績(jī)平均值相對(duì)於規(guī)格中心值之偏移程度 (1)

4、ca之計(jì)算式 規(guī)格公差 = t = 規(guī)格上限 - 規(guī)格下限 = usl-lsl 規(guī)格中心值 = (規(guī)格上限 規(guī)格下限)/2 注意：?jiǎn)芜呉?guī)格因沒(méi)有規(guī)格中心值故不能算ca (2) ca值為製程中心值偏移規(guī)格中心值時(shí)製程能力之矯正值 (non-centering correction) 。 (3)等級(jí)判定：ca值愈小，表示品質(zhì)愈佳(以下為傳統(tǒng)工業(yè)的分級(jí)),50%=1/2,25%=1/4,12.5%=1/8,page 15,ca值圖示,usl,lsl,page 16,3.製程能力指標(biāo)cpk (1) cpk之計(jì)算式,cpk乃是 ca 和 cp 兩值的綜合指標(biāo),也稱為短期的 製程能力指標(biāo) (short-t

5、erm process capability),page 17,usl,lsl,cpk值圖示,page 18,(2)等級(jí)判定：cpk值愈大，表示品質(zhì)愈佳,另有一指標(biāo)稱為ppk ,ppk與cpk公式相同, 但是其標(biāo)準(zhǔn)差乃是採(cǎi)用不同的計(jì)算方式, ppk之計(jì)算乃計(jì)算製程的總變異,包含了組間變異 & 組內(nèi)變異 而cpk之計(jì)算則未包含組間變異,page 19,製程能力名詞,cp : 精度 precision (製程能力) 標(biāo)準(zhǔn)差 離散趨勢(shì) 12.5% 管理問(wèn)題(初件調(diào)整問(wèn)題) cpk : 製程能力綜合指標(biāo) 結(jié)合精度&準(zhǔn)度的指標(biāo) 1.33 製程問(wèn)題(要再區(qū)分是 cp or ca 問(wèn)題),page 20,p

6、age 21,短期製程能力cpk vs 長(zhǎng)期製程能力ppk,短期 : short term 短期變異 sst(組內(nèi)變異) 短期製程能力 cpk 長(zhǎng)期 : long term 長(zhǎng)期變異 slt (組內(nèi)變異+組間變異) 長(zhǎng)期製程能力 ppk,page 22,page 23,sst - often notated as or sigma, is another measure of dispersion or variability and stands for “short-term standard deviation”, which measures the variability of a

7、process or system using “rational” sub-grouping.,where is the range of subgroup j, n the number of subgroups, and d2* depends on the number n of subgroups and the size n of a subgroup (see next slide),page 24,example:,what measurements can be used to describe process variation?,page 25,the differenc

8、e between the standard deviations slt and sst gives an indication of how much better one can do when using appropriate production control, like statistical process control (spc).,short-term standard deviation :,long-term standard deviation :,page 26,the difference between sst and slt,the difference

9、between slt and sst is only in the way that the standard deviation is calculated slt is always the same or larger than sst if slt equals sst, then the process control over the longer- term is the same as the short-term, and the process would not benefit from spc if slt is larger than sst, then the p

10、rocess has lost control over the longer- term, and the process would benefit from spc the reliability of slt is improved if the data is taken over a longer period of time. alternatively slt can be calculated on several occasions separated by time and the results compared to see whether slt is stable

11、,page 27,defining cpk and ppk,cpk and ppk indexes account also for process centring.,page 28,what do these indexes tell us ?,if pp cp, if ppk cpk, then process is affected by special causes. investigate x-bar/r-chart for out-of-control conditions. spc may be effective,if cp = pp, if cpk = ppk, then process is not affected by special causes during the study run. spc would not be effective in this case,if cp = cpk, if pp = ppk, then process perfectly centred,if cpk cp, if ppk