IPC 9191 Table Of Contents
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IPC-9191
General Guidelines for
Implementation of Statistical
Process Control (SPC)
ASSOCIATION CONNECTING
ELECTRONICS INDUSTRIES
2215 Sanders Road, Northbrook, IL 60062-6135
Tel. 847.509.9700 Fax 847.509.9798
www.ipc.org
ANSI/IPC-9191
November 1999 A standard developed by IPC
Supersedes IPC-PC-90
October 1990
FOREWORD
IPC-9191 is a harmonization of IPC-PC-90 and the International Organization for Standardization (ISO) SPC Guideline
11462-1. ISO 11462-1 has been adopted as the foundation for IPC-9191 and is printed in italicized type. Interpretations and
supplemental SPC system requirements, as well as implementation guidelines have been harmonized and printed in normal
type. Companies may adopt this document; the IPC retains full control over the content except for ISO 11462-1, of which
copyright remains with the ISO.
This document is intended to provide information to support the application of process control and related statistical tech-
niques specified in international and industry standards. The ISO 11462-1 sections were prepared by working group 8 of
ISO/ITC 69 SC 4.
Appendix A, Appendix B, Appendix C, and Appendix D of this guideline are for information only.
Introduction
The guideline specified is aimed primarily at increasing production efficiency and reducing cost, by reducing variation in all
processes, from design through to servicing.
This Standard extends the definition of process control to integrate the traditional definitions of statistical process control,
algorithmic process control, and model-based control methods. They are different approaches with the same purpose of
reducing variation in products and in processes.
This Standard also extends the definition and usage of the term parameter to apply to a process parameter or a product
parameter; and to recognize that a product parameter can be either an in-process product parameter or a final-product
parameter. Under specified conditions of measurement, a product parameter can be equivalent to a product characteristic.
Some considerations given in the formulations of this Standard are noted:
(a) Elements of Part 1 of this Standard guide an organization in how to implement an SPC system. Specific tools and tech-
niques that experience has shown useful in applying these elements within processes are catalogued in Part 2 of this
standard, in process of establishment.
(b) To clarify for practitioners, in both parts - Elements of SPC (Part 1) and Tools and Techniques for Operation of These
Elements (Part 2) - ‘‘should’’ indicates:
1. Among several possibilities, one or more are recommended as being particularly suitable and effective, without mention-
ing or excluding others;
2. A certain course of action is preferred but not necessarily required for the economic control of production from a pro-
cess. In both parts, choice of language does not indicate requirements strictly to be followed in order to conform to a
standard and from which no deviation is permitted.
Note: See Appendix D for a detailed explanation of the importance of the distinctions between the three types of param-
eters and their relationship with characteristics.
At the time of publication of IPC-9191, ISO 11462-1 parts 1 and 2 are in their final stages of draft. The IPC SPC Subcom-
mittee will monitor the progress made toward finalization of those documents and incorporate changes as required.
Table of Contents
1 SCOPE......................................................................... 1
1.1 Subject of this Standard........................................ 1
1.2 Aspects Covered ................................................... 1
1.3 Field of Application ............................................. 1
1.3.1 General .................................................................. 1
1.3.2 Production Characteristics Covered ..................... 1
1.3.3 Techniques for Control and Models
of Processes........................................................... 2
1.4 Interpretation ........................................................ 2
2 NORMATIVE REFERENCE(S).................................... 2
2.1 IPC ....................................................................... 3
3 TERM(S) AND DEFINITION(S)................................... 3
4 SPC OBJECTIVES AND ORGANIZATION ............... 4
4.1 SPC Objectives .................................................... 4
4.1.1 General .................................................................. 4
4.1.2 Specific.................................................................. 4
4.2 Financial Motive for SPC..................................... 4
4.2.1 External Failures ................................................... 4
4.2.2 Internal Failures .................................................... 4
4.2.3 Appraisal ............................................................... 5
4.2.4 Prevention.............................................................. 5
4.3 Relationships ........................................................ 5
4.3.1 Relationship Between Traditional and
Automated Process Control.................................. 5
4.3.2 Relationship to Final Product
Conformance-To-Specification ............................. 6
4.4 SPC Organization ................................................ 6
4.4.1 Organizing for SPC Implementation.................... 6
4.4.2 Strategic Planning ................................................. 7
5 CONDITIONS FOR STATISTICAL PROCESS
CONTROL .................................................................. 8
5.1 Management Support............................................ 8
5.2 Understanding of SPC Tools and Methods.......... 8
5.3 Quality System...................................................... 9
6 ELEMENTS OF A STATISTICAL PROCESS
CONTROL SYSTEM ................................................ 10
6.1 Process Documentation and Control Plan.......... 10
6.2 Definition of Process Targets and Limits........... 11
6.2.1 Parameter Identification ...................................... 11
6.2.2
In-Process Product Parameter Identification
........... 11
6.2.3 Process Parameters.............................................. 12
6.3 Measurement System Evaluation and
Control................................................................. 12
6.4 Documented Work Instructions .......................... 12
6.5 Employee Training and Involvement in
Process Data........................................................ 12
6.6 Process Data Recording and Collection............. 13
6.7 Traceability and Production Sequence
Identification........................................................ 13
6.8 Subcontractor Performance Evaluation .............. 14
6.9 Process Input Sequencing................................... 14
6.10 Process Logs ....................................................... 14
6.11 Process Reliability............................................... 14
6.12 Process Output Monitoring System.................... 15
6.13 Process Control System...................................... 15
6.14 Short-Term Variability Assessment .................... 15
6.14.1 Objectives for Parameter Capability
Assessment (PCA) .............................................. 19
6.14.2 Characterize the Distribution.............................. 16
6.14.3 Identification of Specification Limits or
Operating Limits and Target Values................... 16
6.14.4 Determine Parameter Capability (Short Term/
Long Term).......................................................... 16
6.14.5 Parameter Capability Analysis............................ 17
6.15 Long-Term Variability Assessment..................... 18
6.15.1 Cause and Effect Analysis .................................. 18
6.16 Communicating the Results of Process
Analysis............................................................... 19
6.17 Customer Information System............................ 19
6.18 Internal SPC Audits ............................................ 19
6.19 SPC Projects and Teams..................................... 19
6.20 Process Improvement, Optimization, and
Troubleshooting................................................... 19
Appendix A REFERENCES......................................... 21
Appendix B TOOL MATRIX ........................................ 25
Appendix C GLOSSARY OF SYMBOLS.................... 27
Appendix D GL0SSARY OF TERMS.......................... 29
November 1999 IPC-9191
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Figures
Figure 1-1 SPC Implementation Strategic Plan
Example............................................................. 3
Figure 4-1 General Cost of a Quality Report...................... 5
Figure 4-2 Systematic Path for Implementation of SPC..... 6
Figure 4-3 Prevention/SPC Based Process........................ 7
Figure 4-4 Traditional Inspection/Detection
Based Process................................................... 8
Figure 4-5 General Framework for Organizational
Requirements Related to SPC
Implementation .................................................. 9
Figure 5-1 SPC Training Flow and Implementation.......... 10
Tables
Table 4-1 Preventative/SPC Based Quality System vs.
Detection Based Quality System ......................... 7
Table 5-1 Example of an Ongoing Training Plan................. 9
IPC-9191 November 1999
vi
General Guidelines for Implementation
of Statistical Process Control (SPC)
1 SCOPE
This guideline describes the general provisions for imple-
mentation of SPC and is intended for use by individuals in
electronics and other industries involved in the planning,
implementation, and evaluation of an SPC system. This
guideline outlines SPC philosophy, implementation strate-
gies, tools, and techniques. These may be applied in differ-
ent sequences depending on the specific company, opera-
tion, or variable under consideration. These tools are also
used for relating process control and capability to final
product requirements.
This document represents the second revision to the IPC
Statistical Process Control (SPC) Standard. This revision
reflects the principals of SPC represented by the Interna-
tional Organization for Standardization (ISO) Statistical
Methods Technical Committee.
NOTE: Text from ISO 11462-1 is included in this docu-
ment in italics with permission of ISO/TC 69 and has been
approved by ANSI.
1.1 Subject of this Standard Statistical process control
(SPC) concerns the use of statistical techniques and/or sta-
tistical or stochastic control algorithms to achieve one or
more objectives:
1. To increase knowledge about the process;
2. To steer a process to behave in the desired way;
3. To reduce variation of final-product parameters, or in
other ways improve performance of a process.
These guidelines give elements for implementing an SPC
system to achieve the above objectives. The common eco-
nomic objective of statistical process control is to increase
good process outputs produced for a given amount of
resource inputs.
Note 1. SPC operates most effıciently by controlling
variation of a process parameter or an in-process product
parameter that is correlated with a final-product param-
eter; and/or by increasing the process’s robustness against
this variation. A supplier’s final-product parameter may be
a process parameter to the next downstream supplier’s pro-
cess.
Note 2. Although SPC is concerned with manufactured
goods, it is also applicable to processes producing services
or transactions (for example, those involving data, commu-
nications, software, or movement of material).
1.2 Aspects Covered This International Standard pro-
vides elements to guide an organization in planning, devel-
oping, executing, and/or evaluating a Statistical Process
Control system. By implementing those elements deemed
applicable and appropriate by customer and supplier, an
organization may satisfy a requirement to adopt a compre-
hensive and effective SPC system. By also deploying a
quality system for assuring that products and services meet
customer requirements (such as the system defined by ISO
9001), an organization can install the infrastructure to help
hold the gains from its SPC system.
1.3 Field of Application
1.3.1 General This International Standard specifies SPC
system guidelines for use when a supplier’s capability to
reduce variation in processes associated with design or
production needs to be proved, or when a supplier is begin-
ning SPC implementation to achieve such capability.
It is intended that elements in this Standard will be selected
based on their applicability and appropriateness to a spe-
cific process. Elements’ selection, the order in which an
organization implements the elements, and the depth of
elements’ adoption and application by an organization all
depend on factors including: customer needs, market being
served, nature of product or service, technology, and the
nature and speed of production and transaction processes.
It is emphasized that the SPC system guidelines specified in
this standard are complementary (not alternative) to tech-
nical (product) specified requirements and to quality system
requirements. These guidelines specify what elements SPC
systems are recommended to encompass. It is not the pur-
pose of these SPC system guidelines to enforce uniformity
of Statistical Process Control systems. These guidelines are
generic, independent of any specific process, industry, or
economic sector. These guidelines are intended to be
adopted in their present form by organizations implement-
ing SPC, but on occasions may need to be tailored by add-
ing or deleting certain SPC system elements for specific
circumstances. The phrases, ‘‘Where appropriate’’ and
‘‘Where applicable’’ are used to highlight those elements
whose particular application is expected to be more
process-dependent or more market-sensitive.
These guidelines are not intended for contractual, regula-
tory, or certification use.
1.3.2 Production Characteristics Covered This Interna-
tional Standard is applicable in circumstances when:
(a) Variation or deviation from either product requirements
or performance to a target value may occur.
November 1999 IPC-9191
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