Multi-Point Thermocouple Assembly for Crack-Free Ceramic Bake Plates
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Solution Overview
Problem
Existing bake modules for microelectronic workpieces face challenges in accurately measuring temperature, particularly in the outer zones of ceramic bake plates, due to the limitations of straight metal thermocouples, which can cause cracking and inaccurate temperature control.
Innovation Solution
The use of multi-point thermocouples with rectangular or oval shapes, connected at multiple points to the ceramic body via brazed connections, provides improved flexibility and accurate temperature sensing while preventing cracking of the ceramic material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If straight metal thermocouples are used in ceramic bake plates, then temperature measurement is simplified, but cracking of the ceramic material occurs due to thermal expansion mismatch
Solution Approach 1:
The thermocouple is divided into multiple segments or sections along its length, with each segment independently connected to the ceramic body at different points. This segmentation allows each segment to accommodate thermal expansion independently, preventing stress concentration and cracking in the ceramic material while maintaining accurate temperature measurement capability.
Solution Approach 2:
The thermocouple structure is designed with varying properties at different locations - the connection points to the ceramic body are designed with specific flexibility and thermal expansion characteristics, while the sensing portions maintain precise dimensional stability. This local differentiation allows the thermocouple to adapt to thermal expansion at connection points without compromising measurement accuracy elsewhere.
2Ease of manufacture
If single-point thermocouple connections are used, then manufacturing is simpler, but temperature measurement accuracy in outer zones deteriorates
Solution Approach 1:
The thermocouple is divided into multiple segments or sections along its length, with each segment independently connected to the ceramic body at different points. This segmentation allows each segment to accommodate thermal expansion independently, preventing stress concentration and cracking in the ceramic material while maintaining accurate temperature measurement capability.
Solution Approach 2:
The thermocouple transitions from a single-point connection to a multi-point distributed connection along the channel length. This dimensional expansion from point to line contact enables temperature sensing at multiple locations simultaneously, improving measurement accuracy across different zones of the bake plate including outer zones.
3Stability of the object's composition
If rigid thermocouples are used, then structural stability is improved, but flexibility and adaptation to thermal expansion are reduced
Solution Approach 1:
The thermocouple is divided into multiple segments or sections along its length, with each segment independently connected to the ceramic body at different points. This segmentation allows each segment to accommodate thermal expansion independently, preventing stress concentration and cracking in the ceramic material while maintaining accurate temperature measurement capability.
Solution Approach 2:
The thermocouple structure incorporates dynamic characteristics that allow it to adapt to thermal expansion and contraction cycles. The multi-point connection design enables the thermocouple to flex and adjust its position slightly without compromising structural integrity, providing both stability and adaptability throughout temperature cycling operations.
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 solution enables precise temperature control across the bake plate, reducing the risk of ceramic cracking and ensuring accurate temperature measurements, even in high-temperature applications like post exposure bake processes.
Implementation Method 1
a second lead of the thermocouple can be brazed to an inner surface of the ceramic body at a second location remote from the first location
Implementation Method 2
a first lead of the thermocouple can be brazed to an inner surface of the ceramic body at a first location
Data Source
AI summary
Multi-point thermocouples and assemblies are disclosed for ceramic heating structures. The disclosed embodiments provide multi-point connections in distinct areas to provide good temperature-sensing contacts between metal thermocouples and ceramic bodies while also providing improved flexibility. As such, cracking of ceramic bodies for heating structures is avoided. For one embodiment, assemblies including a multi-point thermocouple and a ceramic body are used in bake plates for processing systems that process microelectronic workpieces. The metal thermocouple has a flat surface used for connections to the ceramic body. Preferably, the thermocouple is relatively thin and provides improved connection sites and flexibility.