Multilayer Ceramic Capacitor Electrode Diffusion Stress Control
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Solution Overview
Problem
Multilayer ceramic capacitors face significant cracking issues due to deflection stress caused by the sintering of conductive paste used for external electrodes, particularly because internal electrode layers closer to the end surfaces are thicker, leading to bloating and structural damage.
Innovation Solution
The design incorporates extended electrode portions that facilitate interdiffusion of conductive paste between internal and external electrodes, forming diffusion portions with specific dimensions and compositions, primarily containing Cu and Ni, to prevent excessive diffusion and reduce stress during sintering, thereby minimizing crack generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductive paste is sintered to form external electrodes, then external electrodes are formed and electrical connection is achieved, but deflection stress is generated in the laminated body causing cracks
Solution Approach 1:
The patent applies different properties to different parts of the internal electrode layers. Specifically, the end surface portions are made thinner than the central portions, creating a gradient structure. This local variation in thickness allows the end portions to better accommodate the deflection stress generated during sintering, preventing crack propagation while maintaining electrical connectivity.
Solution Approach 2:
The patent performs preliminary thinning of the internal electrode layers at the end surface portions before the sintering process. By pre-adjusting the thickness distribution, the structure is prepared to withstand the upcoming thermal stress of sintering, preventing crack formation during the electrode formation process.
2Reliability
If internal electrode layers are made thicker at end surface portions to ensure connectivity, then electrical connection is improved, but bloating occurs during sintering generating deflection stress
Solution Approach 1:
The patent creates a non-uniform thickness distribution in the internal electrode layers, with thinner regions at the end surfaces and thicker regions in the center. This local quality variation ensures that connectivity is maintained where needed while preventing excessive stress concentration that would cause bloating and structural failure during sintering.
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 effectively reduces or prevents cracking during sintering, ensures strong connections between external and internal electrodes, and maintains connectivity while preventing excessive diffusion, thus enhancing the reliability and durability of multilayer ceramic capacitors.
Implementation Method 1
The conductive paste diffuses into the internal electrode layers in the process of being sintered. These diffusion portions are defined by interdiffusion of the conductive paste and the internal electrode layers
Data Source
AI summary
A multilayer ceramic capacitor includes a laminated body including ceramic layers, first internal electrode layers, and second internal electrode layers alternately laminated. First and second external electrodes provided on the laminated body include first diffusion portions defined by interdiffusion of the first internal electrode layers and the first external electrode at interfaces between the first internal electrode layers and the ceramic layers, and second diffusion portions defined by interdiffusion of the second internal electrode layers and the second external electrode at interfaces between the second internal electrode layers and the ceramic layers.