NTC Thermistor Composition for Reflow-Stable Resistance
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Solution Overview
Problem
Multilayer thermistor elements exhibit significant changes in characteristics when mounted on circuit boards, particularly in high-temperature and high-humidity environments, leading to instability and variations in resistance values during reflow processing.
Innovation Solution
An NTC thermistor composition comprising 40 to 63 mol % Mn, 10 to 30 mol % Co, 15 to 35 mol % Ni, and 5.9 mol % or less Al, with optional inclusion of 0 to 2.5 mol % Zr, and excluding substantial amounts of Fe and Cu, is used to create thermistor elements with improved thermal stability and reduced resistance variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional thermistor compositions are used, then the elements can be manufactured, but the resistance value varies significantly during reflow processing and in high-temperature environments
Solution Approach 1:
The patent applies parameter changes by precisely controlling the compositional ratios of metal oxides (Mn: 40-63 mol%, Co: 10-30 mol%, Ni: 15-35 mol%, Al: 5.9 mol% or less) to achieve optimal thermal stability and resistance consistency during reflow processing
Solution Approach 2:
The patent uses composite materials by combining multiple metal oxides (MnO2, CoO, NiO, Al2O3) in specific proportions to create a thermistor composition that exhibits enhanced thermal stability and reduced resistance variation compared to single-material solutions
2Reliability
If Fe or Cu is contained in the composition, then the manufacturing cost may be reduced, but the thermal stability decreases and resistance value variation increases
Solution Approach 1:
The patent applies the extraction principle by deliberately excluding Fe and Cu from the thermistor composition, removing these elements that would otherwise degrade thermal stability and increase resistance variation, even though this may increase manufacturing cost
3Reliability
If Ni content is increased to improve thermal stability, then the resistance variation decreases, but the manufacturing cost increases
Solution Approach 1:
The patent optimizes the Ni content parameter within the range of 15-35 mol% to achieve the desired balance between thermal stability and manufacturing cost, avoiding excessive Ni addition while maintaining performance
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 proposed NTC thermistor composition achieves excellent thermal stability and minimal resistance variation even after multiple reflow processes, ensuring reliable performance in high-temperature environments.
Implementation Method 1
Negative temperature coefficient (NTC) thermistor elements have a characteristic that the resistance value decreases as the temperature increases
Data Source
AI summary
An NTC thermistor composition contains 40 to 63 mol % of Mn, 10 to 30 mol % of Co; 15 to 35 mol % of Ni, and 5.9 mol % or less (including 0) of Al.