1、IES TM-26-15Methods forProjecting CatastrophicFailure Rate of LED PackagesIES TM-26-15Methods for Projecting Catastrophic Failure Rate of LED PackagesPublication of this reporthas been approved by IES.Suggestions for revisionsshould be directed to IES.Prepared by:IES Testing Procedures CommitteeIES
2、TM-26-15Copyright 2015 by the Illuminating Engineering Society of North America.Approved by the IES Board of Directors, August 8, 2015, as a Transaction of the Illuminating Engineering Society of North America.All rights reserved. No part of this publication may be reproduced in any form, in any ele
3、ctronic retrieval system or otherwise, without prior written permission of the IES.Published by the Illuminating Engineering Society of North America, 120 Wall Street, New York, New York 10005.IES Standards and Guides are developed through committee consensus and produced by the IES Office in New Yo
4、rk. Careful attention is given to style and accuracy. If any errors are noted in this document, please forward them to the Manager or Director of Technology, at the above address for verification and correction. The IES welcomes and urges feedback and comments. ISBN # 978-0-87995-320-1 Printed in th
5、e United States of America.DISCLAIMERIES publications are developed through the consensus standards development process approved by the American National Standards Institute. This process brings together volunteers representing varied viewpoints and interests to achieve consensus on lighting recomme
6、ndations. While the IES administers the process and establishes policies and procedures to promote fairness in the development of consensus, it makes no guaranty or warranty as to the accuracy or completeness of any information published herein. The IES disclaims liability for any injury to persons
7、or property or other damages of any nature whatsoever, whether special, indirect, consequential or compensatory, directly or indirectly resulting from the publication, use of, or reliance on this document.In issuing and making this document available, the IES is not undertaking to render professiona
8、l or other services for or on behalf of any person or entity. Nor is the IES undertaking to perform any duty owed by any person or entity to someone else. Anyone using this document should rely on his or her own independent judgment or, as appropriate, seek the advice of a competent professional in
9、determining the exercise of reasonable care in any given circumstances.The IES has no power, nor does it undertake, to police or enforce compliance with the contents of this document. Nor does the IES list, certify, test or inspect products, designs, or installations for compliance with this documen
10、t. Any certification or statement of compliance with the requirements of this document shall not be attributable to the IES and is solely the responsibility of the certifier or maker of the statement.IES TM-26-15Prepared by the Solid State Lighting Subcommittee of the IES Testing Procedures Committe
11、eTM-26 Working Group Jianzhong Jiao, Technical CoordinatorSolid-State Lighting SubcommitteeEmil Radkov, ChairK. Haraguchi Y. HiebertM. HodappA. NishidaY. OhnoE. RadkovE. RichmanD. SzombatfalvyR. TuttleC. Andersen*A. BakerP. Behnke*R. BergerR. BergmanB. Besmanoff*C. Bloomfield*E. BretschneiderK Broug
12、hton*J. Burns*D. Chan*J. Choi*P.-T. Chou*A. Chowdhury*G. Connelly*K. Cook*J. Creveling*J. Dakin*R. Daubach*L. Davis*M. Duffy*D. Eckel*P. ElizondoS. Ellersick*D. EllisC. Fox*J. Gaines*C. Galberth*A. Gelder*M. GratherY. Guan*K. HaraguchiT. Hernandez*J. Hickman*Y. HiebertM. Hodapp*J. HospodarskyB. Hou*
13、J. HulettP-C. Hung*A. JacksonD. JenkinsA. Jeon*B. Jeong*J. JiaoJ. Kahn*D. Karambelas*T. Kawabata*T. Koo*M. KotrebaiB. KueblerJ. Lee*R. LeeS. Lee*M. Lehman*J. Leland*K. Liepmann*S. LongoM-H. Lu*R. Ma*V.t Mahajan*J. MarellaM. McClear*G. McKeeJ. Melman*D. Miletich*C. MillerZ. Mooney*M. Nadal*D. Nava*D.
14、 Neal*B. Neale*A. Nishida*M. OBoyle*D. OHare*Y. Ohno*M. ORegan*M. Pabst*D. Park*M. Piscitelli*M. Poplawski*B. Primerano*M. Raffetto*B. Rao*I. Rasputnis*E. RichmanK. Rong*E. Sahaja*M. SapcoeK. ScottG. SteinbergH. Steward*D. Szombatfalvy*K. Tracy*R. TuttleT. Uchida*Y. Wang*Y. Wang*D. Weiss*B. Willcock
15、*V. Wu*W. Xu*S. Yamauchi*J. Yon*R. Young*W. Young*G. Yu*J. ZhangY. Zong* Advisory Member* Honorary MemberIES TM-26-15IES Testing Procedures CommitteeCameron Miller, ChairBecky Kuebler, Vice ChairDavid Ellis, SecretaryJianzhong Jiao, TreasurerC. AndersenL. Ayers*A. BakerP. Behnke*R. BergerR. Bergin*R
16、. BergmanJ. Blacker*C. Bloomfield*E. BretschneiderK. Broughton*E. Carter*D. Chan*P-T. Chou*G. Connelly*J. Dakin*R. Daubach*L. Davis*J. Demirjian*M. Duffy*P. ElizondoD. EllisP. Franck*A. Gelder*M. GratherY. Guan*K. Haraguchi*R. Heinisch*K. Hemmi*T. Hernandez*Y. Hiebert*R. Higley*R. Horan*J. Hospodars
17、kyS. Hua*J. HulettP-C. HungD. Husby*A. JacksonD. Jenkins*D. Karambelas*H. Kashani*T. Kawabata*R. Kelley*T. Koo*M. KotrebaiJ. Lawton*L. Leetzow*J. Leland*K. Lerbs*R. Levin*R. Li*K. Liepmann*S. LongoR. Low*M-H. Lu*J. MarellaP. McCarthyG. McKeeD. Miletich*M. Minarczyk*Z. Mooney*F-X. Morin*M. Nadal*D. N
18、ava*B. Neale*D. OHare*Y. Ohno*J. Pan*D. Park*N. Peimanovic*E. Perkins*M. Piscitelli*G. Plank*E. RadkovD. RandolphC. Richards*E. Richman*K. Rong*M. SapcoeA. Serres*A. SmithR. Speck*L. Stafford*G. SteinbergK. Tracy*R. Tuttle*T. Uchida*K. Wagner*J. Walker*Y. Wang*H. Waugh*D. Weiss*J. Welch*K. Wilcox*B.
19、 Willcock*V. Wu*J. YonR. Young*J. Zhang*Y. Zong* Advisory Member* Honorary MemberIES TM-26-15Please refer to the IES Bookstore after you purchase this IES Standard, for possible Errata, Addenda, and Clarifications, www.ies.org/bookstoreContentsIntroduction.11.0 Scope .12.0 Normative References13.0 D
20、efinitions .13.1 Catastrophic LED Package Failure.13.2 Failure in Time (FIT) Rate.14.0 Description of Failure Rates “Bathtub Curve” 24.1 Early Failure Period .24.2 Stable Failure Rate Period24.3 Wearout Failure Period 25.0 Methods of Failure Rate Projection for the Stable Rate Period 25.1 Prioritiza
21、tion of Catastrophic Failures Analysis and Projection . . . . . . . . . . . . . . . . . . . . . . . 25.2 Convert All Temperatures to Kelvins .35.3 Method 1 Results of Catastrophic Failure Rate Reported in Table Format.35.4 Method 2 Catastrophic Failure Rate Projection Model A .35.4.1 Stress Factor f
22、or Temperature Dependence35.4.2 Stress Factor for Forward Current Dependence.35.4.3 Reporting Results 45.5 Method 3 Catastrophic Failure Rate Projection Model B .45.5.1 Stress Factor for Temperature Dependence45.5.2 Stress Factor for Forward Current Dependence.45.5.3 Reporting Results 4Informative R
23、eferences .4Annex A Weibull Analysis for Catastrophic Failure Rate Projection 5References for Annex A.7IES TM-26-151IES TM-26-15INTRoDuCTIoNWith the completion of IES TM-21-11 Projecting Long Term Lumen Maintenance of LED Light Sources + Addendum B, the LED lighting industry now possesses a standard
24、 method of obtaining projected long-term luminous flux maintenance information for LED packages. The method is com-posed of two steps. During the first step, the LED packages must be tested per ANSI/IES LM-80-15 Approved Method: Measuring Luminous Flux and Color Maintenance of LED Packages, Arrays a
25、nd Modules (and previous versions). The collected measurement data is then used with IES TM-21-11 to make luminous flux maintenance projections including calculations of in-situ temperature inter-polations. However, one relevant characteristic is still unaddressed: the catastrophic failure rate for
26、LED packages. Catastrophic failure rate, similar to luminous flux maintenance, is a reliability property that is essential to successfully design LED lamps and luminaires. Combined with luminous flux main-tenance, catastrophic LED failure rate information is used by LED lamp or luminaire manufacture
27、rs to inform warranty considerations and product appli-cation instructions.In addition to light output decay over time, LED pack-ages also experience catastrophic failures in which no light is produced. These catastrophic failures are typically caused by inadequate product design, pro-cess or improp
28、er usage. Catastrophic failure rates for LED packages are much lower in comparison with other light sources, typically in the range of parts per million hours or parts per billion hours. For practical purposes, LED users, such as LED lamp or luminaire manufacturers, require both luminous flux mainte
29、nance life and catastrophic failure rate to adequately assess overall LED lamps and lumi-naires reliability. This document describes three methods for LED packages catastrophic failure rate projections. 1.0 SCoPEThis document describes three methodologies for projecting the catastrophic failure rate
30、 of LED pack-ages. This document applies to the LED packages as defined in ANSI/IES RP-16-10, Nomenclature and Definitions for Illuminating Engineering. The three methodologies presented are for information only and do not represent a complete set of method-ologies in existence; these represent the
31、methodolo-gies that are publicly available, and have been made available, for publication by the IES. The IES does not endorse any of these specific methods and it is none of the methods described in this document are intended for incorporation or use in any standards publication.2.0 NoRMATIVE REFER
32、ENCES2.1 ANSI / IES RP-16-10, Nomenclature and Definitions for Illuminating Engineering. Illuminating Engineering Society of North America. New York, NY.2.2 NIST “NIST/SEMATECH e-Handbook of Statistical Methods”. Chapter 8 - Assessing Product Reliability. http:/www.itl.nist.gov/div898/handbook/index
33、.htm2.3 Siemens Norm, Failure Rates of Components Expected Values for Optical Components, SN 29500-12. Siemens AG, CT TIM IR SI, Otto-Hahn-Ring 6, 81739 Munich, Germany, Tel.: +49 89 636-40767.2.4 JESD51-51, Implementation of the Electrical Test Method for the Measurement of Real Thermal Resistance
34、and Impedance of Light-Emitting Diodes with Exposed Cooling, April 2012.2.5 JESD85, Methods for Calculating Failure Rates in Units of FITs, July 2001. 2.6 JESD74A, Early Life Failure Rate Calculation Procedure for Semiconductor Components, February 2007.3.0 DEFINITIoNS3.1 Catastrophic LED Package Fa
35、ilureAn LED package that does not emit light when energized is referred to as a catastrophic failure in this document. Individual die failures in a multi-die package are not considered catastrophic failure so long as the DUT (Device Under Test) continues to produce light.3.2 Failure in Time (FIT) Ra
36、teThe frequency with which a catastrophic LED pack-age failure occurs, expressed in failures per one bil-lion (109) hours of operation.2IES TM-26-154.0 DESCRIPTIoN oF FAILuRE RATES “BAThTuB CuRVE” Empirical population failure rates change as LED sourc-es age over time and the general failure rate tr
37、ends can be summarized by a graph such as shown in Figure 1. Because of the shape of this failure rate curve, it has become widely known as the “bathtub curve”.4.1 Early Failure PeriodThe initial region that begins at time zero when a cus-tomer starts to use the product is characterized by a rapidly
38、 decreasing catastrophic failure rate. Typical catastrophic failures that occur during this period of time may be caused by manufacturing and/or mate-rial defects. This region is known as the Early Failure Period (also referred to as Infant Mortality Period from the actuarial origins of the first ba
39、thtub curve plots). This decreasing failure rate typically lasts several to a few hundred hours. The impact of the Early Failure Period can often be minimized by screening, combined with a period of product burn-in at the LED manufacturer. 4.2 Stable Failure Rate PeriodAfter the Early Failure Period
40、, the failure rate levels off and remains relatively constant in typical cases for the majority of the useful life of the product. This long period of relatively constant failure rate is known as the Stable Failure Rate Period (also called the Random, Intrinsic Failures Period). Note that most LED p
41、ackages spend the majority of their lifetimes operating in this flat portion of the “bathtub curve.” During the Stable Failure Rate Period, the probability of catastrophic failure can be modeled by the exponential cumulative distribution function (CDF) over time:, (1)where t = time in hours, and = f
42、ailure rate per hour. 4.3 Wearout Failure PeriodIf LED packages remain in use long enough, the cat-astrophic failure rate begins to increase as materials wear out, and degradation failures occur at an ever-increasing rate. This is the Wearout Failure Period. 5.0 METhoDS oF FAILuRE RATE PRoJECTIoN Fo
43、R ThE STABLE RATE PERIoD5.1 Prioritization of Catastrophic Failures Analysis and ProjectionWhenever possible, the prediction of catastrophic fail-ures over time should be based on experimental observations. In addition, although the Weibull statistical model is used widely, it is important to note t
44、hat other statistical models, such as a mathematical model based on device physics, may be a better fit to the data. All “best fit” models shall be based upon statistically significant sample populations, “typical” manufac-tured parts, well established reliability methodolo-gies, and/or validated ma
45、thematical models based upon device physics.Figure 1: Generic “bathtub curve”3IES TM-26-15In all cases, projections of cumulative catastrophic fail-ures shall not be extended to other regions of the “bath-tub curve” (for example, any projection of random cata-strophic failures will not apply to rapi
46、d wearout failures).Recommendations provided in this section will main-ly address the Stable Failure Rate Period the flat portion of the bathtub curve. It is assumed that this information is most relevant to LED users. Catastrophic failure rate of LED arrays or modules can be determined either by su
47、mmation of the cata-strophic failure rate of each individual LED package, or directly at the LED array or module level using the methods described in this section.For cases for which actual data is not available and FIT calculations based on wear mechanisms of device physics are used should be noted
48、 in the report. Refer to Section of 5.4.3.5.2 Convert All Temperatures to KelvinsThe following formula shall be used to convert the temperatures to the units Kelvin:. (2)Only values in unit Kelvin shall be used in the sub-sequent calculations shown in the following sections.5.3 Method 1 Results of C
49、atastrophic Failure Rate Reported in Table FormatThe Catastrophic LED Failure in Time (FIT) rate can be reported as numerical results in a table format. For each corresponding value, the LED forward cur-rent shall be specified.Table 1 provides an example for using LED junction temperature to report FIT. Table 2 provides an exam-ple for using LED case temperature to report FIT. 5.4 Method 2 Catastrophic Failure Rate Projection Model AFor detailed background information, please refer to Normative Reference 2.3.If the stress factors can be identified, then the LED
