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2000-08

INTERNATIONAL ELECTROTECHNICAL COMMISSION

TECHNICAL COMMITTEE No. 91– ELECTRONICS ASSEMBLY TECHNOLOGY

Maintenance – call for comments/ proposals for amendment/ revision on IEC 60410 –and call for experts for maintenance team

ACET Area 1, in its meeting of 11th April 2000, proposed to revise IEC 60410. Since TC 56 -originally responsible for that publication - had voted not to revise it, ACET Area 1 also proposedthat TC 91 undertake that task (please refer to ACET(0004/Area1Sec)4. This was accepted by ACET in i ts meeting of 13th Apri l 2000 (see ACET(0004/Sec)7A.

The goal of the revision is to introduce the Zero Acceptance Number principle, which can be used

not only by the industries related to TC 91, but also by all the industries of the electronic field.

National Committees are therefore invited to consult their experts from TC 40, TC 47, TC 48,TC 52, TC 56, TC 78, TC 86, TC 91 and TC 93 before submitting their comments. It is alsostrongly recommended that they nominate experts f rom these TCs for the maintenanceteam to be set up.

The P-members are requested to send their comments/ proposals for amendment using the Form8c to facilitate the task of the Secretary in compiling the comments before passing them on to themaintenance team.

Based on the maintenance cycle procedures given in Administrative Circular AC/132/1999, thesequence of events is as follows :• This Document for Comment (DC) is circulated to request comments/ proposals for

amendment and to call for experts in order to set up a maintenance team• The comments received are passed on to the maintenance team• The maintenance team reviews IEC 60410 and makes recommendations by completing the

Maintenance Cycle Report (MCR – Form 11), which is returned to TC 91 Secretary andcirculated to the P-members

• If there are no objections within two months of the circulation of the MCR, then therecommendation will be considered as approved.

Comments/ proposals should be submitted using the IEC Electronic voting system or by e-mail to

[email protected] . In this latter case, there will be no automatic forwarding of the comments to the TCSecretary and a copy will need to be sent directl y to the Secretary of TC 91 by the NationalCommittees. (See AC/64/1999).

Comments/ proposals to be returned by 2000-10-31

mailto:[email protected]:[email protected]:[email protected]

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INTERNATIONAL ELECTROTECHNICAL COMMISSION

––––––––

Sampling plans and procedures for inspection by attributes

FOREWORD

1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising allnational electrotechnical committees (IEC National Committees). The object of the IEC is to promote international co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and in additionto other activities, the IEC publishes International Standards. Their preparation is entrusted to technical committees;any IEC National Committee interested in the subject dealt with may participate in this preparatory work. International,governmental and non-governmental organizations liaising with the IEC also participate in this preparation. The IECcollaborates closely with the International Organization for Standardization (ISO) in accordance with conditionsdetermined by agreement between the two organizations.

2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an internationalconsensus of opinion on the relevant subjects since each technical committee has representation from all interested

National Committees.3) The documents produced have the form of recommendations for international use and are published in the form of

standards, technical reports or guides and they are accepted by the National Committees in that sense.

4) In order to promote international unification, IEC National Committees undertake to apply IEC International Standardstransparently to the maximum extent possible in their national and regional standards. Any divergence between theIEC Standard and the corresponding national or regional standard shall be clearly indicated in the latter.

5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any equipmentdeclared to be in conformity with one of its standards.

6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 60410 has been prepared by IEC technical committee 91: Electronicassembly technology

The text of this standard is based on the following documents:

IEC 60410

FDIS Report on voting

Full information on the voting for the approval of this standard can be found in the report on votingindicated in the above table.

Annex A is Informative

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CONTENTS

Introduction…………………………………………………………………………………………………. 1

1 Scope............................................................................................................................... 5

2 Normative references ....................................................................................................... 5

3 Terms and definitions ....................................................................................................... 5

4 Background ......................................................................................................................7

4.1 Attribute sampling plans .......................................................................................... 7

4.1.1 Continuous sampling ................................................................................... 7

4.1.2 Lot-by-lot attributes......................................................................................8

4.1.3 Lot-by-lot variables ......................................................................................8

4.2 Non-statistical sampling plans .................................................................................8

4.3 Relationship of C=0 plans ........................................................................................9

5 Classification of attributes............................................................................................... 13

5.1 Classification Assignment...................................................................................... 13

5.2 Classification and adjustment of sampling plan criteria........................................... 15

5.3 Process control ..................................................................................................... 15

6 Defects and process deviation indicator (PDI) evaluation ................................................15

6.1 Process control and process improvement requirements........................................ 15

7 Inspection plans ............................................................................................................. 16

7.1 Zero acceptance number-based sampling plans..................................................... 16

7.2 Responsible authority ............................................................................................ 17

7.3 Application ............................................................................................................ 17

7.4 Sampling plan specification ................................................................................... 18

7.5 Submission of product ........................................................................................... 19

8 Classification of defects.................................................................................................. 20

8.1 Customers Detail Specification (CDS) data ............................................................ 20

9 Percent defectives per million opportunities .................................................................... 20

9.1 Classes of DPMO .................................................................................................. 20

9.1.1 DPMO-1 − Functional nonconformances only ............................................. 20

9.1.2 DPMO-2 − Electrical nonconformances ...................................................... 20

9.1.3 DPMO-3 − Visual/mechanical nonconformances ........................................ 21

9.1.4 DPMO-4 − Hermetic nonconformances ...................................................... 21

9.1.5 DPMO-5 All nonconformances .................................................................. 21

9.2 Estimation of DPMO .............................................................................................. 21

9.2.1 DPMO reporting......................................................................................... 219.3 DPMO calculations ................................................................................................ 21

9.3.1 Sampling requirements .............................................................................. 22

10 Use of sampling plans ....................................................................................................22

10.1 Grouping of tests................................................................................................... 22

10.2 Categorization ....................................................................................................... 22

10.3 In-process testing and control................................................................................ 23

10.4 Indirect measuring methods................................................................................... 24

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11 Operating characteristics curves and values ................................................................... 24

Annex A Example of Consensus sampling plan for 3 levels of conformance torequirements IEC 62326-4 Multilayer printed boards ....................................................... 33

Annex B Example of continuous sampling using attributes that have been converted

to variable data in order to achieve process improvement ............................................... 49

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Sampling plans and procedures for inspection by attributes

Introduction

The definition of quality in terms of doing business can use several different words to describe

quality levels. Although terms such as goodness, excellence, optimum and similar terms mightprovide some insight, they are at best subjective or vague. The most widely quoted and accepteddefinition is "Conformance to Requirements".

Now and in the future, IEC standards and specifications need to define the importance of the abilityto achieve "Conformance to Requirements" as the measure of quality. In this context quality doesnot mean perfection or various degrees of perceived perfection. It means efficient production of thequality that the market expects.

Clear description in IEC standards and specifications and their reference to sampling plans in order to insure adherence to customer requirements is essential. The details should be clear as to their implementation or adjustment for evaluation of product to be shipped, the use of process control andSPC, or the applicability for using these principles in controlled experimentation. These principles

relate to:

• STATISTICAL SAMPLING: Where, When, and Why

• ZERO DEFECT STANDARDS: Role of Specifications

• ECONOMICS: AQL vs Cost of Defects

• SPC REDUCED INSPECTION: Rules for Use and Control

Many standards and specifications, then and now, include a great deal of vagueness and safetymargins sometimes referred to as "Fudge Factors". Specifications and standards of this naturemake absolute conformance impractical or unreasonable, and in some cases, impossible. The bestsolution to this situation is to make IEC specifications and standards as realistic and valid to the end

use. This standard is dedicated to help in achieving those goals.

During the Second World War there grew a need to create a technique to secure the quality of products in mass production with a known risk to failure. A technique of accepting or rejectingproduction lots by taking sample of products, investigating this sample and determining the qualitystatus of the whole lot based on the failures found in this sample was developed.

The statistical system was built to optimise the risk of the producer to reject a lot of good quality inhis final control and the customer’s risk to accept a lot of bad quality in his incoming inspection. Aterm Acceptable Quality Level (AQL) was created.

A set of tables, determining the sample sizes based on the size of the basic lot and on the dif ferent

AQLs, was created. Typical AQLs in use were from 0,1% to 4%. For example AQL 1,0% means thatwith a large probability (>95%) the lot with failure percentage larger than 1% will be rejected in thesample inspection.

The AQL system was adopted by the civilian industry after the war, and it was shown to be veryuseful especially in the emerging electronic industry, where large numbers of components were usedto build the final product. It should be understood that at that time the overall number of failures inproducts was in the area of the AQLs used, and the system was an improvement in helping to makecontracts between the producer and the customer.

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When original military standards on sampling were transferred to the civilian world, the principleswere published by the IEC in IEC Publication 410. The many tables in the publication, the AQL-leveldescriptions, and the size of the basic lots were useful, however one or more failures in the samplewere permitted, and the lot still accepted.

The explosion of the electronics industry has lead to a situation where the number of components inone product and the number of products are so large, that the quality level of components and

electronic products with known failures are no longer acceptable. The acceptable number of non-conforming product has been approaching zero in the producer-customer contracts, and is in anycase in the range of parts per million (ppm).

This has lead to the development of new methods of quality assurance like the application of Statistical Process Control (SPC). Because of the low number of permitted non-conforming productaccording to the AQL tables, many would resort to 100% testing or inspection.

At the same time the quality thinking has developed so that the idea to accept fai lures has becomeimpossible, and the use of the AQL tables in the traditional way has been diminishing very rapidly.

1 Scope

This standard establishes sampling plans for inspection by attributes, including sample planselection criteria and implementation procedures. The principles established herein permit the use of different sampling plans that may be applied to an individual attribute or set of attributes, accordingto classification of importance with regard to form, fit and function.

2 Normative references

IEC 60194 Terms and definitions for printed boards, printed board materials and assemblies

IEC 61192-3 Product performance requirements: Part 3: W orkmanship requirements for through-hole mount soldered assemblies

IEC 61193-5 Quality assessment system − Part 5: Registration and analysis of defects on solderedprinted board assemblies

IEC 62326-4 Printed boards − Part 4: Rigid multilayer printed boards with interlayer connections

ISO 9001 Quality systems − Model for quality assurance in design, development, production,installation and servicing

ISO 9002 Quality systems − Model for quality assurance in production, installation and servicing

3 Terms and defini tio ns

For purposes of this standard the definitions in IEC 60194 (some of which are repeated below for convenience) and the following apply.

3.1 Att r ibuteaspect or characteristic of a unit of product defined in terms of actual requirement and allowabledeviation.

a) a requirement that is stated as a measurement with an allowable more and/or less deviation,

b) a requirement stated as an absolute desired condition with allowable anomalies,

c) a requirement stated as an absolute without exception (go/ no-go).

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3.1.2 Cr it ic al at t ri bu tean attribute where a defect, that judgment and experience indicate, is likely to result in hazardous or unsafe conditions for individuals using, maintaining, or depending upon the product; or where adefect is likely to prevent performance or function of a major end item such as a ship, aircraft,computer, medical equipment, or telecommunication satellite.

3.1.3 Major at t ri bu te

an attribute where a defect, other than critical, is likely to result in failure, or to reduce the usability of the unit of product for it’s intended purpose.

3.1.4 M inor at tr ibutean attribute where a defect is not likely to reduce materially the usability of the unit of product for it’sintended purpose, or is a departure from established standards having little bearing on the effectiveuse or operation of the unit.

3.2 Ac cep tab le qual it y l ev el (AQL)maximum percent of defects that can be tolerated as a risk, stated for purposes of samplinginspection. Sample inspection with associated risk tolerance is employed only where all units of product within an inspection lot is expected to completely conform to specification requirements.

3.4 Defect iveunit of product that contains one or more defects.

3.4.1 Cr i ti cal defec t iveunit of product that contains one or more defects of critical attributes, and may also contain defectsof major or minor attributes.

3.4.2 Major defec ti veunit of product that contains on or more defects of major attributes, and may also contain defects of minor attributes, but contains no defects of critical attributes.

3.4.3 M inor defec ti veunit of product that contains one or more defects of minor attributes, but contains no defects of major or critical attributes.

3.5 Inspectionprocess of measuring, examining, testing, or otherwise comparing the unit of product with thespecified requirements.

3.5.1 Inspec t ion by at t r ibu tesinspection of individual attributes (aspects or characteristics) of the unit of product per specifiedrequirements, procedures, and/or instructions.

3.5.2 Inspec ti on l ot

collection of units of product that are identified and treated as a unique entity from which a sample isdrawn and inspected in order to determine conformance with acceptability criteria.

3.5.3 Inspec ti on ratethe number of features per unit of time that can be evaluated at specified false-alarm and escape-rate settings.

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3.6 Risk Managemen t Fac to r (RMF)the maximum tolerable percentage of possible defects within a lot (group) of units, based onapproximately 95% confidence level.

3.7 Shi pm en t-r ead y p rod uctproduct that will be shipped to customer without having to meet any further acceptance criteria.

3.8 Unit of productitem(s) being inspected in order to determine conformance to the requirements, as specified.

a) a single article, a pair, a set, a length, an area, an operation, a volume, a component of an endproduct, or the end product itself.

b) may or not be the same as the unit of purchase, supply, production or shipment.

4 Background

The zero acceptance number plans were originally designed and used to provide equal or greater consumer protection with less inspection than that required by corresponding sampling plans. TheC=0 plans are simple to use and administer since there is greater emphasis on zero defects and

product liability prevention. The concepts stated herein provide a set of attribute plans for lot-by-lotinspection. The acceptance number in all cases is zero. This means that for some level of protection, a sample size is selected and if one or more non-conforming attributes are present, onewill "withhold a lot."

The terminology "withhold the lot" is significant in that it does not necessarily mean rejection. Onedoes not automatically accept or reject the lot if one or more non-conformances are found; rather acceptance only occurs if zero non-conformances are found in the sample.

Withholding the lot forces a review and disposition by engineering/management personnel in regardto extent and seriousness. This relates to whether the attribute was critical, major, or minor, or whether identifying the non-conformance to the requirements was defined as a critical, major, or minor defect.

The word "defective" is commonly used in quality control to describe a part, component, item, or anyother unit of product that contains one or more defects. The word "defect" is commonly used todescribe a particular non-conforming characteristic on a unit of product.

4.1 Attribut e sampling plans

The following clauses provide an overview of lot-by-lot attribute plans while relating them to other plans. Two broad categories of sampling exist. These are:

a) Continuous

b) Lot-by-lot

4.1.1 Con tin uous sampli ng

Continuous sampling is often used when units of product are submitted one at a time. This canapply to assembly lines or other functions where a product moves through various processing steps.Product moving along a conveyor can also be thought of as being a candidate for continuoussampling. The industry has moved away from inspecting quality at the end of the line, thus in-process inspection or sampling is a way in which many companies maintain statistical processcontrol.

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The continuous sampling plan may call for a frequency check i.e., one unit out of five. Should theproducts be good, this frequency check will remain in existence. If however, a unit isnonconforming, 100% inspection is reverted to until the specified number of consecutive conformingproducts result. At that point, the process returns to frequency inspection.

4.1.2 Lot -by-lot attri but es

Lot-by-lot involves units of products that are presented in a group, batch, or lot for inspection, asopposed to being presented one at a time. In these cases, a sample of a specified quantity is drawnand compared with some acceptance criteria. In the past, sampling plans allowed a certain quantityof defectives in the sample; the C=0 plan does not. In C=0 plan, the attributes evaluated either conform or do not conform. Go/no go type gauges are often used in attribute plans.

4.1.3 Lot -by-lot variables

Another lot-by- lot sampl ing procedure involves the analysis of measured characterist ics where theattributes are variable as to their requirement. Variable sampling compared with attribute samplingessentially involves the inspection of a smaller sample size to obtain the same protection afforded byan attribute plan. The economics of these smaller sample sizes, however, are quite often offset bythe calculating involved and the need for obtaining and recording measurement.

Where variables data is required from an inspection operation, variables plans should definitely beconsidered. This is often used in determining the range of conformance in meeting, or beingbetween, the upper or lower specification limit of a requirement. By retaining the records regardingmeeting the target value of a particular requirement, the sampling plan can determine when theprocess is starting to become out-of-control due to the distribution of measurements within thespecified upper and lower acceptance limit. Within variables lot-by-lot sampling, the information isgathered primarily to help ensure the manufacturing of acceptable product by determining thedistance from the target that the lot inspection provides.

4.2 Non-statistic al sampling plans

There are cases where one can visually assure zero defects, although the sample size cannot

logically be defined in terms of statistical risks. Such sample sizes are generally exceptionally lowfor the more important attributes and, therefore, a knowledge of the process and the control factorsis essential.

In order to avoid any confusion in justifying such sample sizes on inspection plans, specific notationsshould be used to avoid any tie-in with statistical risks. The reason for such a selection should benoted, either directly in the plan or in the quality engineering standards.

An example might be a sampling operat ion where just the first and last piece from a lot areinspected dimensionally. A statistical sample may be taken using visual inspection only. Another example might be evaluating a number of products during a particular time sequence. If theproducts are different, the technique can be normalized by evaluating the amount of unit area beingprocessed along a conveyor over a particular time. In this instance, a variety of product can be

measured and evaluated. The system then would be judged in or out of control, depending on non-conformance per unit area over specific time sequences.

The higher index values in the C=0 plans are also used where favorable process control has beendemonstrated and just an audit is required. Although the statistical risks seem high, the risks from apractical standpoint would be exceptionally low.

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4.3 Relationsh ip of C=0 plans

There are many plans from the past that have used the C=>0 concepts. These plans are AcceptableQuality Level (AQL) oriented. Essentially, the AQL is a specified percent that is considered to begood quality. In any sampling plan, an operating characteristic curve can be generated to define therisk of accepting lots with varying degrees of percent non-conforming or defective. These planswent out of favor in the late 1980's, due to the implication that it was good quality to release

shipment-ready products with known, non-conforming attributes.

When the AQL concept is used, a high probability of acceptance associated with the AQLpercentage exists. Normally this is in the order of a .90 to .98 probability of acceptance level. Therisk of rejecting this AQL percentage is in the order of 0.10 to 0.02 probability level. This rejectionrisk is called the "producer's risk."

The assumptions in employing the AQL concept is that some agreement has been reached betweenthe producer and the consumer. Because sampling is used, the producer must assume a risk of having a lot rejected, although the actual percentage defective in the lot is equal to or less thanspecified in the AQL.

If no prior AQL agreement exists, and sampling is to be performed simply because 100% inspectionis impractical, then over-inspection is usually the result. Also, when 100% sampling is impractical,the producer is encouraged to inspect a small number of units of product on less critical attributes.To illustrate the concept, if one were using the C=>0 plans of the past, a 1.0% AQL might be usedfor critical attributes and a 4.0 AQL might be used for major attributes.

As an example, If a lot size were equal to 1300 units of product, although no consumer/producer agreement existed, past plans would recommend to take a sample size of 125 pieces. These plansrecommended that critical attributes have AQLs of 1.0 and that major attributes be judged at 4.0%

AQL. The older plans allowed 3 non-conforming attributes per sample size for the 1.0 AQL, and 10defects for the 4.0 AQL.

One can see that for the less critical characteristics, the sample size remains the same. The

difference is in the acceptance number. That is, to accept the lot for the 1.0% AQL, the samplecontains 3 or less defectives. For the major attribute characteristics, one can accept the lot if thesample contains 10 or less defectives. Because the sample size is the same, there is no reductionin pieces inspected for the major attributes versus the critical attributes.

It is a statistical fact that zero accept number (C=0) plans provide equivalent or greater statisticalassurance than do older plans associated with defect acceptance (C=>0). This can be verified byexamining the operating characteristics (OC) curves, which should normally be provided withsampling plans. Figure 1 shows a typical OC curve from a C=>0 plan. There is a probability scaleon the X-axis and an incoming defective possibility scale on the Y-axis. The curve is generatedthrough probability calculations based on the indicated 125 sample with an acceptable defectnumber of 10. Also shown is the producer's risk, which is a risk of rejecting a good lot of productand the associated consumer's risk, which is the risk of accepting a bad lot of product.

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Figur e 1 Typical OC Curve for C=>0 plan

In addition to the AQL and producer's risk there is a parameter called the Lot Tolerance PercentDefectives (LTPD). This LTPD is considered poor quality. Several sampling plans can have OCcurves pass through the same AQL/producer's risk point. For each of these plans however, therewill be a different LTPD at some constant probability of acceptance level. This probability of acceptance level corresponding to the LTPD is usually low with a 0.10 being widely accepted. Thisprobability level is called the "consumer's risk."

The user of sampling plans must select the plan that will provide reasonably good protection against

accepting lots with a percent defectives not too much greater than the AQL. With the AQL/producer's risk point fixed, the closer the LTPD gets to the AQL, the larger the sample size andthe acceptance number becomes. Figure 2 is a comparison of the C=>0 OC curve and anequivalent OC curve from the zero defect C=0 plan. This example illustrates that the C=0 curve witha small sample of 18 and an accept number of 0 is equivalent or better than the C=0 plan with arelatively large sample of 125 and an acceptance number of 10. The producer's risk probability maybe greater at certain levels with the C=0 plan, however this should have little effect, assuming thatrequirements are accurate.

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Figure 2 OC Curve comparison s between C=>0 and C=0 plans

What industry has tended to do is to measure output, determine yields, then resign to an acceptablelevel of defectives based on the information. These systems, usually AQL-based, remove incentivesto review the validity of specifications, investigate defect causes, or to improve overall productquality.

Table 1 shows a comparison of a set of C=0 plans with previous plans of C=>0.

Table 1 Inspection plan comparis on

AQL Sam ple s ize Ac cept No .

1.0% 125 3C=>0 Plan

4.0% 125 10

As sociat ed AQL Sam ple s ize Ac cept No .

1.0% 42 0C=0 Plan

4.0% 18 0

The C=0 plans provide equal to or greater LTPD protection at the 0.10 "consumer's risk" level.There is also less inspection performed on less critical characteristics or attributes.

All of the C=0 characteristics are shown in Table 2; they are "associated" with the AQL's of the C=>0plans of the past. In all of these plans, equal or greater protection is afforded to the consumer thanthe older techniques. The method of developing the plans provides for simple conversion from pastpractices to the C=0 plans. The table labels these associated AQLs as "index values" because theyare not AQLs. In some of the IEC documents, they had been called Risk Management Factor (RMF).

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Table 2 Risk management factor s/ Index values (Associated AQL)

.010 .015 .025 .040 .065 .10 .15 .25 .40 .65 1.0 1.5 2.5 4.0 6.5 10.0

LOT SIZE SAMPLE SIZE

* * * * * * * * * * * * 5 3 2 2

* * * * * * * * * * 13 8 5 3 2 2

2 − 8

9 − 15

16 − 25 * * * * * * * * * 20 13 8 5 3 3 2

* * * * * * * * 32 20 13 8 5 5 5 3

* * * * * * 80 50 32 20 13 8 7 6 5 4

26 − 50

51 − 90

91 − 150 * * * * * 125 80 50 32 20 13 12 11 7 6 5

* * * * 200 125 80 50 32 20 20 19 13 10 7 6

* * * 315 200 125 80 50 48 47 29 21 16 11 9 7

151 − 280

281 − 500

501 − 1,200 * 800 500 315 200 125 80 75 73 47 34 27 19 15 11 8

1250 800 500 315 200 125 120 116 73 53 42 35 23 18 13 9

1250 800 500 315 200 192 189 116 86 68 50 38 29 22 15 9

1,201 − 3,200

3,201 − 10,000

10,001 − 35,000 1250 800 500 315 300 294 189 135 108 77 60 46 35 29 15 9

1250 800 500 490 476 294 218 170 123 96 74 56 40 29 15 9

1250 800 750 715 476 345 270 200 156 119 90 64 40 29 15 9

35,001 − 150,000

150,001 − 500,000

500,001 and over 1250 1200 1112 715 556 435 303 244 189 143 102 64 40 29 15 9

Note 1: The symbol * indicates to inspect the entire lot

Note 2: If lot size is smaller than the sample size, the entire lot should be inspected.

Note 3: If samples contain no defects, the entire lot is accepted. If the sample contains one or more defects, the entire lotis rejected.

It should be noted that the idea of withholding more lots under the C=0 plans may arise because of the zero accept number. Aside from experience, which has shown that in fact, considerable savingscan be derived, one should consider the following:

a) if the quality is very bad, acceptance numbers greater than zero will not be much help;

b) to allow acceptance numbers greater than zero in the plan, one is in effect authorizing aninspector to accept parts which may not be usable;

c) the zero acceptance number forces a review of any defectives by quality personnel in order for proper disposition to take place;

d) if one is striving for zero defects, it should be obvious that one should not knowingly allowdefectives to be shipped.

C=0 plans were essentially designed to be equal or greater in consumer and average outgoingquality limit protection. Within a particular column of the details shown in Table 2 representing the

Index value or RMF, the operating characteristic curves actually differ for the most part between C=0and C=>0 plans, especially as the lot size increases. The reason for this common feature, inaddition to satisfying the statistical relationship, is that it is generally considered more practical toobtain greater protection on larger lot sizes. Table 3 provides guidance to selection of sample sizes.

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Table 3 Sample size selection gui deline

Defects At tr ibutes

Critical Major Minor

Critical 0.1 1.0 2.5

Major 1.0 2.5 4.0

Minor 2.5 4.0 6.5

The use of constant sample sizes often result in a combination of over-inspection and under-inspection. For a broad range of lot sizes in general, however, in order to develop an inspectionstrategy, an evaluation should be made as to the attribute classification (critical, major, minor). Thislisting of comparisons should identify the RMF (index value) shown in the Table 2 and should allowthe C=0 plans to be used when:

a) manufactured parts are expected to completely conform to specification requirements;

b) less inspection is desired on less critical characteristics;

c) sampling is performed because 100% inspection on all attributes of all units of product isimpractical

d) inspections are not allowed to knowingly accept non-conforming products;

e) auditing is required for assurance of process validation, potential transit damage, certification of suppliers, or inventory verification.

5 Classifi cation of attributes

Attributes are classi fied as part of the process for select ion of sampling plans applied to individualand/or grouped attributes for inspection.

5.1 Classification Assignment

Classification of individual attributes associated with specified requirements is assigned according toimportance or seriousness. Any failure to conform to the ultimate form, fit, function, and intendeduse of the unit of product is usually understood as being nonconforming to the requirements.

Attributes are classi fied as one of the following:

a) Critical

b) Major

c) Minor

Market segment, or intended end use of a unit of product will influence attribute classification. For example: an identical attribute which may be considered as “critical” in the Aircraft market segmentmay be considered “major” or even “minor” in the Consumer market segment.

Table 4 shows basic “Market segments” as an aid for attribute classification.

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Table 4 Worst-Case Use Environment s

Temperature rangesUse Category

Tmin

ºC

Tmax

ºC∆∆∆∆T

1

ºC

tD

hours

Cycles/

year

Typical

years of

service

Ap prox.

Ac cep t.

Failure

Risk %

1. Consumer 0 +60 35 12 365 1-3 1

2. Computers +15 +60 20 2 1460 5 0.1

3. Telecom -40 +85 35 12 365 7-20 0.01

4. Commercial Aircraft

-55 +95 20 12 365 20 0.001

5. Industrial Automotive

Passenger Compartment

-55 +95 20&40

&60&80

1212

1212

185100

6020

10 0.1

6. Military Ground &Ship

-55 +95 40 & 60 1212

100265

10 0.1

7. Space leo geo

-55 +95 3 to 100 112

8760365

5-30 0.001

8. Military Avionics

-55 +95 406080

&20

2221

365365365365

10 0.01

9. Automotive

Underhood

-55 +125 60

&100&140

1

12

100

30040

5 0.1

& = in addition

1) ∆T represents the maximum temperature swing, but does not include power dissipation effects.

Sometimes the contractual agreements between consumer and producer indicate performanceacceptance to an approved standard. IEC 62326-4 is an example of a standard that uses C=0sampling plans. This standard, for multilayer printed boards used in electronic equipment, specifiesperformance requirements in a table.

The table in IEC 62326-4 has established the sampling criteria for each attribute or requirementstated in the standard. These are identified as a Risk Management Factor (RMF) as opposed to the

old AQL identifications. This was done to highlight the recommendation that certain sample sizes"based on the risk management factor" required that the number selected is sufficient to provideprotection on critical attributes through using lower percentage nonconforming parts in the samplebeing evaluated. (see Annex A)

Assignment of classi fication to individual attributes is the responsibil ity of the user/customer. Annex A shows an example of acceptance characterist ics for three levels of product performance.

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5.2 Classification and adjustment of sampling plan criteria

Selection of a sampling plan for an attribute should normally be based upon classification. However,manufacturing process and procedure variability which effects the conformance to the requirementsof a particular attribute should considered. If, as the result of a known process, once set-up,produces consistent results, piece-to-piece within a lot or batch with little to no variability, it is logicaland cost effective to deviate from the strict implementation of a given sampling plan. In this situation

it is possible to apply a non-statistical audit by selecting a lesser RMF sampling plan.

5.3 Process cont rol

Sampling plan application for the electronics industry is best utilized by the assignment of separatesampling decisions based on the critical impact for each characteristic specified. For differentproduct categories, plans are applied to such products as shown, but not limited to:

a) electronic components

b) electromechanical parts

c) mechanical parts

d) product printed boards (printed circuits, printed wiring)

e) component printed boards (printed circuits, printed wiring)

f) hybrid circuits

g) electronic single chip modules

h) electronic multichip modules

i) electronic assemblies

j) electronic backplanes

The sampling risk levels would be applicable to the characteristics of units of a product categorywhere the characteristics are critical to the reliability, customer satisfaction, or product liabilitypotential. A more lenient plan can be applied to characteristics that are normally less critical to

function or attributes that are identified as minor within a particular product category. In addition, themore lenient plans may also be appropriate where there is a known consistency of tooling andautomatic processing.

6 Defects and proc ess deviation indi cator (PDI) evaluati on

Many performance standards list typical defects that are unacceptable and require disposition, e.g.,rework, repair. The manufacturer is responsible for identifying other areas of risk and treating thoseadditional concerns. Such items should be documented on the assembly drawing. Other than theunacceptable defects listed, anomalies and variances from within ‘acceptable’ limits are consideredas process deviation indicators and shall be monitored when their occurrence is observed. Usually,disposition of process deviations revealed by PDIs is not required.

6.1 Process control and process improvement requirements

As the industry matures, inspection at the end of the process is not acceptable to many customers.They require the use of process control methodologies in the implementation and evaluation of processes used to produce electrical and electronic assemblies. Subject to agreement by the user,the manufacturer/assembler may be exempt from performing specific quality conformanceinspection. Thus, sampling by attributes is not a desirable technique even with C=0 inspectionplans, since the practice implies one is inspecting quality into the product at completion of all thework. Nevertheless, the practice helps the systematic path to process control as shown in Figure 3.

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IEC 60410 © IEC:2000 – 16 –

Quality control inspection technique at product

completion (lot inspection)

End-product evaluation for control

and capability

In-process product evaluation for control

and capability

Process parameter evaluation for control

and capability

Continual process improvement

and optimization

Figure 3 Systematic path for implement process contro l

Annex B shows an example of one company's attempt to move down the systematic path. In thatexample, continuous sampling is used as a part of the "In-process product evaluation for control andcapability of a wave soldering operation. The attributes selected are from IEC 61192-3 and are usedto determine process capability based on unit area of product being processed through theattachment system. Sample size was based on a time during which product/unit areas were being

processed.

7 Inspectio n plans

The following paragraphs define procedures for implementation and operation of inspection byattributes using C=0 sampling plans.

7.1 Zero acceptance num ber-based sampli ng plans

There are still some areas, where the attribute sampling has its merits, e.g.:

• The producer of electronic components can control the occurrence of so called roque lots

(something totally wrong), by using sampling, and at the same time in long run to collect valuableinformation of the failures in his process and products. This information can also be used tocalculate Assessed Process Average (APA) figures, if they are needed.

• There are still some areas of failures, like some visual/mechanical failures in complicatedelectromechanical products, where AQLs in traditional form can be of use.

• In the qualification and periodical testing of the components a representative sample has to beselected, because all components can not be tested.

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IEC 60410 © IEC:2000 – 17 –

It is possible to generate the acceptance/reject tables for attribute testing based on zero acceptancenumber. It is very important that no matter what statistical levels are used, the acceptancenumber of failures must be zero . This has a strong psychological meaning, and it builds trustbetween the producer and the customer. This is true, although one has to understand that thestatistical probabilities to have failures are not different with zero and non-zero acceptance numbers,if the statistics used is the same.

There is lot of evidence that the zero failure principle has lead to considerable quality improvementsin production processes in many areas.

Many companies have been verifying components (Capacitors and Resistors) already for many yearshave applying the Zero Acceptance Number principle in the qualification and periodical testingtables. The experiences of this system are good, and the claims of too low quality levels from thecustomer’s side have diminished considerably. This one single point was earlier always the firstobstacle to be overcome to get the customers to accept the use of relevant National, Regional or International Standards as the basis of agreements.

The attribute testing can still be a viable tool in the quality assurance, when only the Zero Acceptance Number of Fai lures is used.

7.2 Responsible authority

When specified by a responsible authority, this standard shall be called up in the specification,contract, inspection instructions or other documents and the provisions set forth herein shall govern.The “responsible authority” shall be designated in one of the control documents listed. It should benoted that the responsible authority will normally be the customer.

7.3 Application

Sampling plans designated in this publication are applicable, but not limited, to inspection of thefollowing:

a) End items

b) Components

c) Raw materials

d) Operations

e) Supplies in storage

f) Maintenance operations

g) Data or records

h) Administrative procedures

These plans are to be used primarily for lots or batches that are generally known to have beenproduced or manufactured under consistent and/or continuous conditions, from a single origination,

and are expected to completely conform to specification requirements. The plans may also be usedfor inspection of isolated lots or batches, but in this latter case, the user may wish to consult theoperating characteristics curves to find a plan that will yield the desired protection. These plansshould normally only be used for completed items, such as out-going (at the supplier) and/or in-coming (at the customer); However the sampling plans may be used in audit situations such as stockaudit for assurance or potential transit damage, or used as part of a supplier certification procedure.

Statistical process control (SPC) methods and procedures should be used during the production/manufacturing steps in process.

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IEC 60410 © IEC:2000 – 18 –

7.4 Sampling plan specification

Normally an RMF and associated sample plan is generally specified by the user/ customer for attributes in each classification, as influenced by market segment and variability factors. There isalso a high impact derived from the technology sector for product in each market segment as shownin Figure 4.

Table 5 is an example of how a user/ customer might specify attribute sample plans for a particular market segment, for either internal or external contractual agreements. These are generalcategorizations and may be more stringent for critical attributes.

Figure 4 Industry markets/ Technology sectors

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IEC 60410 © IEC:2000 – 19 –

Table 5 General sample plan criteri a

per industry markets / technology sectors

High

performance

systems

Harsh

environment

systems

Handheld

systems

Cost

performance

sensit ive

Low cost/

high volume

Automotive .01 0.15 .04 .15 2.5Military .01 0.15 .04 .25 2.5

Communication .015 .025 .065 .25 4.0

Computer .025 0.4 .10 .25 4.0

Business 0.04 .065 .15 .25 4.0

Instrumentation .065 .10 .15 .40 6.5

Industrial .10 .15 .40 1.0 6.5

Consumer .40 .65 2.5 6.5 10

7.5 Submission of product

Quality conformance evaluation are performed on products manufactured and intended to bedelivered to the customer. When quality conformance evaluation is accomplished through samplinginspection techniques, sample size selection shall be taken from table 2. For performance, the RMFfor lot inspection is prescribed in the standard, customer specification, or derived from the examplein table 5. . The lot inspection sample size prescribed is applicable, unless in-process controls havebeen established, with verifiable evidence of correlation to finished product requirements. For thepurpose of the quality conformance inspection, products that are structurally similar may beaggregated into one inspection lot.

For a lot to be accepted, all test specimens of the sample shall conform to the requirements. If aninspection lot is rejected, the manufacturer may inspect 100 % of the lot and screen out the defectiveunits for the defect(s) identified in the sample. The defective units may be reviewed and accepted byagreement between customer and manufacturer. To be accepted, the screened out inspection lotshould be reinspected by selecting an additional sample in the sampling plan per the describedRMF.

When lot inspection techniques are utilized for quality assessment, the manufacturer may reduce thesample size designated in table 2 to the next less stringent RMF shown.

– five consecutive inspection lots, of similar size, have been accepted using the specifiedperformance level and current assessment criteria;

– the time elapsed between the first and fifth inspection lots has been no longer than 12 months;

– the reduced assessment is appl ied to inspection lots of sim ilar size or less;

– the cer tifying record shall indicate and ver ify changes in assessment levels .

This procedure can be undertaken twice, if the same criteria are met. Normal inspection shall beresumed if one inspection lot is rejected.

Lot inspections may be further reduced or discontinued, if process control techniques areestablished, with correlation to the finished product requirements.

Customers shall be made aware of the quality assessment procedures in operation, and shall benotified of reduced lot inspection or changes from lot inspection to in-process testing and control.

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IEC 60410 © IEC:2000 – 20 –

8 Classifi cation of defects

An IEC standard wil l usually contain complete information on quality evaluation for any product to befully compliant with the requirements for various performance levels. The sampling plan data shallspecify the appropriate level of quality conformance inspection from table 2, as well as the attributes(critical, major, minor), and defect characteristics (critical, major, minor).

Unless otherwise specified, specially designed test specimens may be used for carrying out tests for the lot inspection and the periodic inspection.

When specially designed test specimens are to be used, their description shall be included in thedocumentation. They may be based on the appropriate characteristics of the shipment-readyproduct. Consultation between manufacturer and customer is usually necessary.

8.1 Custom ers Detail Specificati on (CDS) data

A customer detail specification should also contain all information necessary to def ine the productclearly and completely. This includes the target acceptance conditions as well as what constitutesnon-conformance.

Care shall be taken to avoid unnecessary requirements. Permissible deviations shall be statedwhere necessary and nominal values without tolerances or simple maxima or minima shall be givenwhere sufficient. Where precise tolerances are necessary for certain products, they shall be appliedand restricted to those products.

9 Percent defectives per milli on opportunities

The objective of the Defect Per Million Opportunities (DPMOs) approach is to characterize thequality of shipment-ready lots of products. This assumes a uniform manufacturing process whichhas controls for eliminating non-representative lots.

Samples, which are drawn at random from the individual lots which comprise the population areassessed based on audits performed on shipment-ready products.

The pass/fail result is used as final lot acceptance data. Lots/batches of products which failacceptance inspection criteria are assumed to be either reprocessed 100% with all nonconformingparts being removed from the lot/batch or the lot/batch is removed from consideration for shipmentand discarded.

9.1 Classes of DPMO

Nonconformances shall be classified by the preparer of the IEC specification under one or more of the following classes (no device shall be counted more than once in any one of the five classes):

9.1.1 DPMO-1 −−−− Functional nonconformances only

Those nonconforming devices which are inoperative.

9.1.2 DPMO-2 −−−− Electrical nonconform ances

Those devices nonconforming to specified parameters which define essential electricalcharacteristics of a product (includes DPMO-1 Electrical).

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IEC 60410 © IEC:2000 – 21 –

9.1.3 DPMO-3 −−−− Visual/mechanical n onconfor mances

Those devices nonconforming to specified parameters which define the essential visual/mechanicalcharacteristics of a product (includes DPMO-1 Visual/mechanical)

9.1.4 DPMO-4 −−−− Hermetic nonconfo rmances

Those devices nonconforming to the hermetic requirements of a product (includes DPMO-1Hermetic).

9.1.5 DPMO-5 All nonc onf ormanc es

All devices nonconforming to any specification requirement of a product. This inc ludes all of DPMO-2, -3, and -4, plus all other specification nonconformances.

9.2 Estim ation of DPMO

Estimation of the nonconformance level in DPMO can be calculated using the assumption thatattribute sample inspection is being conducted for product which has completed all manufacturingprocesses to the criteria being reported. In addition, the manufacturing processes used to produce

the product are maintained statistically in control.

Lots/batches of product which fail acceptance inspection are either reprocessed 100% and all thenonconforming parts removed from the lots/batches or the lots/batches are removed fromconsideration for shipment and discarded.

All reprocessed lots/batches (second or other submissions) are segregated from nonsampledlots/batches. Data from these lots (i.e., other than first submission lots) will not be used in thecompilation of DPMO.

9.2.1 DPMO report ing

For each DPMO value being reported, the manufacturer will specify what parameters were actuallymeasured and used for that calculation. Nonconformities which are not related to parts, such asadministrative errors, shall not be included in these calculations.

Since the plans are on a C=0 basis, the sample size is based on the probability that somepercentage (RMF) nonconforming parts are included in the lot. The probable percentage number should be used in the calculation

Data obtained from assumptions made on lots/batches that were not tested because of a skip lotsampling plan or a waiver of test requirements, cannot be used in any assessment of DPMO.

When products are manufactured at more than one location, data from these different locations maynot be combined to form a composite DPMO value.

9.3 DPMO calcul ations

Estimation of the nonconformance level in DPMO is calculated as follows:

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IEC 60410 © IEC:2000 – 22 –

DPMO # =

1i

n

mi

x

m

i

i

=

=+

∑

∑1

7.0

X 106

That is,

DPMO # = ( )testedinspectednumber Total

innonconformnumber Total g+7.0 X 106

where:

xI is the number of nonconforming parts found in the actual inspection (testing of nI parts from the Ith

lot of m total lots. # is the designated class of DPMO.

9.3.1 Sampling requir ements

XI and nI are determined when performing the final audit or lot acceptance on a lot before it isshipped to a customer. The only requirement on the sampling procedure is that the parts must beselected randomly.

Lots 1 through m must include all lots sampled from lot 1 through lot m.

10 Use of sampli ng plans

There are many ways to apply the C=0 sampling plan criteria. Each application has its merits and it

is important to use the most reliable method which correlates to the products being manufactured.

10.1 Groupi ng of tests

Tests may be subdivided into categories in order to reflect various grouping of inspection.

The categories cover lot inspection and periodic tests. The tests may be destructive and may requirethe use of standard test specimens. The specimens may be included on the production lot or may beproduced separately in conjunction with the production lot. Test specimens should be of the samematerials and processes so as to be representative of the product and the process. If separatespecimens are manufactured, they shall be spaced out in production in such quantities that a goodaverage assessment can be made.

10.2 Categorization

Various techniques can be used to categorize the inspection and quality assessment of the attributesassociated with shipment-ready product. Each category consists of sub groupings depending on theproducts being assessed. Some of these are:

• Category V − Visual Inspection

• Category D − Dimensional Inspection

• Category S − Surface Condition Inspection

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IEC 60410 © IEC:2000 – 23 –

• Category E − Electrical Inspection

• Category P − Physical Inspection

• Category Y − Structure Integrity Inspection

• Category Z inspectionThis category covers all tests which may be necessary in addition to tests of InspectionCategories V, D, S, E, P, and Y to complete an entire test program. Category Z tests are usuallycarried out at intervals of 12 months. They may be carried out progressively within a 12 monthperiod.

10.3 In-process testing and control

In-process testing and control may be applied to any requirements listed in the standard,specification, or Customer Detail Specification (CDS), and is required at some stages. In-processtesting and control data shall be kept as verifiable evidence of conformance to requirements. Datashall be available which verifies correlation to finished product requirements. In process testing andcontrol may be implemented for selected requirements while continuing lot inspection for other requirements. Depending upon the progress made in implementing in-process/process control themanufacturer may prove compliance to specifications with:

− Quality conformance lot inspections;− Finished product control;

− In-process control

− Process parameter control

A manufacturer may choose to use a combination of these techniques to prove conformances torequirements.

When agreement has been reached between customer and manufacturer, in-process testing andcontrol may be substituted for the relevant test(s) and sampling prescribed in the qualityconformance inspection schedule, providing:

− the in-process testing and control is carried out under the authority of the appointed managementrepresentative (chief inspector);

− the process steps or storage periods between in-process testing and the completion of the unitsof product are not likely to affect the characteristics tested;

− the data provided by in-process testing is correlated to the finished product requirements andassures the same level of performance for characteristics as would be demonstrated in theprescribed finished product sampling plan and testing.

End-product statistical control should normally be established prior to implementation of in-processor process parameter control. However, some product requirements are preferably alwaysevaluated in-process.

In process control requirements are indicated in Table 2 as risk management factors. The priorityimplementation code signifies how the sampling should be applied. The codes given in Table 6 canbe used to communicate requirements between the user and the manufacturer.

Table 5 Process cont rol

Code Priori ty implementat ion

C1 In-process and/or process parameter control, required implementation

C2 In-process and/or process parameter control, f irst priority implementation

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IEC 60410 © IEC:2000 – 24 –

C3 In-process and/or process parameter control, second priority implementation

C4 In-process and/or process parameter control, third priority implementation

C5 Periodic laboratory test (in conjunction with related in-process/process control for correlation to testcriteria and product requirements)

10.4 Indir ect measurin g method s

Where appropriate, indirect measuring methods may be substituted for direct methods, providing thenecessary accuracy and calibration are ensured.

EXAMPLE: Instead of directly measuring dimensions, a gauge of suitable characteristics may beused.

Where appropriate, control of a process parameter may be the most effective method of assuringproduct conformance to specification requirements. In this case, the process parameter control maybe accepted as the primary quality assessment method for the affected characteristics, provided thata periodic product inspection for the relevant characteristic(s) is performed.

EXAMPLE: Process control of plating chemistry is the primary method of assuring adhesion of plated on component leads, maintaining process control coupled with periodic shipment-readyproduct inspection is preferred to lot inspection prescribed in a sampling plan.

11 Operating characteris tic s curves and values

The following tables and graphs show the operating curves for single sampling plans with anacceptance number equal to zero. The sample size is indicated in each of the tables and relates tothe following characteristics based on lot size submitted for inspection. These lot sizes are:

a) lot s ize 2-8

b) lot size 9-15

c) lot size 16-25

d) lot size 26-50

e) lot size 51-90

c) lot size 91-150

d) lot size 151-280

e) lot size 281-500

c) lot size 501-1200

d) lot size 1201-3200

e) lot size 3201-10,000

c) lot size 10,001-35,000

d) lot size 35,001-150,000

e) lot size 150,001-500,000

In some instances, special sampling plan tables are desired for small lots. When the associated AQL are 1.5 and below. Above 1.5, the main C=0 tables work well for small lots sizes. Anysampling plans developed for use with associated AQL less than .25 would, for the most part, not bevalid.

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IEC 60410 © IEC:2000 – 25 –

The LTPD for small lot sizes is targeted for the largest lot size range in which a constant sample sizeappears. For example (referring to a C=0 table), for tables associated with an AQL of 1.0, 13 isused at the 91-150 lot size range for .65; 20 is used in the 150-280 range. In other words, thesmaller lots shown in Table 5 have essentially the same LTPD as the targeted LTPD.

Table 5 Small lot characteristics

Lot s ize .25 .4 .65 1.0 1.5

5-10 * * * 8 5

11-15 * * 11 8 5

16-20 * 16 12 9 6

21-25 22 17 13 10 6

26-30 25 17 13 10 6

31-35 28 23 18 12 8

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IEC 60410 © IEC:2000 – 26 –

Sample

size

Probability of acceptance

.10 .25 .50 .75 .90 .95 .992 63.7 46.9 27.5 12.5 5.00 2.50 0.503 46.7 32.5 18.3 8.33 3.33 1.67 0.335 26.0 18.3 10.0 5.00 2.00 1.00 0.20

Figur e 4 Lot size 2-8

Sample

size


.10 .25 .50 .75 .90 .95 .992 66.0 48.3 28.3 12.9 5.00 2.50 0.503 50.0 34.5 19.2 8.61 3.33 1.67 0.335 31.8 20.8 11.3 5.00 2.00 1.00 0.20

8 18.7 12.1 6.25 3.13 1.25 0.62 0.1213 8.46 5.77 3.85 1.92 0.76 0.38 0.07

Figure 5 Lot size 9-15

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IEC 60410 © IEC:2000 – 27 –

Probability of acceptanceSample

size.10 .25 .50 .75 .90 .95 .99

2 67.0 49.0 28.7 13.1 5.04 2.50 0.503 51.4 35.5 19.8 8.80 3.33 1.67 0.33

5 33.9 22.3 11.9 5.20 2.00 1.00 0.208 21.4 13.7 7.18 3.13 1.25 0.62 0.12

13 11.9 7.54 3.85 1.92 0.76 0.38 0.0720 6.40 3.75 2.50 1.25 0.50 0.25 0.05


Sample

size


.10 .25 .50 .75 .90 .95 .993 52.5 36.3 20.2 8.97 3.39 1.67 0.335 35.4 23.2 12.4 5.38 2.00 1.00 0.208 23.2 14.8 7.72 3.31 1.25 0.62 0.12

13 14.2 8.91 4.59 1.92 0.75 0.38 0.0720 8.73 5.42 2.82 1.25 0.50 0.25 0.0532 4.60 2.94 1.56 0.78 0.31 0.15 0.03


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IEC 60410 © IEC:2000 – 28 –

Sample

size


.10 .25 .50 .75 .90 .95 .995 36.1 23.7 12.7 5.47 2.04 1.00 0.198 24.0 15.3 7.98 3.39 1.26 0.62 0.12

13 15.1 9.44 4.86 2.05 0.76 0.38 0.0720 9.70 5.99 3.06 1.29 0.49 0.25 0.5032 5.68 3.48 1.80 0.78 0.31 0.15 0.0350 3.17 1.98 1.00 0.50 0.20 0.10 0.0280 1.23 0.93 0.62 0.31 0.12 0.06 0.01


Sample

size


.10 .25 .50 .75 .90 .95 .995 36.4 23.9 12.8 5.52 2.06 1.01 0.197 27.5 17.6 9.24 3.95 1.47 0.71 0.14

13 15.6 9.71 4.99 2.10 0.77 0.38 0.0720 10.2 6.27 3.19 1.34 0.49 0.24 0.0532 6.21 3.80 1.92 0.81 0.31 0.15 0.0380 2.0 1.24 0.62 0.31 0.12 0.06 0.01


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IEC 60410 © IEC:2000 – 29 –


size.10 .25 .50 .75 .90 .95 .99

6 31.6 20.4 10.8 4.64 1.72 0.84 0.1610 20.2 12.7 6.59 2.79 1.03 0.50 0.09

13 15.9 9.90 5.08 2.14 0.79 0.38 0.0720 10.5 6.47 3.29 1.38 0.51 0.24 0.0532 6.55 4.00 2.03 0.84 0.31 0.15 0.0350 4.10 2.49 1.26 0.53 0.19 0.09 0.02125 1.39 0.85 0.43 0.20 0.08 0.04 0.00



size.10 .25 .50 .75 .90 .95 .99

7 27.8 17.8 9.36 4.00 1.48 0.72 0.1411 18.7 11.7 6.04 2.55 0.94 0.46 0.0916 13.2 8.17 4.17 1.76 0.64 0.31 0.0629 7.41 4.54 2.30 0.95 0.35 0.17 0.0350 4.28 2.60 1.31 0.54 0.20 0.10 0.02125 1.59 0.96 0.48 0.20 0.08 0.04 0.00

Figu re 11 Lot size 281-600

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IEC 60410 © IEC:2000 – 30 –


size.10 .25 .50 .75 .90 .95 .99

11 18.8 11.8 6.07 2.57 0.94 0.46 0.0919 11.3 6.98 3.55 1.49 0.54 0.26 0.05

27 8.08 4.95 2.51 1.05 0.38 0.18 0.0347 4.69 2.85 1.44 0.59 0.21 0.10 0.0275 2.93 1.77 0.89 0.37 0.13 0.06 0.01125 1.73 1.05 0.52 0.21 0.07 0.03 0.00



size.10 .25 .50 .75 .90 .95 .99

9 22.4 14.2 7.37 3.13 1.16 0.56 0.11

13 16.1 10.1 5.17 2.18 0.80 0.39 0.0723 9.46 5.82 2.95 1.24 0.45 0.22 0.0442 5.29 3.22 1.62 0.67 0.24 0.12 0.0273 3.07 1.86 0.93 0.38 0.14 0.06 0.01200 1.11 0.66 0.33 0.13 0.05 0.02 0.00

Figu re 13 Lot size 1201-3200

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IEC 60410 © IEC:2000 – 31 –


size.10 .25 .50 .75 .90 .95 .99

9 22.1 14.1 7.32 3.11 1.15 0.56 0.1115 14.0 8.74 4.48 1.88 0.69 0.33 0.06

29 7.56 4.64 2.35 0.98 0.36 0.17 0.0350 4.47 2.72 1.37 0.57 0.20 0.10 0.0286 2.62 1.59 0.79 0.33 0.12 0.05 0.01189 1.20 0.72 0.36 0.15 0.05 0.02 0.00

Figur e 14 Lot size 3,201-10,000


size.10 .25 .50 .75 .90 .95 .99

9 25.6 15.4 7.38 3.02 1.14 0.55 0.10

15 15.4 8.54 4.40 1.85 0.68 0.33 0.0629 7.61 4.58 2.33 0.97 0.35 0.17 0.0346 4.80 2.93 1.48 0.61 0.22 0.11 0.0277 2.91 1.77 0.89 0.37 0.13 0.06 0.01189 1.20 0.72 0.36 0.15 0.05 0.02 0.00

Figu re 15 Lot size 10,001-35,000

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size.10 .25 .50 .75 .90 .95 .99

9 25.6 15.4 7.70 3.20 1.14 0.55 0.1015 15.4 9.24 4.62 1.92 0.69 0.33 0.06

29 7.94 4.78 2.39 0.98 0.36 0.17 0.0356 4.11 2.48 1.24 0.51 0.18 0.09 0.0196 2.40 1.44 0.71 0.29 0.10 0.05 0.01170 1.35 0.81 0.40 0.16 0.06 0.03 0.00

Figur e 16 Lot size 35,000-150,000


size.10 .25 .50 .75 .90 .95 .99

9 25.6 15.4 7.70 3.20 1.08 0.52 0.10

15 15.4 9.24 4.62 1.92 0.66 0.32 0.0629 7.94 4.78 2.39 0.99 0.35 0.17 0.0364 3.60 2.17 1.07 0.44 0.10 0.07 0.01156 1.48 0.88 0.44 0.18 0.06 0.03 0.00

Figur e 17 Lot size 150,001-500,000

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Annex A

Example of Consensus Sampli ng Plan for 3 Levels

of Conformance to Requirements of

IEC 62326-4 Multilayer Printed Boards

Table 1- Perform ance requirements

NOTE Β The letters "GR" are used to indicate that only the general requirements shall be met. For the explanation of theacronyms, see annex A.

Specif ic requirements for

performance level Assessm en t

Test

code

Character-

is t icsGeneral requirements

A B CRMF(IEC62326-1)

Testspecimen(IEC62326-4-1

Test no.IEC61189-3

Processcontrolcode (IEC62326-1

V VISUALEXAMINATION

V1 Conformity Pattern, marking identificationand material finishes shallcomply with the CDS whenviewed without magnification.There shall be no apparentdefects.

As specified −

Asspecified

−

Asspecified

6,5

4,0

CompletePB/DP

3V04 C4

V2 Appearanceandworkmanship

The boards shall appear tohave been processed in acareful and workmanlikemanner, in accordance withgood current practice.

GR

−

−

GR

−

GR

6,5

4,0

CompletePB/DP

3V01 C4

V3 Plated-throughholes asreceived

Plated-through holes shall beclean and free frominclusions of any sort thatcould affect componentinsertion and solderabilitywhen viewed withoutmagnification.

GR

−

−

GR

−

GR

4,0

2,5

CompletePB

3V04 C4

The number of holes withplating voids shall not exceedthe specified percentage of the total number of plated-through holes when viewedwithout magnification.

5 %

−

−

1 %

−

None

4,0

2,5

C2

The number of holes withplating voids shall not exceedthe specified percentage of the total number of plated-through holes when viewedwithout magnification.

5 %

−

−

1 %

−

None

4,0

2,5

C2

Holes showingplating voids

Total area of plating voidswithin a hole shall not exceedthe specified percentage of the total area.

5 %

−

−

2 %

−

2 %

4,0

2,5

C2

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Test

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Test no.IEC61189-3


The largest dimension of voids shall not exceed thespecified percentage of thehole circumference in thehorizontal plane or the samepercentage of the boardthickness in the verticalplane.

15 %

−

−

10 %

−

5 %

4,0

2,5

C2

V4 Plated-throughholes after microsection

Plated-through holes (levelsB and C) shall be tested inas- received conditioning andafter preconditioningaccording to test code Y4.Voids shall not coincide withinternal or external copper

layers.Remarks 1) All examinations at 100x

magnification

2) Process control data maybe used to supplement/minimize this test.

−

−

GR

−

−

GR

1,5

1,0

A or B(3 holes)

3X09 C1

V4.1 Resin smear atinterface

Resin smear between theedge of the inner layer copper and the continuousplating shall not interruptelectrical continuity or exceedthe specified percentage of inner layer copper thicknessat the interface (see figure 1).

≤30 %

−

−

−

≤15 %

−

−

−

None

2,5

1,5

1,0

C1

V4.2 Circumferentialcracks of copper plating

There shall be nocircumferential cracks of thecopper, or circumferentialseparation of the copper fromthe wall in the plated-throughhole (see figure 2).

GR

−

−

−

GR

−

−

−

GR

2,5

1,5

1,0

C1

V4.3 Copper barrelto holeseparation

There shall be no separationof plating from the hole wallexceeding the specifiedpercentage of the holecircumference (see figure 2).RemarkWhere necessary, this shallbe verified by dimensional

examination using test 3D01.

≤ 50 %

−

−

−

≤ 40 %

−

−

−

≤ 30 %

2,5

1,5

1,0

C1

V4.4 Foil cracking There shall be no foilcracking.

GR

−

−

−

GR

−

−

−

GR

2,5

1,5

1,0

C1

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Test

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Test no.IEC61189-3


V5

V5.1

Conductors

Externalconductors

There shall be neither cracksnor breaks. Imperfectionssuch as voids or edgedefects are permissibleprovided that the conductor width or land area is notreduced by more than thespecified percentage (seefigure 3).Remarks 1) Where necessary, thisshall be verified bydimensional examinationusing test 3D01. 2) In the effective contact

areas there shall be noimperfections. 3) For test specimenssupplied with solderabletemporary protective coatingthe above requirement is notapplicable.

≤ 30 %(no

occur-rence

>10mm)

−

−

≤ 20 %(no

occur-rence

>5mm)

−

≤10 %(no

occur-rence)>3mm)

4,0

2,5

CompletePB

3V02 C3

When specified, theconductors shall be coveredwith a smooth and brightsolder coating with not morethan 5 % of scatteredimperfections, such aspinholes, unwetted or dewetted areas. Theimperfections shall not beconcentrated on one area.

GR

−

−

−

GR

−

−

−

GR

6,5

4,0

2,5

CompletePB

3V02 C1

V5.2 Internalconductors

There shall be neither cracksnor breaks. Imperfectionssuch as voids or edgedefects are permissibleprovided that the conductor width is not reduced by morethan the specifiedpercentage(see figure 3).

Remarks 1)Where necessary, thisshall be verified bydimensional examinationusing test 3D01.

2) This examination shall bein-process.

≤ 30%(no

occur-rence

>10mm)

−

−

≤ 20%(no

occur-rence

>5mm)

−

≤ 10 %(no

occur-rence

>3mm)

4,0 CompletePP

3V02 C3

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Test no.IEC61189-3


V6

V6.1

Particlesbetweenconductors

Externalconductors

Residual metallic particlesare permissible provided thatthe leakage path is notreduced by more than thespecified percentage or toless than the distancerequired for the circuitvoltages in isolated areasdiscounting conductor undercut, edge roughness,spikes, etc. (see figure 3).RemarkWhere necessary, this shall

be verified by dimensionalexamination using test 3D01.

≤ 30%

−

−

≤ 30%

−

≤ 20 %

4,0

2,5

CompletePB

3V02 C3

V6.2 Internalconductors

Residual metallic particlesare permissible provided thatthe leakage path is notreduced by more than thespecified percentage or toless than the distancerequired for the circuitvoltages in isolated areasdiscounting conductor undercut, edge roughness,spikes, etc. (see figure 3).Remarks 1) Where necessary, thisshall be verified bydimensional examinationusing test 3D01. 2) This examination shall bein-process.

≤ 30%

−

−

≤ 20%

−

≤ 10 %

4,0

2,5

CompletePP

3V02 C3

V7 Permanentpolymer coating(includingsolder resist)

The polymer coating patternshall comply with the CDSand the general requirementsgiven below. There shall beno apparent defects.RemarkWhen necessary this shall beverified by dimensionalexamination using test 3D01.

Asspecified

−

−

Asspecified

−

Asspecified

4,0

2,5

CompletePB/DP

3V01 C4

When noted in the CDS that

the polymer coating is usedas an insulation all parts shallbe completely covered.

As

specified

−

−

Asspecified

−

Asspecified

2,5

4,0

C3

Imperfections in the polymer coating on the base material,such as pinholes, smalluncovered areas, scratches,etc. are permitted.

GR

−

−

GR

−

GR

4,0

2,5

C3

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Test no.IEC61189-3


Polymer coating used assolder resist shall cover thetop surface of the conductor and shall be substantially freeof pinholes. At least one or two adjacent conductor edges shall be covered.

GR

−

−

GR

−

GR

4,0

2,5

C3

Board edges and the areasnear slots, notches, etc. shallbe free from polymer coating(as specified on the master drawing when using aproduction board).

GR

−

−

GR

−

GR

4,0

2,5

C3

All metallic areas intended for solder attachment, electrical

contact, or indexing marker shall be free from polymer coating residues.

GR

−

−

GR

−

GR

4,0

2,5

3V02 C2

D DIMENSIONALEXAMINATION

D1 Boarddimensions(externalboundary)

Dimensions includingthickness shall comply withthe CDS.

Asspecified

−

−

Asspecified

−

Asspecified

4,0

2,5

CompletePB (3

places)

3D04 C4

D2 Boardthickness in thezone of edgeboard contacts

The total board thicknessover the edge board contactsshall comply with the CDS.

Asspecified

Β

Β

Asspecified

Β

Asspecified

4,0

2,5

Edgecontactareas of

PB

3D04 C4

D3 Holes (see alsoD8)

D3.1 Diameter Diameters of tooling holes,mounting holes andcomponent holes shallcomply with the CDS.Remark

A recommended range of hole sizes and tolerances aregiven in IEC 61188-6.

Asspecified

−

−

Asspecified

−

Asspecified

4,0

2,5

CompletePB/DP

(10 holesper size)

3D04 C2

D3.2 Platingthickness

The plating thickness shallcomply with the CDS.RemarkExaminations at 400x

magnification.

Asspecified

−

−

Asspecified

−

Asspecified

4,0

2,5

A or B(3holes)

3X09 C1

D4 Slots, cut-outsand notches

The dimensions of applicableslots, cut-outs or notchesshall comply with the CDS.

Asspecified

−

−

Asspecified

−

Asspecified

4,0

2,5

CompletePB

3D04 C3

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Test no.IEC61189-3


D5

D5.1

Conductor width

External layer The width shall comply withany specific dimensionsgiven in the CDS.Remarks 1) To be measured together with V5.1. 2) If no tolerances arestated, the coarse deviationsgiven inIEC 61188-6 shall apply.

Asspecified

−

−

Asspecified

−

Asspecified

4,0

2,5

CompletePB

3D01 C2

D5.2 Internal layer The width shall comply withany specific dimensionsgiven in the CDS.

Remarks 1) To be measured together with V5.2. 2) If no tolerances arestated, the coarse deviationsgiven in IEC 61188-6 shallapply. 3) This measurement shallbe in-process.

Asspecified

−

−

As

specified

−

As

specified

4,0

2,5

CompletePP

3D01 C2

D6 Spacingbetweenconductors

D6.1 External layer The spacing shall complywith any specific dimensiongiven in the CDS.RemarkTo be measured together with V6.1.

Asspecified

−

−

Asspecified

−

Asspecified

4,0

2,5

CompletePB

3D01 C3

D6.2 Internal layer The spacing shall complywith any specific dimensionsgiven in the CDS.Remarks 1) To be measured together with V6.2. 2) This measurement shallbe in-process.

Asspecified

−

−

Asspecified

−

Asspecified

4,0

2,5

CompletePP

3D01 C3

D7 Alignment of hole andconductive

pattern

There shall be no interruptionof the conductive pattern andthere shall be no hole break-

out (land cut off) at the junction of the land and theconductor in excess of thatspecified below. This appliesto both internal and externallayers (see figures 4, 5 and6).

CompletePB (10holes

randomselectionover total

area)

3D01

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D7 Alignment of hole andconductivepattern

There shall be no interruptionof the conductive pattern andthere shall be no hole break-out (land cut off) at the

junction of the land and theconductor in excess of thatspecified below. This appliesto both internal and externallayers (see figures 4, 5 and6).

CompletePB (10holes

randomselectionover total

area)

3D01

D7.1 External patternalignment toplated-throughholes

The requirements shall be asspecified.

Minimum annular width W1 of

external land at conductor junction (see figure 4)

There

shall beno

defectsat

conduc-tive

patternand

through-hole

plating

−

−

W1 ≥0,03mm

−

W1 ≥0,05mm

4,0

2,5

C1

Minimum annular width W1 of external land at the other parts

− Break-out

θ ≤ 90º(see

figure 6)

W1 ≥0,05mm

(seefigure 4)

2,5

D7.2 External patternalignment toplain holesholes

The requirements shall be asspecified.

Nobreakout.

Noconduc-

tor junctionreduction

−

−

Nobreak-out. Noconduc-

tor junction

reduc-tion

−

Nobreak-

out.Mini-mum

annular

width0,4mm

4,0

2,5

C1

D7.3 Internal patternalignment toplated-throughholes

The requirements shall be asspecified.Remarks 1) 100x magnification. 2) Any other adequatemethod may be used.

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Test no.IEC61189-3


Minimum annular width W2 of internal land at conductor

junction (see figure 5)

W2 ≥0,03mm

−

−

−

W2 ≥0,03mm

−

−

−

W2 ≥0,05mm

2,5

1,5

1,0

A or B(3holes)and/or Rfor elec-

tricalcontinuityand/or F

for processcontrol

3X09 C1

Minimum annular width W2 of internal land at the other parts

Break-out

θ ≤ 180º(see

figure 6)−

−

−

Break-

outθ ≤ 90º

(seefigure 6)

−

−

W2 ≥0mm(see

figure 5)

2,5

1,5

1,0

C1

D7.4 Landless holes

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