Gordon Elger | Technische Hochschule Ingolstadt: How do you sinter metal from a salt-based ink without ending up with useless, oversized particles?
00:02:57 - 00:04:10
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How do you sinter metal from a salt-based ink without ending up with useless, oversized particles?
The process of creating a conductive layer from a particle-free ink begins by decomposing a metal salt, like copper formate, to release atomic copper. This atomic copper must then nucleate and grow into nanoparticles. The ideal scenario is to generate a massive number of nucleation sites simultaneously, forming a dense field of very small particles which are ideal for low-temperature sintering.
However, this rapid decomposition creates a significant outgassing problem, as binders and chemical byproducts are released, which can destroy the film's structure. To manage this, the process must be slowed down. This introduces a new, more fundamental challenge: Oswald ripening, a thermodynamic process where smaller, less stable particles dissolve and redeposit onto larger, more stable ones.
This ripening effect is the primary enemy in forming a high-quality conductive film. If left unchecked during a slow, controlled heating process, the initially small particles will grow into large, isolated particles that will not sinter together effectively, resulting in poor conductivity. The key to success lies in actively fighting the Oswald ripening law, typically by incorporating stabilizing additives into the ink formulation that physically or chemically block this undesirable particle growth.
In this short video, you can learn:
* The in-situ process of forming copper nanoparticles from a metal salt precursor.
* The critical trade-off between managing outgassing rates and controlling particle nucleation.
* The concept of Oswald ripening and why it's the primary obstacle to achieving a well-sintered film.
š **Clip Abstract** This clip explains the fundamental challenge of using particle-free metal salt inks for printed electronics. It details the process of in-situ nanoparticle formation and the critical battle against Oswald ripening to achieve a fine, sinterable particle structure.
š Link in comments š
#MetalSaltSintering, #InSituNanoparticleFormation, #OswaldRipening, #ParticleFreeInk, #PrintedElectronics, #AdditiveManufacturing
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00:08:29 - 00:10:19
Your copper formate ink isn't just decomposing, it's evaporating. Are you losing your precursor before it can form a conductive trace?
Your copper formate ink isn't just decomposing, it's evaporating. Are you losing your precursor before it can form a conductive trace?
A deep dive into the thermal behavior of copper formate, a common precursor for particle-free inks, reveals complex and challenging chemistry. Thermogravimetric analysis (TGA) shows that while copper formate can form on copper oxide surfaces around 150Ā°C, its primary decomposition into metallic copper doesn't occur until approximately 200Ā°C. This defines a critical temperature window for processing.
A significant and often overlooked issue is that copper formate can sublimate, or evaporate, at the same temperature it decomposes. This creates a competing reaction pathway where the precursor material can be lost to the gas phase instead of converting into the desired metallic copper film. If the heating rate and temperature are not precisely controlled, this evaporation can lead to a significant reduction in the final copper yield and result in thin, non-conductive traces.
Furthermore, the decomposition reaction itself releases a large volume of gaseous byproducts, including carbon dioxide (CO2) and hydrogen (H2). This massive outgassing event must be managed very carefully through slow, controlled heating profiles. If the process is too rapid, the escaping gas will create a highly porous, uneven, and structurally unsound layer, completely compromising the electrical performance of the printed feature.
In this short video, you can learn:
* The specific temperature window for copper formate decomposition (~200Ā°C).
* The competing processes of decomposition and evaporation that can lead to material loss.
* The significant outgassing of CO2 and H2, which poses a major process control challenge.
š **Clip Abstract** This segment provides a deep dive into the complex chemistry of copper formate, the precursor for many particle-free copper inks. It reveals the critical processing challenge of managing its simultaneous decomposition and evaporation, along with the significant outgassing that must be controlled for successful sintering.
š Link in comments š
#CopperFormateInk, #ThermalDecomposition, #PrecursorSublimation, #OutgassingManagement, #PrintedElectronics, #AdditiveElectronics
00:15:42 - 00:16:54
You've achieved near-bulk conductivity with your printed copper ink, but is it useless within days?
You've achieved near-bulk conductivity with your printed copper ink, but is it useless within days?
The primary goal of developing a conductive ink is achieving high electrical performance, and this particle-free copper system successfully delivers on that front. Through careful optimization of the ink formulation and the sintering process, it is possible to produce printed traces with an electrical conductivity as high as 50% that of bulk copper. This represents an excellent result for a low-temperature, additively manufactured conductor, making it attractive for many applications.
However, this high performance is coupled with a critical reliability flaw: poor environmental stability. The resulting film is pure, slightly porous copper with a high surface area, making it extremely susceptible to oxidation. When exposed to ambient air, the trace's resistivity begins to increase, and this degradation is dramatically accelerated under standard 85Ā°C / 85% relative humidity testing conditions, where the conductivity quickly plummets.
The root cause of this failure is the very purity of the copper film. Unlike many particle-based inks that leave behind a residual organic binder that can offer some protection, this process yields unprotected metal. Therefore, a secondary encapsulation step is not an optional improvement but an absolute necessity for any practical application. This can be achieved by applying a traditional solder resist or by developing advanced inks that incorporate polymers for in-situ encapsulation during the curing process.
In this short video, you can learn:
* How to achieve high electrical conductivity (50% of bulk copper) with particle-free inks.
* The critical reliability issue: rapid oxidation and conductivity loss in ambient and humid environments.
* Why encapsulation is a mandatory step for creating environmentally stable printed copper traces.
š **Clip Abstract** This clip highlights the double-edged sword of using particle-free inks to create pure copper traces. While they can achieve excellent initial electrical conductivity, they are highly susceptible to oxidation, leading to rapid performance degradation unless properly encapsulated.
š Link in comments š
#ParticleFreeCopperInk, #PrintedConductors, #OxidationStability, #EncapsulationTechnology, #PrintedElectronics, #AdditiveElectronics