Multilayer Capacitor Curved Corners Warpage Reduction
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Solution Overview
Problem
Multilayer ceramic capacitors face challenges in achieving high capacitance and reliability due to stepped portions between internal electrodes and dielectric layers, leading to warpage and reduced moisture resistance, especially when trying to reduce size and increase integration density.
Innovation Solution
A multilayer capacitor design with a body having a stack structure of dielectric layers and internal electrodes, featuring curved corners and a specific radius of curvature, along with a margin region of lower dielectric layer density and needle-type pores, to enhance capacitance and moisture resistance reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the thickness of dielectric layer is reduced and number of dielectric layers is increased to achieve high capacitance and reduced size, then capacitance and integration density are improved, but stepped portions between internal electrodes and dielectric layers increase causing warpage and reduced reliability
Solution Approach 1:
The patent applies local quality by creating a margin portion with different density characteristics from the main body. The margin portion has lower density (higher porosity) compared to the denser main body, allowing it to accommodate dimensional changes and stress without compromising the overall capacitance. This local differentiation resolves the contradiction by protecting reliability in critical areas while maintaining high capacitance in the active regions.
Solution Approach 2:
The patent utilizes porous materials by introducing a margin portion with controlled porosity. This porous structure in the margin portion provides compliance to dimensional changes during sintering and reduces stress concentration, preventing warpage and electrode displacement. The porous margin acts as a buffer zone that absorbs mechanical stress while the dense main body maintains electrical performance.
2Productivity
If the number of dielectric layers is increased to achieve high integration density, then capacitance is improved, but the complexity of managing stepped portions and maintaining uniformity increases
Solution Approach 1:
The patent applies segmentation by dividing the capacitor body into two distinct functional zones: a main body with high density for capacitance and a margin portion with lower density for stress management. This segmentation simplifies the overall structure by assigning specific functions to each zone, reducing the complexity of managing stepped portions across multiple layers while maintaining high integration density in the active regions.
3Ease of manufacture
If side surface margin portion thickness is reduced to simplify manufacturing, then manufacturing complexity is reduced, but corner margin portion thickness is also reduced deteriorating moisture resistance reliability
Solution Approach 1:
The patent applies local quality by creating a margin portion with uniform thickness across all surfaces including corners. This local structural feature ensures that corner regions maintain adequate thickness for moisture resistance while the overall manufacturing process remains simplified. The margin portion's consistent thickness distribution prevents the corner thinning problem that occurs with conventional side surface margin reduction.
Data Source
AI summary
A multilayer capacitor includes a body, a plurality of internal electrodes, and an external electrode. A cover portion of the body has curved corners, and a radius of curvature, R, of each of the curved corners and a thickness, T, of the body satisfy a condition of 10 μm≤R≤T/3, and a width, W, and a thickness, T, of the body satisfy a condition of T/W<0.8.