Dielectric Ceramic Grain Control for MLCC Reliability
Solution Overview
Problem
The challenge is to reduce oxygen defect concentration in dielectric ceramic layers of multi-layer ceramic capacitors while maintaining a high dielectric constant, as excessive acceptor elements used to minimize defects can lead to reduced grain size and decreased dielectric constant.
Innovation Solution
A dielectric ceramic with sintered grains of 0.2 to 1.0 μm average grain size and 0.2 to 0.5% oxygen defect concentration, using ABO3 as the primary component with an acceptor element like Sc, Cr, or Mn, sintered in a reducing atmosphere and then oxidized to control defect levels, ensuring a high dielectric constant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a larger quantity of acceptor element is added to reduce oxygen defects, then oxygen defect concentration decreases, but grain size reduces and dielectric constant drops
Solution Approach 1:
The patent applies parameter changes by precisely controlling the acceptor element concentration within 0.01-1.0 mol% and the sintering atmosphere oxygen partial pressure within 10^-2 to 10^-9 atm. This quantitative control allows reduction of oxygen defects while maintaining grain size and dielectric constant, resolving the contradiction between defect reduction and grain growth suppression.
2Reliability
If a larger quantity of acceptor element is added to reduce oxygen defects, then oxygen defect concentration decreases, but dielectric constant drops
Solution Approach 1:
The patent changes the sintering atmosphere parameter (oxygen partial pressure) in addition to acceptor element concentration. By controlling oxygen partial pressure within 10^-2 to 10^-9 atm during sintering, the patent achieves low oxygen defect concentration while maintaining high dielectric constant, resolving the contradiction between defect reduction and dielectric performance preservation.
3Productivity
If the dielectric layers are made thinner to increase stacking density, then capacitance increases, but leak current increases due to carrier movement through oxygen defects
Solution Approach 1:
The patent changes the chemical composition parameters by precisely controlling acceptor element concentration (0.01-1.0 mol%) and sintering atmosphere oxygen partial pressure (10^-2 to 10^-9 atm). This reduces oxygen defect concentration in thin dielectric layers, suppressing carrier movement and leak current while maintaining high capacitance density through increased stacking.
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 effectively reduces oxygen defects and maintains a sufficiently high dielectric constant, enhancing the capacitance and reducing leak current in multi-layer ceramic capacitors.
Implementation Method 1
the dielectric layer is sintered in a reducing ambience to turn the sintered grains constituting the dielectric into a so-called 'core-shell structure' to reduce oxygen defects
Implementation Method 2
sintered in a reducing atmosphere and then oxidized to control defect levels
Implementation Method 3
the probability also increases that the lattice constant and orientation vary according to the Mn-substituted quantity and substitution position in the crystal shells contacting each other, consequently suppressing the grain growth due to sintering
Data Source
AI summary
A dielectric ceramic is formed with sintered grains constituting the dielectric have an average grain size of 0.2 to 1.0 μm and an oxygen defect concentration of 0.2 to 0.5%. An acceptor element is added to the dielectric ceramic by no more than 0.5 mol per 100 mol of the primary component of BaTiO3. The oxygen defect concentration is temporarily increased by reduction and sintering, after which the oxygen defect concentration is reduced through the subsequent re-oxidization process. Crystal strain generated in the re-oxidization process increases the dielectric constant.