Backsheet Cracking

ID: fm:backsheet-cracking
IRI: https://solarlattice.org/kb/fm/backsheet-cracking
Status: active
Also known as: PVFS 1-5
Category: Modules

Backsheet cracking is any crack, burst or scratch in the module backsheet. It can affect only the surface or the whole layer stack. Causes include UV, thermal and mechanical stress, handling damage during transport or installation, poor-quality or mismatched materials, and local overheating from hot cells or hotspots. Cracks may be local, run along busbars or between cells, or cover the whole rear surface. Browning or bubbles may appear where a hot cell caused them. Deep cracks break the electrical insulation. This creates a safety hazard and possible ground faults, and it is worst in wet conditions. Over time, moisture that gets in through the cracks can cause corrosion and delamination, which lower power output. Confirm the failure with a visual inspection of the rear side, followed by insulation testing or wet-leakage testing. Replace modules that pose a direct safety risk or fail insulation or wet-leakage tests, and keep inspecting the modules that stay in service. To prevent it, keep ground fault detection running, check certification and the bill of materials, and inspect modules before installation.

<!-- review notes

sentence 6: support check: partial - VI and (INS) are listed as detection methods, but the passages do not specify rear-side inspection, a sequence, or wet-leakage testing as detection. -->

Claims

`affects`

c1 drafted · lead Backsheet

Quantification of Technical Risks in PV Power Systems tbl=30.r3 h=0950ed925bf5
Degradation and Failure Modes in New PV Technologies – Annex tbl=10.r3 h=8121b95d9f56
Quantification of Technical Risks in PV Power Systems tbl=30.r1 h=3f1be2072673
Degradation and Failure Modes in New PV Technologies – Annex tbl=10.r1 h=a36a38e5f761
Service Life Estimation for Photovoltaic Modules sec=h57 h=6959b882ad79

`caused_by`

c2 verified · fact UV exposure

Weak UV stabilisation of the outer layer leads to photo-oxidation and surface microcracks (type I).

Quantification of Technical Risks in PV Power Systems tbl=30.r3 h=0950ed925bf5
Degradation and Failure Modes in New PV Technologies – Annex tbl=10.r3 h=8121b95d9f56
Degradation and Failure Modes in New Photovoltaic Cell and Module Technologies sec=2.5.1 h=4dfb46bec383

verified by: joshuahamsaverified on: 2026-10-20

c3 drafted · lead Thermal cycling

Thermal cycling drives microcracks to grow into macrocracks in polyamide backsheets.

Service Life Estimation for Photovoltaic Modules sec=h57 h=6959b882ad79

c4 drafted · lead Mechanical stress

Includes external loads and internal stress built in during lamination at busbar positions, plus thermal-expansion mismatch.

Quantification of Technical Risks in PV Power Systems tbl=30.r3 h=0950ed925bf5
Degradation and Failure Modes in New PV Technologies – Annex tbl=10.r3 h=8121b95d9f56
Degradation and Failure Modes in New Photovoltaic Cell and Module Technologies sec=2.5.3 h=eb148eeff8d7

c5 drafted · lead Transport damage

Careless handling can leave local cuts and scratches.

Quantification of Technical Risks in PV Power Systems tbl=30.r3 h=0950ed925bf5
Degradation and Failure Modes in New PV Technologies – Annex tbl=10.r3 h=8121b95d9f56

c6 drafted · lead Installation error

Careless handling during installation can leave cuts and scratches.

Quantification of Technical Risks in PV Power Systems tbl=30.r3 h=0950ed925bf5
Degradation and Failure Modes in New PV Technologies – Annex tbl=10.r3 h=8121b95d9f56

c7 drafted · lead Low-quality material

For example, low UV resistance. The sources name this as a main cause of early failures.

Quantification of Technical Risks in PV Power Systems tbl=30.r3 h=0950ed925bf5
Degradation and Failure Modes in New PV Technologies – Annex tbl=10.r3 h=8121b95d9f56

c8 drafted · lead Material incompatibility

Backsheet and encapsulant that do not suit each other.

Quantification of Technical Risks in PV Power Systems tbl=30.r3 h=0950ed925bf5
Degradation and Failure Modes in New PV Technologies – Annex tbl=10.r3 h=8121b95d9f56

c9 drafted · lead Acetic acid release

Acid from EVA attacks the backsheet's inner layer between cells and weakens it (squared cracks).

Degradation and Failure Modes in New Photovoltaic Cell and Module Technologies sec=2.5.3 h=eb148eeff8d7
Service Life Estimation for Photovoltaic Modules sec=h57 h=6959b882ad79

c10 drafted · lead Humid climate

Hot, humid conditions make cracking and the damage that follows more frequent and more severe.

Quantification of Technical Risks in PV Power Systems tbl=30.r3 h=0950ed925bf5
Degradation and Failure Modes in New PV Technologies – Annex tbl=10.r3 h=8121b95d9f56

review note: support check: partial - Passages say backsheet cracking followed by moisture ingress and corrosion is more frequent and severe in hot, humid conditions. They do not clearly say humidity causes the cracking itself.

c11 verified · fact Hot cell

Local overheating from hot cells breaks down the backsheet chemically, and it then cracks locally (type II).

Degradation and Failure Modes in New Photovoltaic Cell and Module Technologies sec=2.5.2 h=5c74523d4701

verified by: joshuahamsaverified on: 2026-10-20

c12 drafted · lead Module Hotspot from Cell Damage

Hotspots or burn marks can split the backsheet or burst bubbles in it.

Quantification of Technical Risks in PV Power Systems tbl=30.r3 h=0950ed925bf5
Degradation and Failure Modes in New PV Technologies – Annex tbl=10.r3 h=8121b95d9f56
Degradation and Failure Modes in New Photovoltaic Cell and Module Technologies sec=2.5.2 h=5c74523d4701

c13 drafted · lead Backsheet Chalking

Chalking may come before cracking, but it is not a reliable predictor. Cracks also appear without chalking.

Quantification of Technical Risks in PV Power Systems tbl=30.r3 h=0950ed925bf5
Degradation and Failure Modes in New PV Technologies – Annex tbl=10.r3 h=8121b95d9f56
Degradation and Failure Modes in New Photovoltaic Cell and Module Technologies sec=2.5.1 h=4dfb46bec383

review note: support check: partial - Chalking can be a precursor and cracks occur with and without chalking, but the passages treat chalking as a photo-oxidative co-symptom, not a cause.

`presents_as`

c14 drafted · lead Visible backsheet cracks

Cracks, bursts or scratches. They can be local, run along busbars or between cells, or cover the whole surface.

Quantification of Technical Risks in PV Power Systems tbl=30.r1 h=3f1be2072673
Degradation and Failure Modes in New PV Technologies – Annex tbl=10.r1 h=a36a38e5f761
Degradation and Failure Modes in New Photovoltaic Cell and Module Technologies sec=2.5.3 h=eb148eeff8d7

c15 drafted · lead Ground fault alarm or trip

Quantification of Technical Risks in PV Power Systems tbl=30.r5 h=585ab08017de

review note: support check: partial - A broken backsheet can cause a potential ground fault, but the passages do not say it presents as an alarm or trip.

c16 verified · fact Yellow to brown discoloration

Browning often accompanies cracks caused by overheating.

Degradation and Failure Modes in New Photovoltaic Cell and Module Technologies sec=2.5.2 h=5c74523d4701

verified by: joshuahamsaverified on: 2026-10-20

c17 verified · fact Backsheet bubbles or ripples

Burst bubbles or gas formation from local overheating.

Quantification of Technical Risks in PV Power Systems tbl=30.r1 h=3f1be2072673
Degradation and Failure Modes in New PV Technologies – Annex tbl=10.r1 h=a36a38e5f761
Degradation and Failure Modes in New Photovoltaic Cell and Module Technologies sec=2.5.2 h=5c74523d4701

verified by: joshuahamsaverified on: 2026-10-20

`leads_to`

c18 drafted · lead Loss of electrical insulation

Insulation resistance can collapse when the backsheet is cracked through, especially when wet.

Degradation and Failure Modes in New Photovoltaic Cell and Module Technologies sec=2.5.3 h=eb148eeff8d7
Service Life Estimation for Photovoltaic Modules sec=h57 h=6959b882ad79
Quantification of Technical Risks in PV Power Systems tbl=30.r5 h=585ab08017de

c19 drafted · lead Delamination

Moisture gets in through the cracks.

Quantification of Technical Risks in PV Power Systems tbl=30.r5 h=585ab08017de

c20 verified · fact Severe Metallization Corrosion

Deep cracks are often followed by moisture ingress and corrosion.

Quantification of Technical Risks in PV Power Systems tbl=30.r3 h=0950ed925bf5
Degradation and Failure Modes in New PV Technologies – Annex tbl=10.r3 h=8121b95d9f56
Quantification of Technical Risks in PV Power Systems tbl=30.r5 h=585ab08017de

verified by: joshuahamsaverified on: 2026-10-20

`detected_by`

c21 drafted · lead Visual inspection

Degradation and Failure Modes in New PV Technologies – Annex tbl=10.r2 h=4b331eae91fd
Quantification of Technical Risks in PV Power Systems tbl=30.r2 h=ba8af336477f
Quantification of Technical Risks in PV Power Systems tbl=8 h=88163ae58405

c22 drafted · lead Insulation resistance testing

Degradation and Failure Modes in New PV Technologies – Annex tbl=10.r2 h=4b331eae91fd
Quantification of Technical Risks in PV Power Systems tbl=30.r2 h=ba8af336477f
Quantification of Technical Risks in PV Power Systems tbl=8 h=88163ae58405
Degradation and Failure Modes in New PV Technologies – Annex tbl=10.r8 h=b5b29b444147
Quantification of Technical Risks in PV Power Systems tbl=30.r8 h=cf377b6ef813

c23 drafted · lead Wet leakage current test

Degradation and Failure Modes in New PV Technologies – Annex tbl=10.r8 h=b5b29b444147
Quantification of Technical Risks in PV Power Systems tbl=30.r8 h=cf377b6ef813

review note: support check: partial - Wet-leakage test is mentioned only as a criterion for module replacement, not explicitly as a detection method.

c24 drafted · lead Optical profilometry

A research method that used machine learning on surface scans. It found cracks before they could be seen.

Service Life Estimation for Photovoltaic Modules sec=h57 h=6959b882ad79

`mitigated_by`

c25 drafted · lead Module replacement

Replace modules with a direct safety risk or that fail insulation or wet-leakage tests. Squared cracks require replacing every module with the same BOM.