Methods for product accelerated testing
1 Scope
This standard provides guidance on the application of various accelerated testing 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 growth/improvement 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 referenced documents are indispensable for the application of this document. 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 - Part2: Electronic components
IEC 61649:2008 Weibull analysis
IEC 61709 Electronic components - Reliability - Reference conditions for failure rates and stress models for conversion
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
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-191, as well as the following, apply.
3.1.1
item
an individual part, component, device, functional unit, equipment, subsystem, or system that may each be individually considered
Note: The item may consist of hardware, software, people or any combination thereof.
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: The "intervals" could be specified in terms of number of stress applications, durations, or test sequences.
Note 2: The test shall not alter the basic failure modes, failure mechanisms, or their relative prevalence.
3.1.3
acceleration factor
ratio between the item failure distribution characteristics (or reliability measures) of an item when it is subject to stresses in expected use and those the item acquires when the higher level stresses are applied
Note 1: For a test to be effectively accelerated, the acceleration factor is >1.
Note 2: 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: HALT is sometimes spelled out as the highly accelerated life test. However, as a non-measurable accelerated test, it does not provide information on life duration, but on the magnitude of stress which represents the limit of the design.
3.1.5
highly accelerated stress test
HAST
test where applied stresses are considerably increased in order to reduce duration of their application
3.1.6
highly accelerated stress screening
HASS
screening intended to identify latent defects in a product caused by manufacturing process or control errors
3.1.7
highly accelerated stress audit
HASA
process monitoring tool where a sample from a production lot is tested to detect potential weaknesses in a product caused by manufacturing
3.1.8
activation energy
Ea
empirical factor for estimating the acceleration caused by a change in absolute temperature
Note: Activation energy is usually measured in electron volts per degree Kelvin (eV/K).
3.1.9
event compression
increasing stress repetition frequency to be considerably higher than it is in the field
Foreword II
Introduction IV
1 Scope
2 Normative references
3 Terms, definitions, symbols and abbreviations
3.1 Terms and definitions
3.2 Symbols and abbreviations
4 General description of the accelerated test methods
4.1 Cumulative damage model
4.2 Classification, methods and types of acceleration test
5 Accelerated test models
5.1 Type A: qualitative accelerated tests
5.2 Type B and C: quantitative accelerated test methods
5.3 Failure mechanisms and test design
5.4 Determination of stress levels, profiles and combinations in use and test-stress modelling
5.5 Multiple stress acceleration methodology - Type B tests
5.6 Single and multiple stress acceleration for Type B tests
5.7 Acceleration of quantitative reliability tests
5.8 Accelerated reliability compliance or evaluation tests
5.9 Accelerated reliability growth testing
5.10 Guidelines for accelerated testing
6 Accelerated testing strategy in product development
6.1 Accelerated testing sampling plan
6.2 Test stresses and durations
6.3 Testing components for multiple stresses
6.4 Accelerated testing of assemblies
6.5 Accelerated testing of systems
6.6 Analysis of test results
7 Limitations of accelerated testing methodology
Annex A (Informative) Highly accelerated limit test (HALT)
Annex B (Informative) Accelerated reliability compliance and growth test design
Annex C (Informative) Comparison between HALT and conventional accelerated testing
Annex D (Informative) Estimating the activation energy, Ea
Annex E (Informative) Calibrated accelerated life testing (CALT)
Annex F (Informative) Example on how to estimate empirical factors
Annex G (Informative) Determination of acceleration factors by testing to failure
Bibliography
