Practical cases of photovoltaic EVA hot melt adhesive film used for module packaging

As a key material for solar module packaging, photovoltaic EVA hot melt adhesive film has been used in a large number of mature cases in practical applications. In the classic structure of crystalline silicon modules, a layer of EVA adhesive film is laid between the glass and the cells and between the cells and the backplane. After entering the laminator, the air is first evacuated and then heated to about 145 degrees Celsius. The adhesive film melts and flows to fill the gap between the cells and the ribbon, and is then cross-linked and solidified to firmly bond the glass, cells, and backplane into a whole. It also plays the role of water blocking, insulation, UV resistance, and optical coupling.

In a large-scale ground power station project in northwest China, modules with a glass backplate structure were exposed to strong ultraviolet rays, large temperature differences, and sandstorms for a long time. After several years of operation, random inspections showed that the cross-linking degree of the EVA encapsulation layer was still over 80%, the degree of yellowing was slight, and the annual power attenuation of the module was less than 0.5%, verifying the long-term reliability of the packaging. In the Yuguang Complementary Power Station on the southeast coast, the high humidity and salt spray environment has strict requirements on resistance to potential-induced attenuation. After selecting the anti-PID EVA film, the module successfully passed the 1,000-hour damp heat test at 85 degrees Celsius and a relative humidity of 85%, 200 thermal cycle tests and ultraviolet radiation pretreatment tests. There were no bubbles or delamination between the layers, and the peeling strength between the film and the glass remained above 40 Newtons per centimeter.

In terms of process practice, a production line adopts a segmented lamination scheme. It first evacuates at about 60 degrees Celsius for five minutes, then heats up and pressurizes for more than ten minutes. After the board is released, the xylene extraction method is used to measure the cross-linking degree. The batch data is stable between 75% and 90%. The product appearance and electrical performance meet the acceptance requirements of the power station. In addition, double-glass modules also use a combination of EVA and POE through co-extrusion, taking into account both bonding strength and water vapor barrier properties, and have been promoted in large-scale power stations. These cases fully demonstrate that EVA hot-melt adhesive film has become one of the most widely used hot-melt materials in the field of component packaging due to its light transmittance of more than 91%, good melt fluidity and stable cross-linking properties.