The Hidden Threat in Your Solar Module: Finding Voids Around Custom Interconnectors

You’ve done it. After months of development, your new solar module design is ready. It features advanced shingled cells or intricate multi-wire interconnectors, all designed to push efficiency to its limits. The initial prototypes look perfect, pass standard electroluminescence (EL) tests with flying colors, and you’re ready to scale.

But six months later, field tests show unexpected degradation. Performance is dipping, and reliability is in question. The cause? A saboteur invisible to the naked eye: microscopic voids, or air bubbles, trapped deep within the module laminate, right next to those innovative interconnectors.

This scenario is becoming all too common as module technology advances. The very designs that boost performance also create new manufacturing challenges—and finding these hidden flaws requires looking at your modules in a whole new way.

Why Modern Interconnectors Create New Headaches

For years, solar cell interconnectors were relatively simple: flat ribbons. They were predictable and easy to encapsulate. Today, in the race for higher efficiency, we have moved toward far more complex geometries:

• Multi-Busbar (MBB) and Wire-Based Interconnectors: Instead of a few flat ribbons, these use numerous thin, round wires. This reduces resistive losses but creates a complex, bumpy surface.
• Shingled Cells: Overlapping cells eliminate the need for traditional ribbons but create step-like changes in topography.

These new designs are brilliant for capturing more sunlight, but they make life difficult for the encapsulant material (like EVA or POE) during lamination.

The fundamental job of lamination is to use heat and pressure to melt the encapsulant, letting it flow into every nook and cranny and forcing all the air out. With a simple, flat ribbon, this is straightforward. But the uneven surfaces of modern interconnectors create tiny hills and valleys where air can easily get trapped. If the lamination process isn’t perfectly tuned, the encapsulant can flow around these features too quickly, sealing off escape routes for air and forming voids.

These voids are more than just cosmetic imperfections. Research shows they act as catalysts for long-term module failure. Trapped air or moisture expands and contracts with temperature changes, creating stress that leads to delamination. Voids also reduce the amount of light reaching the cell, directly impacting power output.

Seeing the Unseen: Using Acoustic Microscopy to Find Voids

So if you can’t see these voids with standard visual or EL inspection, how do you find them before they cause problems? The answer lies in listening, not looking.

Scanning Acoustic Microscopy (SAM) is a powerful, non-destructive technique that uses high-frequency sound waves to create an image of what’s inside a solid object. Think of it like a medical ultrasound for your solar module.

Here’s how it works in simple terms:

1. A scanner sends a pulse of sound into the module.
2. The sound wave travels through the layers: glass, encapsulant, and cell.
3. As it hits a boundary between different materials (like the encapsulant and a cell), some of the sound is reflected back.
4. If the sound wave encounters a void—an air pocket—the reflection is nearly total and distinctly different.

A sensor detects these reflections, and a computer translates the data into a detailed, layer-by-layer image. A perfectly laminated area looks uniform, while a void shows up as a distinct dark spot, revealing its exact size, shape, and location.

This level of detail is a game-changer. It allows you to pinpoint precisely where the lamination process is failing around your custom interconnectors, giving you the data needed to fix the root cause.

From Detection to Perfection: How to Eliminate Voids

Finding a void is the first step. The real value comes from using that information to refine your manufacturing process. Once acoustic microscopy confirms the presence of voids, you can systematically investigate the cause.

The formation of voids is almost always linked to the lamination recipe—the specific combination of temperature, pressure, and time used to bond the module together. For complex interconnectors, a standard recipe often isn’t enough, requiring a more nuanced approach.

This is where controlled experimentation is critical. By making precise adjustments in a test environment, you can observe the impact on void formation. Key variables to explore include:

• Vacuum Duration: Is the pre-lamination vacuum cycle long enough to pull all the air out from around the complex wires?
• Pressure Application: Does the pressure ramp up too quickly, trapping air before it can escape? A slower, multi-stage pressure profile might be needed.
• Encapsulant Flow: Is the temperature causing the encapsulant to cure too quickly, before it has fully penetrated the complex topography?

By running structured lamination trials and using acoustic microscopy to validate the results of each adjustment, you can develop a robust process that works for your specific module design. The goal is to establish a repeatable recipe for optimizing lamination parameters that ensures a void-free laminate every time.

This iterative, data-driven approach transforms lamination from a „black box“ process into a predictable science, ensuring the long-term reliability and performance of your innovative module designs.

Frequently Asked Questions (FAQ)

1. What exactly is a void in a solar module?
   A void is a small bubble or pocket within the encapsulant layers of a solar module that contains trapped air, moisture, or other gases released during the lamination process.

2. Why are voids such a big problem?
   They can reduce the module’s power output by scattering light. More importantly, they create weak spots that can lead to delamination, moisture ingress, and corrosion over time, significantly shortening the module’s operational lifetime.

3. Can’t I just see voids with my eyes or a standard EL test?
   Micro-voids, especially those deep within the laminate, are often too small to be seen with the naked eye. While an EL test is excellent for detecting cell cracks or electrical issues, it typically cannot identify these lamination defects.

4. What is acoustic microscopy in simple terms?
   It’s a non-destructive inspection method that uses sound waves to see inside an object. By analyzing how sound reflects off different internal layers and defects, it can create a detailed map of things you can’t see, like voids or delamination.

5. Is this issue only relevant for brand-new, experimental module designs?
   While complex geometries like shingled cells and multi-wire interconnectors make void formation more likely, the principles apply to any module. Any change in materials—such as a new encapsulant or backsheet—can alter the ideal lamination process and introduce the risk of voids.

Pushing Innovation Forward, Reliably

The drive for higher efficiency is pushing solar technology into exciting new territory. But with every innovation comes the responsibility to ensure quality and long-term reliability. Hidden threats like micro-voids can undermine the most advanced designs if left unchecked.

By understanding the challenges posed by modern interconnectors and leveraging advanced validation tools like acoustic microscopy, you can turn uncertainty into confidence. This commitment to process validation is what separates a promising idea from a commercially successful product.

If you are in the process of prototyping new solar module concepts, integrating these advanced quality checks early in the development cycle is the surest path to creating modules that not only perform well on day one but for decades to come.