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<p style="margin: 0px 0px 15px; padding: 0px; word-spacing: -1.5px; line-height: 25px; text-indent: 24px; font-family: "Microsoft Yahei";">1、smt工廠的工藝窗口<p style="margin: 0px 0px 15px; padding: 0px; word-spacing: -1.5px; line-height: 25px; text-indent: 24px; font-family: "Microsoft Yahei";">
<p style="margin: 0px 0px 15px; padding: 0px; word-spacing: -1.5px; line-height: 25px; text-indent: 24px; font-family: "Microsoft Yahei";">工藝窗口通常用來描述工藝參數(shù)可用的極限范圍，是“用戶規(guī)格范圍（USL-LSL）”概念在SMT工藝領(lǐng)域的專業(yè)用語。<p style="margin: 0px 0px 15px; padding: 0px; word-spacing: -1.5px; line-height: 25px; text-indent: 24px; font-family: "Microsoft Yahei";">
<p style="margin: 0px 0px 15px; padding: 0px; word-spacing: -1.5px; line-height: 25px; text-indent: 24px; font-family: "Microsoft Yahei";">例如，按照經(jīng)驗，再流焊接的最低溫度一般要比焊料熔點高11~12oC，當使用Sn63P-b37時，合金的熔點為183oC，其最低的再流焊接溫度為195oC左右。在J-STD-020B中，規(guī)定元器件的最高溫度為245oC，這樣SMT加工廠的有鉛工藝可用的工藝窗口為50oC，而不是“245-183”所得的理論上的62oC。這里一定要注意“可用”兩字<p style="margin: 0px 0px 15px; padding: 0px; word-spacing: -1.5px; line-height: 25px; text-indent: 24px; font-family: "Microsoft Yahei";">
<p style="margin: 0px 0px 15px; padding: 0px; word-spacing: -1.5px; line-height: 25px; text-indent: 24px; font-family: "Microsoft Yahei";">2、smt工廠的工藝窗口指數(shù)（PWI）<p style="margin: 0px 0px 15px; padding: 0px; word-spacing: -1.5px; line-height: 25px; text-indent: 24px; font-family: "Microsoft Yahei";">
<p style="margin: 0px 0px 15px; padding: 0px; word-spacing: -1.5px; line-height: 25px; text-indent: 24px; font-family: "Microsoft Yahei";">SMT工廠的工藝窗口指數(shù)（Process Window Index,PWI），是衡量用戶確定的工藝極限值范圍內(nèi)工藝能力適應(yīng)程度的指標，換句話說，就是使用工藝窗口的最大百分比，用于簡單說明工藝是否滿意技術(shù)規(guī)范的要求，其值基本上是Cp倒數(shù)的百分數(shù)。PWI越大，工藝穩(wěn)定性越差，反之，亦然。<p style="margin: 0px 0px 15px; padding: 0px; word-spacing: -1.5px; line-height: 25px; text-indent: 24px; font-family: "Microsoft Yahei";">
<p style="margin: 0px 0px 15px; padding: 0px; word-spacing: -1.5px; line-height: 25px; text-indent: 24px; font-family: "Microsoft Yahei";">PWI=100xMax{（測量值-平均極限值）/（最大極限范圍/2）}<p style="margin: 0px 0px 15px; padding: 0px; word-spacing: -1.5px; line-height: 25px; text-indent: 24px; font-family: "Microsoft Yahei";">     <p style="margin: 0px 0px 15px; padding: 0px; word-spacing: -1.5px; line-height: 25px; text-indent: 24px; font-family: "Microsoft Yahei";">以SMT工廠的在流焊接曲線為例說明，工藝曲線主要控制參數(shù)有升溫速率、預(yù)熱時間、預(yù)熱結(jié)束時間、峰值溫度和熔點以上時間，通過測量與計算，取四個參數(shù)中PWI最大的值作為溫度曲線的PWI。<p style="margin: 0px 0px 15px; padding: 0px; word-spacing: -1.5px; line-height: 25px; text-indent: 24px; font-family: "Microsoft Yahei";">
<p style="margin: 0px 0px 15px; padding: 0px; word-spacing: -1.5px; line-height: 25px; text-indent: 24px; font-family: "Microsoft Yahei";">3、SMT工廠的工藝能力指數(shù)（Cp）<p style="margin: 0px 0px 15px; padding: 0px; word-spacing: -1.5px; line-height: 25px; text-indent: 24px; font-family: "Microsoft Yahei";">
<p style="margin: 0px 0px 15px; padding: 0px; word-spacing: -1.5px; line-height: 25px; text-indent: 24px; font-family: "Microsoft Yahei";"> SMT工廠的工藝能力指數(shù)Cp，臺灣企業(yè)稱為制程能力指數(shù)。反映了用戶的規(guī)格范圍（∂）內(nèi)有多少個6σ，數(shù)值越大，工藝的穩(wěn)定性越高。<p style="margin: 0px 0px 15px; padding: 0px; word-spacing: -1.5px; line-height: 25px; text-indent: 24px; font-family: "Microsoft Yahei";">                           Cp=（USL-LSL）/6σ<p style="margin: 0px 0px 15px; padding: 0px; word-spacing: -1.5px; line-height: 25px; text-indent: 24px; font-family: "Microsoft Yahei";"> 其中，σ標準偏差，反映了數(shù)據(jù)各點到其平均數(shù)距離的平均值，即正態(tài)分布“鐘”形圖形的寬窄，越窄說明SMT加工廠的工藝能力越強；USL為用戶規(guī)格上限，LSL為用戶規(guī)格下限。<p style="margin: 0px 0px 15px; padding: 0px; word-spacing: -1.5px; line-height: 25px; text-indent: 24px; font-family: "Microsoft Yahei";"> <p style="margin: 0px 0px 15px; padding: 0px; word-spacing: -1.5px; line-height: 25px; text-indent: 24px; font-family: "Microsoft Yahei";">一般選取SMT工廠的核心工藝指標進行測量。如再流焊接爐，我們可以測量峰值溫度的在不同負載率的情況下的波動。<p style="margin: 0px 0px 15px; padding: 0px; word-spacing: -1.5px; line-height: 25px; text-indent: 24px; font-family: "Microsoft Yahei";"> <p style="margin: 0px 0px 15px; padding: 0px; word-spacing: -1.5px; line-height: 25px; text-indent: 24px; font-family: "Microsoft Yahei";">工藝能力管理指數(shù)Cpk,反映的是正態(tài)分布“鐘”形圖形的居中性，即Cpk =（USL-u）/（3σ）或（u-LSL）/（3σ）的最小值。其中u為用戶規(guī)格的中心值。<p style="margin: 0px 0px 15px; padding: 0px; word-spacing: -1.5px; line-height: 25px; text-indent: 24px; font-family: "Microsoft Yahei";"> <p style="margin: 0px 0px 15px; padding: 0px; word-spacing: -1.5px; line-height: 25px; text-indent: 24px; font-family: "Microsoft Yahei";">
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