Multilayer Capacitor Grain Ratio Control for Voltage Reliability
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Solution Overview
Problem
As multilayer ceramic capacitors are miniaturized, it becomes challenging to maintain electrical and structural reliability, particularly in terms of withstand voltage characteristics and capacitance.
Innovation Solution
The multilayer capacitor design adjusts the grain size of the dielectric layer across different regions, with specific ratios and thicknesses, to enhance capacitance and withstand voltage reliability, using a barium titanate component and varying molar ratios of barium to titanium, and controlling the grain size in active, cover, and side margin portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the dielectric layer and internal electrode are designed to have reduced thickness to achieve miniaturization, then the size of the multilayer ceramic capacitor is decreased, but the electrical and structural reliability deteriorates
Solution Approach 1:
The patent applies local quality by differentiating the grain size requirements across different regions of the dielectric layer. The active portion (where internal electrodes are disposed) requires a first grain size range for optimal capacitance, while the cover portion and side margin portion require a second grain size range for structural integrity and withstand voltage. This regional differentiation allows the capacitor to achieve miniaturization while maintaining reliability in critical areas.
Solution Approach 2:
The patent employs parameter changes by specifying different grain size ranges for different portions of the dielectric layer. The active portion has grains sized 0.5-2.0 μm, while the cover and side margin portions have grains sized 0.3-1.5 μm. This parameter variation optimizes both capacitance performance and structural reliability, resolving the contradiction between miniaturization and reliability maintenance.
2Quantity of substance
If the grain size of the dielectric layer is reduced to increase capacitance, then the capacitance characteristics are improved, but the withstand voltage characteristics deteriorate
Solution Approach 1:
The patent resolves this contradiction by applying different grain size qualities to different functional regions. The active portion uses larger grains (0.5-2.0 μm) to maximize capacitance through increased dielectric constant, while the cover and side margin portions use smaller grains (0.3-1.5 μm) to maintain withstand voltage strength and prevent breakdown. This spatial differentiation of grain size allows simultaneous optimization of both capacitance and withstand voltage.
Solution Approach 2:
The patent segments the dielectric layer into functionally distinct regions with different grain size characteristics. By dividing the dielectric structure into an active portion (for capacitance) and cover/side margin portions (for voltage resistance), the patent enables each segment to be optimized independently, thereby achieving both high capacitance and high withstand voltage capability.
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 improves capacitance and withstand voltage characteristics by ensuring sufficient grain growth in critical regions while maintaining a dense, uniform structure, thereby enhancing the overall reliability of the capacitor.
Implementation Method 1
a dielectric layer and a plurality of internal electrodes laminated in a first direction with respective dielectric layers interposed therebetween
Data Source
AI summary
A multilayer capacitor includes a body including a plurality of dielectric layers and a plurality of internal electrodes laminated in a first direction, and external electrodes. The body includes an active portion, in which the plurality of internal electrodes are disposed to form capacitance, corresponding to a region between internal electrodes disposed on an outermost side in the first direction, among the plurality of internal electrodes, a cover portion covering the active portion in the first direction, and a side margin portion covering the active portion in a second direction, perpendicular to the first direction, and 1.49<A1/A2<2.50 where A1 is an average grain size of the dielectric layer in a central region of the active portion, and A2 is an average grain size of the dielectric layer in an active-cover boundary portion, adjacent to the cover portion, of the active portion.