IEC TS 62788-5-2:2020

IEC TS 62788-5-2 ®
Edition 1.0 2020-06
TECHNICAL
SPECIFICATION
colour
inside
Measurement procedures for materials used in photovoltaic modules –
Part 5-2: Edge seals – Durability evaluation guideline

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IEC TS 62788-5-2 ®
Edition 1.0 2020-06
TECHNICAL
SPECIFICATION
colour
inside
Measurement procedures for materials used in photovoltaic modules –

Part 5-2: Edge seals – Durability evaluation guideline

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.160 ISBN 978-2-8322-8387-5

– 2 – IEC TS 62788-5-2:2020  IEC 2020
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 6
4 Testing . 7
4.1 General . 7
4.2 Material level tests . 7
4.2.1 Moisture ingress . 7
4.2.2 Adhesion . 7
4.2.3 Dielectric strength . 7
4.2.4 Material specimen UV exposure conditions . 7
4.2.5 Volume resistivity . 8
4.3 Mini-module testing . 9
4.4 Full-size module testing . 11
5 Test report . 12
Annex A (informative) Example of breakthrough time extrapolation . 14

Figure 1 – Material specimen test flow diagram . 8
Figure 2 – Mini-module test flow diagram . 10
Figure 3 – Module test flow diagram . 12
Figure A.1 – Example plot of transient WVTR through a 1 mm thick film of a desiccant
filled polyisobutylene based edge seal at 100 % RH at 85 °C and at 60 °C . 15

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MEASUREMENT PROCEDURES FOR MATERIALS
USED IN PHOTOVOLTAIC MODULES –

Part 5-2: Edge seals –
Durability evaluation guideline

FOREWORD
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Technical Specifications are subject to review within three years of publication to decide
whether they can be transformed into International Standards.
IEC TS 62788-5-2, which is a Technical Specification, has been prepared by IEC technical
committee 82: Solar photovoltaic energy systems.

– 4 – IEC TS 62788-5-2:2020  IEC 2020
The text of this Technical Specification is based on the following documents:
DTS Report on voting
82/1665/DTS 82/1712A/RVDTS
Full information on the voting for the approval of this Technical Specification 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.
A list of all parts in the IEC 62788 series, published under the general title Measurement
procedures for materials used in photovoltaic modules, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific publication. At this date, the publication will be
• transformed into an International standard,
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
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of its contents. Users should therefore print this document using a colour printer.

MEASUREMENT PROCEDURES FOR MATERIALS
USED IN PHOTOVOLTAIC MODULES –

Part 5-2: Edge seals –
Durability evaluation guideline

1 Scope
This part of IEC TS 62788 provides guidelines to assess the ability of an edge seal to prevent
moisture ingress from the edges of PV modules. This document does not cover frame adhesives
(sometimes colloquially referred to as edge seals) which by design do not serve to prevent
moisture ingress to a meaningful degree. Edge seals should keep moisture out, remain adhered,
and maintain electrically insulation from the environment. Much of the testing can be done on
the material level, but given the fact that there are multiple surfaces, materials interactions, and
mechanical stresses, testing on mini modules or modules is necessary. To accomplish this, this
document contains three types of test sample types, materials, mini-modules, and full-size
modules. It is intended that a quick evaluation and comparison can be made using materials
only. This would be followed up by more rigorous tests using mini-modules where all the
interfaces are correctly represented. And finally, full-size module tests are used to evaluate the
actual construction process to allow unanticipated concerns to be addressed.
This document is structured to evaluate the ability of an edge seal and the overall packaging
design to prevent moisture ingress and to provide sufficient electrical insulation according to
accepted qualification standards. It seeks to uncover inadequacies in the permeation properties
of the edge seal, electrical safety issues, or delamination resulting in moisture ingress. Here it
is implied that mini-modules and full-size modules are constructed in accordance with
IEC 61730 series This document does not attempt to evaluate the predicted service life of a
module with respect to overall performance. It is designed to determine at the material level if
the edge seal can keep moisture out, and then to uncover potential failure modes and/or
evaluate the probable effect of manufacturing changes on the performance of edge seals. Test
conditions focus on stresses likely to produce safety, moisture ingress, and debonding related
failure modes.
For the purposes of this document, an edge seal is defined as a polymeric material designed to
be placed between two impermeable (or extremely low permeability) frontsheet and backsheet
materials to restrict moisture ingress from the sides. In some cases, an encapsulant with a
diffusivity much lower than is found in polyethylene-co-vinyl acetate (EVA) may also serve the
purpose of an edge seal and may be evaluated according to this document for comparison.
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 60904 (all parts), Photovoltaic devices
IEC 61215-1:2016, Terrestrial photovoltaic (PV) modules – Design qualification and type
approval – Part 1: Test requirements
IEC 61215-2:2016, Terrestrial photov
...