IEC 61747 1 1 Edition 1 0 2014 08 INTERNATIONAL STANDARD Liquid crystal display devices – Part 1–1 Generic – Generic specification IE C 6 17 47 1 1 2 01 4 08 (e n) ® C opyrighted m aterial licensed to[.]
Order of precedence
In cases of conflicting requirements, the hierarchy of document authority is established as follows: first, the detail specification takes precedence, followed by the blank detail specification, then the family specification if applicable Next in line is the sectional specification, succeeded by the generic specification, the basic specification, and international documents such as IEC references Finally, national documents hold the least authority in this ranking.
The same order of precedence shall apply to equivalent national documents.
Standard environmental conditions
The optimal conditions for measuring characteristics, conducting tests, and ensuring proper operating conditions include a temperature range of 25 ºC ± 5 ºC, a relative humidity between 45 %RH and 75 %RH, and a pressure maintained between 86 kPa and 106 kPa.
Marking
Device identification
The marking on the device shall enable clear identification of the device.
Device traceability
The device shall be provided with a traceability code which enables back-tracing of the device to a certain production or inspection lot.
Packing
The marking on the packing shall state: a) the device identification code; b) the traceability code(s) of the enclosed devices; c) the number of enclosed devices; d) the required precautions, if any
This marking shall be in accordance with custom regulations
NOTE Additional requirements can be specified in the relevant detail specification.
Categories of assessed quality
This specification outlines three categories of quality control for devices, which are organized into a designated and date-coded inspection lot Each lot undergoes testing according to the specified quality categories The acceptance quality levels (AQLs) or lot tolerance percentage defectives (LTPDs) for the inspection group may differ across categories, as detailed in the specification.
The minimum requirements of the categories are as follows:
Category I products fulfill the criteria set for categories II or III Each lot complies with the inspection standards of group A, which encompasses functional tests Additionally, every three months, one lot is assessed to ensure it meets the interconnection ability inspection requirements.
Annually, one lot meets the group B and group C inspection requirements
Category II The lot meets the inspection requirements of group A and group B on a lot- by-lot basis, and of group C on a periodic basis
Category III The lot is 100 % screened and meets the inspection requirements of group A and group B on a lot-by-lot basis, and of group C on a periodic basis
The sectional or blank detail specifications outline the minimum standards for each category These specifications may include additional requirements, such as screening criteria, beyond those specified in the generic, sectional, or blank detail specifications.
Screening
A screening is an examination or test applied to all devices in a lot
All devices in the lot must be screened according to the specified sequences in the relevant detail specification, with defective items removed Alternative sequences may be used only if they do not conflict with the established failure mechanisms If a screening step is integrated into the manufacturing process as outlined in the detail specification, it does not need to be repeated.
Burn-in refers to the process of applying thermal and electrical stress to all devices within a lot for a designated duration This procedure aims to identify and eliminate potential early failures, ensuring the reliability of the devices.
Handling
Adequate warning shall be displayed in the case of harmful products (e.g Be0)
General
Quality assessment involves the process of obtaining qualification approval as outlined in section 5.6, followed by lot-by-lot quality conformance inspections, which may include screening if necessary, and periodic evaluations as specified in the detailed specifications.
Quality assessment tests are categorized into groups A, B, and C, conducted either lot-by-lot or on a periodic basis Additionally, group D tests may be required in certain instances, such as for qualification approval.
Commercially confidential information
Any commercially confidential aspect of the manufacturing process must be clearly identified, and the designated management representative (DMR) is responsible for ensuring compliance with the procedural requirements outlined in the specified quality assessment system.
Formation of inspection lots
An inspection lot can be created by combining multiple production lots if they are produced under similar conditions, including materials, processes, machines, and personnel Additionally, quality control and inspection must be conducted according to guidelines set by the manufacturer in collaboration with the DMR The inspection results must confirm that each production lot meets the necessary quality standards for materials and processing Furthermore, the timeframe for aggregating production lots into a single inspection lot should typically not exceed one week and must not surpass one month unless specified otherwise.
The programme for the aggregation of production lots into inspection lots shall be determined by the DMR and shall be submitted for approval.
Structurally similar devices
Structurally similar components are those manufactured by the same company, featuring nearly identical designs, materials, processes, and methods Test results obtained from one component can be deemed valid for others within the same group, while each component remains separately identifiable.
The relevant specification shall give the requirements for grouping structurally similar components for the purpose of testing for QA and quality conformance inspection
Details concerning grouping are given in the relevant sectional or blank detail specifications.
Granting of qualification approval
The CB shall validate the recommendation and grant the QA, when the requirements of the specific quality assessment system have been met
Manufacturers have the discretion to use either Method a) or b) of the rules of procedure, following the inspection requirements outlined in the sectional or blank detail specifications Samples can consist of structurally similar devices, and in certain instances, group D tests are necessary for qualification approval It is essential to record all variable measurements specified as post-test end-points in the detail specification as variable data.
The qualification report must provide a comprehensive summary of test results for each group and subgroup, detailing the number of devices tested and the number of devices that failed This summary should be based on the data from variables and attributes.
The manufacturer shall retain all data for submission on demand.
Quality conformance inspection
General
Quality conformance inspection shall consist of the examinations and tests of groups A, B, C and D, as specified
For groups B and C inspection, samples may be composed of structurally similar devices
Samples for periodic tests must be selected from one or more lots that have successfully passed both groups A and B inspections Additionally, each individual device must have met the group A measurement requirements specified in the detail specification.
Division into groups and subgroups
The following guidelines shall be used in the preparation of detail specifications
5.6.2.2 Group A inspection (lot-by-lot)
This group mandates that visual inspections and electrical measurements be conducted on a lot-by-lot basis to evaluate the key properties of a device Structural similarity groupings are not allowed unless explicitly stated.
Group A Inspection is divided into appropriate subgroups as follows:
Subgroup A1 This subgroup comprises a visual examination as specified in 6.2.1
Subgroup A2 This subgroup comprises measurements of primary characteristics of the device
Subgroups A3 and A4 may be optional, as they include measurements of secondary device characteristics The appropriate requirements for each device category are specified in the relevant sectional or blank detail specification The decision to use subgroups A3 or A4 for specific measurements primarily depends on the desired quality level for those measurements.
5.6.2.3 Group B inspection (lot-by-lot, except for category I)
This group outlines the procedures for evaluating specific additional properties of the device, encompassing mechanical, climatic, electrical, and optical endurance tests, which can typically be completed within one week or as detailed in the relevant specifications.
This group outlines the periodic procedures for assessing additional properties of devices, including electrical, optical, mechanical, climatic, and endurance tests These assessments are scheduled at intervals of three months for categories II and III, or annually for category I, as specified in the relevant sectional or blank detail specifications.
5.6.2.5 Division of group B and group C into subgroups
To facilitate comparisons and enable transitions between group B and group C when needed, tests within these groups have been organized into subgroups that share the same numbering for corresponding tests.
The division is as given below
Subgroups B1/C1 Comprise measurements that control the dimensional interchange- ability of the devices
Subgroups B2a/C2a Comprise the measurements that assess the electrical and optical properties of the devices of a design nature
Subgroups B2b/C2b include measurements that evaluate additional electrical and optical characteristics of the device, building on the assessments conducted in group A These measurements are performed under varying conditions of voltage, current, temperature, or optical parameters.
Subgroups B2c/C2c Comprise the verification of ratings of the device, where appropriate
Subgroups B3/C3 Comprise the tests intended to assess the mechanical robustness of the device
Subgroups B4/C4 Comprise the tests intended to assess the interconnection ability of the device
Subgroups B5/C5 Comprise the tests intended to assess the ability of the device to withstand climatic stresses, for example change of temperature, sealing
Subgroups B6/C6 Comprise the tests intended to assess the ability of the device to withstand mechanical stresses, for example vibration, shock
Subgroups B7/C7 Comprise the tests intended to assess the ability of the device to withstand long-term humidity
Subgroups B8/C8 Comprise the tests intended to assess the failure characteristics of the device under endurance testing
Subgroups B9/C9 Comprise the tests intended to assess the electrical and optical properties of the device under storage conditions at extremes of temperature
Subgroups B10/C10 Comprise the tests intended to assess the performance of the device during variations of air pressure
Subgroups B11/C11 Comprise the tests on the permanence of marking
Subgroup CRRL Lists a selection of tests and/or measurements made in the preceding subgroups, the results of which shall be presented in the certified record of released lots (CRRL)
These subgroups may not all be required
This group prescribes the procedures to be carried out at intervals of 12 months or for qualification approval only.
Inspection requirements
The statistical sampling procedures described in 5.7 shall be used
Lots that do not pass the quality conformance inspection for either group A or group B will be rejected If a device fails a test in any subgroup during the inspection, the process may be halted, and the lot will be deemed rejected for both groups Additionally, if a lot is withdrawn while failing to meet quality conformance standards and is not resubmitted, it will also be classified as a rejected lot.
Reworked failing lots, when feasible, must only include devices from the original lot and can be resubmitted once per inspection group (A and B) These re-submitted lots should be distinctly marked and kept separate from new lots Additionally, they must undergo random re-sampling and inspection for all criteria of group A.
5.6.3.4 Procedure in case of test equipment failure or operator error
Devices suspected of failing due to faulty test equipment or operator error must be documented in the test record, although they may be excluded from the CRRL A comprehensive explanation detailing the reasons for considering these failures invalid should accompany the submission.
The chief inspector will determine if replacement devices from the same inspection lot can be included in the sample These replacement devices must undergo the same tests as the discarded devices before their failure, as well as any additional specified tests that the discarded devices did not undergo prior to their failure.
5.6.3.5 Procedure in case of failure in periodic tests
A group B failure renders the associated group C tests invalid If periodic inspection tests fail due to reasons unrelated to faults or operator errors, refer to the procedural guidelines outlined in the designated quality assessment system.
Case 1) When a sample fails to satisfy the requirements of a periodic test the DMR (or, where applicable, the local DMR) shall immediately
– suspend further releases under the mark, or certificate of conformity of the component in question, – initiate an investigation to determine the reasons for failure, and
Case 2) The DMR (or, where applicable, the local DMR) shall maintain this suspension until the investigation has been concluded The DMR (or, where applicable, the local DMR) shall then proceed according to the appropriate conditions in case 3), case 4) or case 5)
Case 3) If the failure is concluded to have been due solely to an error in test procedure, a) release under the mark, or certificate of conformity shall be resumed immediately, and b) the correct test procedure shall be applied to a sample drawn from the first available inspection lot If the sample fails the corrected test, action shall be taken as in case-1)
Case 4) If the failure is concluded to be due to an identified manufacturing fault which can immediately be corrected, a) release under the mark, or certificate of conformity of corrected lots shall be resumed immediately, b) the test shall be repeated on the first available corrected lot, and c) if the result of the repeated test is unsatisfactory, the procedure defined in
Case-5) or Case-6) shall be applied as appropriate
Case 5) If the failure is concluded to be due to an identified manufacturing fault which cannot be corrected immediately, but defective components can be detected and rejected by an appropriate eliminating test acceptable to the DMR (or, where applicable, the local DMR), a) release under the mark, or certificate of conformity of accepted components shall be resumed immediately, and b) elimination before submission for acceptance shall be continued until the necessary steps to correct the manufacturing fault have been taken, and until satisfactory results for the periodic test in question have been obtained on a sample from the first available lot presented for inspection after correction
Case 6) If the failure is concluded to be due to an identified manufacturing fault which cannot be corrected immediately and defective components cannot be removed by the application of an eliminating test, the CB shall suspend the QA and withdraw the right to use the mark, or certificate, of conformity for the component in question QA and the right to use the Mark, or Certificate, of Conformity shall be reinstated when the manufacturer can demonstrate, by the successful submission of a sample from a production lot to the periodic test, that the manufacturing fault has been eliminated
Case 7) If the failure cannot be attributed with certainty to a specific error in test procedure or to an identified manufacturing fault, samples from subsequent lots shall then be subjected to all tests in the subgroup of the periodic test in which the failure occurred, on a lot-by-lot basis, and released if these samples pass the test successfully The sample size shall be that designated for the subgroup
Normal periodic testing will resume after two consecutive lots have successfully passed the specified subgroup tests, unless otherwise stated in the generic specification.
Case 8) If the requirements of Case-4), Case-5) or Case-6) are not fulfilled within a reasonable period of time, QA shall be re-examined and may be withdrawn
Case 9) If the duration of the periodic test in question exceeds three months and if special conditions would be appropriate to the particular type of component and the nature or extent of the failure, the relevant specification shall prescribe any special procedure to be followed.
Supplementary procedure for reduced inspection
Manufacturers may utilize a special reduced inspection procedure that permits them to conduct the necessary group B tests during normal inspections on every fourth lot, with a maximum interval of three months, rather than performing these tests on a lot-by-lot basis for all subgroups of the group.
B This special procedure applies to each subgroup which has fulfilled the required conditions
The condition for this change shall be that 10 successive lots have passed group B inspection
Reversion to normal inspection in group B shall be made when a sample has failed to meet a subgroup inspection under the reduced inspection procedure
Periodic tests can be conducted every six months if three consecutive tests have been successfully completed at three-month intervals However, if a sample fails to meet subgroup inspection during the extended interval, the testing frequency will revert to the standard three-month schedule.
Sampling requirements for small lots
Where a lot size is small, the procedures shall refer to 3.6.4 of IEC 60747-10:1991 or 3.5 of
Certified records of released lots (CRRL)
Manufacturers and distributors must clearly identify lots with a mark or certificate of conformity, indicating that the components comply with the relevant detail specifications.
Only components approved against a detail specification registered within the system may receive the mark, or certificate of conformity
Authorization to affix, or to issue, the mark, or certificate, of conformity is suspended or withdrawn if there is persistent non-conformity with the specification.
Delivery of devices subjected to destructive or non-destructive tests
Tests considered as destructive are marked (D) in the sectional or blank detail specifications
Devices that undergo destructive testing must be excluded from the delivery lot However, devices that pass non-destructive environmental tests can be delivered if they are re-tested and meet the requirements of group A.
Delayed deliveries
Prior to the delivery of lots, they must be stored for a specified duration and under conditions outlined in the relevant specifications The lots will undergo a Group A inspection and Group B interconnection ability tests Once these assessments are completed for the entire lot, no additional re-testing will be necessary for the subsequent period.
Supplementary procedure for deliveries
The manufacturer may, at his discretion, supply devices that have met a more severe assessment level than that required.
Statistical sampling procedures
General
For inspections of groups A, B, and C, either the AQL sampling procedure or the LTPD sampling procedure must be employed, as specified in the detailed specification.
AQL sampling plans
See IEC 60410, ISO 2859-1 and ISO 2859-10
There are three types of sampling plans: single, double and multiple When several types of plans are available for a given AQL and code letter, any one may be used.
LTPD sampling plans
See Annex C as an example.
Endurance tests
Endurance tests shall be specified in the detail specification.
Endurance tests where the failure rate is specified
Overview
Failure rate as used in this standard is defined as LTPD expressed as a percentage per thousand hours.
General
Endurance tests shall be conducted in accordance with the procedures mentioned
Endurance tests performed on devices at, or within, their maximum ratings shall be considered non-destructive.
Selection of samples
Endurance test samples must be randomly selected from the inspection lot, as illustrated in Annex C The manufacturer is responsible for determining the sample size for a 1,000-hour test based on the specified failure rate in Table C.1 or the actual lot size indicated in Table C.2.
The acceptance number shall be the one associated with the particular sample size chosen.
Failure
A device that does not meet the end-point limits set for endurance tests at any specified reading interval will be deemed a failure, and this status will carry over to any future reading intervals If a sample fails, the manufacturer has the discretion to terminate the test.
Endurance test time and sample size
The initial endurance test time is set at 1,000 hours whenever a failure rate is specified After successfully passing this 1,000-hour test, the duration of endurance tests can be shortened as outlined in the detailed specifications.
Procedure to be used if the number of observed failures exceeds the
If the failures in endurance tests surpass the acceptance number, the manufacturer has several options: a) withdraw the entire lot, b) add more samples as per section 5.9.6.2, c) extend the testing duration to 1,000 hours if a shorter time was initially selected, or d) screen the lot and resubmit it for testing.
This option is applicable only once per submission, allowing the manufacturer to select a new total sample size, which includes both the initial and additional samples, from Tables C.1.
C.2 from the column specifying the failure rate (Table C.1) or the actual lot size (Table C.2) A quantity of additional units sufficient to increase the sample to the newly chosen total sample size shall be selected from the lot The new acceptance number shall be the one associated with the new total sample size chosen The added sample shall be subjected to the same endurance test conditions and time period as the initial sample If the total observed number of defectives (initial plus added) does not exceed the acceptance number for the total sample, the lot shall be accepted; if the observed number of defectives exceeds the new acceptance number, the lot shall be rejected
5.9.6.3 Extension of endurance test period
If the endurance test duration is less than 1,000 hours and the initial sample shows more failures than the acceptance number, the manufacturer can opt to extend the test duration of the initial sample to 1,000 hours instead of adding more samples A new acceptance number will be determined from Tables C.1 or C.2, corresponding to the largest sample size in the specified column that is less than or equal to the tested sample size Any device that fails during the initial reading will also be deemed a failure at the 1,000-hour mark If the number of defects surpasses the new acceptance number, the lot will be rejected.
Standard atmospheric conditions for electrical and optical measurements
Unless otherwise specified, all electrical and optical measurements are carried out under the atmospheric conditions given in IEC 60749 and IEC 61747-30-1
Atmospheric pressure Between 86 kPa and 106 kPa (860 mbar and 1 060 mbar)
Measurements can be conducted at various temperatures, as long as the device meets the detailed specifications when tested at an ambient temperature of 25 °C ± 1 °C and a relative humidity of 48 % to 52 %, if this is crucial.
Physical examination
Visual examination
Visual inspections must be conducted under standard factory lighting and typical visual conditions, focusing on the accuracy of several key elements: a) the clarity and legibility of markings; b) proper terminal identification; and c) the device's appearance, which should comply with IEC 61747-20 standards.
Dimensions
Dimensions shall be checked in accordance with the specified drawing Examples of typical drawings for LCD modules are shown in Annex B
This test aims to assess the durability of markings after typical handling and cleaning procedures on the device, utilizing Test Xa as outlined in IEC 60068-2-45.
Solvents, rubbing conditions and materials shall be specified in the relevant sectional or blank detail specification
The specimen shall be visually inspected
Electrical and optical measurements
Alternative methods
Measurements may be carried out by using the methods specified or any other method giving equivalent results but, in case of dispute, only the specified method shall be used
NOTE By “equivalent” is meant that the value of the characteristic established by such other methods is within the specified limits when measured using the specified method
The methods for electrical and optical measurements shall be in accordance with IEC 60747 and IEC 60748 They shall be used when required and as prescribed by the detail specification
The methods for electrical and optical measurements not included in IEC 60747 and
IEC 60748 shall be described in the relevant or detail specification.
Precision of measurements
The limits quoted in detail specifications are absolute Measurement inaccuracies shall be taken into account when determining the actual measurement limits.
General precautions
The usual precautions should be taken to reduce measurement errors to a minimum and to avoid damage to the device The most important points of these are given in IEC 60747-1.
Environmental tests
Methods for environmental tests shall be in accordance with IEC 61747-10-2 They shall be used when required and as prescribed by the detail specification They are indicated as
“destructive” or “non-destructive” according to IEC 61747-10-2 When a mandatory sequence of testing is required, it shall be specified in the sectional specification or in the blank detail specification
Methods for environmental tests not included in IEC 61747-10-2 shall be described in the detail specification
Test methods that require observing or applying external forces related to the device's orientation must adhere to the guidelines specified in Annex B regarding the orientation and direction of the applied force.
Mechanical tests
Mechanical testing methods must adhere to IEC 61747-10-1 and should be employed as necessary according to the detail specification If a mandatory testing sequence is needed, it must be outlined in the sectional specification or the blank detail specification.
Methods for mechanical tests not included in IEC 61747-10-1 shall be described in the detail specification
Test methods that require observation or application of external forces must align with the device's orientation and the direction of the applied force, as specified in Annex B.
Examples of outline drawings of liquid crystal display cells
Annex A provides examples of drawings of liquid crystal display cells (see Figures A.1 and
A.2) as well as examples of dimensions of each element (see Table A.1)
Figure A.1 – Example of outline drawings of liquid crystal display cells
Figure A.2 – Example of outline drawings of liquid crystal display cells
Table A.1 – Example of table for dimension of each element
Original dimensions are in millimetres and inches:
Min Nom Max Min Nom Max
The overall dimensions of the device must include any polarizers and diffusers It is essential to specify the nominal dimensions of the observation area and the total number of terminals, accounting for any lacking or non-connected positions Additionally, true geometrical dimensions and positional tolerance should be defined in accordance with ISO 1101, along with the standard pitch.
Annex B shows the orientation of LCD modules (see Figure B.1)
Figure B.1 – Orientation of LCD modules
Lot tolerance percentage defective (LTPD) sampling plans
General
Overview
The following specified procedures are suitable for all quality conformance requirements.
Selection of samples
Samples will be randomly chosen from the inspection lot In the case of continuous production, the manufacturer has the option to select samples at regular intervals during the manufacturing process, as long as the lot complies with the necessary requirements for lot formation.
Failures
Failure of a unit for one or more tests of a subgroup shall be charged as a single failure.
Single-lot sampling method
General
Quality conformance inspection information (sample sizes and number of observed defectives) shall be accumulated from a single inspection lot to demonstrate conformance to the individual subgroup criteria.
Sample size
The sample size for each subgroup must be determined from Tables C.1 or C.2 to meet the specified LTPD Manufacturers have the option to select a larger sample size than required, but the allowable number of failures must not exceed the acceptance number linked to the chosen sample size, as illustrated in Tables C.1 or C.2.
In Table C.2, the LTPD value for sample size determination should correspond to the lot size closest to the actual submitted lot If the actual lot size falls exactly between two values, the manufacturer may choose either lot size If the relevant lot size column lacks an LTPD value that is equal to or less than the specified LTPD, a 100% inspection is required The LTPD value that is numerically closest to the specified LTPD in the appropriate lot size column will be used to determine the sample size.
Acceptance procedure
In the initial sampling process, a predetermined acceptance number is established along with the corresponding number of sample devices based on the specified Lot Tolerance Percent Defective (LTPD) If the number of defective items in the first sample is less than or equal to this acceptance number, the lot is accepted Conversely, if the defectives exceed the acceptance threshold, an additional sample may be taken to ensure compliance with the requirements outlined in section 5.9.6 For all subsequent samplings of the same lot and subgroup, Tables C.1 or C.2 must be utilized to maintain consistency in the inspection process.
Additional sample
The manufacturer is permitted to add extra samples to the initial subgroup, but this can only occur once All added samples must undergo the same tests as the original subgroup The overall sample size, which includes both the initial and additional samples, will be based on the new acceptance number chosen from Tables C.1 or C.2.
Multiple criteria
When a single sample is applied to multiple acceptance criteria, the entire sample for a subgroup must be utilized for all criteria within that subgroup According to Table C.1, the acceptance number corresponds to the largest sample size in the relevant LTPD column that is less than or equal to the sample size used In Table C.2, the acceptance number is determined by the specified LTPD in the appropriate lot size column for the sample size employed.
Manufacturers have the option to inspect 100% of the lot for non-destructive subgroups If the percentage of defective devices in the inspection lot surpasses the defined LTPD value, the lot will be deemed to have failed the relevant subgroup(s).
100 % inspection basis shall also be on a 100 % inspection basis only and in accordance with the tightened inspection LTPD.
Tightened inspection
Tightened inspection shall be performed by testing to the criteria of the next lowest LTPD in
Tables C.1 or C.2 to those specified
Table C.1 presents LTPD sampling plans, detailing the minimum sample sizes required to ensure a 90% confidence level that a lot with a specified percentage of defective devices will not be accepted The acceptance number (c) is defined as \( r = c + 1 \), and the minimum sample sizes are calculated based on device hours required for life testing, multiplied by 1000 The table includes various LTPD percentages, ranging from 50% to 1%, alongside corresponding sample sizes and acceptance numbers, illustrating the relationship between defect rates and the necessary testing samples to maintain quality assurance.
The data presents acceptance numbers and minimum sample sizes for various devices, calculated based on the failure criterion (r = c + 1) The minimum sample sizes, required for life testing in device hours, are multiplied by 1000 Notably, the minimum quality, represented as approximate Acceptable Quality Level (AQL), indicates that to accept an average of 19 out of 20 lots, specific quality thresholds are necessary The sample sizes are derived from the Poisson exponential binomial limit, providing essential insights for quality control in manufacturing processes.
Table C.2 – Hypergeometric sampling plans for small lot sizes of 200 or less
N = lot size n = sample size c = acceptance number (see 5.6.4)
Table C.2 presents the LTPD values for specific single sampling plans, detailing acceptance numbers, sample sizes, and lot sizes The calculations utilize the hypergeometric distribution for lots containing 200 devices or fewer The LTPD is defined as the interpolated percentage of defectives that results in a 0.10 probability of lot acceptance It is important to note that this LTPD may not correspond to a realizable lot percentage of defectives for the given lot size Additionally, the sample sizes and lot sizes are derived by multiplying preceding numbers in their respective sequences by 2 and 5.
Table C.3 – AQL and LTPD sampling plans
Table C.3 presents AQL and LTPD values deemed adequate for maintaining a satisfactory average outgoing quality limit for lot sizes up to 150,000 It is important to highlight that the limiting quality protection shows significant variation with lot size under the AQL plan compared to the LTPD plan.
The table is created by choosing the LTPD value from Table C.1 at an acceptance number of c = 2, ensuring that the sample size closely matches the sample sizes specified for inspection level II, with sample size code letters C through N, as outlined in IEC 60410 and ISO 2859.
Table C.3 may be used provided that the maximum value of the acceptance number of the
LTPD sampling plan is not greater than 4
[1] ISO 9241-3:1992, Ergonomic requirements for office work with visual display terminals
(VDTs) – Part 3: Visual display requirements
[2] ISO 1101, Geometrical product specifications (GPS) – Geometrical tolerancing –
Tolerancing of form, orientation, location and run-out