1、JEDEC STANDARD Statistical Process Control Systems JESD557C (Revision of EIA-557B, January 2006) APRIL 2015 JEDEC SOLID STATE TECHNOLOGY ASSOCIATION NOTICE JEDEC standards and publications contain material that has been prepared, reviewed, and approved through the JEDEC Board of Directors level and
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9、10th Street Suite 240 South Arlington, VA 22201-2107 or refer to www.jedec.org under Standards-Documents/Copyright Information. JEDEC Standard No. 557C -i- STATISTICAL PROCESS CONTROL SYSTEMS Contents Introduction ii 1 Scope . ii 2 References 1 3 Terms and definitions . 1 3.1 Terms and definitions u
10、sed in the document . 1 3.2 Other terms related to SPC/SQC . 4 4 General SPC System Requirements 4 4.1 Overall Quality System 4 4.2 Management Commitment . 4 4.3 SPC System Set Up . 5 5 Performing SPC . 5 5.1 Measurement Equipment Gage Characterization and Capability . 5 5.1.1 Measurement system ana
11、lysis (MSA) 5 5.1.2 Calibration/verification records . 5 5.2 Characterize and classify SPC parameters . 6 5.3 Process Capability 8 5.3.1 Normal or log-normal data Cpk 8 5.3.2 Quantile Cpk . 8 5.3.3 Control limits 9 5.4 Setup per SPC Parameter 9 5.5 Training 9 5.6 Supplier SPC Systems. 10 5.7 Calibra
12、tion . 10 5.8 Self-Audit . 10 Annex A (informative) Control chart constants TL and TU as a function of sample size n . 11 Annex B (informative) SPC Example 12 Annex C (informative) Alternative Control Charts 14 Annex D (informative) Alternative for Quantile Cpk . 16 Annex E (informative) Related boo
13、ks . 17 Annex F (informative) Related guidelines and standards . 19 Annex G (informative) Other terms and definitions . 20 JEDEC Standard No. 557C -ii- Introduction Continuous quality improvement and the achievement of operational and manufacturing excellence are the essence of the total quality phi
14、losophy. One of the major vehicles used for achieving the excellence objective is the application of Statistical Process Control (SPC) techniques. SPC embraces a management philosophy of continuous process improvement that has a primary focus on prevention of outliers or maverick products to be ship
15、ped to customers. After a process has been characterized using statistical techniques (i.e., design of experiments (DOE), capability studies), SPC is a tool that can be applied to control and optimize the process and reduce variability. An acceptable approach toward an SPC system involves the use of
16、 “end-of-process“ data to control the process through the application of SPC techniques. However, the intent of this standard is to emphasize the use of in-process data in order to better control and forecast product quality. This proactive use of SPC in conjunction with other techniques and the app
17、ropriate responsiveness to out-of-control situations serves to make SPC techniques critical in continuous process improvement and achieving excellence. It is well recognized that the implementation of an effective and measurable continuous improvement program, which includes SPC, is an ongoing proce
18、ss. In order for techniques such as SPC to be firmly established throughout all facets of an organization, a strong management commitment must exist. In addition, personnel must be trained, involved, and held accountable in this statistical analysis, control and improvement process. The exact nature
19、 and sophistication of these techniques may vary from manufacturer to manufacturer, depending on the management concepts involved. In recognition of this tendency, this standard provides the general requirements of SPC, including definitions and terminology to promote standardization of best practic
20、es. JEDEC Standard No. 557C Page 1 STATISTICAL PROCESS CONTROL SYSTEMS (From JEDEC Board ballot JCB-15-09, formulated under the cognizance of the JC-14 Committee on Quality and Reliability of Solid State Products.) 1 Scope This standard specifies the general requirements of a statistical process con
21、trol (SPC) system. 2 References The following normative documents contain provisions that, through reference in this text, constitute provisions for this standard. For undated references, the latest edition of the normative document referred to applies. JEDEC JEP132, Process Characterization Guideli
22、ne IS0 10012, Measurement Management Systems - Requirements for Measurement Processes and Measuring Equipment 3 Terms and definitions EIA-557-B defined many terms used in the field of SPC. Many were not actually used in EIA-557-B. In this standard, JESD557C, the terms necessary to understand the tex
23、t are defined in 3.1, other terms are defined in Annex F. 3.1 Terms and definitions used in this document audit: The periodic review of procedures and observation of performed activities to evaluate compliance with requirements. average: The sum of the sample values divided by the number of sample v
24、alues. A measure of location used to estimate the population mean. capability: The ability to meet a specification. capability index: A measure of the relationship between the specification limits and the capability. characteristic: A distinguishing feature of a process or its output on which variab
25、les or attributes data can be collected. characterization: A description of the characteristics of a product or process by mathematical modeling, design of experiments, or statistical data evaluation. NOTE Methods of statistical data evaluation are described in JESD557 and JEP132. JEDEC Standard No.
26、 557C Page 2 3.1 Terms and definitions used in this document (contd) common cause: A source of natural variation that affects all the individual values of the process output being studied. NOTE In control chart analysis common causes appear as part of the random process variation. control chart: A g
27、raphic representation of a process characteristic showing plotted values of some statistic gathered from that characteristic, a central line and one or two statistically derived control limits. control limits: The maximum allowable variation of a process characteristic due to common causes alone. NO
28、TE 1 Variation beyond a control limit may be evidence that special causes are affecting the process. NOTE 2 Control limits are calculated from process data and are usually represented as a line (or lines) on a control chart. They are not to be confused with engineering specification limits. Cpk: See
29、 “process capability index (Cpk)”. critical (process) node: A node in the process flow whose output has a significant impact on the process. data point: A value that is either observed or calculated. individual: A single unit or a single measurement of a characteristic. mean: The sum of the populati
30、on values divided by the number of values in the populationa measure of location (central tendency) equal to the center of gravity of the population. median: The middle value in a group of measurements when arranged from lowest to highesta measure of location. NOTE When the number of measurements is
31、 an even number, the average of the two middle values is used as the median. node: A definable point in the process at which form, fit, or function of the product or service is altered. normal distribution; Gaussian distribution: A continuous, symmetrical, bell-shaped frequency distribution for vari
32、ables data. NOTE When measurements have a normal distribution, about 68.26% of all individuals lie within plus or minus one standard deviation unit of the mean; about 95.44% lie within plus or minus two standard deviation units of the mean; and about 99.73% of all individuals lie within plus or minu
33、s three standard deviation units of the mean.* out-of-control: A set of data with the mean value or sigma of a sample violating the control limit out-of-spec: A set of data with at least one value violating the spec limit. parameter: A measurable characteristic. JEDEC Standard No. 557C Page 3 3.1 Te
34、rms and definitions used in this document (contd) population: The collection of all possible values of a given characteristic. probability: The relative frequency with which an outcome takes place over a very large number of trials in each of which the outcome could have occurred. process: (1) A com
35、bination of people, procedures, methods, machines, materials, measurement equipment, and/or environment for specific work activities to produce a given product or service. (2) A repeatable sequence of activities with measurable inputs and outputs. process capability: The capability of a process to m
36、eet its specification. process capability index (Cpk): A measure of the relationship between the process specification limits and its capability. process capability study: A study that quantifies natural process variability. run: A number of consecutive points, usually seven or eight, above or below
37、 the centerline. sample: A set of individuals taken from a population. special cause; assignable cause: A source of variation that is intermittent, unpredictable, or unstable and affects only some of the individual values of the process output being studied. specification limits: The boundaries for
38、judging acceptability of a particular characteristic. standard deviation: A measure of the spread or variation in a probability distribution (population standard deviation) or in a sample of values measured on the output from a process (sample standard deviation). statistic: A value calculated from
39、or based upon sample data used to make inferences about a parameter of the population from which the sample came. statistical control: The conditions describing a process from which all special causes of variation have been eliminated and only common causes remain. statistical process control (SPC):
40、 A method of quality control that uses statistical methods in order to monitor and control a process. statistical quality control (SQC): Statistical methods and procedures used to document and ensure compliance with requirements. target: The desired value for a statistic of a characteristic or param
41、eter of a process node. trend: The movement of a process in a consistently increasing or decreasing direction. variation: The difference among individual outputs of a process. NOTE The sources of variation can be grouped into two major classes: common causes and special causes. JEDEC Standard No. 55
42、7C Page 4 3.2 Other terms related to SPC/SQC For other terms and definitions related to SPC but not used in the text, see Annex F. 4 General SPC System Requirements The general requirements of an SPC system are provided in the following paragraphs, however, the paragraphs are not provided in any pre
43、scribed order. The general requirements of an SPC system shall encompass, but are not limited to, the following elements: a) Overall quality system b) Management commitment c) SPC system documentation d) Critical process nodes e) Gage characterization and capability f) Process characterization and c
44、apability g) Control system documentation h) On-line/off-line control i) Training j) Supplier SPC systems k) Calibration l) Preventive maintenance m) Self audit 4.1 Overall Quality System A prerequisite to the effective implementation of SPC is the existence and adequate application of the basic ele
45、ments of an overall quality system. A quality system shall be documented and capable of being audited. The basic elements are described in various documents such as ANSI/ISO/TS16949ff. The quality system shall comply with the applicable standard requirements. 4.2 Management Commitment Management sha
46、ll: empower personnel with responsibility, authority, and provide sufficient resources to implement and maintain an SPC system, and periodically review and document the status of the SPC system. JEDEC Standard No. 557C Page 5 4.3 SPC System Set Up The manufacturer shall document and implement a plan
47、 for an SPC system. The implementation plan shall contain regulations for the following topics: scope: delineate areas of the company to which the SPC system applies, definition of the organizational unit being responsible for the SPC system ( in this standard called SPC Steering Committee (SSC), ta
48、sk and responsibilities of the SSC, training matrix for all user of SPC, description of the SPC process, System documentation requirements, and Review and Audit of the SPC system. 5 Performing SPC For information how to apply SPC for process characterization refer to JEP132. All process chosen to be
49、 characterized by SPC shall be documented. Documentation shall contain: Process description, and Control plan containing all measurement systems needed for SPC. 5.1 Measurement Equipment Gage Characterization and Capability All equipment used for SPC shall be in calibration. Characterization and capability studies of test equipment and gages shall be performed to show variance, limitations and repeatability of the measurement equipment. All studies shall be documented and substantiated by data. 5.1.1 Measurement system analysis (MSA) Statistical studies shall be con
