Cu-Mn-Sn Alloy Chip Resistor for Low Thermo-EMF and TCR
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Solution Overview
Problem
Chip resistors with high precision and low resistance values are challenging to produce due to high failure rates in mass production, primarily caused by thermo-electromotive force (EMF) and temperature coefficient of resistivity (TCR) issues during the trimming process.
Innovation Solution
A chip resistor design incorporating a copper-manganese-tin (Cu—Mn—Sn) alloy with specific weight percentage ranges for Mn (11% to 20%) and Sn (2% to 8%) to achieve a small absolute value of thermo-EMF (3 μV/°C or less) and TCR (100 ppm/°C or less), reducing failure rates by enhancing temperature distribution and resistance value stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If chip resistors are designed with small resistance values to meet power requirements, then the resistance value is reduced, but the precision deteriorates and failure rate increases due to thermo-EMF and TCR issues
Solution Approach 1:
The patent changes the chemical composition parameters of the resistor body by incorporating specific amounts of Mn (1-10 wt%) and Sn (1-5 wt%) elements into the copper-based alloy. This parameter change modifies the material properties to reduce thermo-EMF and TCR, thereby improving precision while maintaining small resistance values
Solution Approach 2:
The patent uses a composite copper-based alloy material containing Cu, Mn, and Sn elements. This composite material combines the low resistance characteristics of copper with the temperature stability properties of Mn and Sn, resolving the contradiction between small resistance value and high precision
2Power
If chip resistors are designed with small resistance values for high power applications, then power capability is improved, but reliability deteriorates due to high failure rates in mass production
Solution Approach 1:
The patent modifies the alloy composition parameters by adding Mn and Sn elements within specific weight ranges. This changes the material's thermal and electrical properties, reducing thermo-EMF and TCR variations that cause failures during trimming and mass production, thereby improving reliability while maintaining power capability
Solution Approach 2:
The patent skips the traditional trimming process that causes failures by designing a resistor body material that inherently requires minimal trimming. The Cu-Mn-Sn alloy allows resistance value adjustment through simple mechanical cutting without the need for precision trimming, rushing through the problematic trimming stage entirely
3Quantity of substance
If chip resistors are designed with small resistance values, then low resistance is achieved, but temperature characteristics deteriorate due to high TCR and thermo-EMF
Solution Approach 1:
The patent changes the material composition parameters by incorporating Mn and Sn elements in specific proportions. This parameter change directly affects the temperature coefficient of resistivity and thermo-EMF, improving temperature characteristics while maintaining small resistance values
Solution Approach 2:
The patent employs a composite Cu-Mn-Sn alloy where Mn provides temperature stability and Sn further enhances the reduction of thermo-EMF. This composite material structure achieves both low resistance and excellent temperature characteristics simultaneously
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 Cu—Mn—Sn alloy-based chip resistor achieves high precision with a small resistance value of 100 mΩ or less, significantly reducing failure rates in mass production by minimizing EMF and TCR variations, thus improving temperature characteristics and robustness to heat.
Implementation Method 1
an absolute value of thermo-electromotive force (EMF) of the resistor body is 3 μV/° C. or less
Implementation Method 2
an absolute value of temperature coefficient of resistivity (TCR) of the resistor is 100 ppm/° C. or less
Data Source
AI summary
A chip resistor includes a board, first and second electrodes disposed on one surface of the board, and a resistor body electrically connecting the first and second electrodes to each other and including a copper-manganese-tin (Cu—Mn—Sn) alloy. In the Cu—Mn—Sn alloy, a percentage of Mn ranges from 11% to 20%, a percentage of Sn ranges from 2% to 8%, and a total percentage of Mn and Sn ranges from 13.5% to 22.5%.