MLCC Side Margin Terbium Doping for Crack Resistance
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Solution Overview
Problem
Multilayer ceramic capacitors face challenges in achieving high mechanical strength and moisture resistance due to issues like void generation, interfacial cracks, and uneven sintering, which affect their capacitance and reliability, particularly during the manufacturing process where the dielectric composition for side margins is not differentiated from the ceramic body, leading to poor adhesion and increased risk of crack formation.
Innovation Solution
The use of a barium titanate-based dielectric composition with terbium as a lanthanide rare earth element in the side margins, where the terbium content ratio is optimized between 0.110 and 2.333, ensures improved sintering driving force, densification, and interface bonding, enhancing the mechanical strength and moisture resistance of the multilayer ceramic capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the dielectric composition for side margins is not differentiated from the ceramic body, then manufacturing process is simplified, but adhesion between internal electrodes and margins deteriorates and crack formation increases
Solution Approach 1:
The patent applies different dielectric compositions to different regions of the capacitor. The side margins use a dielectric composition containing barium titanate and specific amounts of bismuth oxide (0.1-1.0 wt%) and zinc oxide (0.1-1.0 wt%), while the ceramic body uses a different composition. This local differentiation improves adhesion between internal electrodes and margins, prevents crack formation, and enhances overall reliability without significantly complicating the manufacturing process.
2Productivity
If high sintering driving force material is applied, then sintering speed increases, but electrode and dielectric layer unevenness increases causing withstand voltage drop
Solution Approach 1:
The patent carefully controls the composition parameters of the dielectric material, specifically limiting bismuth oxide to 0.1-1.0 wt% and zinc oxide to 0.1-1.0 wt%. This parameter optimization provides moderate sintering driving force that maintains reasonable sintering speed while preventing excessive grain growth and material aggregation. The controlled composition ensures uniform electrode and dielectric layer formation, maintaining manufacturing precision and withstand voltage characteristics.
3Quantity of substance
If dielectric is thinned to increase capacitance, then capacitance increases, but local reduction in dielectric thickness occurs causing withstand voltage drop
Solution Approach 1:
The patent addresses the withstand voltage issue by differentiating the dielectric composition in the side margins from the ceramic body. The margin dielectric contains optimized amounts of bismuth oxide (0.1-1.0 wt%) and zinc oxide (0.1-1.0 wt%), which improves densification and fills interface gaps more effectively. This local composition optimization compensates for the reduced dielectric thickness, maintaining withstand voltage resistance while allowing the overall dielectric to be thinned for increased capacitance.
4Ease of manufacture
If margin portion is attached by physical compression before sintering, then margin formation is simplified, but adhesive force is insufficient causing margin removal and interfacial cracks
Solution Approach 1:
The patent changes the chemical composition parameters of the dielectric material in the side margins to include specific amounts of bismuth oxide (0.1-1.0 wt%) and zinc oxide (0.1-1.0 wt%). This compositional modification enhances the chemical bonding capability and adhesion strength between the margin portion and internal electrodes during sintering, preventing margin removal and interfacial crack formation while maintaining a relatively simple manufacturing 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
This approach effectively prevents void formation, improves adhesion between internal electrodes and margins, and secures a uniform oxide layer, resulting in enhanced mechanical strength and high temperature/moisture resistance reliability of the multilayer ceramic capacitors.
Implementation Method 1
a sintered body having a rigid body is formed through a high temperature heat treatment
Implementation Method 2
the interface bonding force should be improved by forming an oxide layer on the end joining surface by reaction with the internal electrode
Data Source
AI summary
A multilayer ceramic capacitor includes a ceramic body including first and second surfaces opposing each other, and third and fourth surfaces connecting the first and second surfaces, a plurality of internal electrodes disposed inside the ceramic body, exposed from the first and second surfaces, and having an end exposed from the third surface or the fourth surface, and a first side margin and a second side margin respectively disposed on the first and second surfaces, from which end portions of the plurality of internal electrodes are exposed. The first and second side margins include a base material powder of a barium titanate-based base powder and a subcomponent. The subcomponent includes terbium (Tb) as a first subcomponent including a lanthanide rare earth element, and a content ratio of the terbium (Tb) to a content of the first subcomponent (RE) excluding the terbium (Tb) satisfies 0.110≤Tb/RE≤2.333.