JCC Solar Encapsulation Film JCC-105W (white EVA Film)

JCC Solar Encapsulation Film JCC-105W is a white ethylene-vinyl acetate (EVA) encapsulant film formulated for rear-side lamination in crystalline silicon photovoltaic modules. The product is manufactured as a thermosetting single-layer film with a nominal thickness range of 0.40 mm to 0.60 mm and a roll-face width tolerance of ±2 mm. The filler package that produces the white appearance is dispersed without reducing crosslink density below the lamination specification; gel content after cure is specified at ≥75% by ASTM D2765-16. The melt mass-flow rate is controlled between 15 g/10 min and 35 g/10 min at 190 °C/2.16 kg under ISO 1133-1:2022. JCC-105W is intended for use in vacuum lamination at platen temperatures from 145 °C to 155 °C, with dwell times of 8 min to 18 min depending on module stack thermal mass. This grade differs from transparent EVA in that it is positioned behind the cell string to reflect light from the inter-cell gap back into the active cell aperture, whereas transparent EVA is used for front-side optical transmission. Compared with polyolefin elastomer encapsulants, JCC-105W retains conventional EVA processability but requires the same acetic acid management and corrosion mitigation measures as other EVA formulations.

How does white EVA alter rear-side optical collection in a laminated module?

The primary function of JCC-105W is not transmissive but reflective. The film reflects the portion of light that passes through the front glass, anti-reflective coating, cell-gap spacing, and ribbon-free regions. The reflected component is scattered internally at the rear interface and can be collected by total internal reflection at the front surface or by adjacent cell edges. The total hemispherical reflectance of white EVA measured over the 400 nm to 700 nm band by ASTM E1331-15 typically falls between 88% and 94%. This value is substantially higher than that of transparent EVA, which shows a reflectance below 10% in the same configuration and relies on the backsheet or cell metallization for rear reflection. For modules with 2.0 mm cell spacing and 1.5 mm cell-to-laminate edge offset, the white rear-side layer can contribute a module power gain of 0.5% to 2.0% relative to transparent EVA when measured by current-voltage curve correction to standard test conditions under IEC 60904-1:2020 and ASTM G173-03. The effect is negligible behind fully metallized active cell areas because the white layer is covered by the cell, but it remains relevant for gap-light recovery and for light reflected from the backsheet at high incidence angles.

Rheology, cure state, and adhesion parameters

During lamination, JCC-105W passes through a melt-flow phase followed by peroxide-initiated crosslinking. The melt mass-flow rate is specified at 15 g/10 min to 35 g/10 min under ISO 1133-1:2022. In a three-chamber vacuum laminator operating at a membrane pressure of 0.10 MPa ±0.02 MPa and a platen setpoint of 150 °C, the film reaches a viscosity sufficiently low to fill cell gaps and busbar topography before the gel point is reached. The gel point, defined by a gel content of 50% to 60% under ASTM D2765-16, is typically reached after 3 min to 5 min at 150 °C; the final gel content after a full cure cycle is ≥75%. Adhesion to glass and backsheet is a released variable that depends on the silane primer package and laminate cool-down profile. Peel adhesion to soda-lime glass, tested by ASTM D903-98 at 180° peel and 100 mm/min, is specified at ≥50 N/cm for glass-side laminates after cure. Backsheet adhesion is lower for fluoropolymer backsheets unless a corona or plasma pre-treatment is applied; for polyester-based backsheets, values of 40 N/cm to 60 N/cm are typical. The white filler increases melt viscosity relative to unfilled transparent EVA at the same vinyl acetate content, which reduces edge outflow but also increases the risk of bubble entrapment if the cold pre-cure dwell is shortened below 2 min.

In production-scale layup systems, roll unwinding of JCC-105W at room temperature below 18 °C can produce telescoping and intermittent film curl on semi-automatic cutting tables. The problem is caused by the differential contraction of the white filler-loaded layer compared with the unmodified EVA matrix after slitting. Conditioning the roll at 23 °C ±2 °C and 40% to 60% relative humidity for 12 h before slitting reduces curl-related misalignment in automatic layup. Moisture uptake remains a processing boundary: exposed film at relative humidity above 60% for more than 4 h should be dried at 60 °C for 4 h before lamination to avoid bubble formation and edge delamination after damp-heat exposure. The film is supplied with a polyethylene release liner that must be removed before layup without folding the cut sheet; folded sheets recover some flatness only at 25 °C and cannot be re-flattened by rolling pressure alone.

When white EVA is combined with transparent backsheets or bifacial glass

The use of a white rear-side encapsulant behind the cell plane is not limited to opaque backsheet modules. In monofacial glass-glass configurations, JCC-105W can be positioned between the cell string and the rear transparent backsheet or glass to increase rear-internal reflectance while retaining some rear transmittance for bifacial operation. The rear-side irradiance gain in bifacial modules is reduced by the rear layer of white EVA because the white film scatters incident rear light before it reaches the cell rear surface. Published data for this specific configuration is limited; module manufacturers typically evaluate the trade-off by measuring rear-side power gain at irradiance levels of 100 W/m², 200 W/m², and 400 W/m² with a rear-side albedo of 0.3 and determining the optimum gap between cell strings. In transparent backsheet modules, white EVA can substitute for a white backsheet in the gap region while retaining a transparent backsheet for rear-side visual inspection, but the total rear-side reflectance is lower than that of a full white backsheet. The selection of JCC-105W therefore depends on the ratio of cell-gap area to active cell area and on the required rear-side transmittance for bifacial power gain. For monofacial modules with glass/backsheet stacks, the white film is used over the full rear side; in bifacial glass-glass stacks, it is commonly pattern-cut to expose the cell areas or replaced by transparent EVA with a white scattering grid.

The following table summarizes the property set required for inward inspection of JCC-105W. The values are consolidated from public encapsulation film data sheets and standard test conditions; they are not a substitute for the manufacturer’s certified certificate of analysis.

Compared with transparent EVA, the JCC-105W formulation has a higher melt viscosity at the same platen temperature because the white filler particles restrict molecular mobility during the flow phase. This reduces the probability of adhesive bleed into the cell busbar region, but it also narrows the processing window for complete wet-out of textured glass and backsheet primer layers. In contrast, transparent EVA exhibits lower viscosity and is more tolerant of fast pump-down cycles. The white filler also increases the modulus of the cured film from approximately 4–6 MPa for transparent EVA to approximately 7–10 MPa at 25 °C when measured by dynamic mechanical analysis; this affects thermo-mechanical stress transfer during thermal cycling. The difference from polyolefin elastomer encapsulants is more pronounced: polyolefin grades generally absorb less moisture than EVA when tested by ASTM D570-22, and they often require lamination temperatures 10 °C to 20 °C higher than EVA depending on octene content, while showing different silane-adhesion behavior with glass and polyamide backsheets. Black EVA encapsulates the same resin system as transparent EVA but incorporates carbon black, which absorbs rather than scatters light; it is used only where module aesthetics or backsheet hiding is required, not for gap-light recovery.

Damp-heat aging, acetic acid output, and corrosion of cell metallization are controlled by cure state and glass transition

Because JCC-105W is an EVA-based encapsulant, it undergoes hydrolytic deacetylation under elevated temperature and humidity. The acetic acid generation rate increases when the vinyl acetate content is high and when the laminate is insufficiently crosslinked. The minimum gel content of 75% specified by ASTM D2765-16 is therefore not a cosmetic requirement; it is the primary control against excessive free acetate mobility. Laminates with gel content below 70% show higher acetic acid concentrations after damp-heat aging at 85 °C and 85% relative humidity for 1000 h under IEC 61215-2:2021 MQT 13, and accelerated cell finger corrosion has been observed in such undercured laminates when combined with silver paste that is not corrosion-stabilized. The white filler can influence the acetic acid pathway by adsorbing moisture at the filler-polymer interface. Published data for this specific grade is limited; however, film suppliers generally recommend rear-side EVA with a gel content above 75% and measurement of wet leakage current on the finished module rather than on the film alone. JCC-105W should be tested on the actual module stack with the selected backsheet and the selected cell metallization because acetic acid concentration is a system property, not an encapsulant-only property. The product is also expected to maintain dielectric strength sufficient for the end-module requirements of IEC 61730-1:2023, but certification must be completed on the finished module, not on the film alone.

Storage life is defined by the manufacturer as 6 months from delivery when stored in original unopened polyethylene-aluminum barrier bags at 25 °C or below. Once the barrier bag is opened, the film should be used within 3 days if the layup room humidity exceeds 60%, or within 7 days if humidity is controlled below 40%. Partially used rolls should be resealed with desiccant and placed in a horizontal cradle to prevent radial creep. Cold rolls must not be placed directly into a warm layup room because condensation on the release liner transfers to the film surface and causes microbubbles at the glass interface. The film should not be stored near open containers of silanes, peroxides, or solvent-based cleaning agents because the plasticizer-free EVA surface can absorb volatile organics and develop localized adhesion failure.

Controlling filler dispersion and optical uniformity during cast-film extrusion

Filler dispersion in white EVA is a direct determinant of reflectance and localized adhesion. Agglomerates larger than 20 µm produce visible white specks and can reduce peel strength because the filler particle acts as a stress concentrator at the glass interface. Film production for JCC-105W is typically performed on a cast-film line with a single-screw extruder L/D ratio of 30:1 or higher and melt filtration through a 100 µm or finer screen pack. The filler is pre-dispersed into the EVA carrier resin before final extrusion; poor dispersion in this masterbatch stage cannot be corrected by downstream melt pumping alone. Optical uniformity is inspected by transmitted-light vision systems, and film with a gray-level variation greater than 2.0% across the web is rejected because it indicates filler migration or non-uniform thickness. For module makers, incoming inspection should include a 45° incident light check for surface haze defects and a thickness profile measurement across the roll using an automated capacitance gauge. Variations greater than ±0.03 mm across a 200 mm span can produce local undercure in the thick regions and overcure in the thin regions, leading to non-uniform gel content and a higher risk of post-lamination delamination.

For supply into the European Economic Area, JCC-105W is accompanied by a REACH statement of compliance under Regulation (EC) No 1907/2006 and a Restriction of Hazardous Substances declaration under 2011/65/EU Annex II. The film is not intended for food-contact applications and does not carry a FDA 21 CFR 177.1520 olefin polymer clearance. For module manufacturers, the film must still be assessed in the finished article under the Waste Electrical and Electronic Equipment Directive and the EU EcoDesign requirements for photovoltaic modules, where applicable.