César Omar Ramírez Quiroz | FOM Technologies: Think slot-die coating a wafer is easy? Here are 4 fluid dynamics and surface tension problems that can kill your yield.
11:05 - 12:24
Other snippets from this talk
Summary of the clip:
Think slot-die coating a wafer is easy? Here are 4 fluid dynamics and surface tension problems that can kill your yield.
Applying a continuous coating method like slot-die to a discrete substrate like a silicon wafer introduces a unique set of process engineering challenges. The primary issue is achieving uniform film quality across the entire surface, especially at the edges. Unlike a continuous roll-to-roll process, every wafer has a start and an end point for the coating, and these edge regions must possess the same high quality as the bulk area to maximize the active area and prevent yield loss, a non-trivial fluid dynamics problem.
A significant materials science challenge arises from the interaction between the functional ink and the wafer itself. Perovskite inks, for example, often have high capillary forces that cause the liquid to wick underneath the wafer during coating. This contamination of the wafer's underside can react with metal contacts or chucks, severely compromising device reliability and long-term stability. To mitigate this, an additional, time-consuming cleaning step must be added to the production line, which directly reduces overall throughput and increases cost.
Furthermore, the physics of the slot-die process itself creates inherent non-uniformities at the beginning and end of the deposition. The "leading edge" (where coating starts) and "trailing edge" (where it stops) are governed by complex, thermodynamically-driven fluid dynamics that result in thickness and morphology variations. These instabilities are difficult to eliminate and must be carefully managed. The problem is compounded by the "pseudo-square" shape of modern wafers, which have rounded corners that further complicate the goal of achieving a perfectly uniform, edge-to-edge coating.
In this short video, you can learn:
* The fundamental challenge of achieving perfect edge-to-edge quality when coating discrete wafers.
* How ink wicking and capillary forces can contaminate the backside of a wafer, impacting reliability.
* The physics behind leading and trailing edge instabilities that create coating defects.
* The added complexity of coating modern wafers with non-perfectly-square shapes.
📋 **Clip Abstract**
This clip provides a technical deep-dive into the critical, physics-based challenges of applying slot-die coating to discrete silicon wafers. It details four key failure modes, including edge-effect instabilities, ink wicking and contamination, and issues arising from wafer geometry.
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#SlotDieCoating, #FluidDynamics, #EdgeEffects, #InkWicking, #PrintedElectronics, #AdditiveElectronics
This is a highlight of the presentation:
The role of slot-die coating in the
future of photovoltaics.
More Highlights from the same talk.
05:56 - 08:33
Why are 95% of perovskite PV researchers using a fabrication method that's useless for industrial production?
Why are 95% of perovskite PV researchers using a fabrication method that's useless for industrial production?
The photovoltaic community celebrates record-breaking lab-scale efficiencies, such as the 34.6% achieved for a perovskite-silicon tandem cell. However, these "hero" results are almost exclusively produced using spin-coating, a deposition technique that is fundamentally non-scalable due to its high material waste and incompatibility with large-area or high-throughput manufacturing. This creates a significant and often misleading gap between what is reported in academic literature and what is achievable in an industrial setting, masking the true state of readiness for commercialization.
When a "scalability filter" is applied—considering only results from industrially viable methods like slot-die coating, blade coating, or spray coating—the landscape of record efficiencies changes dramatically. The most relevant record for a single-junction perovskite cell is not 26.1% (spin-coated) but 23.2%, achieved via slot-die coating. This figure represents a much more realistic benchmark for what industry can currently target, highlighting the critical importance of focusing R&D efforts on scalable deposition processes from the outset.
This disconnect is starkly quantified by analyzing the body of scientific literature: for every 20 research papers published on perovskites using spin-coating, only one uses a scalable technique like slot-die coating. This 20-to-1 ratio points to a systemic issue in the research ecosystem. It suggests a potential lack of awareness, a shortage of accessible and affordable scalable coating equipment in academic labs, or an "infrastructure gap" that is severely hindering the translation of promising lab discoveries into real-world, manufacturable products.
In this short video, you can learn:
* The critical difference between non-scalable "hero cell" efficiencies and industrially relevant benchmarks.
* Why slot-die coating is the current record holder for scalable single-junction perovskite solar cell efficiency.
* The staggering 20-to-1 ratio of non-scalable vs. scalable methods in academic research and its implications for the industry.
📋 **Clip Abstract**
This analysis reveals the critical "scalability gap" in perovskite PV research, contrasting misleading lab-scale records with industrially relevant achievements. It highlights a 20-to-1 disparity in publications favoring non-scalable methods, arguing for a strategic shift in R&D focus toward manufacturable processes.
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#PerovskitePV, #SlotDieCoating, #SpinCoating, #ScalableDeposition, #PrintedElectronics, #FlexibleElectronics
14:29 - 16:48
How a 16-second slot-die process replaced a 3-minute spin-coating step, saved 98% of material, and reduced failure rates in microchip fabrication.
How a 16-second slot-die process replaced a 3-minute spin-coating step, saved 98% of material, and reduced failure rates in microchip fabrication.
This clip presents a powerful industrial case study, demonstrating the value of slot-die coating beyond photovoltaics in the demanding field of micro-device manufacturing. The objective was to replace a conventional spin-coating process used to apply a functional protective layer onto a wafer containing 10,000 individual microchips prior to dicing. A key deficiency of spin-coating is its reliance on centrifugal force, which results in poor film uniformity and conformal coverage over the pre-existing, complex topography of the micro-devices.
By replacing the spin-coater with a slot-die system, the deposition process became a more passive and controlled material delivery. Cross-sectional analysis of the coated wafers revealed that the slot-die method produced a significantly more homogeneous and conformal protective layer across the intricate device structures. The most compelling result was an unexpected improvement in final product quality: after the slot-die coated wafers were returned to the factory for dicing and final processing, they exhibited a measurably lower device failure rate, directly linking the superior coating quality to improved yield.
The commercial and operational metrics underscore the transformative impact of this process change. The cycle time per wafer was slashed from 3 minutes (including 2 minutes of robotic handling) to just 16 seconds, representing an 11-fold increase in throughput. Critically, the slot-die process is nearly 100% efficient in material transfer, eliminating the 98% material waste inherent to spin-coating—a massive cost reduction. This solution also solved the classic edge-coating problem, achieving a uniform film to within one millimeter of the wafer's physical edge.
In this short video, you can learn:
* Why slot-die coating provides superior film uniformity over complex topographies compared to spin-coating.
* The direct correlation between advanced coating quality and a reduction in final device failure rates and yield improvement.
* How to achieve massive gains in manufacturing throughput (11x) and material savings (98%) by replacing spin-coating.
📋 **Clip Abstract**
This case study details the successful replacement of a slow, wasteful spin-coating process with a high-throughput slot-die solution in microchip manufacturing. The switch not only increased processing speed by 11x and cut material waste by 98%, but also improved coating quality and reduced final device failure rates.
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#SlotDieCoating, #SpinCoatingReplacement, #MicrochipFabrication, #ConformalCoating, #PrintedElectronics, #AdditiveManufacturing