Dielectric Ceramic Mixed Crystal Structure for Capacitor Reliability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Laminated ceramic capacitors face challenges in achieving a balance between high temperature load characteristics and temperature characteristics of capacitance when the dielectric ceramic layer thickness is reduced to less than 1 μm, and there is difficulty in controlling the solid solubility of rare earth elements effectively.
Innovation Solution
A dielectric ceramic with a mixed crystal structure comprising first and second crystal grains, where the first grains have a minute amount of rare earth elements as a solid solution and the second grains have a core-shell structure, with specific ratios of these grains to achieve a balance between high temperature load and capacitance characteristics, and a laminated ceramic capacitor manufactured using this dielectric ceramic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the dielectric ceramic layer thickness is reduced to less than 1 μm to achieve smaller size and higher capacitance, then the size and capacitance are improved, but the balance between high temperature load characteristics and temperature characteristics of capacitance deteriorates
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where only the shell portion contains rare earth elements as solid solution, while the core remains free of rare earth elements. This localized distribution allows the capacitor to maintain high temperature load characteristics through the rare earth-containing shell while preserving temperature characteristics of capacitance through the rare earth-free core, enabling layer thickness reduction to less than 1 μm without sacrificing reliability
Solution Approach 2:
The patent uses composite materials by combining two types of crystal grains: first crystal grains with rare earth elements as solid solution and second crystal grains without rare earth elements. This composite grain structure enables the dielectric ceramic to simultaneously achieve high temperature load characteristics from the rare earth-containing grains and temperature characteristics of capacitance from the rare earth-free grains, resolving the contradiction at ultra-thin layer thicknesses
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 enables laminated ceramic capacitors to maintain favorable high temperature load characteristics and temperature characteristics of capacitance even at reduced layer thicknesses, with a long lifetime of 150 hours or more under direct-current voltage at 150°C, and compliance with X5R characteristics of EIA standards.
Implementation Method 1
a first crystal grain including the main phase grains by themselves or including the main phase grains having therein the rare earth element R in a minute amount present as a solid solution
Data Source
AI summary
A dielectric ceramic (and capacitor containing it) balancing high temperature load characteristics and temperature characteristics of capacitance even when layer thickness is less than 1 μm has a mixture of different crystal grains containing a barium titanate compound as the main constituent. The first crystal grains can contain rare earth element solid solution region 1 at the surface layer section. The second crystal grains have a core-shell structure including a shell section having a rare earth element solid solution present. The first and second crystal grains are 12% to 84% f and 16% to 88%, respectively, of the total number of crystal grains.