Multi-Layer Ceramic Capacitor Grain Size Control
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Solution Overview
Problem
Multi-layer ceramic capacitors face a trade-off between achieving small size and high capacitance, as reducing grain size for higher density layering decreases the dielectric constant, compromising electrical insulation and voltage endurance.
Innovation Solution
The development of a multi-layer ceramic capacitor with uniformly grown dielectric grains, characterized by a dispersion of average grain size less than 4, and an average size between 300 nm and 1000 nm, ensuring a high specific dielectric constant and improved reliability, achieved through sintering and controlled addition of MgO.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the grain size of dielectrics is reduced to increase density and reduce dielectric layer thickness, then the capacitance increases, but the dielectric constant drops due to the sizing effect
Solution Approach 1:
The patent applies parameter changes by precisely controlling the grain size of dielectric particles within a specific range (0.1 to 0.2 μm) and adjusting the MgO content (0.05 to 3.0 mol per 100 mol of Ba3-xCaxTiO3) to optimize both density and dielectric constant. This resolves the contradiction by finding the optimal parameter values that satisfy both requirements simultaneously.
Solution Approach 2:
The patent uses composite materials by combining Ba3-xCaxTiO3 with MgO as an acceptor element. This composite approach allows the fine-grained dielectric structure to maintain high dielectric constant through the synergistic effect of the base material and MgO additive, overcoming the typical sizing effect that reduces dielectric constant in fine-grained materials.
2Volume of moving object
If the dielectric layer thickness is reduced to achieve smaller capacitor size, then the device size decreases, but the voltage endurance deteriorates due to electric field concentration at electrode projections
Solution Approach 1:
The patent changes the surface morphology parameter by controlling grain growth to create a uniformly flat dielectric layer surface. This surface uniformity prevents the formation of deep gaps that would cause electrode projections and electric field concentration, thereby maintaining voltage endurance even in thin dielectric layers.
Solution Approach 2:
The patent applies beforehand cushioning by pre-forming a uniformly flat dielectric surface through controlled grain growth before electrode deposition. This preventive measure eliminates the root cause of future electric field concentration and voltage breakdown, cushioning against potential reliability failures in thin-layer capacitors.
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
This approach results in a capacitor with a high specific dielectric constant and extended life characteristics, maintaining a flat dielectric layer surface and preventing electrical conductivity issues, thereby achieving large capacitance and reliability.
Implementation Method 1
growing the dielectric grains to a grain size of 0.35 to 0.65 μm, in the process of reducing the thickness of the dielectric layer to approx. 1 μm
Implementation Method 2
In general, Mg is added as an acceptor element to suppress the reduction of dielectrics due to sintering
Implementation Method 3
the smaller the grain size, the larger the grain boundary becomes where movement of oxygen vacancy migration in the electrostatic field (electric field migration) is inhibited
Data Source
AI summary
A multi-layer ceramic capacitor has a structure where the dispersion, nd, of average grain size of the dielectric grains constituting the dielectric layer (a value (D90/D10) obtained by dividing D90 which is a grain size including 90% cumulative abundance of grains by D10 which is a grain size including 10% cumulative abundance of grains) is smaller than 4.