Planar Heating Element with Parallel PTC Traces for Uniform Temperature
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Solution Overview
Problem
Existing planar heating elements with meander-shaped PTC resistive structures face challenges in achieving uniform temperature distribution due to varying line breadths, leading to hotspots and high current densities, which can cause electromigration and hinder efficient heating.
Innovation Solution
A planar heating element with a PTC resistive structure featuring internal and external conductive traces of different resistances, connected in parallel, ensures a uniform temperature distribution by utilizing the trace with lower resistance for greater heating power, preventing hotspot formation and stabilizing the temperature across a defined surface region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a meander-shaped PTC resistive structure is used, then the heating function is provided, but the temperature distribution becomes non-uniform due to varying line breadths causing hotspots
Solution Approach 1:
The PTC resistive structure is segmented into multiple parallel conductive traces instead of a single meander path. This segmentation distributes the current flow across multiple paths, preventing localized overheating and achieving more uniform temperature distribution across the heating element surface.
Solution Approach 2:
Different regions of the heating element are designed with different line breadths to compensate for thermal losses. Regions with higher thermal losses have larger line breadths to provide additional heating power locally, while regions with lower losses have smaller line breadths, achieving uniform overall temperature distribution.
2Power
If a meander-shaped PTC resistive structure is used, then heating is provided, but the resistance becomes relatively large requiring high voltage for energy supply
Solution Approach 1:
Multiple parallel conductive traces are merged into a single equivalent electrical path, reducing the total resistance of the heating element. The parallel configuration allows current to flow through multiple paths simultaneously, effectively lowering the overall resistance and enabling operation at lower voltages while maintaining adequate heating power.
3Power
If high current densities are used for heating, then heating power is increased, but electromigration occurs
Solution Approach 1:
The total current is segmented and distributed across multiple parallel conductive traces, reducing the current density in each individual trace. This segmentation maintains the required total heating power while preventing electromigration in any single trace, thereby improving the reliability and lifespan of the heating element.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves a homogeneous temperature distribution within a defined surface region, limiting the heated zone and preventing hotspots, while allowing for efficient heating with a lower total resistance and reduced energy consumption, and can function as both a heating element and temperature sensor.
Implementation Method 1
the PTC resistive structure has—at least approximately—a homogeneous, respectively uniform, temperature distribution... the resistive structure is connected with an electrical voltage source... the ohmic resistance increases with rising temperature
Implementation Method 2
PTC resistive structures are distinguished by the feature that the ohmic resistance increases with rising temperature, wherein the functional dependence is highly linear over a large temperature range
Data Source
AI summary
A planar heating element comprising a PTC resistive structure, which is arranged in a defined surface region of a first surface of a support substrate. The electrical connection contacts for connection to an electrical voltage source are associated with the PTC resistive structure, wherein the PTC resistive structure—starting from the two electrical connection contacts—has at least one internal conductive trace and a parallel connected, external conductive trace. The internal conductive trace has a greater resistance than the external conductive trace and the resistances of the internal conductive trace and external conductive trace are so sized that upon applying a voltage an essentially uniform temperature distribution is present within the defined surface region.