Example of the Process Capability Platform

This example uses the Semiconductor Capability.jmp sample data table. The variables represent standard measurements that a semiconductor manufacturer might make on a wafer as it is being processed. Specification limits for the variables have been entered in the data table through the Column Properties > Spec Limits property.

1.	Select Help > Sample Data Library and open Semiconductor Capability.jmp.

2.	Select Analyze > Quality and Process > Process Capability.

3.	Select PNP1, PNP2, NPN2, PNP3, IVP1, PNP4, NPN3, and IVP2, and click Y, Process.

4.	Select Label Overall Sigma Points from the Goal Plot red triangle menu.

Click OK.

Example Results for Semiconductor Capability.jmp

The Goal Plot in Example Results for Semiconductor Capability.jmp shows the spec-normalized mean shift on the x-axis and the spec-normalized standard deviation on the y-axis for each variable. The triangular region defined by the red lines in the bottom center of the plot is the goal triangle. It defines a region of capability index values. You can adjust the goal triangle using the Ppk slider below the plot. When the slider is set to 1, note that PNP1, PNP3, IVP1, and IVP2 are outside of the goal triangle and possibly out of specification.

The Capability Box Plots report shows a box plot for each variable in the analysis. The values for each column are centered by their target value and scaled by the specification range. It appears that the majority of points for IVP1 are above its upper specification limit (USL), and the majority of points for IVP2 are less than its target. PNP2 seems to be on target with all data points inside the specification limits.

Launch the Process Capability Platform

Launch the Process Capability Platform by selecting Analyze > Quality and Process > Process Capability.

Process Capability Launch Window

The Process Capability launch window contains the following options:

Y, Process

Assigns the variables that you want to analyze.

Nest Subgroup ID Column

Assigns a column to define the subgroups for the selected process columns.

Produces a separate report for each level of the By variable. If more than one By variable is assigned, a separate report is produced for each possible combination of the levels of the By variables.

Specify Alpha Level

Specifies the significance level for confidence limits.

Show Spec Limits Dialog

Specifies how to handle columns that do not have specification limits.

Within-Subgroup Variation Statistic

Specifies if the within sigma is calculated using standard deviations or ranges.

Note: The Transform menu is not available for the Select Column list in the Process Capability launch window. Right-click a column heading in the data table and select New Formula Column to create a transform column for use in Process Capability. See Using JMP for more information about creating new formula columns.

The Process Capability launch window also contains two outlines that enable you to specify subgroups or historical sigma information for the process variables.

Use the Process Subgrouping options to control subgrouping. The panel entitled Subgroup with allows you to specify a subgroup ID column or a constant subgroup size.

•	To specify a subgroup ID column for a process variable, select the ID column from the Select Columns List on the left, select a process from the Process List on the right, and click the Nest Subgroup ID Column button.

•	To specify a constant subgroup size, select a process from the Process List on the right, enter a subgroup size for Set Constant Subgroup Size, and click the Subgroup by Size button. The Subgroup by Size button and Set Constant Subgroup Size appear when you select Constant Subgroup Size.

Use the Historical Information options to specify a historical sigma value to be used in the analysis of the selected process columns. To specify a historical sigma for a process variable, select a process from the Process List on the right, enter a value for Set Historical Sigma, and click the Use Historical Sigma button.

After you click OK on the launch window, the Spec Limits window appears if any of the columns do not contain limits and you did not select No (skip columns with no spec limits) on the launch window. The Spec Limits window also appears if you select Yes on the launch window. Otherwise, the Process Capability report window appears.