Multilayer Ceramic Capacitor Outer Layer Composition
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Solution Overview
Problem
Multilayer ceramic capacitors face reliability issues due to cracks caused by internal stress resulting from the difference in thermal shrinkage coefficients between ceramic dielectric layers and conductive layers, which are not effectively addressed by existing technologies.
Innovation Solution
The design includes a multilayer ceramic capacitor with specific dimensions and composition ratios for outer and inner layers, where the thickness-direction second outer layer section is greater than the first outer layer section, and the width-direction outer layers are larger than the thickness-direction outer layers, with a higher Si content at the boundary and in the outer portion, and a higher rare earth element or Mn content in the inner portion, to enhance adhesion and reduce internal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the outer layer section or the multilayer unit is increased, then the reliability against external stress is improved, but cracks occur at the boundary between the multilayer unit and the outer layer section during firing due to internal stress
Solution Approach 1:
The patent applies local quality by creating an intermediate layer with a specific Si content (0.5-2.0 mass%) that differs from both the outer layer section and the multilayer unit. This intermediate layer is positioned specifically at the boundary region to manage thermal stress locally, allowing the overall structure to maintain higher reliability while preventing cracks during firing.
Solution Approach 2:
The patent changes the chemical composition parameter (Si content) to resolve the contradiction. By controlling the Si content in the intermediate layer to be within 0.5-2.0 mass%, the thermal stress at the boundary is optimized, enabling the structure to withstand both external stress and internal thermal stress without cracking.
2Strength
If the Si content is increased in the outer layer section, then the adhesion force is improved, but the internal stress during firing increases causing cracks
Solution Approach 1:
The patent applies local quality by creating distinct Si content zones: the outer layer section has higher Si content (2.0-5.0 mass%) for strong adhesion, while the intermediate layer has controlled Si content (0.5-2.0 mass%) to manage thermal stress. This localized composition variation allows the structure to achieve both strong adhesion and crack resistance during firing.
Solution Approach 2:
The patent segments the ceramic dielectric layer into different regions with different Si content characteristics. The outer layer section, intermediate layer, and multilayer unit each have distinct Si content ranges, creating a gradient structure that balances adhesion requirements with thermal stress management during firing.
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 significantly reduces or prevents cracks caused by internal stress, improving the reliability and yield of multilayer ceramic capacitors by increasing the adhesion force between ceramic dielectric and conductor materials, thus enhancing the capacitors' performance and manufacturing efficiency.
Implementation Method 1
cracks may occur due to an internal stress produced by the difference in the coefficients of thermal shrinkage between the ceramic dielectric layers and the conductive layers when the body of the multilayer ceramic capacitor is subjected to firing
Data Source
AI summary
A multilayer ceramic capacitor includes a multilayer unit, thickness-direction first and second outer layer sections, and width-direction first and second outer layer sections. A dimension of the thickness-direction second outer layer section is greater than a dimension of the thickness-direction first outer layer section. The thickness-direction second outer layer section includes an inner portion and an outer portion. A composition ratio of Si to Ti in a ceramic dielectric layer included in the outer portion is higher than that in the inner portion. A Si content ratio is higher in a boundary portion between the outer portion and the inner portion. A thickness dimension of the multilayer unit is greater than a width dimension thereof, and width dimensions of the width-direction first and second outer layer sections are greater than a thickness dimension of the thickness-direction first outer layer section.