Wim Deferme | Hasselt University: Is fully curing your conductive ink *before* thermoforming a mistake? This two-step thermal process reveals a counter-intuitive path to lower resistance.
00:06:15 - 00:08:30
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Is fully curing your conductive ink *before* thermoforming a mistake? This two-step thermal process reveals a counter-intuitive path to lower resistance.
When creating 3D electronics, the process sequence of printing, curing, and forming is critical to the final electrical performance. This analysis compares two distinct thermal processing strategies. The first is a conventional approach: screen printing the conductive ink, fully curing it at 120°C to achieve maximum conductivity, and then subjecting the rigid, cured circuit to the heat and strain of thermoforming.
A novel, two-step approach is proposed and tested: after printing, the ink is only "pre-dried" at a lower temperature (60°C). This stabilizes the ink on the substrate without fully cross-linking the binder, leaving it more pliable. The circuit is then thermoformed, and the heat from the forming process itself completes the cure. Data shows the pre-dried ink's resistance drops during the thermoforming heat step, and while it increases slightly from the physical strain, the final resistance is significantly lower (around 40 ohms) than the fully cured sample (around 65 ohms).
The underlying mechanism is that fully curing the ink first makes the conductive trace more brittle. The subsequent mechanical stress of 3D forming introduces micro-cracks and damage, permanently degrading its conductivity. By keeping the ink more flexible during the forming stage, the two-step process allows the conductive network to conform to the new shape before it is locked in place, resulting in a more robust and lower-resistance final 3D circuit.
In this short video, you can learn:
* The difference between pre-drying and full curing for thermoformable inks.
* How a two-step curing process can yield superior electrical performance in 3D electronics.
* The mechanism behind ink degradation when a fully cured trace is subjected to thermoforming strain.
📋 **Clip Abstract** Discover a crucial process optimization for thermoforming printed electronics. This clip demonstrates why a partial "pre-dry" of conductive ink before 3D forming results in lower final resistance compared to a full cure, by minimizing stress-induced damage.
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#ThermoformableElectronics, #ConductiveInkCuring, #TwoStepCuringProcess, #3DElectronicsFabrication, #PrintedElectronics, #FlexibleElectronics
This is a highlight of the presentation:
ACT-3D_Assembly and Connection Technology for 3D plastic carriers
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00:08:30 - 00:09:51
How do you choose the right conductive ink when your circuit needs to stretch into a 3D shape? It's a critical trade-off between conductivity and durability.
How do you choose the right conductive ink when your circuit needs to stretch into a 3D shape? It's a critical trade-off between conductivity and durability.
The core challenge in creating 3D formed electronics is that the conductive ink must stretch without breaking or significantly increasing in resistance. This clip analyzes the performance of six different conductive inks under mechanical strain, simulating the thermoforming process. The results show a wide variation in both initial resistance and how that resistance changes as the ink is stretched, highlighting that no single ink is perfect for all applications.
A key finding is the trade-off between high initial conductivity and stretchability. Inks with the lowest starting resistance often cannot withstand high levels of strain before their resistance skyrockets, indicating cracking and failure of the conductive path. Conversely, inks specifically formulated for high elongation and flexibility may start with a higher base resistance, making them unsuitable for applications that require low power loss or carry significant current.
Based on this data, a practical selection guide is presented for product developers and engineers. For applications with low strain but active power needs (requiring low resistance), specific inks (Ink A, Ink E) are recommended. For high-strain applications like capacitive touch sensors where absolute conductivity is less critical (passive power requirements), a different set of more mechanically robust inks (Ink E, Ink F) is the optimal choice, providing a clear decision-making framework.
In this short video, you can learn:
* How to evaluate conductive ink performance under mechanical strain.
* The fundamental trade-off between an ink's conductivity and its stretchability.
* A framework for selecting the optimal ink based on your application's specific strain and power requirements.
📋 **Clip Abstract** Not all conductive inks are created equal, especially when thermoforming is involved. This analysis reveals the critical trade-off between initial conductivity and performance under strain, providing a clear framework for selecting the right ink for your specific 3D electronics application.
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#ConductiveInk, #StretchableElectronics, #3DElectronics, #Thermoforming, #PrintedElectronics, #WearableElectronics
00:02:07 - 00:03:38
Why does your plastic substrate warp and ruin your printed circuit during heating? The secret lies in its thermomechanical properties.
Why does your plastic substrate warp and ruin your printed circuit during heating? The secret lies in its thermomechanical properties.
Before you can successfully thermoform a printed circuit, you must select a polymer substrate that can withstand the thermal and mechanical stresses of the process. Key material properties, such as the storage modulus and the thermal expansion coefficient, are critical indicators of a substrate's suitability. These properties dictate how the material behaves when heated, which is a necessary step for both curing the ink and making the plastic pliable enough for forming.
This clip provides a stark visual example of what happens when an unsuitable substrate is chosen. When heated to just 120°C—a typical ink curing temperature—the substrate deforms and shrinks uncontrollably, rendering any printed circuit on its surface useless. This demonstrates that even before the physical forming pressure is applied, thermal instability can lead to complete process failure, highlighting the importance of material science in manufacturing.
The analysis of these properties leads to a down-selection of promising candidates for in-mold electronics (IME) and 3D electronics. Based on their superior thermal stability and formability, materials like PMMA (acrylic), PC (polycarbonate), PETG, and ABS are identified as suitable substrates for further investigation. This foundational step of proper material selection is essential for developing a reliable and repeatable manufacturing process for 3D hybrid electronics.
In this short video, you can learn:
* Which thermomechanical properties (e.g., storage modulus) are critical for selecting thermoformable substrates.
* How to identify and avoid substrates with poor thermal stability that can ruin your device before it's even formed.
* Which common polymers, like polycarbonate and PMMA, are well-suited for 3D printed electronics applications.
📋 **Clip Abstract** The success of a 3D thermoformed electronic device begins with the right plastic substrate. This clip explains the critical role of thermomechanical properties like storage modulus and shows why materials like polycarbonate and PMMA are preferred for their stability during heating.
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#ThermomechanicalProperties, #PlasticSubstrates, #ThermalStability, #InMoldElectronics, #PrintedElectronics, #3DElectronics