Nickel Powder Morphology Control for Reliable Thin-MLCC Electrodes
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Solution Overview
Problem
Existing methods for producing multilayer ceramic capacitors (MLCCs) fail to adequately suppress crack occurrence and improve breakdown voltage, despite reducing connected particles, which are crucial for reliability when electrode and dielectric layers are thinned.
Innovation Solution
A metal powder with a nickel content of 99.5% or more, characterized by specific particle ratios and impurity contents, is produced using a CVD method with controlled cooling to minimize capsule-shaped connected particles, ensuring a narrow particle size distribution and reduced curvature, thereby enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If classification treatment is performed to remove coarse particles, then the number of coarse particles is reduced, but capsule-shaped coarse connected particles remain that cannot be removed by classification
Solution Approach 1:
The invention applies preliminary action by controlling the CVD reaction conditions before classification treatment to suppress the generation of capsule-shaped coarse connected particles. By optimizing reaction temperature, gas flow rates, and precursor concentrations during the powder production stage, the harmful particle morphology is prevented from forming in the first place, making subsequent classification more effective and improving reliability.
Solution Approach 2:
The invention employs parameter changes by adjusting CVD reaction parameters including temperature gradients, gas composition ratios, and residence time to control particle formation. These parameter modifications suppress the formation of capsule-shaped connected particles while maintaining fine particle size distribution, thereby resolving the contradiction between manufacturing precision and reliability.
2Volume of moving object
If electrode and dielectric layers are thinned to reduce capacitor size, then capacitance density is improved, but oversintering of electrode occurs causing short circuits
Solution Approach 1:
The invention applies local quality by producing metal powder with highly uniform and controlled local particle characteristics. The CVD process ensures each particle has consistent size, shape, and surface properties within the fine particle range. This uniformity prevents localized oversintering events that would cause short circuits in thinned electrode layers, while maintaining the reduced capacitor size.
3Quantity of substance
If connected particles are reduced to improve capacitance, then capacitance decrease is suppressed, but crack occurrence and breakdown voltage issues remain
Solution Approach 1:
The invention applies preliminary action by controlling particle morphology during CVD production before the powder is used in capacitor manufacturing. By suppressing capsule-shaped connected particle formation at the source through optimized reaction conditions, the invention prevents reliability issues while maintaining the reduced connected particle count needed for high capacitance.
Solution Approach 2:
The invention converts the potential harm of connected particles into a benefit by carefully controlling their formation. The CVD process parameters are optimized to allow some connected particle formation (which maintains capacitance) while suppressing the harmful capsule-shaped morphology (which causes cracks). This transforms what would be purely harmful connected particles into a controlled feature that maintains electrical performance without compromising reliability.
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 provides a metal powder suitable for high-yield production of MLCCs with improved reliability and reduced oversintering, addressing the limitations of previous methods by ensuring consistent quality and performance even with thin electrode and dielectric layers.
Implementation Method 1
a reaction step of reacting the metal compound gas with a reducing gas to produce metal powder
Implementation Method 2
a cooling step of cooling a generated metal powder
Implementation Method 3
producing a metal powder by performing a CVD reaction
Data Source
AI summary
A metal powder in which 99.5 mass % or more of the metal component is Ni, the ratio of metal particles having the ratio S/DPV of the minor axis S of the metal particles to the equal volume sphere equivalent diameter DPV of the metal particles is 0.92 or less and the ratio DPV/DPV50 of the equal volume sphere equivalent diameter DPV to the volume-based median diameter DPV50 is 1.8 or more is 1.0 vol % or less, and the volume-based median diameter DPV50 of the metal particles is 0.08 to 0.35 μm. Furthermore, the S content per a specific surface area of 1 m2/g is preferably 70 to 600 ppm, and similarly, the O content is preferably 1200 to 7000 ppm.