IEC TS 62788-8-1:2024

Measurement procedures for materials used in photovoltaic modules - Part 8-1: Electrically conductive adhesive (ECA) - Measurement of material properties

IEC TS 62788-8-1:2024 defines test methods and datasheet reporting requirements for key characteristics of ECA used in photovoltaic modules, involving mechanical characteristics, adhesive characteristics, electrical characteristics, thermal characteristics, etc.
The object of this document is to offer a standard test procedure to ECA manufacturers for product design, production and quality control, and to PV module manufacturers for the purpose of material screening, material inspection, process control, and failure analysis.
This document is intended to be applied to ECA used in solar PV modules. For non-conductive adhesives or tapes used in PV modules, the applicable test methods except for electrical characteristics in this document may be used.

General Information

• Status: Published
• Publication Date: 10-Jun-2024
• 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: 26-Apr-2024
• Completion Date: 11-Jun-2024

Standards Content (Sample)

IEC TS 62788-8-1 ®
Edition 1.0 2024-06
TECHNICAL
SPECIFICATION
Measurement procedures for materials used in photovoltaic modules –
Part 8-1: Electrically conductive adhesive (ECA) – Measurement of material
properties
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IEC TS 62788-8-1 ®
Edition 1.0 2024-06
TECHNICAL
SPECIFICATION
Measurement procedures for materials used in photovoltaic modules –

Part 8-1: Electrically conductive adhesive (ECA) – Measurement of material

properties
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.160  ISBN 978-2-8322-8735-4

– 2 – IEC TS 62788-8-1:2024 © IEC 2024
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 8
4 Test procedures . 12
4.1 General . 12
4.2 General characteristics . 12
4.2.1 Visual inspection . 12
4.2.2 Density . 12
4.2.3 Viscosity . 13
4.2.4 Thixotropic index . 14
4.2.5 Fineness . 15
4.3 Mechanical characteristics . 16
4.3.1 Tensile strength / elongation at break . 16
4.3.2 Storage normal modulus and loss normal modulus . 19
4.4 Adhesive characteristics . 21
4.4.1 Lap shear strength . 21
4.4.2 Peel strength . 23
4.5 Electrical characteristics . 25
4.5.1 Volume resistivity . 25
4.5.2 Contact resistivity . 28
4.6 Thermal characteristics . 32
4.6.1 Coefficient of thermal expansion (CTE). 32
4.6.2 Solids content . 34
4.7 Conditions of use . 35
4.7.1 General . 35
4.7.2 Shelf life . 35
4.7.3 Pot life . 36
5 Uniform characterization form (UCF) . 37
5.1 Purpose . 37
5.2 Details of the UCF . 37
5.3 Reporting requirements . 38
6 Data sheet . 38
6.1 Purpose . 38
6.2 Details of the data sheet . 38
6.3 Reporting requirements . 39
7 Product identification sheet (label) . 39
Annex A (normative) Sampling for lap shear strength test . 40
A.1 Sampling for on-line test . 40
A.2 Sampling for off-line test . 41
Annex B (normative) Sampling for volume resistivity test . 42
Annex C (normative) Sampling of contact resistivity between silver electrode and ECA . 44
Annex D (normative) Sampling of contact resistivity between PV ribbon and ECA . 46
Annex E (informative) Estimate of deviation and elimination of outliers . 49

E.1 General . 49
E.2 Estimate of deviation . 49
E.3 Z score . 49
E.4 Outliers elimination . 49
Bibliography . 51

Figure 1 – Shape of dumb-bell test specimen (ISO 37:2017) . 16
Figure 2 – Die for dumb-bell test specimen . 16
Figure 3 – Schematic diagram of tensile strength and elongation at break test . 18
Figure 4 – Schematic diagram of modulus specimen installation . 20
Figure 5 – Schematic diagram of lap shear strength test . 22
Figure 6 – Schematic diagram of peel strength test (180° peel) . 24
Figure 7 – Schematic diagram of volume resistivity test tooling . 26
Figure 8 – Schematic diagram of volume resistivity test . 27
Figure 9 – Schematic diagram of contact resistivity test between ECA and silver

electrode . 30
Figure 10 – Schematic diagram of contact resistivity test between ECA and PV ribbon . 31
Figure 11 – LR scatter plot and linear fit curve . 31
Figure 12 – Schematic diagram of ECA life time at various stages . 35
Figure A.1 – Schematic sampling diagram of lap shear strength test (on-line) . 40
Figure A.2 – Picture of ECA on the top of the electrode of a solar cell . 40
Figure A.3 – Picture of a final specimen slice cut from the bonded assembly . 41
Figure A.4 – Schematic sampling diagram of lap shear strength test (off-line) . 41
Figure B.1 – Schematic sampling diagram of volume resistivity test . 42
Figure B.2 – Picture of a volume resistivity test specimen after curing . 43
Figure C.1 – Schematic sampling diagram of ECA and silver electrode contact
resistivity test . 44
Figure C.2 – Schematic of an EVA and electrode contact resistivity test specimen . 45
Figure D.1 – Schematic sampling diagram of ECA and PV ribbon contact resistivity test . 47
Figure D.2 – Schematic of an ECA and PV ribbon contact resistivity test specimen . 48

Table 1 – Dimensions of dies for dumb-bell test specimens . 17
Table 2 – Uniform characterization form (UCF) for an ECA . 37
Table 3 – Minimum required characteristics for the datasheet . 39
Table E.1 – Contact resistance between ECA and silver electrode . 49
Table E.2 – Contact resistance between ECA and silver electrode with z scores . 50

– 4 – IEC TS 62788-8-1:2024 © IEC 2024
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MEASUREMENT PROCEDURES FOR MATERIALS USED
IN PHOTOVOLTAIC MODULES –
Part 8-1: Electrically conductive adhesive (ECA) –
Measurement of material properties

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