Material incompatibility

Material incompatibility means that materials in the module laminate, mainly the encapsulant and the backsheet, react badly with each other or with each other's breakdown products. One example is acetic acid released when EVA encapsulant breaks down. It can corrode ribbons and cell gridlines, promote PID and delamination, and attack the backsheet. Mismatched backsheet and encapsulant pairs cause most premature backsheet failures. Backsheet cracking is the main case, and deep cracks let in moisture that leads to corrosion. Chemical reactions at the layer interfaces can also cause backsheet delamination, which shows up as bubbles, ripples or peeling layers. Delamination near the edge or the junction box is a safety risk. Additives can migrate between the encapsulant and backsheet films, causing adhesion loss, delamination or discoloration. Changing to new backsheet types, such as transparent ones, raises this risk again. These problems usually appear only after several years in the field. They are more frequent and severe in hot and humid conditions, and usually every module built from the same bill of materials is affected. To reduce exposure, choose suitable materials, prove compatibility with accelerated ageing tests, and check the IEC 61215 certificate and bill of materials. Cracked backsheets can sometimes be repaired with a coating or tape to restore insulation. Squared cracks caused by acetic acid cannot be repaired, and the modules have to be replaced.

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• sentence 1: support check: partial - Passages say materials can be incompatible with each other and with degradation by-products, with encapsulant/backsheet playing a major role, but "mainly the encapsulant and backsheet" as the definition is somewhat stronger than stated.
• sentence 3: support check: partial - Passages say incompatible combinations (with low-quality material) cause most premature degradation failures and deep cracking is followed by moisture ingress and corrosion, but not that mismatches alone cause most backsheet failures or that cracking is the main case.
• sentence 6: support check: partial - Cracks appearing after several years, hot-humid severity and whole-BOM impact are stated, but only for cracking (type III) and not the delamination/additive migration problems generally, and "usually every module" is stated for cracking only. -->