Multilayer Ceramic Capacitor Electrode Structure for Crack Reduction
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Solution Overview
Problem
Multilayer ceramic capacitors face challenges in minimizing cracks during firing, which can lead to reduced reliability due to the difference in thermal shrinkage between ceramic dielectric layers and metal inner electrodes, especially when the dielectric layer thickness is minimized to increase capacitance.
Innovation Solution
The design incorporates a thin portion of the inner electrode with a thickness smaller than the main facing portion, extending from the end portion towards the side surfaces, which helps control the shrinkage behavior of the dielectric layer and reduce stress, thereby minimizing the likelihood of cracks during firing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the dielectric layer thickness is minimized to increase capacitance, then the capacitance increases, but the likelihood of cracks occurring during firing increases
Solution Approach 1:
The inner electrode is designed with varying thickness: a thinner portion (second thickness) at the end portion and a thicker main facing portion (first thickness). This local variation in electrode thickness creates corresponding variations in dielectric layer thickness, allowing the dielectric to better accommodate thermal shrinkage stresses during firing while maintaining high capacitance in the main region.
Solution Approach 2:
The patent changes the thickness parameter of the inner electrode along its length, creating a gradient structure. The thickness ratio between the main facing portion and the end portion is controlled within specific ranges (0.5-2.0) to optimize both capacitance and crack resistance during the firing process.
2Quantity of substance
If the inner electrode is maximized to achieve large capacitance, then the capacitance increases, but the dielectric layer covering the inner electrode is minimized, causing cracks during firing
Solution Approach 1:
The inner electrode thickness is locally optimized: the main facing portion has sufficient thickness to provide high capacitance, while the end portion has reduced thickness to ensure adequate dielectric layer coverage. This prevents cracks in the dielectric layer during firing while maintaining the required capacitance performance.
3Reliability
If a thin portion is added to the inner electrode to control shrinkage, then the structure becomes more complex, but the crack resistance improves
Solution Approach 1:
The inner electrode is segmented into two distinct regions: a main facing portion and an end portion with different thicknesses. This segmentation allows each region to serve different functions - the main portion provides capacitance while the thinner end portion controls thermal shrinkage, improving crack resistance without requiring entirely new structural concepts.
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 configuration effectively reduces the occurrence of cracks and structural flaws in multilayer ceramic capacitors, enhancing their reliability and performance by managing thermal shrinkage differences between ceramic and metal components.
Implementation Method 1
the difference in thermal shrinkage between ceramic dielectric layers and metal inner electrodes
Data Source
AI summary
A multilayer ceramic capacitor includes a multilayer body including a dielectric layer and an inner electrode alternately laminated, first and second main surfaces opposed to each other in a lamination direction, first and second side surfaces opposed to each other in a width direction orthogonal or substantially orthogonal to the lamination direction, and first and second end surfaces opposed to each other in a length direction orthogonal or substantially orthogonal to the lamination direction and the width direction, and, on each of the first and second end surfaces, an outer electrode coupled to the inner electrode. The inner electrode includes a main facing portion and a thin portion, a thickness of the thin portion is smaller than a thickness of the main facing portion, and the thin portion extends from an end portion of the main facing portion in the width direction to the first or second side surface.