Cr-Fe-M Alloy Strain Gauge for Stable TCR and High Gauge Factor
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Solution Overview
Problem
Existing strain gauges face challenges in achieving a high gauge factor and stability against temperature changes due to variations in production steps, particularly those containing chromium, oxygen, and nitrogen, making it difficult to produce strain resistors with consistent performance.
Innovation Solution
A strain gauge using a Cr100-x-yFexMy alloy, where M represents one or more elements from Nb, Mo, and W, allows for a gauge factor of 10 or more and a temperature coefficient of resistance within ±1000 ppm/°C, without requiring precise control of crystal structure or reactive gas components, enabling production with a general-purpose sputtering apparatus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thin-film resistor containing chromium, oxygen, and nitrogen with optimized heat treatment is used to reduce temperature coefficient of resistance, then the temperature coefficient of resistance is reduced to ±100 ppm/°C or less, but variations in production steps make it difficult to stably produce strain resistors with high gauge factor and consistent temperature characteristics
Solution Approach 1:
The invention changes the compositional parameters of the alloy from Cr-O-N system to Cr-Fe-M system (where M is Nb, Mo, Ta, or W). This compositional parameter change fundamentally alters the material's temperature coefficient of resistance characteristics, enabling stable TCR values without requiring precise control of production parameters like heat treatment conditions. The new alloy composition inherently provides the desired electrical properties.
Solution Approach 2:
The invention extracts and eliminates the problematic reactive gas components (oxygen and nitrogen) from the production process. By removing these elements that require precise control during production, the invention simplifies the manufacturing process and eliminates the sensitivity to production step variations while maintaining or improving the temperature coefficient of resistance stability.
2Reliability
If reactive gas components such as oxygen and nitrogen are used in the production process to achieve desired electrical properties, then the strain resistor can exhibit high gauge factor, but the production process becomes complex and requires precise control
Solution Approach 1:
The invention extracts and removes the reactive gas components (oxygen and nitrogen) from the production process entirely. By using a Cr-Fe-M alloy composition that does not require these reactive gases for formation, the invention simplifies the production process while maintaining the ability to achieve high gauge factor values through the inherent properties of the alloy composition.
Solution Approach 2:
The invention creates an inert production environment by eliminating the need for reactive gas components. The Cr-Fe-M alloy can be produced without requiring controlled atmospheres of oxygen or nitrogen, effectively replacing the need for reactive gas processing with an inert or simplified production approach.
3Manufacturing precision
If precise control of crystal structure and reactive gas components is implemented to achieve high gauge factor and stable temperature characteristics, then performance requirements are met, but productivity decreases and production becomes more difficult
Solution Approach 1:
The invention changes the fundamental compositional parameters from Cr-O-N to Cr-Fe-M alloy system. This parameter change results in material properties that are less sensitive to production variations, allowing consistent performance to be achieved through simpler production methods and thereby increasing productivity without sacrificing performance consistency.
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 Cr100-x-yFexMy alloy strain gauge achieves high gauge factor stability and resistance to temperature changes, ensuring high quality and ease of production, while eliminating the need for precise control of reactive gases, thus enhancing productivity and consistency.
Implementation Method 1
a strain resistor which changes in resistance as the strain resistor deforms in response to an external force
Implementation Method 2
the necessity of reactive gas components such as oxygen and nitrogen in the production process is eliminated. The present invention further provides an alloy for strain resistors which gives the strain resistor to be provided in the strain gauge, and a sensor including the strain gauge
Data Source
AI summary
A strain gauge includes a film-shaped strain resistor having an alloy composition of Cr100-x-yFexMy, where the element M is one or two or more selected from the group consisting of Nb, Mo, Ta, and W, x representing the ratio of Fe added may be preferably 0.8 or more and 11.2 or less in terms of atomic percentage, and y representing the ratio of M added may be preferably more than 0 and less than or equal to 7.7 in terms of atomic percentage.