The Technical Secrets of EVA and Back Sheet Cutting and Laying

In photovoltaic module manufacturing, the cutting and laying processes for EVA adhesive film and back sheet materials function like precision gears meshing together, directly determining the module's power generation efficiency, durability, and safety. This article analyzes the technical essentials of these two core processes. 

I. EVA Cutting and Laying: The “Optical Heart” of Modules

Material Properties Determine Process Precision

EVA film must maintain a stable light transmittance above 91% while retaining elasticity across temperatures from -40°C to 85°C. Fully automated cutting equipment employs laser positioning and tension control systems to limit errors within ±0.5mm, preventing bubbles during lamination. 

The “Sandwich Principle” of Layering

The lamination process follows the “glass-EVA-cell-EVA-back sheet” structure, with key technical points including:

• Temperature Control: EVA must be preheated to 60-70°C before lamination to soften and expel air

•    Tension Balancing: Servo-motor driven layering devices maintain tension fluctuations <0.5N/m

•    Positioning Accuracy: CCD vision systems achieve millimeter-level alignment between cells and EVA

II. Back Sheet Cutting: The Module's “Protective Armor”

The Technical Trade-offs in Material Selection

The back sheet must balance insulation properties, weather resistance, and adhesive strength. Mainstream solutions include:

• TPT Structure: Fluoropolymer film/PET/fluoropolymer film triple-layer composite, with UV aging resistance up to 25 years

• KPK Structure: Polyester film partially replaces fluoropolymer film, reducing costs by 30% but shortening lifespan to 15 years

• Coated Backsheet: SiO₂ anti-reflective coating boosts light transmittance by 2%, but requires additional dust removal processes

Sheeting cutting parameters must be adjusted based on material properties: fluorinated backsheets require low-temperature cutting blades (≤80°C) to prevent fluoropolymer film brittleness, while coated backsheets necessitate control of nanoparticle contamination.

Industrial Impact of Cutting Precision

Industry standards mandate the following backsheet dimensional tolerances:

• Length/width deviation: ±1mm (standard modules), ±0.5mm (bifacial modules)

• Diagonal deviation: ≤2mm

• Edge burr height: <0.1mm

III. Process Synergy: From Individual Machine Optimization to System Integration

Equipment Interlocking Control Technology

MES system enables real-time data exchange between EVA/backing sheet cutting and laying equipment:

• Cutting machines automatically adjust feed speed based on laminator cycle times

• Laying stations dynamically compensate for tension fluctuations via force feedback sensors

• In-line vision inspection systems assess cutting edge quality

Environmental Control System

Cleanliness and temperature/humidity management are critical for process stability:

• Cutting workshop maintains Class 100,000 cleanliness to prevent dust adhesion

• Laying area humidity controlled at 30%-50% RH to avoid EVA moisture absorption

• Vacuum pre-de-gassing before lamination reduces residual air content <0.1%

Inadequate environmental control can increase module EL defect rates by 2-3 times.

IV. Technological Evolution Directions

Intelligent Upgrades

AI vision inspection systems are replacing manual sampling inspections, capable of identifying cutting defects as small as 0.02mm. 

Material Innovation

POE film exhibits a volume resistivity three orders of magnitude higher than EVA, effectively mitigating PID effects. Biodegradable backsheet materials have entered pilot-scale testing, offering a potential solution to fluoropolymer film environmental pollution.

Process Integration

Integrated “cutting-laying-lamination” equipment reduces breakage rates by minimizing material handling distances.