Guinevere Strack | UMass Lowell: Is interface oxidation acting as an unwanted parasitic resistor in your printed electronics designs?
12:37 - 14:31
Other snippets from this talk
Summary of the clip:
Is interface oxidation acting as an unwanted parasitic resistor in your printed electronics designs?
Directly printing resistive carbon-based inks onto bare copper terminations introduces a significant fabrication hurdle: copper oxidation. This thin oxide layer acts as an unintended series resistor at the ink-to-metal interface, introducing a non-zero contact resistance that distorts the targeted resistance values.
This parasitic interface contact resistance manifests as a persistent 4 to 8 ohm shift when plotting resistance versus resistor length. For relatively low-value targets, such as a 50-ohm embedded resistor, a parasitic resistance of this magnitude introduces unacceptable manufacturing errors and degrades circuit precision.
To mitigate this contact resistance, developers can passivate the copper terminations with gold (using electroless nickel immersion gold, or ENIG), which reduces the parasitic intercept to below 1 ohm. However, introducing wet chemical plating steps adds significant processing complexity, drives up labor and raw material costs, and represents a major environmental hotspot in the life cycle assessment.
In this short video, you can learn:
* How copper oxidation at the ink-termination interface creates an unintended series resistor, introducing a persistent 4 to 8 ohm offset.
* The impact of contact resistance on low-value target passives and how surface passivation with gold drops this parasitic resistance to sub-ohm levels.
* The manufacturing and environmental trade-offs of integrating wet electroless nickel immersion gold (ENIG) plating steps into additive print lines.
š **Clip Abstract** This clip addresses the issue of copper termination oxidation acting as a parasitic series resistor at the ink-metal interface of printed electronics. It explores how gold passivation successfully reduces this contact resistance error, while weighing the resulting manufacturing and environmental cost trade-offs.
š Link in comments š
#ContactResistance, #CopperOxidation, #ENIG, #PrintedResistors, #PrintedElectronics, #AdditiveElectronics
This is a highlight of the presentation:
Printed Resistors for Low-Cost Sustainable, Semi-Additive PCBs
Future of Electronics RESHAPED USA 2026
10-11 June 2026
Computer History Museum, Mountain View, California, USA
Organised By:
TechBlick
More Highlights from the same talk.
05:05 - 07:31
Why do embedded resistors still suffer from 20% tolerance errors despite starting with high-precision foils?
Why do embedded resistors still suffer from 20% tolerance errors despite starting with high-precision foils?
Conventional embedded resistors rely on thin-film subtractive processes using specialized Ticer foils (such as nickel-chrome alloys) to achieve a low thermal coefficient of resistance (TCR). While these vacuum-deposited metallic layers offer a tight 5% manufacturing tolerance as supplied, subsequent photolithography and multi-step etching stages degrade this precision significantly, pushing final tolerances up to 20% and driving up system costs.
To bypass these complex subtractive steps and avoid expensive proprietary foils, developers are turning to additive manufacturing. By combining standard photolithography for copper termination pads with printed carbon-based resistive inks, it is possible to simplify the processing steps, reduce costs, and alter board form factors via direct compaction.
However, moving from subtractive metallic foils to additive polymer thick films introduces novel manufacturing challenges. Achieving tight tolerances, ensuring reliable contact resistance at the printed ink-to-copper interface, and matching curing profiles to substrate thermal budgets remain critical bottlenecks in transitioning printed passives to high manufacturing readiness levels (MRL).
In this short video, you can learn:
* Why standard vacuum-deposited Ticer foils degrade from 5% to 20% tolerance during conventional PCB patterning steps.
* How additive printed carbon-based resistive inks can replace expensive embedded foils to lower processing costs and optimize board compaction.
* The processing trade-offs when transitioning from subtractive multi-stack lithography to simplified direct-write ink deposition on copper terminations.
š **Clip Abstract** This clip contrasts conventional subtractive embedded resistor technologies like Ticer foils with modern additive printed carbon-based ink alternatives. It highlights how subtractive manufacturing degrades tolerances to 20% and explores how additive printing can lower production costs while improving board compaction.
š Link in comments š
#EmbeddedResistors, #ResistiveInks, #TicerFoils, #PolymerThickFilm, #PrintedElectronics, #AdditiveElectronics
09:30 - 10:46
Can your PCB survive the high-temperature cure required to stabilize printed carbon-based resistors?
Can your PCB survive the high-temperature cure required to stabilize printed carbon-based resistors?
A primary material incompatibility in printed electronics arises when matching the thermal curing profile of high-performance resistive inks with the glass transition temperature (Tg) of standard PCB laminates. High-stability resistive inks, such as polyimide-based carbon formulations, often require curing temperatures around 200 degrees Celsius to achieve complete polymer cross-linking.
If these inks are cured below their target threshold, the polymer matrix remains under-cured, causing the electrical properties to drift wildly between manufacturing batches. This results in unstable thermal coefficients of resistance (TCR) and poor resistance reproducibility, rendering the passives unusable for precision circuit designs.
Conversely, exposing standard glass-reinforced epoxy resin substrates to these elevated curing temperatures can exceed the substrate's Tg, causing delamination, warping, and mechanical degradation. Resolving this conflict between the ink's high thermal cross-linking demands and the laminate's thermal limits is a critical step in advancing printed electronics up the MRL scale.
In this short video, you can learn:
* The critical role of the substrate's glass transition temperature (Tg) when integrating high-temperature cured inks onto standard epoxy-resin boards.
* Why incomplete cross-linking in polyimide-based carbon inks leads to severe batch-to-batch resistance drift and unstable TCR performance.
* The engineering conflict between achieving high-reliability resistor properties and protecting the mechanical integrity of the underlying PCB laminate.
š **Clip Abstract** This clip examines the thermal processing incompatibility between high-performance resistive carbon inks and standard glass-epoxy PCB laminates. It explains how under-curing polyimide-based inks below 200 degrees Celsius to protect the board leads to unstable electrical drift and poor thermal coefficients of resistance.
š Link in comments š
#PrintedResistors, #GlassTransitionTemperature, #PolymerCrossLinking, #ThermalCoefficientOfResistance, #PrintedElectronics, #AdditiveElectronics