You’ve done everything right. The materials are top-grade, the layup is perfect, and the lamination cycle completes without a hitch. But when the module cools, you see them: tiny, frustrating bubbles trapped near the ribbons or scattered under the backsheet.

It’s a common problem that leaves even experienced teams scratching their heads. Most assume the vacuum pump didn’t pull out all the air. But what if the real culprit isn’t the air you’re trying to remove, but the gases you didn’t even know were there?

The truth is, your lamination chamber is the stage for a hidden race—a race between removing air, evacuating material gases, and the encapsulant melting. Winning this race is the key to a flawless, bubble-free module.

THE HIDDEN CULPRIT: WHEN YOUR MATERIALS START TO „BREATHE“

Before a single bubble forms, a process called „outgassing“ begins. Think of it as the materials themselves exhaling. The EVA encapsulant and polymer backsheets used in your module stack contain trapped volatile compounds from their manufacturing process. As the laminator heats up, these compounds turn into gas.

Here’s the critical insight from our process research: this outgassing often starts aggressively around 80°C, long before the lamination chamber reaches its peak temperature of 140-150°C.

At this early stage, the EVA is still softening. It hasn’t fully melted or cross-linked. This creates a crucial, but often missed, window of opportunity. If you can remove these volatiles before the EVA becomes a liquid barrier, you prevent them from being trapped forever. Miss this window, and the molten encapsulant seals them in. As the temperature continues to rise, these trapped gases expand and form bubbles.

THE VACUUM PUMP-DOWN: A TALE OF TWO JOBS

This is where we need to rethink the role of the vacuum in the solar module lamination process. Its job isn’t just to remove the atmospheric air from the chamber. It has a second, more delicate task: to gently coax out the volatiles released during outgassing.

A standard, single-step vacuum process—where the pump simply goes to maximum power as quickly as possible—is great for removing air. However, it’s terrible for managing outgassing. Pulling a hard vacuum too quickly can cause the EVA to melt and seal the edges of the module before the inner materials have had a chance to release their trapped gases.

This is why an optimized process uses a multi-step vacuum curve.

Let’s break down the optimized curve (Curve B) in the graph:

1. Initial Fast Pump-Down: This first phase removes the bulk of the air from the chamber. It happens quickly, while the module is still relatively cool.

2. The „Outgassing Plateau“: This is the magic step. Here, the vacuum is held at an intermediate level for a specific duration while the temperature rises into the 80-110°C range where outgassing is most active. This plateau creates the perfect conditions for volatiles from the EVA and backsheet to escape the stack before the encapsulant flows and seals them in.

3. Final Pump-Down: Once the outgassing phase is complete, the vacuum is pulled down to its final, low level to remove any remaining air and ensure a tight, void-free bond as the module cures.

This intelligent, profiled approach works with the material physics, not against it.

WHY YOUR MATERIAL STACK CHANGES EVERYTHING

So, is there one perfect vacuum curve that works for every module? Absolutely not.

Every component in your module has a unique outgassing signature. A new brand of EVA, a different backsheet supplier, or even a novel type of anti-reflective coating on the glass can completely change the outgassing dynamics. The recipe that produced perfect modules yesterday might create a bubbly mess today simply because one material was swapped out.

This is why successful innovation requires thorough material compatibility testing. By analyzing how a specific bill of materials (BOM) behaves under real industrial conditions, we can define a precise vacuum and temperature recipe tailored to that exact stack.

„Many labs can test a material’s properties in isolation. The real challenge is understanding how it behaves in a complete system, interacting with other materials under dynamic heat and pressure. That’s the gap we close.“
— Patrick Thoma, PV Process Specialist

Running controlled experiments in a full-scale R&D environment allows you to measure the outgassing profile and build a lamination recipe that ensures reliability from the very first prototype.

THE COST OF GETTING IT WRONG (AND THE PAYOFF OF GETTING IT RIGHT)

Lamination bubbles aren’t just a cosmetic flaw. They are pockets of failure waiting to happen. These voids can lead to:

• Delamination: The layers of the module separate over time.
• Moisture Ingress: Water vapor can penetrate the module, causing corrosion and power loss.
• Reduced Module Lifespan: The physical stress from trapped gas can degrade materials and lead to premature failure.
• Warranty Claims: Field failures are expensive, not just financially but also to a brand’s reputation.

Conversely, a properly optimized lamination process delivers more than just a perfect-looking module. It builds in long-term reliability, ensures bankability, and gives you the process control to confidently scale production or develop new solar module concepts with novel materials.

YOUR LAMINATION QUESTIONS, ANSWERED

What exactly are the „volatiles“ in outgassing?

They are chemical residues left over from the polymer manufacturing process. In EVA, for example, the curing process can release byproducts like acetic acid. These are the substances that turn into gas when heated inside the laminator.

Can’t I just use a stronger vacuum pump to solve the problem?

A stronger pump might remove air faster, but it won’t solve the outgassing issue. The problem isn’t the final vacuum level; it’s the timing of the vacuum relative to the material’s heating and outgassing rate. A brute-force approach often makes the problem worse by sealing the module perimeter too early.

At what temperature does outgassing become a problem?

Our applied research shows significant outgassing begins around 80°C for many common EVA and backsheet materials. This is well below the final lamination temperature, which is why a process that only considers the peak temperature will always miss the critical outgassing window.

How do I find the right vacuum curve for my materials?

The only reliable way is through systematic, data-driven testing. By building prototype modules with your specific material stack and using sensors to monitor the process, you can map the outgassing behavior and engineer the ideal vacuum curve. This involves creating and testing different recipes until bubble formation is eliminated and adhesion is maximized.

FROM BUBBLES TO BREAKTHROUGHS

The next time you see a bubble in a solar module, don’t just think „trapped air.“ Think „missed opportunity.“ That bubble is a sign that the lamination process wasn’t synchronized with the material’s natural behavior.

By understanding the delicate dance between temperature, outgassing, and vacuum, you can transform your lamination process from a source of frustration into a competitive advantage. It’s about moving beyond standard recipes and into the realm of precision process engineering—where every module is a perfect expression of its design.