Machine Capability
Machine Capability
        Mario Perez-Wilson
        President
        Advanced Systems Consultants
                  v
                        "Machine/Process Capability Study"
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ISBN 1-883237-10-6
                                                      vi
                                                                                                               M/PCpS™
Table of Contents
FOREWORD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv
PREFACE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii
Section 1
Definition of a Process              .................................1
Definition of Capability               ................................1
Definition of Process Capability                   ..........................1
Definition of Machine/Process Capability Study                             ..............3
The Capability of the Parts Makes the Capability of the
  Whole             ...........................................6
Strategy for Implementing a Machine/Process Capability
  Study Program          .......................................7
Rank Order the Sub-processes and Machines . . . . . . . . . . . . . . . . . . . . 8
M/PCpS Teams                   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
M/PCpS Coordinator                 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Important Roles of Team Members                      . . . . . . . . . . . . . . . . . . . . . . . . 11
Pareto Principle         . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Stages of the Machine/Process Capability Study Methodology . . . . . 27
Section 2
1st Stage: Process Delineation - Machine Definition
Introduction       . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Types of Data            . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Scales of Measurement                    . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Cause and Effect Diagrams                    . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Brainstorming            . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Four Steps for Machine Definition                      . . . . . . . . . . . . . . . . . . . . . . . . 39
Section 3
1st Stage: Process Delineation - Sub-Process Definition
Four Steps for Sub-Process Definition       . . . . . . . . . . . . . . . . . . . . 51
Section 4
2nd Stage: Metrology Characterization - Measurement
Definition
Introduction            . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Four Steps for Measurement Definition                   . . . . . . . . . . . . . . . . . . . . 63
Section 5
2nd Stage: Metrology Characterization - Gauge Capability
Introduction           . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Accuracy           . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Precision          . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
Repeatability and Reproducibility                    . . . . . . . . . . . . . . . . . . . . . . . . . 80
Six Steps for Gauge Capability                   . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
Section 6
3rd Stage: Capability Determination - Machine Definition
Introduction             . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
Frequency Distributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
Measures of Central Tendency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
Measures of Spread . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
Measures of Shape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
Percentiles      . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
The Ogive Curve        . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
Normal Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
Standard Normal Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
Machine and Process Potential, Cp . . . . . . . . . . . . . . . . . . . . . . . . . . 116
Machine and Process Capability, Cpk                    . . . . . . . . . . . . . . . . . . . . . . . 118
Short and Long Term Capability Studies . . . . . . . . . . . . . . . . . . . . . . 121
Ten Steps for Machine Capability . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
Section 7
4th Stage: Optimization - Reduction of Variability
Introduction              . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
Experimentation - An iterative process . . . . . . . . . . . . . . . . . . . . . . . 183
Factorial Designs                   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
Experimental Design Funnel              . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
Multi-Vari Charts   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
Ten Steps for Reduction of Variability                  . . . . . . . . . . . . . . . . . . . . . 191
Section 8
5th Stage: Control - Preventive Control
Introduction     . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217
Control Charts         . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
PosiTrol Plans       . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235
Five Steps for Preventive Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239
Section 9
Standard Worksheets and Forms                        . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
Section 10
Example
"Guggenheim" Wafer Back Sizing                              . . . . . . . . . . . . . . . . . . . . . . . . 272
Plasma Etch Process                       . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283
Flowchart of the Machine/Process Capability Study
Methodology             . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307
Appendices              . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313
 Six Sigma or + Six Sigma                     . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 314
 Likert Scale for PWB Solder Deposition                             . . . . . . . . . . . . . . . . . . . . 316
 Nonparametric Statistical Tests                        . . . . . . . . . . . . . . . . . . . . . . . . . . 317
 Relationship Between the Range Average and Sigma . . . . . . . . . . . 318
 Charting the Range against the UCL for the Range                                   . . . . . . . . . . . . 321
 Transforming from the Normal Distribution to a Standard
   Normal Distribution                      . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322
 Fitting a Continuous Curve                     . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323
 Possibilities of M/PCpS at the end of the Capability
   Determination Stage                      . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324
 Objective of an M/PCpS Study                         . . . . . . . . . . . . . . . . . . . . . . . . . . . 325
 Cumulative Normal Distribution Table . . . . . . . . . . . . . . . . . . . . . . 326
 Unilateral Normal Distribution Table . . . . . . . . . . . . . . . . . . . . . . . . 327
 Minitab Instructions for the Capability Determination Stage . . . . . 329
References          . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339
Index     . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343
About the Author              . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351
Comments from Our Customers                           . . . . . . . . . . . . . . . . . . . . . . . . . . . 352
Letters: Motorola - Six Sigma                       . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354
Order Form            . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357
Foreword
In recent years, American industry has made some progress in product design through
techniques such as the design of experiments. Products have been made more
"robust" against "noise" and environmental factors through parameter design and
tolerance design. Yet, the process that produces the product is often treated as a
stepchild. Development engineers do not feel responsible for the process. They
relegate that to the process engineer, who, in turn, is heavily dependent on the supplier
of the equipment used in the process. And all of them use arbitrary process
specifications, antiquated procedures and hit-and-miss experiences in determining
process parameters. The result is confusion, finger-pointing, low yields and the high
cost of poor quality.
A cooking analogy can be used to describe the chaos in production processes. The
task is to bake a cake. But imagine the quality of the cake if the cook had no recipe,
no knowledge of the ingredients or their respective quantities! Yet industry moves
along blithely with little knowledge of which are the important process variables that
must be tighly controlled and which are the unimportant variables where costs can be
substantially reduced. In short, poor process characterization and optimization are of
epidemic proportions in industry.
                                                                  Keki R. Bhote
                                                    Senior Corporate Consultant
                                          Quality and Productivity Improvement
                                                                   Motorola Inc.
Preface
An attempt was made to illustrate the complete methodology using the same
manufacturing process example. However, to simplify the explanation of
certain steps a different manufacturing process was utilized.         The
manufacturing process operation selected to demonstrate the methodology is
the Wafer Sizing operation done on silicon wafers in the semiconductor
industry. Other areas of the methodology have been demonstrated using a
Printed Wiring Board (PWB) wave soldering system, a fuze assembly
operation, and an electronic component manufacturing process.
The methodology utilizes many techniques and problem solving tools that are
usually covered independently. In the methodology, these tools and techniques
have been incorporated in sequential order of execution, and integrated into one
logical approach for optimizing manufacturing processes and machines. Some
of the techniques are: Design of Experiments (Full Factorial Design and
Fractional Factorial Designs), Analysis of Variance, Yates Algorithm, Pareto
Diagrams, Concentration Diagrams, Ishikawa Diagrams, Control Chart,
PosiTrol Plans, Pre-control, etc.
The book is divided into ten sections. The first section describes the author's
derivation of the Machine/Process Capability Study methodology. It also
suggests how the methodology should be implemented in a manufacturing
environment. Sections two through eight present the five stages of the M/PCpS
pages describing the methodology have "M/PCpS" in its place. Section nine
presents all the standard worksheets (forms) used for guiding the user through
the methodology and for complete documentation of the study. Finally, section
ten contains a complete example of a M/PCpS study.
To the academic reviewers of this book, I must confess that this book is not for
you, but rather for the individuals (engineers, managers and practitioners) in the
manufacturing world struggling to find a method for reducing variation in their
processes.
                                                              Mario Perez-Wilson
                                           Kowloon, Hong Kong , December 10, 1988
The cumulative normal distribution table gives the area under the curve from
minus infinity to the z-score or z value chosen.
µ Z Value +
Percent of product that falls below the                                               Percent of product that falls ouside the
USL = 45 comes from the Table:                                                        USL = 45 is equal to:
                                                              AA                                                                            A
                                                                                                                                        Percent of product
                                                                                                                                       outside specification
              15            30      37.5
                                     X        45                                                   15          30       37.5
                                                                                                                        X       45
                                                                                                                                            A
                                               Cumulative Normal Distribution
        Z            0.00          0.01            0.02        0.03        0.04       0.05         0.06       0.07             0.08     0.09               Z
        0.0         0.500 00       0.503 99        0.507 98   0.511 97   0.515 95   0.519 94      0.523 92   0.527 90       0.531 88   0.535 86           0.0
        0.1         0.539 83       0.543 79        0.547 76   0.551 72   0.555 67   0.559 62      0.563 56   0.567 49       0.571 42   0.575 34           0.1
        0.2         0.579 26       0.583 17        0.587 06   0.590 95   0.594 83   0.598 71      0.602 57   0.606 42       0.610 26   0.614 09           0.2
        0.3         0.617 91       0.621 72        0.625 51   0.629 30   0.633 07   0.636 83      0.640 58   0.644 31       0.648 03   0.651 73           0.3
        0.4         0.655 42       0.659 10        0.662 76   0.666 40   0.670 03   0.673 64      0.677 24   0.680 82       0.684 38   0.687 93           0.4
        0.5         0.691 46       0.694 97        0.698 47   0.701 94   0.705 40   0.708 84      0.712 26   0.715 66       0.719 04   0.722 40           0.5
        0.6         0.725 75       0.729 07        0.732 37   0.735 65   0.738 91   0.742 15      0.745 37   0.748 57       0.751 75   0.754 90           0.6
        0.7         0.758 03       0.761 15        0.764 24   0.767 30   0.770 35   0.773 37      0.776 37   0.779 35       0.782 30   0.785 23           0.7
        0.8         0.788 14       0.791 03        0.793 89   0.796 73   0.799 54   0.802 34      0.805 10   0.807 85       0.810 57   0.813 27           0.8
        0.9         0.815 94       0.818 59        0.821 21   0.823 81   0.826 39   0.828 94      0.831 47   0.833 97       0.836 46   0.838 91           0.9
        1.0         0.841 34       0.843 75        0.846 13   0.848 49   0.850 83   0.853 14      0.855 43   0.857 69       0.859 93   0.862 14           1.0
        1.1         0.864 33       0.866 50        0.868 64   0.870 76   0.872 85   0.874 93      0.876 97   0.879 00       0.881 00   0.882 97           1.1
        1.2         0.884 93       0.886 86        0.888 77   0.890 65   0.892 51   0.894 35      0.896 16   0.897 96       0.899 73   0.901 47           1.2
        1.3         0.903 20       0.904 90        0.906 58   0.908 24   0.909 88   0.911 49      0.913 08   0.914 65       0.916 21   0.917 73           1.3
   A high value of Cp does not guarantee that the process is capable of producing
   product within specification. Furthermore, the whole distribution of the
   process, might not overlap with the specification range. The process potential
   does not measure the location of the average of the actual spread with respect
   to the center (target) of the allowable spread, it only compares their widths.
   The capability index, Cpk, measures the degree of centering of the actual
   process spread with respect to the allowable spread.
   The Cp may only be calculated when two sided specifications are available.
   Numerical properties such as addition and averages, cannot be applied to the
   Cp because it is a unitless index and would not yield meaningful information.
                                                  Engineering Specification or
                                                    what engineer judgment                         What the
                                                    establishes as allowable                       customer
           Allowable Spread                       for that machine or process.
Cp =                                                                                               WANTS.
             Actual Spread                         The spread from the data                        What the
                                                 collected from the machine or                     customer
                                                             process.                               GETS.
                                   AA
              LSL          ALLOW ABLE
                                           USL
                             SPREAD                       [ USL      LSL ]
                                    AA
                                  ACTUAL
                                  SPREAD
                                       X
                                                         6 x S where S is based on a large
                                                               sample size (Long term study)
15 30 45
 Formula:
                                          USL       LSL             (Short Term Study)
                         Cp =
                                             8 x S
                                                                                       A
                                                                 LSL            ALLOWABLE             USL
                                                                                  SPREAD
Actual Process Data:
                                                                                     T
                                                                                       A
  Mean, X : 34
                                                                                       A
   Standard Deviation, S: 3.75
                                                                                       A
                45 - 15               30
   Cp =                           =             = 1.33
                                                                                       A
               6 x 3.75               22.5
                                                                 15                 30 X                45
                                                                                       ACTUAL
                                                                                       SPREAD                   6xS
Actual Process Data:
   Mean, X : 60                                                       45 - 15     30
                                                         Cp =                  =                    = 1.33
   Standard Deviation, S: 3.75                                        6 x 3.75   22.5
                                                                         A
                LSL               ALLOWABLE         USL
                                    SPREAD
                                                                         A
                                                               Defective units:       100%
                                      T
                                                                         A
                                                                         A
                                                                       ACTUAL
                                                                       SPREAD                6xS
                                                                         A
                 15                   30             45
                                                                         AX
                                                  X     LSL      ; USL   X               }
                      Cpk =       {Smallest of:       3xS            3xS
                          AA                                                      A
               LSL            T          USL                     LSL             T            USL
                           AA                                                     A
                                                                                  A
               15            X            45
              Distribution Mean is centered
             to the Target of the Specification
                                                                 15
                                                                                  A  X        45
                                                              Distribution Mean is NOT centered
                                                               to the Target of the Specification
                          A
deviations.                                     Specification: 30 + 15
                                                                                                      {
                          AA
            LSL                               USL
                         Target
                                                                                          Target
                                                                                                         Tolerance
                                  USL X            (One Half)
                                                                                 Actual Process Data:
                                                   Allowable
                           AA
                                                    Spread                             X = 30
                                                                                     S = 3.75
                                                        (One Half)                          45 - 30    15
                                                                                   Cpk =            =       = 1.33
                                  3xS                     Actual
                                                                                           3 x 3.75   11.25
                                                          Spread
                          AA
process potential, Cp.
             LSL                              USL
                            T                            (One Half)
                                                         Allowable                Actual Process Data:
                                                          Spread
                                                                                       X = 34
                           AA
                                      USL X
                                                                                     S = 3.75
                                                                                            45 - 34    11
                                                                                   Cpk =            =       = 0.98
                                                        (One Half)                         3 x 3.75   11.25
                                       3xS                Actual
                                                          Spread                              45 - 15     30
                                                                                     Cp =              =      = 1.33
                                  34                                                          6 x 3.75   22.5
             15                               45
                                  X
In the next example, the sampling distribution is not centered with the target, T,
of the specification. The standard deviation is very large and even if the
distribution were centered, the process would still not be capable. The process
potential is less than 1.0, which indicates that centering the distribution would not
make the process capable. To make this process capable, the standard deviation
has to be reduced.
                                       AA
            LSL            T                  USL
                                                                                  Actual Process Data:
                                                     USL X
                                                                                      X = 37.5
                                        AA
                                                                                      S = 7.82
                                                                                             45 - 37.5     =    7.5 = 0.32
                                                                                   Cpk =
                                                                                              3 x 7.82         23.46
                                                    3xS
                                                                                     Cp =     45 - 15           30
                                                                                                          =                 = 0.639
                                       37.5                                                   6 x 7.82         46.92
             15                               45
                                       X
Machine Capability
Interpretations of the Normal Probability Paper plots.
                                                                          A
                                        +3σ
                                                                          A
                                                                          A
                                        µ
                                        −3σ
                                        −4σ
                                                                          A
                 Negatively Skewed
               LSL                USL                        Negatively Skewed
                                                                                 A
                                        +4σ
                                        +3σ
                                                                                 A
                                        µ
                                                                                 A
                                                                                 A
                                        −3σ
                                        −4σ
                                                                                 A
               Positively Skewed                             Positively Skewed
              LSL                 USL
                                        +4σ
                                                            A
                                        +3σ
                                                            A
                                                            A
                                        µ
                                        −3σ
                                        −4σ
                                                            A
Machine/Process Capability Study                            Advanced Systems Consultants
© 1989-2014, Mario Perez-Wilson               152   P.O. Box 5257, Scottsdale, AZ 85261, Tel: (480) 423-0081
                                                                                            M/PCpS™
                         Stage 3: Capability Determination
                                        µ
                                                                   A
                                                                   A
                                        −3σ
                                        −4σ
                                                                   A
              Leptokurtic
            (Kurtosis >> 3.0)
                                                       Peaked Distribution
                                                                   A
         LSL                      USL
                                        +4σ
                                                                   A
                                        +3σ
                                        µ
                                                                   A
                                                                   A
                                        −3σ
                                        −4σ
                                                                   A
 Non-Capable Machine/Process
          Bimodal                                    Bimodal Distribution
         LSL                      USL
                                        +4σ
                                        +3σ
                                        −3σ
                                        −4σ
         4        0         1          1         1          0         0           0              1            1       1   2         2          2
         5        0         1          1         1          1         1           1              2            2       2   0         0          0
         6        0         1          1         1          2         2           2              0            0       0   1         1          1
         7        0         2          2         2          0         0           0              2            2       2   1         1          1
         8        0         2          2         2          1         1           1              0            0       0   2         2          2
         9        0         2          2         2          2         2           2              1            1       1   0         0          0
        10        1         0          1         2          0         1           2              0            1       2   0         1          2
        11        1         0          1         2          1         2           0              1            2       0   1         2          0
        12        1         0          1         2          2         0           1              2            0       1   2         0          1
        13        1         1          2         0          0         1           2              1            2       0   2         0          1
        14        1         1          2         0          1         2           0              2            0       1   0         1          2
        15        1         1          2         0          2         0           1              0            1       2   1         2          0
        16        1         2          0         1          0         1           2              2            0       1   1         2          0
        17        1         2          0         1          1         2           0              0            1       2   2         0          1
        18        1         2          0         1          2         0           1              1            2       0   0         1          2
        19        2         0          2         1          0         2           1              0            2       1   0         2          1
        20        2         0          2         1          1         0           2              1            0       2   1         0          2
        21        2         0          2         1          2         1           0              2            1       0   2         1          0
        22        2         1          0         2          0         2           1              1            0       2   2         1          0
        23        2         1          0         2          1         0           2              2            1       0   0         2          1
        24        2         1          0         2          2         1           0              0            2       1   1         0          2
        25        2         2          1         0          0         2           1              2            1       0   1         0          2
        26        2         2          1         0          1         0           2              0            2       1   2         1          0
        27        2         2          1         0          2         1           0              1            0       2   0         2          1
                450     4                                 210       4    0 s e 5 µm 1 µm 2 5 0 3 2 0                              6 /9        10
                      rpm000 rp                                 0 rp sec      c    /s e c /s e c 0 p s i                                           µm
                                                                                                                                                        /s e
                                      m                             m
               Level for each experimental factor in run # 27.
                                        Wafer Thickness
                      LSL                                                              USL
        X: 253.38
        S:   2.18
   Cpk:        1.89
     Cp:       1.99
70
60
50
40
30
20
10
                AA                           A
                    LSL USL
 X: 0.769
                                                                                       Before
 S: 1.10                                                                          Experimentation
                                             A
Cp: 1.51                                                                          (Distribution #1)
                 AA                          A
                                             A
                  A  0     10 15
                                             A
                                           30 31.25     45 47.86
                                                                              Consistency
                                                   Uniformity
                                                                                                               T
                                                                              End Point
                                                                Selectivity
                                       Etch Rate
                                                                                                                            LEVEL OF
                                                                                                               O
                                                                                                                          INDEPENDENT
                                                                                                               T
                                                                                                               A
        INDEPENDENT                                                                                            L
 Pressure                              24           22          15               20                            81
 N2                                    24           20          12               10                            66
 SF 6                                  22           22           4               10                            58
 CHF 3                                 20           18           9                8                            54
 T.S. Upper Electrode                   7            5                            7                            19
 T.S. Bottom Electrode                  9            8          13                9                            36
 T.S. Chamber                          12            8           4               12                            36
 P.S. Throttle Valve                   19           13           3               19                            54
 P.S. Pump System                      19           13           3               19                            54
 P.S. Transducer Accuracy              19           12           3               19                            53
 P.S. Chamber Vacuum Integ.            18           13               3           19                            53
 E.S. Detector                                                                   18                            18
 E.S. High Voltage                                                               18                            18
 E.S. Wave Length                                                                18                            18
 E.S. Gain                                                                       18                            18
 E.S. Window                                                                     10                            10
 E.S. Cleanliness                                                                10                            10
  B.C.S. Clamping Spring               11           15               5           11                            42
  B.C.S. He Flow Pressure               9           12               4            9                            34
  B.C.S. Wafer Placement                2           10               1            2                            15
  B.C.S. Wafer Flatness                 2           10           1                2                            15
  P.S. Matching Efficiency             21           10          12               21                            64
  P.S. Phase Splitter                  20           10          12               21                            63
  P.S. RF Power                        22           10          13               22                            67
  Gas Flow Consistency                 20           14          15               20                            69
  Gap Parallelism                      16           20               3           16                            54
  Gap Spacing Accuracy                 16           20               4           10                            50
  Shower Head                          13           18               3            8                            42
  Environment
  Manpower                             17                4           2             1                           24
  Wafer Thickness                      18                8      13                 3                           42
        10000
         9900
         9800
         9700
         9600                                                                                       Wafer's Center
         9500
         9400                                            Slope = 462 Å
         9300
         9200
         9100        Wafer's Edge
         9000
                1     2      3       4     5   6     7      8    9       10     11     12    13         14      15
Silicone Nitride
Substrate
        7400
        7200
        7000
        6800
                                                                                                     Wafer's Center
        6600
        6400
        6200                                       Slope = 1,278Å
        6000
        5800          Wafer's Edge
        5600
        5400
                1     2      3         4   5   6     7      8     9       10     11     12     13        14      15
                    AAAAAAAAAAAAA
© 1994, Advanced Systems Consultants
                                                            Substrate
           LSL                                            USL
                                                       LSL                                                USL
                                 X = 6268.2                                    X = 6882.73
                                 R = 230                                       R = 1209
                                 S = 50.24                                     S = 389.32
                                 Cp = 1.56                                     Cp = 0.22
                                 Cpk = 1.56                                    Cpk = 0.22
Silicone Nitride
                                                          Substrate
© 1994, Advanced Systems Consultants
Appendix A
 + Six Sigma
Appendix B
 Likert Scale for PWB Solder Deposition
Appendix C
 Nonparametric Statistical Tests
Appendix D
 Relationship Between Average and Sigma
Appendix E
 Charting the Range in a GR&R Study
Appendix F
 Transforming a Normal Distribution to a Standard Normal Distribution
Appendix G
 Fitting a Continuous Curve
Appendix H
 Possibilities of M/PCpS After the Capability Determination Stage
 Objective of M/PCpS Studies
Appendix I
 Cumulative Normal Distribution Table
 Unilateral Normal Distribution Table
Appendix J
 Minitab Instructions for the Capability Determination Stage
Motorola, on Thursday, January 15, 1987, defined Six Sigma as having plus or minus
six sigmas (±6s) or standard deviations within specification limits. In other words,
given a particular product characteristic, which has a design specification, that design
specification has an upper specification limit, USL, and a lower specification limit,
LSL, these two limits demarcated a design tolerance. Motorola held the design
tolerance to be such, that it should allow to fit twelve (±6) sigmas or twice the
process variation.
Theoretically, under the above stated condition, a process would have Cp=2, Cpk=2,
in-process yield around 99.9999998%, and a defective rate below 0.002 parts-per-
million (PPM). For all practical purposes, + Six Sigma implies zero-defects.
What is the objective of + Six Sigma? To reduce the process variation, such that
twelve standard deviations will fit within specification limits, and to center the mean
in the middle of the specification limits.
6σ 6σ
                                                    99.73%
                                                    95.45%
                                                    68.26%
          -6σ    -5σ    -4σ       -3σ   -2σ   -1σ     µ      +1σ   +2σ    +3σ     +4σ    +5σ     +6σ
                                                99.994%
                                              99.999939%
                                              99.9999998%
           Sigma Level
              (± xσ)                                               Cp            Cpk            PPM
Yields, sigmas, Cp, Cpk and PPM levels when + sigmas coincide with specification limits.
References
American National Standards Institute, (1985), Guide for Quality Control Charts,
ANSI Z1.1-1985 (ASQC B1-1985)
Box, G.E.P, Hunter, W.G., and Hunter, J.S. (1978), Statistics for Experimenters,
New York: John Wiley & Sons, Inc.
Charbonneau, H.C., and Webster, G.L. (1978), Industrial Quality Control, New
Jersey: Prentice-Hall, Inc.
Downie, N.M., and Starry, A.R. (1977), Descriptive and Inferential Statistics,
New York: Harper & Row, Publishers, Inc.
Duncan, A.J. (1974), Quality Control and Industrial Statistics, Illinois: Richard
D. Irwin, Inc.
Ford Motor Company, Inc., (1983), Continuing Process Control and Process
Capability Improvement, Statistical Methods Office, Operations Support Staffs,
Ford Motor Company.
Ford Motor Company, Inc., (1980), Machine Capability Studies, Ford Motor
Company.
Juran, J.M., Gryna, F.M. and Bingham, R.S. (1974), Quality Control Handbook,
New York: McGraw-Hill Book Co.
Juran, J.M., and Gryna, F.M. (1970), Quality Planning and Analysis, New
York: McGraw-Hill Book Co.
Keeney, K.A. (1987), "What is Process Capability", Machine and Tool BLUE
BOOK, September 1987, pp. 65-67.
Koosis, D. (1985), Statistics, New York: John Wiley & Sons, Inc.
Love, S.F. (1983), Planning and Creating Successful Engineering Designs, Los
Angeles: Advanced Professional Development, Inc.
Sullivan, L.P. (1986), "Japanese Quality Thinking at Ford", Quality, April 1986,
pp. 32-34.
Walpole, R.E., and Myers, R.H. (1972), Probability and Statistics for Engineers
and Scientists, New York: The Macmillan Company.
Index
A                                   Centiles, 107
A2 Factor, 165                      Charts:
Accuracy, 67                         Average, 168
Actual Spread, 116                    c, 219, 233
Allowable Spread, 116                Control, 167, 218
Attribute Data, 30                   Individuals, 220-233
Attributes Measurement, 219          MR, 220-233
Average, 101                         Multi-vari, 188
Average:                             np, 219, 233
  Chart, 168                         p, 219, 233
  Range, 90                          Pareto, 17
                                     Shewhart, 217
B                                    u, 219, 233
Best Fit Line, 149                   X & R, 161, 218, 233
Between-Piece Variation, 189        Concentration Diagrams, 194
Between-Operator Variation, 78      Continuous Data, 30
Bimodal Distribution, 153           Control Chart, 167, 218
Blank Forms and Worksheets, 253     Control Chart Flowchart, 233
Brainstorming, 37                   Control Limits, 161
                                    Corrective Action Logs, 217
C                                   Cp, 99, 116, 126, 171, 325
c Charts, 219                       Cpk, 99, 116, 126, 171, 325
C&E, 29                             Cumulative Frequency, 107-9, 145
C&E Cross-Reference                 Cumulative Frequency
  Table, 45-49, 58-9, 134-5,         Distribution, 109
  195-6, 198, 273-4, 285, 296       Cumulative Normal
CAL, 217                             Distribution, 113, 326
Capability, 1                       Customer-Supplier Variation, 79
Capability:                         Cyclical Variation, 188, 189
  Determination, 99
  Index, 99, 171                    D
Cause and Effect (C&E), 29          D3 Factor, 165
Cause and Effect Diagram, 34-6      D4 Factor, 165
Cell Width, 100                     Data:
Center Line (CL), 168                 Attribute, 30
                                      Coded, 140
Index Continued
Index Continued
Index Continued
Index Continued
Index Continued
U                                   W
u Charts, 219, 233                  Wafer Gauging System, 41, 44
u Distribution, 112                 Wafer Soldering System, 198
UCL, 165                            Wafer Transportation System, 41, 44
Unilateral Normal Distribution      Within-Piece Variation, 188
  Table, 327-8                      Within-Operator Variation, 75
Upper Control Limit (UCL), 165      Work Holding System, 41, 44
Upper Specification Limit, 116      Worksheets:
                                     Blank, 253
V                                    Standard, 253
Validation, 213
Variable Data, 30                   X
Variables:                          X & R Chart, 161
  Dependent, 42                     X & R Chart Worksheet, 161
  Independent, 5, 44-7, 184         X-Bar, 163
  Response, 42                      X-Double Bar, 164
  Trivial Many, 5, 7, 17
  Vital Few, 5, 7, 17               Z
Variation:                          Z Scores, 112, 174
  Between-Piece, 189                Z Value, 113, 174
  Between-Operator, 78
  Cyclical, 188-9
  Family of, 188
  Material, 79
   Mario Perez-Wilson is the founder and CEO of Advanced Systems Consultants and
author of nine books: Machine/Process Capability Study - A Five Stage Methodology
for Characterizing Manufacturing Processes, Multi-Vari Chart and Analysis, Design
of Experiments, The Total Control Methodology - A Preventive Approach for Total
Control during Production, Six Sigma - Understanding the Concept, Implications and
Challenges, Positrol Plans and Logs, ANOVA - Analysis of Variance for Simple and
Complex Experiments, PCB Process Characterization - Applying M/PCpS to the PCB
Industry and Gauge R&R Studies - For Destructive and Non-destructive Testing.
   Mr. Perez-Wilson has conducted seminars for over 18,000 individuals in Brazil,
Belgium, People’s Republic of China, Germany, Hong Kong, India, Japan, Korea,
Malaysia, Mexico, Philippines, Singapore, Sweden, Taiwan, and the United States,
and is currently listed in The International Who's Who in Quality.
  "Good, practical approach to tackling difficult                 "The most comprehensive methodology I have seen
  manufacturing problems. Good class notes, and                   to date for people who are serious about improving
  straightforward, concise approach."                             machine/process capabilities and who are willing to
                                                                  work at it without looking for the proverbial short
                                Stephen V. Crowder                term windfall."
                       Senior Member Technical Staff
                               Sandia National Labs                                                          John Toto
                                                                                           Director, Quality Assurance
  "The industry would do very well if people and                                                           Semi-Alloys
  companies would make a deep commitment to the
  M/PCpS methodology"                                             "Excellent   material    and     presentation    on
                                                                  Machine/Process Capability. Instructor has excellent
                                          Pat Friend              working knowledge of material"
                                      Sales Engineer
                       Panasonic Factory Automation                                                       Merv Dunn
                                                                                          Vice President Total Quality
  "Great format. Simplistic approach from start to                                                    Arvin Industries
  finish of a complex problem -Machine/Process
  Capability. Good explanation of not only how but                "Your book is one of the easiest and useful ones I
  with capability studies done in real life. Both                 have ever seen. With your presentations and book
  theoretical and practical approaches in one. A class            people are gaining the knowledge to do things right
  that all production, engineering and managers should            from the very beginning (knowledge so much needed
  take."                                                          in the American Companies)."
  "The real genius of the Machine/Process Capability              "I have taken classes with Deming and Montgomery
  Study course is that it ties together and organizes all         but this class was by far the best. Mario's approach is
  the tools for process improvement. I've taken many              very simple and practical. I look forward to taking
  courses on S.P.C. and process improvement that have             further classes with him."
  presented one piece of the puzzle, but none of the
  courses have put it all together as well as what Mario                                                  David Butler
  does in the Machine/Process Capability course. This                                  Director of Package Operations
  is by far the best training course I have taken."                                                  Olin Interconnect
                                    Scott P. Gucciardi
                                         QA Engineer
                                    Welch Allyn Corp.
"A concise and lively presentation of a set of               "Step by step book clearly moves you through the
fundamental tools and a simple application of their          capability study process. Format is well documented
use to control processes.."                                  throughout the book."
"Mario takes a no-nonsense approach to provide               "The course goes to the heart of process
designers and manufacturers with what they need to           improvement. This methodology is as complete as I
know and use M/PCpS."                                        have seen."
"This is a very good course toward 6 Sigma quality.          "The Methodology is very well structured and
It is a "life statistics", I encourage all manufacturing     planned. The tools I learned are very powerful!"
engineers to attend this class."
                                                                                               Carlos A. Pinheiro
                                   Tony C. R. Tsai                                       Site Coordinator (Brazil)
                                 R & QA Manager                                                Multek/Flextronics
                      Motorola Electronics , Taiwan
                                                             "... Mario Perez-Wilson has significantly added value
"A very systematic step-by-step approach to                  by organizing these techniques into a workable
understand the behavior of a manufacturing process.          methodology and demonstration how it can be
This methodology should be made known to all                 applied to produce the desired results."
manufacturing operations."
                                                                                              George Melchiorsen
                                       Nakkina VRK                                              Quality Engineer
                             Process/ IE Task Leader                                            Hewlett Packard
                                   Motorola (P) Ltd.
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