Whether you’re evaluating module designs or refining a production line, every decision comes down to one question: will this asset deliver its promised performance for the next 25 years?
Yet, a threat invisible to the naked eye could be undermining your work. Microcracks, minuscule fissures in solar cells, can form and spread during manufacturing and installation. Over a module’s lifetime, they can lead to power losses as high as 60-80 percent, making them the silent killer of project ROI.
The challenge isn’t just knowing that microcracks exist; it’s understanding precisely where they originate and how to stop them before they’re permanently sealed into a module. This requires moving beyond simple pass/fail checks to a systematic, multi-stage approach that traces a crack’s lifecycle from a single cell to a finished panel.
This guide offers that framework, walking through the primary stress points in module production—cell handling, stringing, and lamination—and explaining how to use advanced diagnostics to build a zero-tolerance policy for cell damage.
The Lifecycle of a Microcrack: Key Stress Points in Production
Microcracks don’t appear spontaneously. They are the result of specific mechanical and thermal stresses applied at different stages of the manufacturing process. Understanding this sequence is the first step toward effective control.
Each stage is both a risk, a point where cracks can be induced or worsened, and an opportunity to detect and mitigate them with the right process controls.
Stage 1: Cell Handling and Stringing – The First Point of Failure
The journey from a single cell to a string is where the first, and often most critical, damage occurs. Modern cells are thinner and more fragile than ever, making them highly susceptible to mechanical stress.
Stress Source:
The primary culprits are often the automated processes themselves. Robotic pick-and-place arms can exert uneven pressure, while thermal stress from soldering or bonding can create localized tension within the cell’s crystalline structure. Even slight miscalibrations in handling equipment can initiate fractures that are completely invisible at this stage.
Detection Method: Pre-Lamination Electroluminescence (EL)
Performing high-resolution EL imaging on cells and strings before they enter the laminator is the most crucial quality gate. An EL test passes an electrical current through the cells, causing them to emit near-infrared light. A camera captures this light, revealing any inactive or damaged areas, like microcracks, as dark lines or zones.
It’s the difference between a clean bill of health and a hidden defect waiting to spread.
Process Adjustments and Mitigation:
Catching cracks here allows for immediate corrective action. Data from cell-level EL testing provides the insights needed to refine your production line. Through a structured program of Process Optimization & Training, engineers can adjust gripper pressures, optimize soldering temperature profiles, and implement handling protocols that dramatically reduce initial cell damage. This proactive step prevents flawed cells from ever making it into a finished module.
Stage 2: Lamination – Sealing in Quality or Sealing in Defects
The lamination process is designed to protect the cells by encapsulating them. However, the combination of heat and pressure required can transform minor, stable microcracks into module-defining failures.
Stress Source:
During lamination, the module stack is subjected to significant mechanical pressure and temperatures often exceeding 140°C. This process can cause existing microcracks to propagate, and any mismatch in the coefficient of thermal expansion (CTE) between the glass, encapsulant, cells, and backsheet can introduce new stresses as the module cools.
Detection Method: Post-Lamination EL Verification
A final EL inspection after lamination validates the integrity of your entire assembly process. It answers a critical question: Did the lamination process preserve the integrity of the strings, or did it introduce new damage? This step confirms that your process parameters are optimized and that the selected materials are compatible under real industrial conditions.
Process Adjustments and Mitigation:
If post-lamination EL reveals crack propagation, the data points directly to necessary adjustments. This could involve modifying the pressure and temperature cycles or re-evaluating material choices. Our applied research environment for Material Testing & Lamination Trials allows material suppliers and module developers to test different encapsulants and backsheets under real production conditions to find the most resilient combination.
Diagnostic Showdown: Why EL Testing is Superior for Crack Detection
When evaluating diagnostic tools, a common question arises: why not just use Infrared (IR) thermography? While IR is useful for detecting hotspots in finished modules, it only identifies the effect of a problem, not its root cause.
Electroluminescence, on the other hand, finds the cracks themselves. Research confirms that EL testing provides 90-95 percent better results for detecting microcracks than IR thermography. This distinction is crucial for long-term reliability.
As the image shows, EL reveals the full network of fractures, while IR only flags the areas that have become hot enough to register. Critically, research from Nature shows that hotspots and potential fire hazards often form in cells with intermediate crack sizes. These are cracks that may not immediately cause a significant power drop but represent a ticking time bomb for future failure. Only EL can reliably detect them early.
Quote: Relying on IR alone is like waiting for the smoke alarm to go off. EL imaging allows us to find the faulty wiring before the fire ever starts. It provides the high-fidelity data needed to move from a reactive to a proactive quality strategy. — Patrick Thoma, PV Process Specialist
The Bottom Line: Protecting Long-Term Yield and Bankability
Implementing a multi-stage microcrack detection strategy isn’t just about improving quality—it’s about protecting the financial viability of a solar asset. By identifying and eliminating cell damage before it’s sealed into a module, you directly impact long-term performance and reduce investment risk.
The data gathered allows you to:
- Prevent Catastrophic Power Loss: Avoid the 60-80 percent degradation that severe microcracks can cause over time.
- Improve Manufacturing Yield: Reduce scrap and rework by catching defects at their source.
- Validate New Designs: De-risk innovation by ensuring new materials and cell structures can withstand the production process. Our Prototyping & Module Development services use this exact methodology to turn ambitious concepts into reliable products.
- Increase Asset Bankability: Provide investors and insurers with certified, data-backed proof of module quality and long-term durability.
By shifting from a simple final inspection to an integrated, process-wide monitoring system, you transform quality control from an expense into a strategic advantage.
Frequently Asked Questions
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Is this level of testing really necessary for standard PERC modules?
Absolutely. While newer technologies like TOPCon and HJT are known for being more fragile, even standard modules are subject to the same mechanical and thermal stresses. With warranties extending to 25 and 30 years, ensuring long-term reliability from day one is essential for any module technology to be considered bankable. Proactive testing prevents minor issues from becoming major warranty claims down the line. -
Can’t we just use higher-resolution cameras for our existing EL system?
Higher resolution helps, but the strategy is more important than the hardware alone. The key is implementing quality gates between process steps—specifically before and after lamination. This allows you to isolate where the damage is occurring. Without this stage-by-stage approach, you can only see the final result, not the root cause. -
How does this process work in a real-world R&D setting like PVTestLab?
Our clients rent our entire full-scale production line, complete with our expert process engineers. We work collaboratively to define the testing protocol. You can bring your materials or module designs, run them through our industrial-grade stringers and laminators, and get immediate EL data at each critical stage. We then help you interpret that data to make actionable improvements to your design or manufacturing process. -
What about cracks induced by transport or installation?
While this guide focuses on manufacturing, the same principles apply. A module built with a zero-tolerance policy for manufacturing defects is inherently more resilient to the stresses of transportation and handling. A clean EL image from the factory serves as a perfect baseline to assess any damage that may occur later in the value chain.
Build Your Modules on a Foundation of Certainty
Microcracks are an avoidable threat, but only with a process built on precision, measurement, and control. By tracing their lifecycle and implementing targeted diagnostic checks, you can move from hoping for reliability to engineering it.
If you’re ready to validate a new module design, test a new material, or optimize your production process against the threat of microcracks, your next step is to test it under real industrial conditions.
Schedule a consultation with a PVTestLab process engineer to discuss your project.