MLCC Dielectric Composition for Low-Temperature Sintering
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Solution Overview
Problem
The manufacturing of multilayer ceramic capacitors with thin dielectric layers faces challenges in preventing grain growth of metal particles during firing, leading to reduced dielectric layer thickness and inadequate coverage of internal electrodes, which is exacerbated by the volatility of Li compounds used in low-temperature firing methods.
Innovation Solution
Incorporating phosphorus (P) and silicon (Si) in the dielectric layers, which segregate at grain-boundary triple points, forming a low-melting point and low-viscosity glass that allows for low-temperature sintering without volatilization, maintaining a high dielectric constant and enabling thicker, higher-capacity capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If Li compound is added to enable low-temperature firing, then firing temperature can be reduced, but Li volatilizes and prevents low-temperature firing
Solution Approach 1:
The patent introduces P and Si as intermediary elements that form a low-melting-point glass phase. This glass phase acts as a flux that promotes sintering at lower temperatures without the volatility problems of Li compounds. The P-Si glass phase mediates the sintering process, enabling low-temperature firing while maintaining material stability.
Solution Approach 2:
The patent changes the chemical composition parameters of the dielectric layer by incorporating specific ratios of P and Si elements. This compositional parameter change transforms the firing characteristics, allowing the material to sinter effectively at lower temperatures through the formation of a eutectic glass phase with lower melting point than the base ceramic material.
2Manufacturing precision
If firing temperature is reduced to prevent grain growth, then internal electrode coverage is improved, but sintering becomes insufficient
Solution Approach 1:
The patent utilizes phase transition of the P-Si-containing dielectric material during firing. At the low firing temperature, a glass phase forms and undergoes viscous flow, which densifies the ceramic body and fills pores without requiring high-temperature sintering. This phase transition mechanism enables adequate sintering density to be achieved at lower temperatures where grain growth is suppressed.
Solution Approach 2:
The dielectric layer is designed as a composite material containing Ba-Ti-O perovskite phase combined with P-Si glass phase. This composite structure allows the crystalline perovskite to maintain its high dielectric constant while the glass phase provides low-temperature sintering capability and densification, thereby achieving both good coverage and sufficient sintering density.
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 enables low-temperature sintering while maintaining a high dielectric constant, allowing for the production of larger-capacity and thinner multilayer ceramic capacitors with improved electrode coverage, overcoming the limitations of existing methods.
Implementation Method 1
P and Si segregate in at least one of grain-boundary triple points of three ceramic particles to form a low-melting point and low-viscosity glass
Implementation Method 2
low-temperature sintering without volatilization
Implementation Method 3
P and Si segregate in at least one of grain-boundary triple points of three ceramic particles
Data Source
AI summary
A multilayer ceramic capacitor that includes a ceramic body including a stack of a plurality of dielectric layers and a plurality of first and second internal electrodes; and first and second external electrodes provided at each of both end faces of the ceramic body. Each of the plurality of dielectric layers contain Ba, Ti, P and Si. The plurality of dielectric layers include an outer dielectric layer located on an outermost side in the stacking direction; an inner dielectric layer located between the first and second internal electrodes; and a side margin portion in a region where the first and second internal electrodes do not exist. In at least one of the outer dielectric layer, the inner dielectric layer and the side margin portion, the P and the Si segregate in at least one of grain-boundary triple points of three ceramic particles.