Multilayer Ceramic Capacitor Grain Growth Control
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Solution Overview
Problem
Multilayer ceramic capacitors with thin dielectric layers face issues of short circuits and low insulation reliability due to partial thinness during grain growth, leading to reduced electrostatic capacity and mean time to failure.
Innovation Solution
A multilayer ceramic capacitor design with dielectric layers containing a perovskite compound of Ba and Ti, along with Si, Dy, Mg, Al, Mn, and V, where the Ba/Ti molar ratio is 1.0073 to 1.0083, and the number of crystal grains per layer is 1.9 or less, with a thickness variation of 14.0% or less, which inhibits grain sliding and metal ball formation, thereby reducing short-circuit rates and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If thin dielectric layers are used to achieve compact size, then the capacitor size is reduced, but short circuits and low insulation occur due to partial thinness during grain growth
Solution Approach 1:
The patent changes the chemical composition parameters of the dielectric layer by adding specific amounts of Si (0.7-1.2 parts by mole relative to 100 parts by mole of Ti), Dy (0.9-1.1 parts by mole), Mg (0.24-0.34 parts by mole), Al (0.17-0.23 parts by mole), Mn (0.09-0.11 parts by mole), and V (0.04-0.06 parts by mole). This composition modification suppresses abnormal grain growth and metal ball formation, ensuring uniform dielectric layer thickness and preventing short circuits while maintaining compact capacitor size
Solution Approach 2:
The patent creates a composite dielectric material system based on Ba-Ti perovskite structure with multiple dopant elements (Si, Dy, Mg, Al, Mn, V). This composite material approach leverages the synergistic effects of different elements: Si provides fluidity to suppress grain sliding, Dy controls grain growth, and other elements work together to prevent metal ball formation, thereby achieving both compact size and high reliability
2Quantity of substance
If grain growth is promoted to increase electrostatic capacity, then electrostatic capacity increases, but thickness variation of dielectric layers increases causing short circuits
Solution Approach 1:
The patent optimizes the chemical composition parameters of the dielectric layer, specifically controlling the content of Si (0.7-1.2 parts by mole relative to Ti), Mg (0.24-0.34 parts by mole), and other elements. These parameter changes suppress abnormal grain growth during sintering, ensuring uniform crystal grain size and consistent dielectric layer thickness across the entire layer, thereby preventing short circuits while maintaining high electrostatic capacity
Solution Approach 2:
The patent introduces Si as an intermediary element that provides fluidity to the dielectric material during grain growth. This fluidity acts as a mediator that allows crystal grains to adjust and pack uniformly, suppressing thickness variations and preventing the formation of thin spots that would lead to short circuits, while still permitting adequate grain growth for high capacitance
3Temperature
If Mg content is reduced to lower grain growth starting temperature, then metal ball formation is suppressed, but dielectric layer uniformity may be affected
Solution Approach 1:
The patent precisely controls the Mg content parameter within a narrow range (0.24-0.34 parts by mole relative to 100 parts by mole of Ti) and combines it with specific amounts of other elements (Si: 0.7-1.2, Dy: 0.9-1.1, Al: 0.17-0.23, Mn: 0.09-0.11, V: 0.04-0.06 parts by mole). This multi-parameter optimization lowers the grain growth starting temperature to suppress metal ball formation while the synergistic effect of all dopant elements maintains dielectric layer uniformity through coordinated control of grain growth and material fluidity
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 effectively reduces short-circuit rates, increases electrostatic capacity, and improves mean time to failure while maintaining thin dielectric layers, ensuring high reliability and stability.
Implementation Method 1
The dielectric layers in the effective section contain crystal grains having a perovskite compound containing Ba and Ti
Implementation Method 2
The ceramic crystal grains have Si, which has fluidity, on the surfaces thereof. External pressure application causes crystal grains to slide on the surfaces of crystal grains
Implementation Method 3
The metal (e.g., Ni) in the inner electrode layers tends to form balls upon heat application. The heat application to the multilayer body causes the metal contained in the inner electrode layers to form balls and push away surrounding crystal grains in the dielectric layers
Implementation Method 4
The grain growth starting temperature can be lowered by reducing the Mg content of the dielectric layers of the multilayer ceramic capacitor according to the present invention. The formation of balls from the metal contained in the inner electrode layers can be suppressed by lowering the grain growth starting temperature
Implementation Method 5
a multilayer ceramic capacitor that has reduced short-circuit rate, large electrostatic capacity, and improved mean time to failure (MTTF) while including thin dielectric layers
Data Source
AI summary
A multilayer ceramic capacitor that includes outer electrodes and a multilayer body having stacked inner electrode layers and dielectric layers. The dielectric layers in an effective section contain, relative to 100 parts by mole of Ti, 0.7 to 1.2 parts by mole of Si, 0.9 to 1.1 parts by mole of Dy, 0.24 to 0.34 parts by mole of Mg, 0.17 to 0.23 parts by mole of Al, 0.09 to 0.11 parts by mole of Mn, and 0.04 to 0.06 parts by mole of V. The dielectric layers have a Ba/Ti molar ratio of 1.0073 to 1.0083.