Multilayer Ceramic Capacitor W-Shaped Capacitance Distribution
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Solution Overview
Problem
The challenge is to maintain the CR product of multilayer ceramic capacitors at an adequate level as the dielectric layer thickness decreases below 1.0 μm, as existing methods struggle to prevent a drop in capacitance and insulation resistance.
Innovation Solution
The multilayer ceramic capacitor design features internal electrode layers laminated with dielectric layers, where the capacitance distribution forms a gradual increase from both sides towards the center, ensuring the CR product is maintained even at thinner dielectric layers by optimizing the capacitance distribution of unit capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the dielectric layer thickness is reduced to increase capacitance and reduce size, then the capacitance increases and device size decreases, but the CR product (capacitance × insulation resistance) drops
Solution Approach 1:
The patent applies local quality by creating different capacitance characteristics in different regions of the dielectric layer. Specifically, the capacitance per unit area is made larger near the center of the dielectric layer and smaller near the electrode edges, achieving a W-shaped capacitance distribution. This non-uniform capacitance distribution compensates for the overall reduction in CR product caused by thinning the dielectric layer, thereby maintaining reliable capacitor performance while enabling higher total capacitance and smaller device size.
2Quantity of substance
If the dielectric layer thickness is reduced to 1.0 μm or less to further increase capacitance density, then the capacitance per unit volume increases, but the CR product drops significantly making the capacitor unreliable
Solution Approach 1:
The patent applies parameter changes by modifying the capacitance distribution profile across the dielectric layer thickness. When the dielectric layer is thinned to 1.0 μm or less, the invention adjusts the capacitance per unit area to form a W-shaped distribution with peaks near the center and valleys near the edges. This parameter adjustment in capacitance distribution compensates for the reduced dielectric thickness, maintaining the CR product at adequate levels while achieving high capacitance density.
3Reliability
If the grain size and volume ratio of dielectric layer crystal are limited to prevent CR product drop, then the CR product is maintained, but accurate control is difficult due to manufacturing limitations
Solution Approach 1:
The patent applies inversion by reversing the conventional approach to controlling CR product. Instead of trying to precisely control grain size and crystal volume ratio in the dielectric layer (which is difficult due to manufacturing limitations), the invention inverts the problem by controlling the capacitance distribution profile directly. By creating a W-shaped capacitance distribution with specific peak and valley positions, the patent achieves CR product maintenance through a more manufacturable parameter control approach.
Data Source
AI summary
A multilayer ceramic capacitor, whose CR product can be prevented from dropping with certainty even at a thickness of 1.0 μm or less, includes multiple unit capacitors wherein a part constituted by two adjacent internal electrode layers in the laminating direction and one dielectric layer present between the two internal electrode layers is defined as a unit capacitor. The capacitances of the unit capacitors arranged in the laminating direction exhibit a distribution that gradually increases from both ends in the laminating direction toward the inside, while gradually decreasing from the two apexes of increase toward the center in the laminating direction.