Multilayer Ceramic Capacitor Side Margin Grain Control
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Solution Overview
Problem
Existing methods for producing large-capacitance and small-size multilayer ceramic capacitors are disadvantaged by the risk of short circuits between internal electrode layers due to sagging electrode ends and inadequate printing and lamination accuracy, which reduces the reliability of the capacitors.
Innovation Solution
A multilayer ceramic capacitor design featuring internal electrode layers extending to end surfaces with a dielectric ceramic layer in between, and a side margin structure that includes ceramic grains with smaller diameters between electrode ends to increase interface resistance and prevent short circuits, along with a specific composition and structure for the external electrodes and side margins to enhance adhesion and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If internal electrode layers are extended to end surfaces to increase capacitance, then capacitance increases, but short circuit between adjacent internal electrode layers occurs due to sagging
Solution Approach 1:
The patent applies different ceramic grain diameter characteristics to different regions of the dielectric ceramic layer. Specifically, the region between ends of internal electrode layers in the width direction has ceramic grains with smaller diameter than the central region, creating local quality differences that increase interface resistance precisely where short circuits are most likely to occur, while maintaining overall capacitor performance
Solution Approach 2:
The patent changes the physical parameter of ceramic grain diameter in specific regions of the dielectric ceramic layer. By controlling the ceramic grain diameter to be smaller in the region between electrode ends compared to the center region, the invention modifies the electrical resistance parameter locally to prevent short circuits while preserving capacitance
2Volume of moving object
If cutting margin is reduced to achieve smaller size, then capacitor size decreases, but printing accuracy and lamination accuracy deteriorate
Solution Approach 1:
The patent creates a side margin structure with distinct inner and outer layers having different properties. The inner layer is bonded to the green chip lateral surface while the outer layer provides additional margin, allowing the capacitor to achieve smaller overall size while maintaining sufficient printing and lamination accuracy through this differentiated local structure
3Area of stationary object
If side margin is formed by bonding ceramic green sheet to lateral surface, then internal electrode layer can extend over entire width, but sagging of internal electrode layer ends occurs during compression
Solution Approach 1:
The patent forms a side margin with an inner layer bonded to the green chip lateral surface and an outer layer on the outermost side. This differentiated structure provides local support to the internal electrode layer ends through the inner layer's bonding, preventing sagging during compression while maintaining the expanded electrode area for high capacitance
Solution Approach 2:
The side margin structure with its inner layer bonded to the lateral surface is prepared in advance before final assembly. This preliminary structural support prevents sagging of the internal electrode layer ends during subsequent compression and sintering processes, ensuring stability before the capacitor is put into service
Data Source
AI summary
A multilayer ceramic capacitor includes a laminate including a dielectric ceramic layer and first and second internal electrode layers laminated in a lamination direction, and first and second external electrode connected to the internal electrode layers. The laminate includes a central layer portion, a peripheral layer portion sandwiching the central layer portion, and a side margin sandwiching the central layer portion and the peripheral layer portion. The side margin includes an inner layer and an outer layer. In a cross section including a lamination direction and a width direction obtained by cutting the laminate at the center in a longitudinal direction of the laminate, the ceramic grains in the dielectric ceramic layer between ends of the internal electrode layers in the width direction have a smaller diameter than the ceramic grains in the dielectric ceramic layer at the center of the central layer portion in the width direction.