MLCC Ceramic Hardness Uniformity for Breakdown Reliability
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Solution Overview
Problem
Multilayer ceramic capacitors (MLCCs) face challenges with reduced breakdown voltage (BDV) and mean time to failure (MTTF) as they become smaller, necessitating improvements in reliability.
Innovation Solution
A multilayer ceramic capacitor design with a ceramic body having a small difference in indentation hardness (HIT) between the upper and lower portions, achieved by controlling the indentation hardness through the use of a specific binder composition and manufacturing process, specifically using a polyvinyl butyral (PVB) binder with a glass transition temperature between 80°C and 90°C, to ensure uniform hardness across the thickness direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If multilayer ceramic capacitors are miniaturized to meet demand for smaller electronic devices, then device size is reduced, but breakdown voltage and mean time to failure decrease
Solution Approach 1:
The patent applies local quality by creating a density gradient within the ceramic body, where the density varies from the upper portion to the lower portion. Specifically, the density of the lower portion is controlled to be higher than that of the upper portion, with the density ratio (lower/upper) maintained between 0.95 and 1.05. This localized variation in density distribution addresses the reliability issue in miniaturized capacitors by optimizing the mechanical strength and electrical properties in different regions, thereby improving breakdown voltage and mean time to failure without increasing overall device size.
2Manufacturing precision
If pressure is applied during sintering to improve density, then manufacturing precision improves, but indentation hardness difference between upper and lower portions increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the density distribution parameter during the sintering process. Instead of applying uniform pressure, the patent optimizes the pressure application parameters to achieve a specific density gradient where the lower portion density is 0.95 to 1.05 times the upper portion density. This parameter optimization ensures that while density uniformity is improved for manufacturing precision, the indentation hardness difference between upper and lower portions is maintained within acceptable limits, resolving the contradiction between these two requirements.
Data Source
AI summary
A multilayer ceramic capacitor includes a ceramic body having a dielectric layer between first and second internal electrodes. The ceramic body satisfies the following conditional equation:0≤(a-b)/a≤0.1[Conditional Expression]wherea: Indentation hardness (HIT) of a lower portion of the ceramic bodyb: Indentation hardness (HIT) of an upper portion of the ceramic body