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5、ICE This document has been taken directly from the original TechAmerica document and contains only minor editorial and format changes required to bring it into conformance with the publishing requirements of SAE Technical Standards. The release of this document is intended to replace the original wi
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15、ay obtain permission to reproduce a limited number of copies by entering into a license agreement with our distributors. For distributor information please see our web site www. techamerica.org/ or contact TechAmerica at 703-284-5355 TechAmerica Process Improvement Guidelines EIA-832 Revision Descri
16、ption of change Date - Initial Release May 2000 PROCESS IMPROVEMENT GUIDELINESCONTENTSPage1 Introduction 12 Purpose 13 Scope 14 General outline 15 Specific steps 35.1 Identify and prioritize improvement opportunities 35.2 Map process 35.3 Analyze variation in measuring and test equipment 45.4 Identi
17、fy critical process parameters 45.5 Define a process sampling plan 55.6 Create a process control and monitoring plan 55.7 Define a corrective action plan for out-of-control conditions 55.8 Continuous process improvement 56 Further refinements 67 Training and education 6AnnexesA Error of measurement
18、study - example 7B Identifying critical process parameters soldering process example 9C Example of training matrix 11D References 12iEIA-832Page 1Process Improvement Guidelines1 IntroductionSuccess oriented manufacturers are or have adopted a business philosophy, focused on deliveringquality product
19、s quickly, while increasing their profit margins. These manufacturers arecontinuously looking for process improvement opportunities that give them the greatest return ontheir investment. To accomplish this, process control techniques have gained wide acceptanceand are used, in some form, in most man
20、ufacturing environments. This being the case, theassumption is that these businesses have already analyzed their manufacturing processes,assigned measures and are collecting data about those processes. After analyzing processmeasurement data, the steps taken to determine what improvements could or s
21、hould be made,and how those changes are implemented is what is known as process improvement. This isgenerally where most businesses fall short of maximizing process and profit potential as processimprovement decisions are influenced by less tangible factors such as corporate culture, markettrends, r
22、esource conflicts, etc., which makes this a difficult area of business to define andmanage.There has been considerable literature published about process control such as Statistical ProcessControl (SPC) and Statistical Quality Control (SQC), but there has been limited useful help inthe area of proce
23、ss improvement. To be truly successful, each business must have a soundapproach for evaluating their process controls, measurement techniques, other relevantcontributing factors, corporate goals and the forum by which process improvement decisions aremade. These guidelines were developed to take som
24、e of the mystery out of process improvementby presenting a logical sequence of events that should take place, and proven tools that can beuseful in this process.2 PurposeTo guide a manufacturer through a methodology for analyzing, modeling, controlling, validatingand improving products and services
25、through the use of effective and measurable engineeringpractices.3 ScopeThe procedure outlined in this document is applicable to any manufacturing or service process.It may be used on part of a process or and entire process or a series of sequential processes.4 General OutlineThe process improvement
26、 cycle, as outlined in EIA-599 “National Electronic ProcessCertification Standard” consists of three parts: Process Characterization, Process Optimizationand Process Control.Process Characterization is the determination of relationships between process parameters andprocess outputs or product charac
27、teristics. Process Optimization is the mechanism to provide forEIA-832Page 2continuous improvement as equipment and materials technology changes. Process control is thecontinual elimination of unexpected variation from processes or the development of processesrobust to unexpected variation. These th
28、ree activities form the backbone of any good processimprovement program. This document will present a more detailed description of these activitiesin a way that will guide the users through all of the necessary components that are a part of thethree major processes.Once a process is proven to be via
29、ble (i.e., it can be successfully implemented for the intendedpurpose with the expected results), it becomes a candidate for improvement.An outline of the process improvement process is presented below. This outline links the threemajor parts of process improvement defined in EIA-599 to their compon
30、ent parts and also intothe process of continuous improvement going forward.Process CharacterizationI. Identify & Prioritize Improvement OpportunitiesA. AreasB. ProcessesC. Select teamII. Map processA. Develop flow diagramIII. Analyze Variation in Measuring and Test EquipmentA. Perform measurement sy
31、stem characterizationB. P/T ratioC. Reproducibility (Correlation between multiple test equipment)D. Establish monitors and control of equipment using SPCIV. Identify critical process parametersA. Use DOE, FMEA, QFD, ETC.B. Develop process model (cause and effect model)C. Validate model with dataD. P
32、erform process capability study (short and long tem)Process Optimization and ControlV. Define a process sampling PlanA. Use rational subgroupsVI. Create a process control and monitoring planA. Establish statistical tool to control variationB. Establish statistical limitsEIA-832Page 3VII. Define a Co
33、rrective Action Plan for Out-of-Control ConditionsContinuous Process ImprovementA. Compute Cp, CpkB. Set baseline for process and establish improvement objectivesC. Implement improvement plansThe next section of this document will provide more in-depth descriptions of these activities.5 Specific Ste
34、ps5.1 Identify and Prioritize Improvement OpportunitiesAny business consists of many processes, all competing for attention. In order to determinewhere to deploy ones limited resources is always a problem. If the customers of a business areused as a primary focus along with business profitability in
35、terests, the process of selection ofprocesses for improvement can be simplified. Areas such as customer concerns, market impact,high scrap or rework operations and unpredictable operations usually present improvementopportunities. Techniques to aid in further selection include: Quality Function Depl
36、oyment (QFD) Business Process Analysis Design of Experiments (DOE) Fault Tree Analyses Cost of Quality Cycle Time Analysis Failure Mode and Effects Analysis (FMEA) Pareto ChartsThe areas or processes identified as opportunities for improvement should be ranked in order ofimportance, with special att
37、ention to critical process steps. A critical process step is one that hasmajor impact on manufacturability, quality, performance, reliability or perceived customersatisfaction.Once a process is selected, a team is formed to effect the improvement process. Such a team isusually a cross functional gro
38、up of people led by a member of the organization that is responsiblefor the process.5.2 Map ProcessA process flow diagram should be developed to graphically illustrate the process as follows: Sequential process steps and/or material flow Relationship between process stepsEIA-832Page 4 Rework loops L
39、ist process step, set-ups, inputs (i.e. temperature, pressure, force, water flow, solderangle) List outputs (i.e. EPI thickness, pull strength, failure mode) Decision points Process control and yield pointsA complete list of process inputs and outputs may not be available at the start of a project b
40、utmay be altered or refined as the project progresses (through a designed experiment, for instance).5.3 Analyze Variation in Measuring and Test EquipmentOnce the team determines the process characteristics to be measured, it is critical to evaluate themeasurement test systems for those characteristi
41、cs. Measuring and test equipment is subject tovariation. Unless the measuring and test equipment used to collect data is both accurate andrepeatable a meaningful process analysis cannot be made. Excessive variation in themeasurement and test equipment may mask important variations in the process bei
42、ng analyzed.Equipment must be evaluated for both accuracy (calibration) and precision (reproduci-bility). The acceptability of a measurement system maybe evaluated by either precision-to-tolerance (P/T) ratio for two-sided specifications or by percent measurement error (%error) forone-sided specific
43、ations. Recommended (but not required) levels are P/T 30% and % error10%. A typical example is included in Annex A.If more than one piece of equipment is used to make certain measurements (in high-volumeapplications), it is important to perform correlation studies to compare reproducibility betweens
44、ystems. It is then necessary to establish monitors and controls to ensure system stability overtime using statistical process control.Some of the key elements or measurement and test system SPC include:Identification of critical measurement parametersEstablishment of measurement errorSelection of NI
45、ST traceable (if available) and/or monitoring (?Golden?) standardsDetermination on sample size and frequency of measurement for each standardSelection of statistical tools (i.e. control charts) to monitor/control variationDevelopment and implementation of corrective action procedure (CAP) for out-of
46、-controlconditions (OCC)5.4 Identify Critical Process ParametersHaving identified a list of inputs and outputs in Step 5.2, it is necessary to identify those that arecritical to the process. In order to effectively accomplish this, it is necessary to develop aEIA-832Page 5process model (cause and ef
47、fect) between the input(s) and output(s). A preliminary model canbe developed using DOE, QFD, FMEA or other physical (theoretical) or design relationships buta final mathematical relationship between the inputs and outputs must eventually be developedand validated. Models can be developed at several
48、 levels. Two important models are in-processproduct models that describe product characteristics during processing and end-product modelsthat describe the ability of a product to satisfy a customer requirementOnce a model is developed, it must be validated. This is typically done through designedexp
49、erimentation. Such techniques produce mathematical models via a regression analysis. Themodel produced is an equation of the response as a function of one or more independentvariables (i.e. it relates in an obvious way, the process output to the critical inputs). See examplein Annex B, particularly the development of the model used to describe the process. Note:extrapolation of a model outside the experimental region is
