Multilayer Ceramic Capacitor Side Margin Ni Gradient
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Solution Overview
Problem
Existing methods for producing large-capacitance and small-size multilayer ceramic capacitors face challenges in minimizing cracking due to differences in shrinkage between dielectric ceramic layers and side margins during the sintering process.
Innovation Solution
A multilayer ceramic capacitor design with a laminate structure that includes a central layer portion with alternately laminated internal electrode layers and dielectric ceramic layers, surrounded by peripheral and side margins made of ceramic material, where the Ni content is higher at the surface portions of the peripheral and side margins, promoting better adhesion and matching shrinkage behaviors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the side margin is made thin to increase effective area of internal electrode layers, then the capacitance increases and size decreases, but cracks occur in the sintered laminate due to shrinkage difference
Solution Approach 1:
The patent applies local quality by creating a non-uniform Ni content distribution within the side margin. The surface portion of the side margin has a higher Ni content (0.5-5 mass%) compared to the inner portion (0.1-3 mass%), which locally enhances adhesion and shrinkage matching at the critical interface with the dielectric ceramic layer, preventing cracks while maintaining thin overall dimensions.
Solution Approach 2:
The patent changes the compositional parameter (Ni content) of the side margin material to resolve the contradiction. By adjusting the Ni content to be higher at the surface portion compared to the inner portion, the material properties are optimized to match shrinkage behavior with the dielectric ceramic layer, preventing cracks even when the side margin is made thin for high capacitance density.
2Reliability
If the Ni content is increased at the surface portion of the side margin, then adhesion and shrinkage matching improve, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-forming the side margin with a non-uniform Ni content distribution during the lamination stage, before sintering. The green sheet for the side margin is prepared with the desired compositional gradient, which is then maintained through the sintering process. This preliminary preparation simplifies manufacturing compared to post-sintering modifications.
Solution Approach 2:
The patent uses composite materials by creating a side margin with spatially varying composition (different Ni content at surface versus inner portions). This composite structure, with graded material properties, achieves both strong adhesion to the dielectric ceramic layer and appropriate shrinkage matching, while the entire structure is formed in a single lamination and sintering process.
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
The design reduces the likelihood of cracking by ensuring the shrinkage behavior of the dielectric ceramic layer matches that of the peripheral and side margins, enhancing the reliability and stability of the multilayer ceramic capacitor.
Implementation Method 1
a method of producing a multilayer ceramic capacitor, a method of alternately laminating green sheets and internal electrode layers before sintering to form a green chip, sintering the green chip
Implementation Method 2
a crack may occur in a sintered laminate due to the difference in shrinkage between the side margin and the dielectric ceramic layer sandwiched between the internal electrode layers in a sintering step
Data Source
AI summary
A multilayer ceramic capacitor includes a laminate including a dielectric ceramic layer and first and second electrode layers laminated in a lamination direction, and first and second external electrodes respectively connected to the first and second 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 first and second internal electrode layers and the first and second external electrodes include Ni. In a cross section including the lamination direction and a width direction, a Ni content of the peripheral layer portion is larger at a surface portion than at a central portion in a thickness direction, and a Ni content of the side margin is larger at a surface portion than at a central portion in a thickness direction of the side margin.