Nickel Powder Surface Oxidation for Multilayer Ceramic Electrodes
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Solution Overview
Problem
Fine nickel powders used in multilayer ceramic electronic components are prone to over-sintering, leading to structural defects, increased electrical resistance, and reduced reliability due to incomplete resin decomposition and residual carbon, especially when fired in a nonoxidizing atmosphere.
Innovation Solution
A nickel powder with a mean particle size of 0.05 to 1.0 μm, featuring a thin oxidized surface layer with controlled oxygen and carbon content, and optionally sulfur, to reduce catalytic activity and prevent resin decomposition at low temperatures, ensuring a dense and continuous electrode film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If extremely fine nickel powder with particle size of 1 μm or less is used to reduce electrode thickness, then miniaturization and high multilayering are achieved, but the nickel particles are over-sintered during firing, voids appear in the inner electrodes, and electrical resistance increases
Solution Approach 1:
The patent applies parameter changes by controlling the oxygen content of nickel powder within 0.5 to 5.0 wt.% and particle size within 0.1 to 1.0 μm. This optimization prevents over-sintering during firing while maintaining electrical conductivity, resolving the contradiction between miniaturization and electrical continuity.
Solution Approach 2:
The patent uses composite material by forming a core-shell structure where nickel powder with controlled oxygen content serves as the core. This composite structure prevents excessive sintering and maintains electrode integrity even at reduced thickness, addressing the contradiction between miniaturization and reliability.
2Productivity
If nickel powder with high catalytic activity is used in a nonoxidizing atmosphere during binder removal, then the process is efficient, but the resin decomposes explosively at low temperatures, causing structural defects
Solution Approach 1:
The patent changes the parameter of oxygen content in nickel powder to 0.5-5.0 wt.%, which reduces catalytic activity. This prevents explosive decomposition of resin during binder removal in nonoxidizing atmosphere, eliminating structural defects while maintaining process efficiency.
Solution Approach 2:
The patent converts the harmful high catalytic activity of nickel into a beneficial controlled catalytic activity by introducing specific oxygen content. This controlled oxygen content prevents explosive resin decomposition while maintaining efficient binder removal, turning a harmful property into a beneficial one.
3Volume of moving object
If the thickness of ceramic sheets and inner electrode layers is reduced to achieve miniaturization, then component size is reduced, but the electrode film becomes discontinuous and electrical resistance increases
Solution Approach 1:
The patent optimizes nickel powder parameters including particle size (0.1-1.0 μm) and oxygen content (0.5-5.0 wt.%) to prevent over-sintering. This enables formation of continuous electrode films even at reduced thickness, achieving miniaturization without sacrificing film continuity.
4Quantity of substance
If nickel powder is used instead of noble metal powder to reduce cost, then manufacturing cost is reduced, but oxidation occurs during firing in nonoxidizing atmosphere, compromising reliability
Solution Approach 1:
The patent changes the chemical composition parameter by controlling oxygen content in nickel powder to 0.5-5.0 wt.%. This creates a protective oxidized layer that prevents further oxidation during firing, maintaining reliability while using cost-effective nickel instead of noble metals.
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 solution effectively reduces residual carbon, prevents structural defects, and maintains excellent electrical properties and strength, even in highly miniaturized components with thin layers, by stabilizing the oxidized surface layer and minimizing the catalytic activity of the nickel powder.
Implementation Method 1
a nickel powder having a mean particle size of 0.1 to 0.8 μm and an oxygen content of 0.5 to 5.0 wt. % and is subjected to surface oxidation
Implementation Method 2
a nickel powder, which inherently has a high catalytic activity, acts as a catalyst for decomposition of the resin binder and tends to accelerate the decomposition process
Implementation Method 3
such extremely fine nickel powders are easily sintered, the nickel particles are over-sintered during firing of the capacitor, voids appears in the inner electrodes due to grain growth
Implementation Method 4
because the starting temperature of sintering is extremely low and sintering is started at an early stage during firing and also because volume expansion and shrinkage are induced by a redox reaction
Data Source
AI summary
A nickel powder with a mean particle size of 0.05 to 1.0 μm, the nickel powder having a thin oxidized layer of nickel on a surface thereof, an oxygen content of 0.3 to 3.0 wt. % and a carbon content of 100 ppm or less per specific surface area of 1 m2/g of the powder, in a weight proportion of carbon to the nickel powder of unit weight. When the powder is used for a conductive paste for forming inner electrode layers of a multilayer electronic component, it enables a decrease in the residual carbon amount after a binder removal process, thereby making it possible to obtain a multilayer ceramic electronic component excellent electrical characteristics and high reliability in which electrode layers excelling in continuity are formed without decreasing the strength and electrical characteristics of the electronic component or creating structural defects.