Micro-hotplate Heating Structure for Uniform Temperature
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Solution Overview
Problem
Current micro-hotplate devices for gas sensors suffer from non-uniform temperature distribution, leading to inefficiencies in power consumption, accuracy, and reliability, with existing solutions either increasing process complexity or thermal mass, or failing to adequately address temperature uniformity.
Innovation Solution
A micro-hotplate device with a heating structure featuring concentric tracks and spaces, where outer tracks are narrower than inner tracks, and the width and spacing of inner tracks remain substantially constant, ensuring uniform heat distribution and minimizing thermal losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a uniform heat source pattern is used in the micro-hotplate, then the manufacturing process is simple, but the temperature distribution across the active area becomes non-uniform due to conductive heat losses to the frame
Solution Approach 1:
The heating structure implements local quality by varying the track width across different radial positions. Inner tracks have greater width than outer tracks, creating non-uniform heat generation that compensates for the non-uniform heat losses. This local variation in heating intensity ensures that regions with higher conductive losses (near the frame) receive proportionally more heat, achieving uniform temperature distribution across the active area.
2Temperature
If additional heat spreading plates are added to improve temperature uniformity, then temperature gradients are reduced, but the process complexity and thermal mass increase
Solution Approach 1:
The invention extracts the heat spreading function from a separate additional layer and integrates it directly into the heating structure itself. By incorporating the heat spreading capability within the heating tracks of the existing membrane layer, the patent eliminates the need for separate heat spreading plates and their associated fabrication steps, thereby reducing process complexity while maintaining temperature uniformity.
Solution Approach 2:
The heating structure and heat spreading function are merged into a single integrated component. The heating tracks simultaneously perform both heating and heat spreading functions, eliminating the need for separate heat spreading layers. This merging reduces the number of fabrication steps and lowers process complexity while achieving the desired temperature uniformity.
3Temperature
If additional heat spreading plates are added to improve temperature uniformity, then temperature gradients are reduced, but the thermal response time increases due to increased thermal inertia
Solution Approach 1:
The invention extracts the heat spreading function from separate additional thermal mass layers and integrates it into the heating structure within the existing membrane layer. This eliminates the need for additional thermal mass, thereby maintaining fast thermal response time while still achieving uniform temperature distribution through the integrated heat spreading capability of the heating tracks.
4Temperature
If the heater track width is varied to improve temperature uniformity, then temperature distribution improves, but the manufacturing precision requirements increase
Solution Approach 1:
The heating structure employs asymmetric track width design where inner tracks have greater width than outer tracks. This intentional asymmetry is designed to compensate for the asymmetric heat loss pattern (higher near the frame). The asymmetric geometry is implemented using standard photolithography patterning processes, making it manufacturable with conventional precision capabilities.
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
This design achieves optimal temperature uniformity in the active area, enhancing the sensitivity, reliability, and efficiency of gas sensors while reducing power consumption and thermal response time.
Implementation Method 1
a resistive heating structure is deposited in order to heat the active area of the membrane to a given desired temperature
Implementation Method 2
The temperature uniformity of the active area is a critical factor for good sensor efficiency, i.e. for an optimum usage of the consumed power
Data Source
Figure 1~5
Figure 2~3
Figure 4a~4d
AI summary
The present invention relates to a micro-hotplate device comprising a frame, a membrane, an active area comprising at least one active layer, and a heating structure designed to heat said active layer, said heating structure having concentric tracks and comprising inner tracks (20) and inner spaces (22) and outer tracks (24) and outer spaces (26) as being the one or two tracks and spaces located the furthest away from the center of the heating structure, characterized in that said outer tracks (24) are designed to be located closer to their neighboring tracks and/or are designed to have a width which is lower thanthose of the inner tracks (20), the width and the spacing of said inner tracks (20) being substantially constant.