Core-Shell Dielectric Ceramic Composition for Stable MLCC Capacitance
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Solution Overview
Problem
Multilayer ceramic electronic devices face challenges in maintaining high electrostatic capacity and insulation properties due to fluctuations in firing temperature and oxygen partial pressure, leading to reduced mass productivity and reliability.
Innovation Solution
A dielectric ceramic composition with a core-shell structure, comprising a perovskite structure expressed by BaCaTiO3, incorporating rare earth elements like gadolinium and manganese, and barium titanate composite oxides, which suppresses changes in electrostatic capacity and enhances insulation properties across a wide firing atmosphere.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the firing temperature is increased to thicken the shell portion and improve electrostatic capacity, then the electrostatic capacity increases, but the manufacturing precision deteriorates due to the need for precise temperature control
Solution Approach 1:
The patent changes the chemical composition parameters of the dielectric ceramic by incorporating specific rare earth elements (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) and metal elements (Mg, Mn, Fe, Co, Ni, Cu, Zn) in controlled amounts. This composition modification allows the shell portion to achieve the desired electrostatic capacity enhancement without requiring extremely precise firing temperature control, as the compositional buffer absorbs temperature variations.
Solution Approach 2:
The patent creates a composite dielectric ceramic material with a core-shell structure where the shell contains a combination of rare earth elements and metal elements added to barium titanate or barium calcium titanate. This composite structure enables the shell to provide both the electrostatic capacity enhancement and the buffering effect against firing temperature fluctuations, resolving the contradiction between capacity improvement and manufacturing precision.
2Ease of manufacture
If a large amount of oxygen vacancies occur in barium titanate grains during firing in a reducing atmosphere, then the insulation properties significantly reduce, but using inexpensive base metals like Ni, Cu, or Sn for internal electrodes requires reducing atmosphere firing
Solution Approach 1:
The patent introduces rare earth elements and metal elements as intermediary substances that mediate between the reducing atmosphere firing process and the barium titanate grains. These elements act as oxygen vacancy compensators, filling or stabilizing oxygen vacancies that would otherwise form during reducing atmosphere firing, thereby maintaining insulation properties while allowing the use of inexpensive base metal internal electrodes.
Solution Approach 2:
The patent converts the potentially harmful effect of reducing atmosphere firing (which creates oxygen vacancies and reduces insulation) into a beneficial process. By pre-incorporating rare earth and metal elements into the dielectric ceramic composition, the reducing atmosphere becomes effective for forming inexpensive base metal internal electrodes while the incorporated elements prevent excessive oxygen vacancy formation, thus converting a harmful condition into a beneficial manufacturing approach.
3Productivity
If the firing temperature fluctuates, then the electrostatic capacity changes, but high mass productivity requires faster firing cycles
Solution Approach 1:
The patent applies beforehand cushioning by pre-incorporating rare earth elements and metal elements into the dielectric ceramic composition before firing. These elements create a compositional buffer that cushions against electrostatic capacity changes caused by firing temperature fluctuations. This allows faster firing cycles for high mass productivity while the pre-built compositional buffer maintains electrostatic capacity stability despite temperature variations.
4Quantity of substance
If the shell portion becomes thicker to improve electrostatic capacity, then the electrostatic capacity increases, but the device complexity increases due to precise control requirements
Solution Approach 1:
The patent changes the compositional parameters of the shell portion by incorporating rare earth elements and metal elements, which fundamentally alters how the shell achieves its function. Instead of relying solely on thickness control (which requires precise manufacturing control), the compositional modification provides an inherent mechanism for electrostatic capacity enhancement that is more tolerant of manufacturing variations, thereby reducing device complexity.
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 dielectric ceramic composition effectively stabilizes electrostatic capacity and improves insulation properties, enabling higher mass productivity and reliability by controlling the firing temperature and oxygen partial pressure fluctuations.
Implementation Method 1
a first crystal grain having a perovskite structure expressed by a general formula of BaCaTiO3, and having a core portion and a shell portion surrounding the core portion and containing a rare earth element and manganese
Implementation Method 2
transition to a low temperature of the generation of large electrostatic capacity near the Curie temperature, where barium titanate exists at around 125° C., changing from the ferroelectric phase to the paraelectric phase
Data Source
AI summary
A dielectric ceramic composition includes a first crystal grain that has a perovskite structure expressed by a general formula of BaCaTiO3, and has a core portion and a shell portion surrounding the core portion and including a rare earth element and manganese, and a second crystal grain in which an elemental ratio of total of barium and calcium to titanium is 0.70 or less and a main component is barium calcium titanate.