A module can look flawless coming off the laminator and still carry a defect invisible to the naked eye — a trapped pocket of air between the layers that will concentrate heat and stress for the next 25 years.

What a Bubble Void Actually Is

A crystalline silicon module fuses glass, EVA encapsulant, cells, a second encapsulant layer, and backsheet together under heat and vacuum during lamination. A bubble void forms when gas or air gets trapped between those layers during that process — sometimes visible as a “blister,” sometimes microscopic and only detectable through imaging. Either way, a void is a point of zero adhesion: a structural weak spot where moisture accumulates and thermal stress concentrates for the rest of the module’s service life.

Where Voids Actually Come From

Inadequate vacuum cycles are the most direct cause — insufficient vacuum pressure or too-short dwell time before pressure application leaves air pockets trapped, a risk that grows on high-speed lines where cycle time gets aggressively compressed. Adhesive outgassing compounds this: EVA cross-linking releases chemical by-products, and if temperature or ramp rate is too aggressive, those by-products turn gaseous faster than the vacuum system can clear them. Surface contamination and residual moisture on cells or backsheet turn to steam under lamination heat, and oils or dust from earlier manufacturing steps prevent uniform wetting, leaving gaps that become voids. Improper material storage plays a quieter role — EVA is hygroscopic and absorbs ambient moisture if not kept climate-controlled, and encapsulant rolls that haven’t acclimated to cleanroom temperature create cold spots that cause uneven melting and trapped air.

Why a Few Small Bubbles Actually Matter

Voids change local thermal conductivity, preventing heat dissipation over a cell and creating hotspots capable of permanently damaging the cell or even scorching the backsheet. As a zero-adhesion site, a void expands under ordinary thermal cycling into large-scale delamination. Voids also serve as ready-made moisture pathways to metallic interconnects and busbars, accelerating oxidation and raising resistance. And by compromising encapsulant insulation locally, voids contribute to leakage current and Potential Induced Degradation, accelerating field power loss well beyond what the void’s physical size would suggest.

Adhesive Chemistry That Reduces Void Risk

Polyolefin elastomers (POE) are gaining share over traditional EVA for high-efficiency PERC and bifacial cells partly because of lower water vapor transmission and no acetic-acid byproduct, but also because POE formulations are increasingly engineered with flow characteristics that displace air more effectively during the early stages of lamination. Low-outgassing encapsulant grades are designed to complete cross-linking without releasing large volumes of volatile compounds, directly reducing the load on the vacuum system and the odds of process-induced bubbles. At the module edge — the most moisture-vulnerable location — UV-curable sealants reach full strength in seconds rather than through a slow thermal cure, preventing the layer-shifting that can introduce air into the perimeter seal; thixotropic formulations stay exactly where applied rather than running into gaps. For junction-box bonding specifically, pressure-sensitive adhesives or structural tapes avoid the voiding that liquid silicones can develop during their longer atmospheric moisture-cure window, and comparing cure speed between UV-cure adhesive and epoxy is worth reviewing when a slow-curing chemistry is itself contributing to void formation. Email Us for guidance selecting a low-outgassing encapsulant or edge-sealant chemistry for a specific lamination line.

Process Parameters Worth Auditing

Vacuum should be pulled to at least 1 mbar before the heating plate contacts the laminate — cutting this phase short to save cycle time is a common but avoidable cause of trapped air. The transition from vacuum to pressure needs to be gradual rather than a sudden diaphragm “slam,” which can trap air pockets before they migrate to the edges. Regular temperature mapping across laminator platens catches cold spots that cause localized poor flow and bubble formation before they show up as a yield problem. Plasma or corona surface-activation treatment ahead of lamination cleans surfaces at a molecular level and raises surface energy, letting encapsulant spread more evenly and displace air more completely — particularly valuable with newer low-surface-energy backsheet materials. Environmental control matters just as much as the lamination recipe itself: encapsulant should live in a dry room and reach the line only in quantities needed for immediate use, and automated lay-up stations reduce the human-error nucleation points — fingerprints, stray hair — that bubbles tend to form around.

Finding Voids Before They Reach the Field

Electroluminescence imaging remains the standard defect-detection method, and while it’s best known for cracked cells, it also reveals poor contact and delamination from larger voids as dark irregularities in the emitted infrared pattern. Ultrasonic scanning, more common on high-end or aerospace-grade arrays, maps laminate density directly and catches even small air gaps between glass and encapsulant. Internal accelerated-aging testing matters as much as certification testing — if bubbles appear after 1,000 hours of damp heat testing (85°C / 85% humidity) per IEC 61215, that’s a sign the adhesive system or lamination process was already marginal even though the module looked perfect leaving the factory.

Where This Gets Harder

Thinner silicon wafers and flexible thin-film modules on plastic substrates are inherently more susceptible to moisture-driven voiding than rigid glass modules. Glass-glass construction, while eliminating backsheet-related failure modes, raises the stakes on getting vacuum and outgassing stages right in the first place — trapped gas inside an impermeable glass-glass sandwich has no path to escape the way it might through a traditional backsheet. Real-time sensor-equipped “smart” laminators that detect and correct for air pockets during the vacuum cycle itself represent the next step manufacturers are exploring to get ahead of this problem.

Conclusion

Bubble voids are a manufacturing-process defect with decades-long consequences, not a cosmetic imperfection, and eliminating them comes down to disciplined vacuum-cycle control, surface activation, and adhesive chemistry working together rather than any single fix. Incure’s low-outgassing encapsulant-compatible and UV-curable edge-sealing adhesives are formulated to minimize gas entrapment during PV lamination. Contact Our Team to review adhesive selection or lamination process parameters for your production line.

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