Beyond the Flat Surface: The Art and Science of Void-Free Lamination for Shingled Solar Modules

Imagine looking at a beautifully tiled roof. From a distance, it appears as a single, uniform surface. But up close, you see the intricate overlaps and small gaps that give it structure and strength. The design of a shingled solar module is surprisingly similar. While it boasts higher power density by overlapping cells, this clever design introduces a hidden challenge—a complex, uneven landscape that standard manufacturing processes can’t handle.

Getting the lamination right for these modules isn’t just a quality check; it’s the difference between a high-performance asset and a panel destined for premature failure. The secret lies in understanding the delicate dance between encapsulant material, vacuum, and pressure.

The Shingled Challenge: A Problem of Hills and Valleys

In a traditional solar module, solar cells sit side-by-side with small, uniform gaps between them. The lamination process is relatively straightforward: place the materials, pull a vacuum to remove air, and then apply heat and pressure to bond everything together.

Shingled modules, however, break this flat-plane rule. By overlapping cells to eliminate the need for busbars and maximize the active surface area, the design creates a series of tiny steps. These overlaps aren’t just a visual quirk; they are a critical process challenge, creating a network of microscopic hills and valleys across the entire module.

Specifically, these overlaps create inter-cell gaps that are approximately 0.5 to 1.5 mm deep. During lamination, the encapsulant material—typically a polymer like EVA or POE—must flow into every one of these gaps to create a solid, weatherproof seal. If it fails, you’re left with trapped air: the enemy of module reliability.

The Lamination Trap: Why Standard Processes Create Hidden Flaws

You might think that applying a strong vacuum would simply suck all the air out. But it’s not that simple. The problem boils down to timing and physics.

A standard single-stage vacuum process often traps air pockets in these gaps because the encapsulant seals the edges before the air can be evacuated. Think of it like trying to put a lid on a container of water too quickly; you trap air bubbles inside. In a laminator, the encapsulant around the high points of the shingled cells melts and seals first, creating a „lid“ over the deeper gaps and trapping the air within.

These trapped air bubbles, or „voids,“ are far more than cosmetic defects. They are ticking time bombs that can lead to catastrophic failures:

• Delamination: Air and moisture in the voids can expand and contract with temperature changes, eventually pushing the layers of the module apart.
• Hotspots: Voids act as insulators, preventing heat from dissipating properly. This can create localized hotspots that degrade the cells and reduce performance.
• Moisture Ingress: A void can provide a pathway for moisture to seep into the module, causing corrosion and short circuits.

The consequences are severe. Research has shown that such flaws, especially those allowing moisture ingress, can reduce a module’s lifetime by over 50%.

The Solution: A Multi-Stage „Breathing“ Process

So, how do you get the air out before sealing it in? The answer is to move away from a simple „on/off“ vacuum process and adopt a more intelligent, multi-stage approach. You have to give the module time to breathe.

This involves creating a sophisticated lamination recipe that carefully controls vacuum and pressure in stages, working in sync with the melting behavior of the encapsulant.

As Patrick Thoma, PV Process Specialist at PVTestLab, states: „The key is controlling the viscosity curve of the encapsulant against the vacuum profile. We need the air out before the material flows, but we also need enough flow to fill the void completely without stressing the delicate cell connections.“

This advanced technique works by:

1. A Gentle First Vacuum Stage: A moderate vacuum is initially applied, allowing the majority of the air to escape from the large spaces in the lamination chamber and from within the module stack itself.
2. A Deep Second Vacuum Stage: As the encapsulant begins to soften but before it fully liquefies, the vacuum is pulled deeper. This „lures“ the stubborn, trapped air out of the tiny shingled gaps before the escape routes are sealed off.
3. Controlled Pressure Application: Only after the air has been fully evacuated is pressure applied to ensure the now-liquid encapsulant flows into every crevice, creating a perfect, void-free bond.

The results of this methodical approach are dramatic. Data from our own process optimization trials show that a two-stage vacuum followed by a controlled pressure ramp-up reduces void formation in shingled modules by over 95% compared to standard processes. This demonstrates how deep process knowledge transforms a manufacturing step into a competitive advantage.

It’s Not Just About the Recipe

Achieving a perfect, void-free result requires more than just a good vacuum profile. The choice of encapsulant, the specific geometry of the cell overlap, and even ambient climate conditions all play a role. That’s why comprehensive material testing & lamination trials are essential to fine-tune the process for a specific module design.

By understanding the unique properties of each material, engineers can create a tailored lamination recipe that produces robust, reliable, and high-performance modules. This foundational work is a critical part of any successful Prototyping & Module Development program.

Frequently Asked Questions (FAQ)

What exactly is a shingled solar module?

A shingled solar module is a design where solar cells are sliced into strips and then overlapped, like shingles on a roof. This method eliminates the need for ribbon interconnects on the cell front, reducing resistive losses and increasing the active solar-collecting area of the module, which boosts overall efficiency.

What is an encapsulant?

An encapsulant is a polymer material (commonly Ethylene Vinyl Acetate – EVA, or Polyolefin Elastomer – POE) used in solar modules. Its job is to bond the solar cells, glass, and backsheet together, provide electrical insulation, and protect the cells from moisture, vibration, and impact for decades.

Why are air voids so bad for a solar panel?

Air voids are small pockets of trapped air within the module’s layers. They are harmful for three main reasons:

1. They can trap moisture, which leads to corrosion.
2. They act as insulators, leading to hotspots that can permanently damage cells.
3. They create weak points where the layers can separate (delaminate) under thermal stress.

Can’t you just use more pressure to force the air out?

Unfortunately, no. Applying excessive pressure creates its own set of problems, including cracking the ultra-thin solar cells or inducing mechanical stress on the delicate electrical connections between the shingled strips. The solution is finesse, not force—removing the air first, then applying just enough pressure for a perfect bond.

From Theory to Production

The transition to high-efficiency designs like shingled cell modules is an exciting leap forward for the solar industry. However, it also underscores that innovation in module design must be met with equal innovation in process engineering.

Understanding the fundamental challenge—the microscopic topography of shingled cells—is the first step. The next is to apply a scientific, data-driven approach to developing a lamination process that can overcome it. By mastering this crucial step, manufacturers can unlock the full potential of shingled technology, delivering modules that are not only more powerful but also built to last.