Multilayer Ceramic Capacitor Internal Electrode Thickness Design
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Solution Overview
Problem
Multilayer ceramic capacitors face issues with radiating cracks due to copper diffusion into internal electrodes during firing, leading to increased short rates, as copper's diffusion coefficient is significantly higher than nickel's, causing volumetric expansion and reliability concerns.
Innovation Solution
The multilayer electronic component design includes internal electrodes with end portions thicker than the central portions, with a thickness ratio of 1.1≤t2/t1≤1.5, and incorporates a Ni-Cu alloy to control copper diffusion, preventing radiating cracks and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the dielectric layer and internal electrode are thinned to miniaturize the capacitor and increase capacity, then the size is reduced and capacitance increases, but copper diffusion to the internal electrode increases causing radiating cracks
Solution Approach 1:
The internal electrode is designed with non-uniform thickness, where the end portion thickness t2 is greater than the central portion thickness t1 (t2/t1 ≥ 1.05). This local variation in thickness provides enhanced copper diffusion resistance at the end portions where cracks typically initiate, while maintaining thin overall dimensions for miniaturization and high capacitance.
Solution Approach 2:
The thickness ratio t2/t1 is controlled within a specific range (1.05 ≤ t2/t1 ≤ 1.3) to optimize the balance between preventing copper diffusion and maintaining capacitor performance. This parameter control ensures sufficient reliability while achieving miniaturization and high capacitance goals.
2Quantity of substance
If the internal electrode thickness is reduced to increase capacitance, then the capacitance increases, but the diffusion of copper to nickel in the internal electrode increases due to concentration gradient
Solution Approach 1:
The internal electrode employs local quality variation with thicker end portions that specifically address copper diffusion at critical regions. This localized thickening creates a diffusion barrier where needed while maintaining thin central portions to maximize capacitance through increased electrode surface area.
Solution Approach 2:
The internal electrode uses a composite Ni-Cu alloy structure where nickel provides base conductivity and copper content is controlled to balance diffusion resistance and electrical properties. The non-uniform thickness distribution works synergistically with the alloy composition to manage copper diffusion while maintaining high capacitance.
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 design effectively reduces radiating cracks and enhances the reliability of multilayer ceramic capacitors by limiting copper diffusion, even when the dielectric and internal electrode thicknesses are minimized, ensuring sufficient reliability and capacitance.
Implementation Method 1
the diffusion coefficient of copper (Cu) at 750° C. is about 100 times higher than that of nickel (Ni)... the diffusion of copper (Cu) to nickel (Ni) is larger than that of nickel (Ni) to copper (Cu)
Data Source
AI summary
A multilayer electronic component includes a body including a dielectric layer and internal electrodes alternately stacked with the dielectric layer interposed therebetween, and an external electrode disposed on the body and connected to the internal electrodes . An end portion of at least one of the internal electrodes in a longitudinal direction of the body is thicker than a central portion of the internal electrode, and a ratio t2/t1 of a thickness t2 of the end portion to a thickness t1 of the central portion satisfies 1.1≤t2/t1≤1.5.