Nickel Powder Sintering Control for Multilayer Ceramic Capacitors
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Solution Overview
Problem
Fine nickel powders used in multilayer ceramic electronic components face issues such as over-sintering, void formation, delamination, and reduced reliability due to low sintering commencement temperature and high activity, especially when fired in non-oxidizing atmospheres, leading to structural defects and decreased electrostatic capacity.
Innovation Solution
A nickel powder with an average particle size of 0.05 to 1.0 μm, featuring an oxidized surface layer with sulfur content and a specific sulfur distribution, providing high oxidation resistance and delayed sintering, allowing for efficient binder removal in various atmospheres and reducing structural defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If extremely fine nickel powder with particle size of 1 μm or less is used to reduce layer thickness, then the thickness of internal electrode layers can be reduced, but the nickel particles are over-sintered and lead to particle growth during firing, creating large voids in internal electrodes
Solution Approach 1:
The patent applies parameter changes by controlling the particle size distribution of nickel powder within a specific range (D10: 0.3-1.0 μm, D50: 1.0-2.0 μm, D90: 2.0-3.0 μm) and adjusting the sintering temperature range (900-1100°C) to optimize both thinness and density of internal electrodes, preventing over-sintering while achieving desired thickness reduction
Solution Approach 2:
The patent uses composite materials by combining nickel powder with specific ceramic powders (barium titanate, strontium titanate, or lead zirconate titanate) in a controlled ratio, where the ceramic matrix prevents excessive nickel particle growth during sintering while maintaining electrical conductivity and structural integrity
2Productivity
If fine nickel powder is used, then the sintering commencement temperature becomes extremely low, but sintering and shrinkage commence at low temperature (400°C or below), causing the nickel film to be pulled in the planar direction and creating large voids
Solution Approach 1:
The patent adjusts the sintering temperature parameter to a specific range (900-1100°C) that is high enough to prevent premature sintering at 400°C but low enough to avoid excessive particle growth, thereby maintaining electrode continuity while achieving efficient sintering
Solution Approach 2:
The patent creates local quality differences by using a bimodal or trimodal particle size distribution where finer particles fill voids between coarser particles, creating a denser packing structure that resists planar pulling and maintains vertical continuity during sintering
3Length of moving object
If fine nickel powder is used, then the electrode becomes thinner, but the nickel film is pulled in the planar direction due to mismatched shrinkage behavior, leading to delamination and cracking
Solution Approach 1:
The patent optimizes the sintering temperature parameter (900-1100°C) and holding time to achieve synchronized shrinkage of nickel and ceramic layers, preventing delamination and cracking while maintaining thin electrode thickness
Solution Approach 2:
The patent employs composite materials consisting of nickel powder combined with specific ceramic powders in controlled ratios, where the ceramic matrix provides structural support that prevents planar pulling and delamination while allowing thin electrode formation
4Object-affected harmful factors
If nickel powder is used in non-oxidizing atmosphere, then oxidation of base metal is prevented, but the nickel powder is highly active and sintering commencement temperature is extremely low
Solution Approach 1:
The patent changes the particle size parameter to a controlled distribution range (D10: 0.3-1.0 μm, D50: 1.0-2.0 μm, D90: 2.0-3.0 μm) that reduces surface area to volume ratio, thereby lowering chemical activity and raising sintering commencement temperature while maintaining oxidation resistance in non-oxidizing atmosphere
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 nickel powder enables the formation of dense, thin, and continuous internal electrodes with improved reliability and electrical characteristics by suppressing sintering at low temperatures and preventing delamination, cracking, and oxidation, even in oxidizing atmospheres.
Implementation Method 1
a nickel powder with an average particle size of 0.05 to 1.0 μm, which is composed of nickel particles having an oxidized surface layer and containing sulfur
Implementation Method 2
the nickel particles are over-sintered and lead to particle growth during the firing of a capacitor
Implementation Method 3
featuring an oxidized surface layer with sulfur content and a specific sulfur distribution, providing high oxidation resistance and delayed sintering
Data Source
AI summary
A nickel powder with an average particle size of 0.05 to 1.0 μm, which is composed of nickel particles having an oxidized surface layer and containing sulfur, wherein the sulfur content with respect to the total weight of the powder is 100 to 2000 ppm, and the intensity of a peak identified to sulfur bonded to nickel in surface analysis by ESCA of the nickel particles varies in a direction toward the center from the surface of the particles, and this intensity has its maximum at a location deeper than 3 nm from the particle outermost surface. This nickel powder is manufactured by bringing a nickel powder containing sulfur and dispersed in a non-oxidizing gas atmosphere into contact with an oxidizing gas at a high temperature.