You’ve done everything right. The cells are perfectly aligned, the glass is flawless, and the backsheet is immaculate. You run the lamination cycle, and as the new frameless module cools, you see it: a sticky, uneven bead of encapsulant oozing from the edges.
This frustrating phenomenon, known as „squeeze-out,“ isn’t just a cosmetic issue. For manufacturers working with high-performance materials like Polyolefin Elastomer (POE), it’s a critical process control failure that compromises edge sealing, affects module dimensions, and leads to significant material waste.
The good news? It’s a solvable problem. The solution lies not in using less material or simply lowering the temperature, but in understanding how your encapsulant behaves under heat and pressure.
Why Does POE ‚Squeeze Out‘ Even Happen?
To get to the root of the problem, we need to talk about rheology—a term for the science of how materials flow. Think of POE encapsulant as a high-tech glue in your solar module sandwich. It’s fantastic for long-term durability and protecting against potential-induced degradation (PID), especially in bifacial and frameless designs.
However, its viscosity (or thickness) is extremely sensitive to temperature.
When you heat POE during lamination, it doesn’t just soften; its viscosity plummets. There’s a critical temperature window where it transforms from a manageable solid into a very low-viscosity liquid.
The graph above tells a clear story. As the temperature climbs from 100°C to 140°C, the POE’s ability to resist flow drops dramatically. If you apply full lamination pressure while the material is in this super-fluid state, it has nowhere to go but out the sides. This is the „squeeze-out“ moment.
The Problem with Uncontrolled Flow in Frameless Modules
For a framed module, a little squeeze-out might be hidden by the aluminum frame. But for a frameless module, the edge is the first line of defense against the elements. Uncontrolled flow creates several critical vulnerabilities:
- Compromised Edge Sealing: An inconsistent edge makes it difficult to apply a proper edge seal, leaving the module vulnerable to moisture ingress, which can lead to corrosion and delamination over time.
- Dimensional Inaccuracy: Excess material can alter the final dimensions of the module, causing problems with racking and installation.
- Material Waste: Every gram of POE that squeezes out is wasted, directly impacting your cost per module.
- Equipment Contamination: The sticky residue can build up on laminator belts and plates, requiring frequent and time-consuming cleaning.
This isn’t just an annoyance; it’s a direct threat to module quality, reliability, and manufacturing efficiency.
A Tale of Two Lamination Cycles: The Standard vs. The Optimized
Many manufacturers start with a standard, single-stage lamination cycle: load the module, apply vacuum, ramp up the heat and pressure, and hold until cured. While this works for some materials, it’s often the primary cause of squeeze-out with high-flow POE.
Why? Because it pushes the highly fluid POE out before it has a chance to begin its cross-linking (curing) process.
But what if we could control the flow before it becomes a problem? This is where a data-driven, optimized approach makes all the difference. By understanding the material’s rheology, we can design a process that lets the POE „set“ slightly before applying full pressure.
The difference is night and day.
The module on the left, made with a standard process, shows significant, uneven squeeze-out. The one on the right, using an optimized cycle, has a clean, perfectly contained edge. This level of precision is crucial when prototyping new solar modules and aiming for a design that is both reliable and scalable.
The Secret Sauce: A Two-Step Lamination Profile
The key to achieving this clean edge is a two-step temperature and pressure profile. Instead of a single rush to the final curing temperature, the process is split into two distinct phases.
Phase 1: The Gelling Stage
The cycle begins by heating the module to a lower intermediate temperature—for instance, 135°C. This is the sweet spot just before the viscosity completely collapses. The module is held here under minimal pressure for a few minutes. This gives the POE enough time to start cross-linking and build internal strength, transforming from a liquid into a more stable gel. Think of it like letting Jell-O begin to set before you add fruit; it prevents everything from sinking to the bottom.
Phase 2: The Curing Stage
Once the POE is in this more viscous, gel-like state, it’s far less likely to flow uncontrollably. Now, the temperature is ramped up to the final curing temperature (e.g., 150°C), and full lamination pressure is applied. This ensures a strong, void-free bond across the entire module while keeping the encapsulant neatly contained within the glass-backsheet sandwich.
This methodology, developed through rigorous material testing and controlled lamination trials, demonstrates that process control is just as important as material selection.
Putting It Into Practice: Key Takeaways
Controlling POE squeeze-out is an achievable goal for any manufacturer. It boils down to a few core principles:
- Know Your Material: Don’t treat all encapsulants the same. Obtain rheological data for your specific POE to identify its critical temperature window.
- Rethink Your Recipe: A one-size-fits-all lamination cycle is a recipe for inconsistency. A multi-stage process that respects the material’s properties will yield far better results.
- Test and Verify: Theory and data sheets provide the map, but real-world trials are where you find the treasure. Running controlled experiments is the only way to dial in the perfect times, temperatures, and pressures for your specific module design and equipment. Ultimately, physical results are the only true validation.
Frequently Asked Questions (FAQ)
What is an encapsulant in a solar module?
An encapsulant is a polymer material (like POE or EVA) that serves as an adhesive layer to bond the solar cells, glass, and backsheet together. It also provides electrical insulation and protects the cells from moisture, vibration, and impact.
Why is POE used instead of the more common EVA for some modules?
POE offers superior resistance to moisture and potential-induced degradation (PID), making it an ideal choice for high-efficiency technologies like bifacial and n-type cells, which are more sensitive to these factors. Its durability is especially valuable in frameless designs.
Does this ’squeeze-out‘ issue affect framed modules too?
Yes, it can happen with framed modules, but the frame often hides the problem or helps contain the flow. For frameless modules, however, the edge is fully exposed, making squeeze-out a critical quality and reliability issue that must be controlled.
Can’t I just use a thinner sheet of POE to prevent squeeze-out?
While it might seem logical, reducing the amount of encapsulant is risky. An insufficient amount can lead to voids, poor adhesion, and delamination—far more severe failure modes than squeeze-out. The correct approach is to control the flow of the properly specified amount of material.
Your Next Step in Mastering Module Lamination
Taming POE squeeze-out is a perfect example of how thorough process knowledge transforms a common manufacturing headache into a competitive advantage. By moving beyond a „one-size-fits-all“ approach and embracing a data-driven lamination strategy, you can produce higher quality, more reliable, and more consistent frameless modules.
Understanding the theory is the first step. The next is putting it into practice. For teams looking to validate new materials or optimize their production recipes, working in an applied research environment allows you to test these principles on industrial-scale equipment. This gives you the data-driven confidence needed to perfect your process before scaling up.