Planar Heater Structure With CTE-Matched Insulating Layer
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Solution Overview
Problem
Planar heating ovens face challenges with insulating materials that lose their insulating properties at temperatures above 200 °C, and existing solutions do not provide adequate insulation and adhesive force at high temperatures like 500 °C.
Innovation Solution
A structure comprising a metal substrate with an insulating layer and an electrically conductive layer, where the difference in coefficient of thermal expansion between the substrate and insulating layer is 4 ppm/K or less, ensuring stable insulating properties and adhesive force even at high temperatures, achieved through a process of coating and heat-treating insulator, electrode, and conductive compositions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If enamel is used as insulating material in commercial ovens, then insulating properties are provided at low temperatures, but insulating properties are lost at temperatures of 200 °C or higher
Solution Approach 1:
The patent changes the material parameters by selecting an insulating layer material with specific coefficient of thermal expansion (CTE) properties. The insulating layer is designed to have a CTE of 5.44 ppm/K to match the metal substrate, preventing thermal degradation and maintaining insulating properties at high temperatures up to 500 °C or higher.
Solution Approach 2:
The patent uses a composite structure consisting of a metal substrate and an insulating layer with specific material properties. The insulating layer is formulated as a composite material that maintains both adhesive bonding to the metal substrate and electrical insulation at high temperatures, overcoming the limitations of conventional enamel materials.
2Ease of manufacture
If the coefficient of thermal expansion difference between metal substrate and insulating layer is large, then manufacturing is easier, but adhesive force between substrate and insulating layer deteriorates at high temperatures
Solution Approach 1:
The patent precisely controls the coefficient of thermal expansion parameter of the insulating layer to be 5.44 ppm/K, matching the metal substrate. This parameter optimization ensures that thermal expansion stresses are minimized during heating and cooling cycles, maintaining strong adhesive bonding between the substrate and insulating layer at high temperatures while remaining manufacturable.
3Reliability
If insulating material is used to prevent short circuits, then electrical insulation is provided, but thermal stress increases due to coefficient of thermal expansion mismatch
Solution Approach 1:
The patent optimizes the coefficient of thermal expansion parameter of the insulating layer to match the metal substrate (5.44 ppm/K). This parameter matching eliminates thermal stress caused by expansion mismatch during temperature cycling, while the layer maintains its electrical insulation function to prevent short circuits between conductive elements.
Solution Approach 2:
The insulating layer acts as an intermediary between the metal substrate and conductive elements. It provides electrical insulation to prevent short circuits while its matched thermal expansion properties allow it to mediate thermal stresses, preventing delamination or cracking during high-temperature operation.
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 provides uniform heating and insulation at temperatures up to 500 °C, reducing thermal stress and maintaining insulating properties, while ensuring a strong adhesive force between the substrate and insulating layer, improving energy efficiency and heat distribution.
Implementation Method 1
a difference in a coefficient of thermal expansion (CTE) between the metal substrate and the insulating layer is 4 parts per million per degree Kelvin change in temperature (ppm/K) or less
Implementation Method 2
structures having insulating properties even at a high temperature of 500 °C or higher
Implementation Method 3
a desirable adhesive force between a substrate and an insulating layer
Data Source
Figure 1~2A
Figure 2B~2C
Figure 3
AI summary
Provided are a structure, a planar heater including the same, a heating device including the planar heater, and a method of preparing the structure. The structure includes a metal substrate, an insulating layer disposed on the metal substrate, an electrode layer disposed on the insulating layer, and an electrically conductive layer disposed on the electrode layer, wherein a difference in a coefficient of thermal expansion (CTE) between the metal substrate and the insulating layer is 4 parts per million per degree Kelvin change in temperature (ppm/K) or less.