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【正文】 Variation Acknowledgements ? Benny Matthiassen (NMP CMT, Copenhagen, Denmark) ? Frank Adler (NMP Alliance, Dallas, USA) ? Joni Laakso (NMP Ramp。 NOKIA 2001 The Sources of Process/System Variation Methods Operators Customer Satisfaction Material Environment Equipment Process 7 169。 NOKIA 2001 Measurement Report In most cases we measure only one part per cavity for measurement report 11 169。 NOKIA 2001 E1 E2 E3 E4 E5 The Nokia Process Verification Process Black diamonds to be fixed by E3 (often a change of a white diamond) Proposal for black diamonds to be discussed with Supplier. Max: 105,85 Ongoing Process Control (SPC) Tolerances applied to drawing 1 part/cavity measured for measurement report White diamonds(s) to be agreed White diamonds(s) to be discussed with supplier 10 parts/cavity measured for measurement report Capability study: Requirement: Cp and Cpk by E3. Quantities to be agreed with supplier. Minimum 5 parts pr 1/2 hour in 10 hours measured for each cavity = 100 parts. Can vary depending on tool capacity, . stamped parts (see DMY00019EN) 15 169。 NOKIA 2001 “ Population Parameters” ? = Population mean ? = Population standard deviation Population versus Sample Population ? An entire group of objects that have been made or will be made containing a characteristic of interest Sample ? The group of objects actually measured in a statistical study ? A sample is usually a subset of the population of interest “ Sample Statistics” x = Sample mean s = Sample standard deviation 18 169。), a measure of central tendency, is the mean or average of all values in the population. When only a sample of the population is being described, mean is more properly denoted as (xbar) : x20 169。 n=5 23 169。 NOKIA 2001 The difference between sST and sLT ?The difference 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 shortterm, and the process would not benefit from SPC ?If sLT is larger than sST, then the process 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 pared to see whether sLT is stable 27 169。 NOKIA 2001 Defining Cpk and Ppk ???????ststpk sm e anU SLsL SLm e anC*3,*3m i nSample mean Process variation 3s Process variation 3s Mean LSL USLMean LSL USL Nominal dim ???????ltltpk sm e anU SLsL SLm e anP*3,*3m i nCpk and Ppk Indexes account also for process centring. 31 169。 NOKIA 2001 Cpk With a 2sigma safety margin 3 sST + 3 sST LCL UCL LSL USL Mean value = Nominal value or Target ?Requirement for Cp and Cpk is min. is a ratio of = 5/3 or 10/6. 6 * standard deviation 10 * standard deviation 2 * standard deviation 2 * standard deviation 34 169。 Cpk are based on the short term variation which may not represent the long term reject rate 37 169。3*s LSL USL A) LSL USL B) LSL USL C) USL LSL D) 40 169。 NOKIA 2001 Estimate Cp and Cpk? D USL LSL D) Nominal Mean USL LSL 6*s USL Mean Mean LSL 3*s 44 169。 NOKIA 2001 Data Collection Sheet () 48 169。 NOKIA 2001 Exercise 3: Cpk Data Spreadsheet ? Open spreadsheet Data exercice . Dim 13 is identical to the data from the previous exercises. ? Verify the results from the previous exercises for dimension 13. ? Analyse the remaining data sets an ment the process, should any actions be made? Remember to create and look at the charts. 52 169。 NOKIA 2001 Cpk Confidence Limits with a sample size of 100 and a nominal Cpk of
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