Methods for product accelerated testing

IEC 62506:2013 provides guidance on the application of various accelerated test techniques for measurement or improvement of product reliability. Identification of potential failure modes that could be experienced in the use of a product/item and their mitigation is instrumental to ensure dependability of an item. The object of the methods is to either identify potential design weakness or provide information on item dependability, or to achieve necessary reliability/availability improvement, all within a compressed or accelerated period of time. This standard addresses accelerated testing of non-repairable and repairable systems. It can be used for probability ratio sequential tests, fixed duration tests and reliability improvement/growth tests, where the measure of reliability may differ from the standard probability of failure occurrence. This standard also extends to present accelerated testing or production screening methods that would identify weakness introduced into the product by manufacturing error, which could compromise product dependability. Keywords: test techniques for measurement or improvement of product reliability

Méthodes d'essais accélérés de produits

La CEI 62506:2013 fournit des recommandations pour l'application de diverses techniques d'essais accélérés permettant de mesurer ou d'améliorer la fiabilité des produits. L'identification des modes de défaillance potentiels qui pourraient être rencontrés lors de l'utilisation d'un produit/entité donné(e) et la manière d'y remédier contribuent à assurer la sûreté de fonctionnement d'une entité. L'objectif est soit d'identifier les faiblesses potentielles de la conception et fournir des informations sur la sûreté de fonctionnement de l'entité, soit d'atteindre l'amélioration nécessaire de la fiabilité/disponibilité, dans les deux cas en comprimant ou en accélérant la période d'essai requise. La présente norme couvre les essais accélérés de systèmes non réparables et réparables. Elle peut être utilisée pour des essais progressifs à taux de probabilité, des essais à durée fixe et des essais d'amélioration/croissance de la fiabilité, lorsque la mesure de la fiabilité peut être différente de la probabilité normalisée d'occurrence de défaillance. La présente norme décrit également des méthodes d'essais accélérés ou de déverminage de la production qui permettraient d'identifier les faiblesses induites par une éventuelle erreur de fabrication du produit et qui risqueraient de ce fait d'en compromettre la sûreté de fonctionnement. Mots clés: techniques d'essais permettant de mesurer ou d'améliorer la fiabilité des produits

General Information

Status
Published
Publication Date
17-Jun-2013
Technical Committee
Current Stage
PPUB - Publication issued
Start Date
18-Jun-2013
Completion Date
18-Jun-2013
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IEC 62506
Edition 1.0 2013-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Methods for product accelerated testing
Méthodes d'essais accélérés de produits
IEC 62506:2013
---------------------- Page: 1 ----------------------
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IEC 62506
Edition 1.0 2013-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Methods for product accelerated testing
Méthodes d'essais accélérés de produits
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX XD
ICS 03.120.01; 21.020 ISBN 978-2-83220-861-8

Warning! Make sure that you obtained this publication from an authorized distributor.

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® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – 62506 © IEC:2013
CONTENTS

FOREWORD ........................................................................................................................... 5

INTRODUCTION ..................................................................................................................... 7

1 Scope ............................................................................................................................... 8

2 Normative references ....................................................................................................... 8

3 Terms, definitions, symbols and abbreviations .................................................................. 9

3.1 Terms and definitions .............................................................................................. 9

3.2 Symbols and abbreviated terms ............................................................................. 11

4 General description of the accelerated test methods....................................................... 12

4.1 Cumulative damage model .................................................................................... 12

4.2 Classification, methods and types of test acceleration ........................................... 14

4.2.1 General ..................................................................................................... 14

4.2.2 Type A: qualitative accelerated tests ......................................................... 15

4.2.3 Type B: quantitative accelerated tests ....................................................... 15

4.2.4 Type C: quantitative time and event compressed tests .............................. 16

5 Accelerated test models ................................................................................................. 17

5.1 Type A, qualitative accelerated tests ..................................................................... 17

5.1.1 Highly accelerated limit tests (HALT) ......................................................... 17

5.1.2 Highly accelerated stress test (HAST) ....................................................... 21

5.1.3 Highly accelerated stress screening/audit (HASS/HASA) ........................... 21

5.1.4 Engineering aspects of HALT and HASS ................................................... 22

5.2 Type B and C – Quantitative accelerated test methods .......................................... 23

5.2.1 Purpose of quantitative accelerated testing ............................................... 23

5.2.2 Physical basis for the quantitative accelerated Type B test methods .......... 23

5.2.3 Type C tests, time (C ) and event (C ) compression ................................. 24

1 2

5.3 Failure mechanisms and test design ...................................................................... 26

5.4 Determination of stress levels, profiles and combinations in use and test –

stress modelling .................................................................................................... 27

5.4.1 General ..................................................................................................... 27

5.4.2 Step-by-step procedure ............................................................................. 27

5.5 Multiple stress acceleration methodology – Type B tests ....................................... 27

5.6 Single and multiple stress acceleration for Type B tests ........................................ 30

5.6.1 Single stress acceleration methodology ..................................................... 30

5.6.2 Stress models with stress varying as a function of time – Type B

tests .......................................................................................................... 37

5.6.3 Stress models that depend on repetition of stress applications –

Fatigue models .......................................................................................... 38

5.6.4 Other acceleration models – Time and event compression......................... 40

5.7 Acceleration of quantitative reliability tests ............................................................ 40

5.7.1 Reliability requirements, goals, and use profile .......................................... 40

5.7.2 Reliability demonstration or life tests ......................................................... 42

5.7.3 Testing of components for a reliability measure ......................................... 47

5.7.4 Reliability measures for components and systems/items ............................ 48

5.8 Accelerated reliability compliance or evaluation tests ............................................ 48

5.9 Accelerated reliability growth testing ..................................................................... 50

5.10 Guidelines for accelerated testing ......................................................................... 50

5.10.1 Accelerated testing for multiple stresses and the known use profile ........... 50

5.10.2 Level of accelerated stresses .................................................................... 51

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62506 © IEC:2013 – 3 –

5.10.3 Accelerated reliability and verification tests ............................................... 51

6 Accelerated testing strategy in product development ...................................................... 51

6.1 Accelerated testing sampling plan ......................................................................... 51

6.2 General discussion about test stresses and durations ........................................... 52

6.3 Testing components for multiple stresses .............................................................. 53

6.4 Accelerated testing of assemblies ......................................................................... 53

6.5 Accelerated testing of systems .............................................................................. 53

6.6 Analysis of test results .......................................................................................... 53

7 Limitations of accelerated testing methodology ............................................................... 53

Annex A (informative) Highly accelerated limit test (HALT) .................................................. 55

Annex B (informative) Accelerated reliability compliance and growth test design ................. 59

Annex C (informative) Comparison between HALT and conventional accelerated

testing .................................................................................................................................. 74

Annex D (informative) Estimating the activation energy, E .................................................. 75

Annex E (informative) Calibrated accelerated life testing (CALT) ......................................... 77

Annex F (informative) Example on how to estimate empirical factors ................................... 79

Annex G (informative) Determination of acceleration factors by testing to failure ................. 84

Bibliography .......................................................................................................................... 87

Figure 1 – Probability density functions (PDF) for cumulative damage, degradation,

and test types ....................................................................................................................... 13

Figure 2 – Relationship of PDFs of the product strength vs. load in use ................................ 18

Figure 3 – How uncertainty of load and strength affects the test policy ................................. 19

Figure 4 – PDFs of operating and destruct limits as a function of applied stress ................... 20

Figure 5 – Line plot for Arrhenius reaction model .................................................................. 34

Figure 6 – Plot for determination of the activation energy ...................................................... 35

Figure 7 – Multiplier of the test stress duration for demonstration of required reliability

for compliance or reliability growth testing ............................................................................ 45

Figure 8 – Multiplier of the duration of the load application for the desired reliability ............ 46

Figure B.1 – Reliability as a function of multiplier k and for combinations of parameters

a and b .................................................................................................................................. 61

Figure B.2 – Determination of the multiplier k ........................................................................ 64

Figure B.3 – Determination of the growth rate ....................................................................... 73

Figure D.1 – Plotting failures to estimate the activation energy E ........................................ 76

Figure F.1 – Weibull graphical data analysis ......................................................................... 81

Figure F.2 – Scale parameter as a function of the temperature range ................................... 82

Figure F.3 – Probability of failure as a function of number of cycles ∆T = 50 °C .................... 83

Figure G.1 – Weibull plot of the three data sets .................................................................... 85

Figure G.2 – Scale parameters’ values fitted with a power line .............................................. 86

Table 1 – Test types mapped to the product development cycle ............................................ 14

Table A.1 – Summary of HALT test results for a DC/DC converter ........................................ 56

Table A.2 – Summary of HALT results from a medical system ............................................... 57

Table A.3 – Summary of HALT results for a Hi-Fi equipment ................................................. 58

Table B.1 – Environmental stress conditions of an automotive electronic device ................... 63

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– 4 – 62506 © IEC:2013

Table B.2 – Product use parameters ..................................................................................... 67

Table B.3 – Assumed product use profile .............................................................................. 71

Table B.4 – Worksheet for determination of use times to failures .......................................... 72

Table B.5 – Data for reliability growth plotting ....................................................................... 73

Table C.1 – Comparison between HALT and conventional accelerated testing ...................... 74

Table F.1 − Probability of failure of test samples A and B ..................................................... 80

Table F.2 – Data transformation for Weibull plotting .............................................................. 80

Table G.1 – Voltage test failure data for Weibull distribution ................................................. 84

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62506 © IEC:2013 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
METHODS FOR PRODUCT ACCELERATED TESTING
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 62506 has been prepared by IEC technical committee 56:

Dependability.
The text of this standard is based on the following documents:
FDIS Report on voting
56/1503/FDIS 56/1513/RVD

Full information on the voting for the approval of this standard can be found in the report on

voting indicated in the above table.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

---------------------- Page: 7 ----------------------
– 6 – 62506 © IEC:2013

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62506 © IEC:2013 – 7 –
INTRODUCTION

Many reliability or failure investigation test methods have been developed and most of them

are currently in use. These methods are used to either determine product reliability or to

identify potential product failure modes, and have been considered effective as
demonstrations of reliability:
– fixed duration,
– sequential probability ratio,
– reliability growth tests,
– tests to failure, etc.

Such tests, although very useful, are usually lengthy, especially when the product reliability

that has to be demonstrated was high. The reduction in time-to-market periods as well as

competitive product cost, increase the need for efficient and effective accelerated testing.

Here, the tests are shortened through the application of increased stress levels or by

increasing the speed of application of repetitive stresses, thus facilitating a quicker

assessment and growth of product reliability through failure mode discovery and mitigation.

There are two distinctly different approaches to reliability activities:

– the first approach verifies, through analysis and testing, that there are no potential failure

modes in the product that are likely to be activated during the expected life time of the

product under the expected operating conditions;

– the second approach estimates how many failures can be expected after a given time

under the expected operating conditions.

Accelerated testing is a method appropriate for both cases, but used quite differently. The first

approach is associated with qualitative accelerated testing, where the goal is identification of

potential faults that eventually might result in product field failures. The second approach is

associated with quantitative accelerated testing where the product reliability may be estimated

based on the results of accelerated simulation testing that can be related back to the use of

the environment and usage profile.

Accelerated testing can be applied to multiple levels of items containing hardware or software.

Different types of reliability testing, such as fixed duration, sequential test-to-failure, success

test, reliability demonstration, or reliability growth/improvement tests can be candidates for

accelerated methods. This standard provides guidance on selected, commonly used

accelerated test types. This standard should be used in conjunction with statistical test plan

standards such as IEC 61123, IEC 61124, IEC 61649 and IEC 61710.

The relative merits of various methods and their individual or combined applicability in

evaluating a given system or item, should be reviewed by the product design team (including

dependability engineering) prior to selection of a specific test method or a combination of

methods. For each method, consideration should also be given to the test time, results

produced, credibility of the results, data required to perform meaningful analysis, life cycle

cost impact, complexity of analysis and other identified factors.
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– 8 – 62506 © IEC:2013
METHODS FOR PRODUCT ACCELERATED TESTING
1 Scope

This International Standard provides guidance on the application of various accelerated test

techniques for measurement or improvement of product reliability. Identification of potential

failure modes that could be experienced in the use of a product/item and their mitigation is

instrumental to ensure dependability of an item.

The object of the methods is to either identify potential design weakness or provide

information on item dependability, or to achieve necessary reliability/availability improvement,

all within a compressed or accelerated period of time. This standard addresses accelerated

testing of non-repairable and repairable systems. It can be used for probability ratio

sequential tests, fixed duration tests and reliability improvement/growth tests, where the

measure of reliability may differ from the standard probability of failure occurrence.

This standard also extends to present accelerated testing or production screening methods

that would identify weakness introduced into the product by manufacturing error, which could

compromise product dependability.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and

are indispensable for its application. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60068 (all parts), Environmental testing

IEC 60300-3-1:2003, Dependability management – Part 3-1: Application guide – Analysis

techniques for dependability – Guide on methodology

IEC 60300-3-5, Dependability management – Part 3-5: Application guide – Reliability test

conditions and statistical test principles
IEC 60605-2, Equipment reliability testing – Part 2: Design of test cycles
IEC 60721 (all parts), Classification of environmental conditions
IEC 61014:2003, Programmes for reliability growth
IEC 61164:2004, Reliability growth – Statistical test and estimation methods

IEC 61124:2012, Reliability testing – Compliance tests for constant failure rate and constant

failure intensity
IEC 61163-2, Reliability stress screening – Part 2: Electronic components
IEC 61649:2008, Weibull analysis

IEC 61709, Electronic components – Reliability – Reference conditions for failure rates and

stress models for conversion
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62506 © IEC:2013 – 9 –
IEC 61710, Power law model – Goodness-of-fit tests and estimation methods

IEC 62303, Radiation protection instrumentation – Equipment for monitoring airborne tritium

IEC/TR 62380, Reliability data handbook – Universal model for reliability prediction of

electronics components, PCBs and equipment

IEC 62429, Reliability growth – Stress testing for early failures in unique complex systems

3 Terms, definitions, symbols and abbreviations

For the purposes of this document, the term and definitions given in IEC 60050-191:____, as

well as the following, apply.

NOTE Symbols for reliability, availability, maintainability and safety measures follow those of

IEC 50060-191:1990, where available.
3.1 Terms and definitions
3.1.1
item
subject being considered

Note 1 to entry: The item may be an individual part, component, device, functional unit, equipment, subsystem, or

system.

Note 2 to entry: The item may consist of hardware, software, people or any combination thereof.

Note 3 to entry: The item is often comprised of elements that may each be individually considered. See "sub-

item", definition 191-41-02 and "indenture level", definition 191-41-05.

Note 4 to entry: IEC 60050-191:1990, first edition, identified the term “entity” as a synonym, which is not true for

all applications.

Note 5 to entry: The definition for item given in the first edition is a description rather than a definition. This new

definition provides meaningful substitution throughout this standard. The words of the former definition form the

new note 1.
[SOURCE: IEC 60050-191:—, definition 191-41-01] [1]
3.1.2
step stress
step stress test

test in which the applied stress is increased, after each specified interval, until failure occurs

or a predetermined stress level is reached

Note 1 to entry: The ‘intervals’ could be specified in terms of number of stress applications, durations, or test

sequences.

Note 2 to entry: The test should not alter the basic failure modes, failure mechanisms, or their relative

prevalence.
[SOURCE: IEC 60050-191:—, definition 191-49-10]
3.1.3
acceleration factor

ratio between the item failure distribution characteristics or reliability measures (e.g. failure

intensities) of an item when it is subject to stresses in expected use and those the item

acquires when the higher level stresses are applied for achieving a shorter test duration

—————————
Figures in square brackets refer to the Bibliography.
---------------------- Page: 11 ----------------------
– 10 – 62506 © IEC:2013

Note 1 to entry: For a test to be effectively accelerated, the acceleration factor is >1.

Note 2 to entry: When the failure distribution Poisson is assumed with constant failure rate, then the acceleration

factor corresponds to the ratio of time under stress in use vs. time under increased stress in test.

3.1.4
highly accelerated limit test
HALT

test or sequence of tests intended to identify the most likely failure modes of the product in a

defined stress environment

Note 1 to entry: HALT is sometimes spelled out as the highly accelerated life test (as it was originally named in

error). However, as a non-measurable accelerated test, it does not provide informatio

...

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