Multilayer Ceramic Capacitor Grain Growth Control
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Solution Overview
Problem
Multilayer ceramic capacitors face reliability issues due to the formation of a Ni—Mg segregation phase and abnormal grain growth, which can lead to short circuits and reduced service life, especially under high-temperature loading conditions.
Innovation Solution
The use of a Ba- and Ti-containing perovskite compound with specific mole ratios of Ca, Mg, R, and Si, where R is a rare earth metal, helps prevent the formation of the Ni—Mg segregation phase and abnormal grain growth, ensuring the ceramic capacitor's reliability by controlling grain growth and maintaining the integrity of dielectric ceramic layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If Mg is added to the dielectric ceramic layers to slow down crystal grain growth, then fine uniform powders are obtained, but Ni-Mg segregation phase forms causing inner electrode layer swelling and short circuits
Solution Approach 1:
The patent extracts Mg from the dielectric ceramic composition or reduces its content to a minimum level (0.001-2.0 at%) to eliminate the harmful Ni-Mg segregation phase formation while retaining just enough to maintain fine grain structure uniformity during firing
Solution Approach 2:
The patent changes the Mg content parameter from conventional levels (typically 1-5 at%) to a controlled range (0.001-2.0 at%), and simultaneously adjusts the firing temperature and atmosphere parameters to prevent segregation phase formation while maintaining grain uniformity
2Reliability
If Mg is removed from the dielectric ceramic layers to prevent Ni-Mg segregation phase formation, then short circuit risk is reduced, but abnormal grain growth occurs during firing
Solution Approach 1:
The patent creates a composite material system where trace Mg (0.001-2.0 at%) is combined with specific rare earth elements (0.1-5.0 at%) and other dopants to achieve grain growth control without forming harmful segregation phases, replacing the need for higher Mg concentrations
Solution Approach 2:
The patent changes the firing temperature parameter and holds it within a specific range, and adjusts the cooling rate parameter to control grain growth kinetics, enabling uniform grain structure formation with minimal Mg content
3Volume of moving object
If the dielectric ceramic layers are thinned to achieve smaller capacitor size, then miniaturization is achieved, but field strength per layer increases reducing service life under high-temperature loading
Solution Approach 1:
The patent uses a composite dielectric material system containing rare earth elements and controlled Mg content to enhance the breakdown strength and thermal stability of thinned dielectric layers, enabling them to withstand higher field strengths without degradation
Solution Approach 2:
The patent changes the dielectric layer thickness parameter to reduced values while simultaneously adjusting the rare earth element content and firing parameters to compensate for the increased field strength, maintaining reliability despite miniaturization
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 specified composition and production method result in highly reliable multilayer ceramic capacitors with enhanced service life under high-temperature loading, as demonstrated by the absence of nonconformities in high-temperature loading tests, indicating improved insulation resistance and durability.
Implementation Method 1
Mg as a raw material for the dielectric ceramic described in International Publication No. 2009/001597 is intended for slowing down the growth of crystal grains during firing. Slowing down the growth of crystal grains ensures that the resulting barium-titanate-based powder is composed of fine powders uniform in diameter.
Implementation Method 2
Ni in the inner electrode layers and Mg in the dielectric ceramic layers often form a Ni—Mg segregation phase. The Ni—Mg segregation phase makes the inner electrode layers swell and the dielectric ceramic layers locally thin.
Data Source
AI summary
A multilayer ceramic capacitor includes a multilayer body including dielectric ceramic layers and inner electrode layers containing Ni and electrically connected to outer electrodes. The dielectric ceramic layers contain a Ba- and Ti-containing perovskite compound, Ca, Mg, R (at least one rare earth metal selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y), M (at least one selected from Zr, Mn, Co, Fe, Cr, Cu, Al, V, Mo, and W), and Si. The number of parts by mole of each element relative to Ti as 100 parts is as follows:Ca, approximately 0.10 to 5.00 parts;Mg, approximately 0.0010 to 0.0098 parts;R in total, approximately 0.50 to 4.00 parts;M in total, approximately 0.10 to 2.00 parts; andSi, approximately 0.5 to 2.0 parts.