IEC 62892:2019

Extended thermal cycling of PV modules - Test procedure

IEC 62892:2019 defines a test sequence that extends the thermal cycling test of IEC 61215-2. It is intended to differentiate PV modules with improved durability to thermal cycling and evaluate modules for deployment in locations most susceptible to thermal cycling type stress. This document is based on the ability for 95 % of the modules represented by the samples submitted for this test to pass an equivalency of 500 thermal cycles, as defined in IEC 61215‑2:2016, 4.11.3, with a maximum power degradation of less than 5 %. Provisions are also provided to reduce overall test time by increasing the maximum cycle temperature and/or the number of modules submitted for test.
The test procedure in this document was developed based on analysis of the stress on tin-lead solder bonds on crystalline silicon solar cells in a glass superstrate type package. Changes to lead-free solder have an effect on the acceleration factors but not enough to change the overall results of this test. Monolithic type modules with integral cell interconnection do not suffer from this specific type of stress but there are still electrical connections within the module, for example between the integrated cell circuit and the module bus bars, that may be subject to wear out from thermal cycling. Flexible modules (without glass) are not stressed in the same way as those with glass superstrates or substrates, therefore use of the equivalency factor employed in this document may not be applicable to these modules.

Cycle thermique étendu de modules PV - Procédure d'essai

l'IEC 62892:2019 définit une séquence d'essais qui étend l'essai de cycle thermique de l'IEC 61215-2. Il est destiné à différencier les modules photovoltaïques avec une meilleure durabilité par rapport au cycle thermique et à évaluer les modules pour un déploiement dans les lieux plus exposés aux contraintes de cycle thermique. Le présent document repose sur l'aptitude pour 95 % des modules représentés par les échantillons soumis à cet essai à supporter avec succès l'équivalent de 500 cycles thermiques, conformément à la procédure définie dans l'IEC 61215-2:2016, 4.11.3, avec une dégradation maximale de puissance inférieure à 5 %. Des dispositions sont également fournies pour réduire la durée totale des essais en augmentant la température maximale du cycle et/ou le nombre de modules soumis à l'essai.
La procédure d'essai décrite dans le présent document a été élaborée sur la base d'une analyse des contraintes exercées sur des assemblages soudés en alliage plomb-étain sur des cellules solaires en silicium cristallin au sein d'un ensemble de type superstrat de verre. Des modifications apportées à une soudure sans plomb ont un effet sur les facteurs d'accélération, mais pas de manière suffisante pour modifier les résultats globaux de cet essai. Les modules de type monolithique avec interconnexion intégrale des cellules ne souffrent pas de ce type de contrainte spécifique, mais il persiste des connexions électriques à l'intérieur du module, par exemple entre le circuit intégré de la cellule et les barres omnibus du module, qui peut subir une usure due aux cycles thermiques. Les modules souples (sans verre) ne subissent pas les mêmes contraintes que ceux qui comportent des superstrats ou des substrats de verre. Par conséquent, l'utilisation du facteur d'équivalence employé dans le présent document peut ne pas convenir à ces modules.

General Information

• Status: Published
• Publication Date: 16-Apr-2019
• ICS: 27.160 - Solar energy engineering
• Technical Committee: TC 82 - Solar photovoltaic energy systems
• Drafting Committee: WG 2 - TC 82/WG 2
• Current Stage: PPUB - Publication issued
• Start Date: 17-Apr-2019
• Completion Date: 22-Mar-2019

Overview

IEC 62892:2019 is an international standard developed by the International Electrotechnical Commission (IEC) that specifies an extended thermal cycling test procedure for photovoltaic (PV) modules. This standard builds upon the existing thermal cycling test defined in IEC 61215-2, focusing on enhanced durability assessment and evaluation of PV modules intended for deployment in environments susceptible to thermal cycling stress. The test arrangement aims to simulate real-world temperature fluctuations to assess the long-term resilience and performance stability of PV modules, particularly those with glass superstrates containing crystalline silicon solar cells.

Key Topics

• Extended Thermal Cycling Test
  IEC 62892 outlines a test sequence that extends the number of thermal cycles well beyond those required in IEC 61215-2, targeting a minimum equivalency of 500 cycles. The testing ensures that at least 95% of tested modules exhibit no more than 5% power degradation after completing these cycles.

• Applicability and Scope
  The procedure focuses primarily on crystalline silicon PV modules with tin-lead solder bonds in glass superstrate packaging. It is also applicable to modules with lead-free solder, although acceleration factors may vary. However, monolithic modules and flexible PV modules without glass substrates may require separate considerations, as their interconnections and stress mechanisms differ.

• Sampling and Test Conditions
  Modules tested must be randomly sampled from production batches already certified under IEC 61215 and IEC 61730 series standards. The procedure allows for test time reduction by increasing maximum cycle temperatures or testing a larger sample size, balancing accuracy and efficiency.

• Pass Criteria and Evaluation
  Modules passing the extended thermal cycling test must demonstrate less than a 5% reduction in maximum power compared to initial evaluations, verifying their long-term durability against temperature-induced mechanical stresses.

• Acceleration Factors and Climate Suitability
  Annex B of IEC 62892 provides guidance on acceleration factors reflecting different deployment climates. This helps manufacturers and certification bodies determine the necessity of extended thermal cycling based on geographic temperature profiles.

Applications

• PV Module Quality Assurance
  Manufacturers can use IEC 62892 to benchmark and ensure improved durability of their PV module designs against thermal cycling, increasing reliability and customer confidence.

• Product Development and Differentiation
  Extended thermal cycling testing serves as a valuable tool for R&D teams aiming to enhance solder bond reliability and electrical interconnections within modules, especially for crystalline silicon technology.

• Regulatory and Certification Compliance
  Testing according to IEC 62892 supports compliance in markets with harsher thermal environments, enabling certification bodies to validate module suitability for deployment in regions with significant temperature fluctuations.

• Risk Assessment for Deployment Locations
  The standard assists end-users and system integrators in selecting PV modules that withstand thermal stress typical of their specific climate, contributing to the longevity and performance consistency of solar installations.

Related Standards

• IEC 61215 Series
  Provides foundational design qualification and type approval test requirements for terrestrial PV modules, including the baseline thermal cycling test that IEC 62892 extends.

• IEC 61730 Series
  Addresses PV module safety qualifications, covering construction and testing to ensure module safety standards are met alongside durability.

• IEC TS 62941
  Offers guidelines to increase confidence in PV module design qualification and type approval, complementing the extended thermal cycling evaluations.

• IEC TS 61836
  Defines terms, definitions, and symbols related to solar photovoltaic energy systems, standardizing language across IEC documents.

Keywords

PV module testing, thermal cycling test, IEC 62892, extended thermal cycling, photovoltaic durability, solder bond reliability, crystalline silicon solar panels, PV module certification, thermal stress evaluation, PV module accelerated aging, IEC 61215 extension, solar panel quality assurance, photovoltaic climate adaptation.

Standards Content (Sample)

IEC 62892 ®
Edition 1.0 2019-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Extended thermal cycling of PV modules – Test procedure

Cycle thermique étendu de modules PV – Procédure d'essai

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IEC 62892 ®
Edition 1.0 2019-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Extended thermal cycling of PV modules – Test procedure

Cycle thermique étendu de modules PV – Procédure d'essai

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.160 ISBN 978-2-8322-6598-7

– 2 – IEC 62892:2019 © IEC 2019
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 Sampling . 7
5 Marking and documentation . 7
6 Modifications . 8
7 Test procedure . 8
7.1 Initial evaluations . 8
7.2 Thermal cycling test . 8
7.2.1 Purpose . 8
7.2.2 Apparatus . 8
7.2.3 Procedure . 8
7.3 Final evaluations . 9
7.4 Requirements . 10
8 Reporting. 10
Annex A (normative) Calculation of the required number of thermal cycles . 11
Annex B (informative) Acceleration factors based on deployed climate . 14
Bibliography . 17

Figure A.1 – Number of equivalent cycles as a function of maximum cycle temperature
over maximum module operating temperature . 11
Figure A.2 – Survivorship plot for a Weibull distribution with a shape parameter of 6
and a survivorship probability of 95% at 500 cycles . 12
Figure B.1 – Plot of module cell temperature over the course of one day to illustrate
the maximum temperature, maximum temperature change and temperature reversal
terms . 14
Figure B.2 – Combination of factors that indicate extended thermal cycling is advised
for a specific location . 15

Table 1 – Number of required thermal cycles, N . 9
R
Table A.1 – Effect of sample size on test time . 13
Table B.1 – Cell temperature factors . 15
Table B.2 – Module and mounting specific model parameters . 16

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EXTENDED THERMAL CYCLING OF PV MODULES –
TEST PROCEDURE
FOREWORD
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International Standard IEC 62892 has been prepared by IEC technical committee 82: Solar
photovoltaic energy systems.
The text of this International Standard is based on the following documents:
FDIS Report on voting
82/1537/FDIS 82/1560/RVD
Full information on the voting for the approval of this International Standard can be found in the
report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

– 4 – IEC 62892:2019 © IEC 2019
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the specific document. At this date, the document will be
• reconfirmed,
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IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
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INTRODUCTION
The IEC 61215 series defines test requirements for the design qualification of flat-plate PV
modules for long-term operation in general open-air climates. IEC TS 62941 provides technical
guidance in application of the type-approval testing.
This document, IEC 62892, supplements IEC 61215 by providing an extended thermal cycling
test intended to differentiate PV modules with improved durability to thermal cycling and
evaluate modules for deployment in locations most susceptible to thermal cycling type stress.

– 6 – IEC 62892:2019 © IEC 2019
EXTENDED THERMAL CYCLING OF PV MODULES –
TEST PROCEDURE
1 Scope
This document defines a test sequence that extends the thermal cycling test of IEC 61215-2. It
is intended to differentiate PV modules with improved durability to thermal cycling and evaluate
modules for deployment in locations most susceptible to thermal cycling type stress . This
document is based on the ability for 95 % of the modules represented by the samples submitted
for this test to pass an equivalency of 500 thermal cycles, as defined in IEC 61215-2:2016,
4.11.3, with a maximum power degradation of less than 5 %. Provisions are also provided to
reduce overall test time by increasing the maximum cycle temperature and/or the number of
modules submitted for test.
The test procedure in this document was developed based on analysis of the stress on tin-lead
solder bonds on crystalline silicon solar cells in a glass superstrate type package. Changes to
lead-free solder have an effect on the acceleration factors but not enough to change the overall
results of this test. Monolithic type modules with integral cell interconnection do not suffer from
this specific type of stress but there are still electrical connections within the module, for
example between the integrated cell circuit and the module bus bars, that may be subject to
wear out from thermal cycling. Flexible modules (without glass) are not stressed in the same
way as those with glass superstrates or substrates, therefore use of the equivalency factor
employed in this document may not be applicable to these modules.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 61215-1:2016, Terrestrial photovoltaic (PV) modules – Design qualification and type
approval – Part 1: Test requirements
IEC 61215-1-1, Terrestrial photovoltaic (PV) modules – Design qualification and type approval
– Part 1-1: Special requirements for testing of crystalline silicon terrestrial photovoltaic (PV)
modules
IEC 61215-1-2, Terrestrial photovoltaic (PV) modules – Design qualification and type approval
– Part 1-2: Special requirements for testing of thin-film Cadmium Telluride (CdTe) based
photovoltaic (PV) modules
IEC 61215-1-3, Terrestrial photovoltaic (PV) modules – Design qualification and type approval
– Part 1-3: Special requirements for testing of thin-film amorphous silicon based photovoltaic
(PV) modules
IEC 61215-1-4, Terrestrial photovoltaic (PV) modules – Design qualification and type approval
– Part 1-4: Special requirements for testing of thin-film Cu(In,GA)(S,Se) based photovoltaic
(PV) modules
___________
Guidance is provided in Annex B to assess if this test is warranted for the targeted deployment location.

IEC 61215-2:2016, Terrestrial photovoltaic (PV) modules – Design qualification and type
approval – Part 2: Test procedures
IEC 61730-1, Photovoltaic (PV) module safety qualification – Part 1: Requirements for
construction
IEC 61730-2, Photovoltaic (PV) module safety qualification – Part 2: Requirements for testing
IEC TS 61836, Solar photovoltaic energy systems – Terms, definitions and symbols
IEC TS 62915, Photovoltaic (PV) modules – Type approval, design and safety qualification –
Retesting
IEC TS 62941:2016, Terrestrial photovoltaic (PV) modules – Guideline for increased confidence
in PV module design qualification and type approval
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC TS 61836 as well as
the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
equivalent cycles
number of thermal cycles that imparts the same amount of solder fatigue damage
4 Sampling
Modules for these tests shall be taken at random from a production batch or batches of a module
type that is already certified to IEC 61215, IEC 61730-1 and IEC 61730-2. The modules shall
have been manufactured from specified materials and components in accordance with the
relevant drawings and process sheets and have been subjected to the manufacturer's normal
inspection, quality control and production acceptance procedures. The modules shall be
complete in every detail and shall be accompanied by the manufacturer's handling, mounting
and connection instructions.
The relation between the number of modules submitted for testing and the required number of
cycles is detailed Table 1 and Annex A. A minimum of three modules shall be submitted for
testing, two for the actual testing and one as control.
Because these tests are designed for accelerated stress testing of production modules,
engineering samples are not allowed.
5 Marking and documentation
Each module shall include clear and indelible markings as defined in IEC 61215-1. Modules
shall be supplied with documentation conforming to the requirements in IEC 61215-1.
Documentation consistent with the requirements of Clause 4 of IEC TS 62941:2016 shall also
be available for inspection by the test agency to ensure adequacy of the Quality Management
System.
– 8 – IEC 62892:2019 © IEC 2019
6 Modifications
Changes in material selection, components and manufacturing process that would trigger
retesting of the 200 thermal cycles leg in IEC TS 62915 would also require retest to this
document.
7 Test procedure
7.1 Initial evaluations
a) Visual inspection in accordance with IEC 61215-2 Module Qualification Test (MQT) 01.
b) Maximum power determination in accordance with IEC 61215-2 MQT 02.
c) Insulation test in accordance with IEC 61215-2 MQT 03.
d) Wet current leakage test in accordance with IEC 61215-2 MQT 15.
7.2 Thermal cycling test
7.2.1 Purpose
The purpose of the thermal cycling test is to determine the ability of the PV modules to withstand
thermal mismatch, fatigue, and other stresses caused by rapid, non-uniform or repeated
changes of temperature.
7.2.2 Apparatus
In accordance with IEC 61215-2:2016, 4.11.2.
7.2.3 Procedure
In accordance with IEC 61215-2:2016, 4.11.3 with the following modifications:
a) The maximum temperature of the cycle (T ) may be increased above 85 °C to reduce the
MAX
number of required cycles according to Table 1. (T ) shall be specified by the submitting
MAX
party and recorded in the test report.
b) During the thermal cycling test set the continuous current flow during the heat up cycle to
the technology specified current in IEC 61215-2 at temperature from –40 °C to
(T ) –5 °C. During cool down, the –40 °C dwell phase and temperatures above
MAX
) –5 °C the continuous current shall be reduced to no more than 1,0 % of the
(T
MAX
measured STC peak power current to measure continuity.
c) The number of cycles shall be as shown in Table 1. Annex A may be used to calculate the
required number of thermal cycles when more than 10 modules are submitted for test or
when T –85 °C>25 °C.
MAX
Table 1 – Number of required thermal cycles, N
R
T –85 Number of modules submitted for test
MAX
°C 2 3 4 5 6 7 8 9 10
0 731 683 651 627 609 593 580 569 559
1 711 665 634 611 592 577 565 554 544
2 693 647 617 594 577 562 550 539 530
3 674 630 601 579 562 547 535 525 516
4 657 614 585 564 547 533 521 511 502
5 640 598 570 549 533 519 508 498 489
6 623 583 555 535 519 506 495 485 477
7 608 568 541 521 506 493 482 473 465
8 592 553 528 508 493 481 470 461 453
9 577 539 514 495 481 468 458 449 441
10 563 526 501 483 469 457 447 438 430
11 549 513 489 471 457 445 436 427 420
12 535 500 477 459 446 434 425 417 409
13 522 488 465 448 435 424 414 406 399
14 509 476 454 437 424 413 404 396 390
15 497 465 443 427 414 403 394 387 380
16 485 453 432 416 404 394 385 378 371
17 473 443 422 406 394 384 376 368 362
18 462 432 412 397 385 375 367 360 353
19 451 422 402 387 376 366 358 351 345
20 441 412 393 378 367 358 350 343 337
21 430 402 383 369 358 349 342 335 329
22 420 393 375 361 350 341 334 327 321
23 411 384 366 353 342 333 326 320 314
24 401 375 358 344 334 326 319 312 307
25 392 367 349 337 327 318 311 305 300

NOTE The relationship employed to calculate the number of required cycles in Table 1 is based on a Coffin-Manson
style empirical relationship for solder thermal fatigue and a one-parameter Weibull analysis and dictates that 95 %
of the modules represented by the samples submitted for this test will pass an equivalency of 500 qualification level
thermal cycles [1, 2] . This relationship is applicable for both PbSn and Pb-free solders. FEM simulations of a PV
module have demonstrated that this relationship results in a conservative estimate for equivalency [3]. These
simulations show that softening of the module’s encapsulant at high temperatures will result in a faster rate of solder
damage accumulation. Therefore, while prescribing a higher maximum cycle temperature will reduce the overall test
time, the equivalency of that test, or overall stress, may be greater than intended.
7.3 Final evaluations
a) Visual inspection in accordance with IEC 61215-2 MQT 01.
b) Maximum power determination in accordance with IEC 61215-2 MQT 02.
c) Insulation test in accordance with IEC 61215-2 MQT 03.
d) Wet leakage current test in accordance with IEC 61215-2 MQT 15.
e) Bypass diode functionality test in accordance with IEC 61215-2 MQT 18.2.
___________
Numbers in square brackets refer to the Bilbiography.

– 10 – IEC 62892:2019 © IEC 2019
When implementing the tests from IEC 61215-2, the requirements of the technology specific
standards (IEC 61215-1-1, IEC 61215-1-2, IEC 61215-1-3 and IEC 61215-1-4) shall be taken
into account.
7.4 Requirements
The requirements are as follows:
– no interruption of current flow during the test;
– no evidence of major visual defects, as defined in IEC 61215-1:2016, Clause 7;
– the degradation of maximum output power shall not exceed 5 % of the value measured
before the test;
– insulation resistance shall meet the same requirements as for the initial measurements.
– any by-pass diodes shall still function as diodes.
NOTE Electroluminescence imaging may be a useful technique to image the location of failed, or failing, solder
bonds.
8 Reporting
Following completion of the testing, a report of the tests, with measured performance
characteristics and details of any failures and re-tests, shall be prepared by the test agency.
The report shall contain the detail specification for the module. Each test report shall include at
least the following information:
a) a title;
b) name and address of the test laboratory and location where the tests were carried out;
c) unique identification of the report and of each page;
d) name and address of client, where appropriate;
e) description and identification of the item tested;
f) characterization and condition of the test item;
g) date of receipt of test item and date(s) of test, where appropriate;
h) reference to sampling procedure;
i) any deviations from, additions to, or exclusions from, the test method and any other
information relevant to a specific tests, such as environmental conditions and the test
procedure used to validate that the by-pass diodes were functional at the end of the test
sequence;
j) measurements, examinations and derived results supported by tables, graphs, sketches and
photographs as appropriate including maximum power loss observed after all of the tests,
dry and wet insulation resistance changes due to the tests and evidence of changes that
might ultimately lead to performance degradation;
k) a statement of the estimated uncertainty of the test results (where relevant);
l) a signature and title, or equivalent identification of the person(s) accepting responsibility for
the content of the report, and the date of issue;
m) where relevant, a statement to the effect that the results relate only to the items tested;
n) a statement that the report shall not be reproduced except in full, without the written
approval of the laboratory.
A copy of this report shall be kept by the manufacturer for reference purposes.

Annex A
(normative)
Calculation of the required number of thermal cycles
There are two factors that together determine the required number of thermal cycles, N , as
R
tabulated in Table 1:
a) Maximum cycle temperature, T (°C).
MAX
b) Number of modules submitted for test, n.
The first step is to determine the equivalent number of cycles, N . It is a function of T . This
e MAX
number of cycles will impart an equivalent amount of solder fatigue damage as 500 qualification
level cycles (–40 °C to 85 °C) as defined in IEC 61215-2, MQT 11. The relationship between
T and N is:
MAX e
−2
( )
𝑁𝑁 = 150470𝑇𝑇 +40 exp� � (A.1)
𝑒𝑒 𝑀𝑀𝑀𝑀𝑀𝑀
𝑇𝑇 +273
𝑀𝑀𝑀𝑀𝑀𝑀
Formula (A.1) defines how increasing the maximum cycle temperature over 85 °C can reduce
the potential number of cycles and therefore overall test time, Figure A.1. This formula is based
on a Coffin-Manson style empirical relationship for solder thermal fatigue [1, 2]. This
relationship is applicable for both PbSn and Pb-free solders. FEM simulations of a PV module
have demonstrated that this relationship results in a conservative estimate for equivalency [3].
These simulations show that softening of the module’s encapsulant at high temperatures will
result in a faster rate of solder damage accumulation. Therefore, while prescribing a higher
maximum cycle temperature will reduce the overall test time, the equivalency, or overall stress,
of that test may be greater than intended.
0 5 10 15 20 25
T -85 (°C)
max
IEC
Figure A.1 – Number of equivalent cycles as a function of maximum
cycle temperature over maximum module operating temperature
Number of equivalent cycles, N
e
– 12 – IEC 62892:2019 © IEC 2019
The number of samples submitted for test, n, and the number of equivalent thermal cycles, N ,
e
determine the number of required thermal cycles, N :
R
⁄
1 6
−𝑁𝑁
𝑒𝑒
𝑁𝑁 =� � (A.2)
𝑅𝑅
𝑛𝑛ln(0,95)
This formula is derived from a one-parameter Weibull analysis and dictates that 95 % of the
modules represented by the samples submitted for this test will pass an equivalency of
500 qualification level thermal cycles with a relative maximum power degradation of less than
5 %. The Weibull shape parameter is chosen to be 6 [1]. A survivorship plot with a Weibull
parameter of 6 and a survivorship probability of 95 % at 500 cycles is presented in Figure A.2
to illustrate the assumed distribution. In this distribution the characteristic lifetime (63,5 %
failure probability) is 820 cycles, a 1 % failure (a relative power degradation > 5 %) is observed
by 378 cycles, and 99 % failure by 1 057 cycles.
The result of formula (A.2), N is the number of thermal cycles the sample size of n modules
R,
is required to pass this document.
0,8
0,6
0,4
0,2
0 400 800 1 200
Number of cycles
IEC
Figure A.2 – Survivorship plot for a Weibull distribution with
a shape parameter of 6 and a survivorship probability of 95 % at 500 cycles
The following is an example of how to calculate the number of required thermal cycles:
c) Chose thermal cycling parameters:
= 95 °C
T
MAX
n = 2 modules
d) Calculate the equivalent number of cycles:
−2
𝑁𝑁 = 150470(95+40) exp� � = 385
𝑒𝑒
95+273
e) Calculate the number of required thermal cycles
Survival probability
1⁄6
−385
𝑁𝑁 =� � = 563
𝑅𝑅
2∙ ln(0,95)
Table A.1 is included to illustrate the effect of sample size on the number of required cycles
and consequential test time.
Table A.1 – Effect of sample size on test time
Number of modules Required number of cycles Overall test time
n N days
R
2 563 69,9
3 526 65,3
4 501 62,2
5 483 60,0
6 469 58,2
7 457 56,7
– 14 – IEC 62892:2019 © IEC 2019
Annex B
(informative)
Acceleration factors based on deployed climate
Analysis has shown that certain climates tend to be more damaging to the PV module’s solder
bonds [3]. These climates are typically characterized by high ambient temperatures and partly
cloudy days. The purpose of this Annex is to provide guidance on how to assess if a specific
deployment location warrants extended thermal cycling to properly evaluate a module’s
durability against solder bond thermomechanical fatigue.
The rate of solder fatigue damage has been demonstrated to depend on three factors of a
module’s temperature history:
= mean daily maximum cell temperature;
= mean daily maximum cell temperature change;
r(55) = temperature reversal term.
T
c max
r (55)
0 24
Time (h)
IEC
Figure B.1 – Plot of module cell temperature over the course of one day to illustrate the
maximum temperature, maximum temperature change and temperature reversal terms
These factors are illustrated on a representative plot of module cell temperature over the course
of one day in Figure B.1. The temperature reversal term, r(55), is the number of times the cell
temperature history increases and decreases across 55 °C (in Figure B.1, r(55)=4).
To determine if a specific location warrants extended thermal cycling these three factors shall
be evaluated, over the course of one-year, for that location from 60 min time-averaged module
cell temperature data. Higher resolution temperature data shall be down sampled to a 60 min
time average for this analysis to be accurate. While the and terms are the average
of the daily values observed for the year, the r(55) term is the sum for the entire year. The plot
in Figure B.2 illustrates the combination of factors that indicate extended thermal cycling is
advised for that location. It is based on FEM simulations that equate the solder fatigue damage
accumulated through accelerated thermal cycling to that accumulated through on-sun
deployment in a variety of climates [3]. The defined regions in the plot represent climate
characteristics where a 25-year on sun deployment exceeds the equivalent solder fatigue
damage imparted by 200 to 250 accelerated thermal cycles.
Temperature
∆T
To use the plot, find the intersection of the and values determined from the analyzed
module cell temperature history. If the r(55) factor is greater than the value indicated in that
shaded region of the plot, the weather pattern for the specific location analyzed is particularly
damaging and extended thermal cycling is advised.
50 Phoenix
Freiburg
22 24 26 28 30 32 34
∆T (°C)
IEC
Figure B.2 – Combination of factors that indicate extended
thermal cycling is advised for a specific location
For illustrative purposes, the factors for two cities, Freiburg Germany and Phoenix Arizona, are
plotted in Figure B.2. The three terms for these cities are presented in Table B.1. Because
r(55)= 396 for Phoenix, extended thermal cycling is advised. For Freiburg (r(55)= 38), however,
extended thermal cycling may not be required to properly assess a modules thermomechanical
fatigue resistance in that location.
Table B.1 – Cell temperature factors
City r(55)
°C
°C
Phoenix, AZ 52,1 33,2 396
Freiburg, DE 30,2 21,5 38
In the absence of one-year’s worth of module cell temperature data, a one-year history of
module cell temperature may be synthesized by examining meteorological data for a specific
location. If developed, it is encouraged to use a manufacture’s model specific to the module
and intended mounting configuration. Alternatively, the following generic method may be
employed:
a) Collect a dataset containing one-year’s worth of ambient temperature, T , wind speed,
amb
WS, and total global irradiance, E, recorded at regular intervals.
b) Down sample that data to 60 min time averaged values.
c) Calculate the 60 min time average module cell temperature for an entire year:
∆𝑇𝑇
𝑇𝑇 =𝑇𝑇 +𝐶𝐶∙𝐸𝐸exp(𝑎𝑎+𝑏𝑏∙𝑊𝑊𝑊𝑊)+𝐸𝐸
𝑐𝑐𝑒𝑒𝑐𝑐𝑐𝑐 𝑎𝑎𝑎𝑎𝑎𝑎
𝐸𝐸
𝑜𝑜
T (°C)
c max
– 16 – IEC 62892:2019 © IEC 2019
where E is the reference solar irradiance of 1 000 W/m , ∆T represents the temperature
o
difference between the cell and module at this reference irradiance and C a prefactor of 1
with units of ˚Cm /W . The coefficients a and b depend on the module type and mounting
configuration and are provided for a number of configurations in Table B.2[4].
Table B.2 – Module and mounting specific model parameters
Module type Mount a b
∆T
°C
glass/cell/glass open rack -3,47 -0,0594 3
glass/cell/glass close roof -2,98 -0,0471 1
glass/cell/polymer open rack -3,56 -0,075 3
glass/cell/polymer insulated back -2,81 -0,0455 0

Bibliography
[1] R. B. Abernethy, The New Weibull Handbook–Fifth Edition", 2007
[2] K. C. Norris and A. H. Landzberg, "Reliability of Controlled Collapse Interconnections",
IBM Journal of Research and Development, vol. 13, pp. 266-271, 1969
[3] N. Bosco, T. Silverman, and S. Kurtz, "Climate Specific Solder Thermal Fatigue Damage
in PV Modules", Microelectronics Reliability, vol. 62, pp. 124-129, July 2016
[4] D. L. King, W. E. Boyson, and J. A. Kratochvil, "Photovoltaic array performance model",
Sandia National Laboratories SAND2004-3535, 2004

___________
– 18 – IEC 62892:2019 © IEC 2019

SOMMAIRE
AVANT-PROPOS . 19
INTRODUCTION . 21
1 Domaine d'application . 22
2 Références normatives . 22
3 Termes et définitions . 23
4 Echantillonnage . 23
5 Marquage et documentation . 24
6 Modifications . 24
7 Procédure d'essai . 24
7.1 Evaluations initiales . 24
7.2 Essai de cycle thermique . 24
7.2.1 Objet . 24
7.2.2 Appareillage . 24
7.2.3 Procédure . 24
7.3 Evaluations finales . 25
7.4 Exigences . 26
8 Rapports. 26
Annexe A (normative) Calcul du nombre de cycles thermiques exigés . 27
Annexe B (informative) Facteurs d'accélération en fonction du climat du site de
déploiement . 31
Bibliographie . 34

Figure A.1 – Nombre de cycles équivalents en fonction de la différence entre la
température maximale du cycle et la température maximale de fonctionnement du
module . 28
Figure A.2 – Courbe de survie pour une distribution de Weibull avec un paramètre de
forme de 6 et une probabilité de survie de 95 % pour 500 cycles . 29
Figure B.1 – Courbe de la température des cellules d'un module sur une journée,
montrant la température maximale, la variation de la température maximale et les
termes d'inversion de la température . 31
Figure B.2 – Combinaison de facteurs indiquant qu'il est conseillé de pratiquer des
cycles thermiques étendus pour un lieu spécifique . 32

Tableau 1 – Nombre de cycles thermiques exigés, N . 25
R
Tableau A.1 – Effet de la taille d'échantillon sur la durée des essais . 30
Tableau B.1 – Facteurs de température de cellule . 32
Tableau B.2 – Paramètres de modèle spécifiques au montage et au module . 33

COMMISSION ÉLECTROTECHNIQUE INTERNATIONALE
____________
CYCLE THERMIQUE ÉTENDU DE MODULES PV –
PROCÉDURE D'ESSAI
AVANT-PROPOS
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