Zach Kelly | Heraeus Electronics: Is your printed heater secretly wasting energy by heating the busbars instead of the active material?
00:08:52 - 00:11:31
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Is your printed heater secretly wasting energy by heating the busbars instead of the active material?
A common pitfall in large-format printed heater design is neglecting the "resistance balance" between the silver conductor busbars and the active PTC carbon cells. If the busbar resistance is too high relative to the PTC resistor, the busbars themselves will undergo significant Joule heating. This not only wastes energy but also creates dangerous localized hotspots along the main silver traces while leaving the target areas underheated.
Additionally, long traces introduce path-dependent resistance variations across the circuit. In poorly balanced layouts, current naturally favors shorter electrical paths, causing severe thermal non-uniformity from the top to the bottom of the heater. To eliminate these parasitic path dependencies, the resistance of the active PTC material must be engineered to be orders of magnitude greater than that of the entire busbar network.
By widening the silver busbar traces and optimizing the conductor layout, engineers can drive the busbar resistance down to negligible levels. This ensures that the applied voltage drops almost entirely across the active PTC elements, yielding a uniform thermal profile and diverting 100% of the heating power to where it is actually needed.
In this short video, you can learn:
* The mechanics of "resistance balance" and how improper ratios trigger parasitic busbar heating.
* Why long, high-resistance conductor traces lead to path-dependent thermal non-uniformity.
* Designing low-resistance busbar paths to ensure 100% power allocation to the active PTC units.
📋 **Clip Abstract** This clip highlights a collaborative case study debugging a printed heater that suffered from severe parasitic busbar heating. Zach Kelly details the mathematical modeling and design adjustments needed to achieve proper resistance balance and uniform heat distribution.
#PrintedHeaters, #ResistanceBalance, #PTCCarbon, #JouleHeating, #PrintedElectronics, #FlexibleElectronics
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00:00:29 - 00:02:24
Why settle for complex control circuits when your heater's material physics can regulate itself?
Why settle for complex control circuits when your heater's material physics can regulate itself?
Traditional metallic heaters exhibit a linear change in resistance as temperature rises, requiring external sensors and control loops to prevent thermal runaway or overshoot. In contrast, polymeric positive temperature coefficient (PTC) heaters utilize a near-exponential resistance response at a specific threshold. This rapid resistance jump creates an inherent negative feedback loop, choking off current and rendering the system entirely self-regulating.
To quantify this effect, developers look at the resistance magnification factor (R factor), which normalizes the resistance at elevated temperatures against room-temperature baselines. Heraeus typically targets an R factor between 2x and 10x depending on the specific application needs. This exponential shift ensures rapid heat-up times since designers do not have to throttle early-stage power to prevent temperature overshoot.
By eliminating the physical footprint and failure points of external thermistors and microcontrollers, printed PTC heaters offer a highly reliable and simplified design. This makes them ideal for safety-critical applications like over-current protection, specialized thermal sensors, and localized smart heating elements.
In this short video, you can learn:
* The physical distinction between linear metallic heaters and exponential polymeric PTC heaters.
* How the resistance magnification factor (R factor) dictates the self-limiting temperature range.
* Engineering advantages of self-regulation, including minimized overshoot and rapid thermal response.
📋 **Clip Abstract** This clip introduces the operating principles of positive temperature coefficient (PTC) polymer heaters and how they achieve self-regulating thermal behavior. Zach Kelly explains the importance of the resistance magnification factor (R factor) in eliminating external sensors and controllers.
#PolymerPTCHeaters, #SelfRegulatingThermal, #ResistanceMagnificationFactor, #PrintedPTC, #PrintedElectronics, #FlexibleElectronics
00:03:59 - 00:05:25
How do you scale printed heater geometry to match low-voltage vs. high-voltage power profiles?
How do you scale printed heater geometry to match low-voltage vs. high-voltage power profiles?
Designing an optimized printed PTC heater requires balancing both ink chemistry and precise physical layout. The process starts by defining core parameters such as target temperature, driving voltage, desired thermal wattage, and environmental load. From there, engineers choose between high-resistivity and low-resistivity PTC paste variants to establish the correct baseline sheet resistance.
The physical pattern layout—specifically the gap between the conductor busbars and the width of the PTC resistor cells—is a critical design lever. Adjusting the cell spacing directly scales the electric field intensity across the carbon-polymer matrix. By modifying these dimensions, designers can tailor the final resistance of the heating grid without altering the chemical formulation of the ink.
As a general rule of thumb, low-voltage designs demand tight cell spacing on the order of one millimeter to maximize current draw at low potentials. Conversely, high-voltage systems require significantly wider spacing to prevent dielectric breakdown and maintain controlled, uniform heat generation across the substrate.
In this short video, you can learn:
* The primary steps to configure a printed heater based on voltage, wattage, and thermal load.
* How high-resistivity and low-resistivity ink variants are selected to dial in target sheet resistance.
* Geometric design rules for cell spacing, including the 1mm spacing benchmark for low-voltage circuits.
📋 **Clip Abstract** Zach Kelly outlines the essential design and layout principles for engineering printed polymer heaters. He explains how manipulating cell spacing and choosing the right ink resistivity enables safe, efficient performance across varying voltage thresholds.
#PrintedHeaters, #PTCHeaters, #ConductiveInks, #SheetResistance, #PrintedElectronics, #FlexibleElectronics