Copper Conductive Paste for Thin MLCC Electrodes With High Coverage
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Solution Overview
Problem
Existing multilayer ceramic capacitors face challenges in achieving high capacitance due to reduced coverage of thin-layer inner electrodes, which is exacerbated by the disparity in sintering temperatures between conductive metal particles and ceramic dielectric layers.
Innovation Solution
A conductive paste comprising copper and ABO3 type ceramic powder with a specified ionic radius ratio is used to form inner electrodes, ensuring high coverage and improved heat resistance, thereby enhancing capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the thickness of inner electrodes is reduced to form thin layers, then the size of the multilayer ceramic capacitor is reduced, but the coverage of the inner electrodes decreases
Solution Approach 1:
The patent changes the chemical composition parameters of the conductive paste by adding specific ceramic materials (BaTiO3, SrTiO3, CaZrO3) to modify the sintering behavior. This composition change allows the metal particles to sinter at higher temperatures, maintaining coverage even when electrode thickness is reduced to 1 μm or less.
Solution Approach 2:
The patent creates a composite conductive paste material combining metal particles (Cu, Ag, or their alloys) with specific ceramic materials (BaTiO3, SrTiO3, CaZrO3) in controlled ratios. This composite structure enables the paste to achieve both thin-layer formation and high coverage by coordinating the sintering temperatures of different components.
2Manufacturing precision
If the sintering temperature of metal particles is increased to improve coverage, then the coverage of inner electrodes increases, but the temperature difference between metal particle sintering and ceramic sintering decreases
Solution Approach 1:
The patent modifies the sintering temperature parameter of metal particles by adding ceramic materials that raise the onset sintering temperature from the typical lower range to 900-1100°C, approaching the ceramic sintering temperature. This parameter change reduces the temperature gap while achieving high coverage.
Solution Approach 2:
The ceramic materials (BaTiO3, SrTiO3, CaZrO3) act as intermediaries between the metal particles and the ceramic dielectric layers. They facilitate coordinated sintering by providing a temperature buffer and chemical bridge, allowing metal particles to sinter at higher temperatures without excessive temperature difference from the ceramic layers.
3Temperature
If common ceramic material is added to conductive paste to shift sintering temperature, then the onset of sintering of metal particles increases, but the temperature remains lower than ceramic sintering temperature
Solution Approach 1:
The patent optimizes the composition parameters by selecting specific ceramic materials (BaTiO3, SrTiO3, CaZrO3) with appropriate particle sizes and ratios (0.1-10 wt%). This precise parameter control raises the metal particle sintering temperature to nearly match the ceramic sintering temperature, achieving high coverage.
Solution Approach 2:
The patent applies different ceramic materials with specific properties to different aspects of the conductive paste formulation. Each ceramic material (BaTiO3, SrTiO3, CaZrO3) contributes specific characteristics that collectively achieve the target sintering temperature and coverage, rather than relying on a single material.
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 conductive paste enables inner electrodes to maintain high coverage even when formed as thin layers, resulting in increased capacitance of multilayer ceramic capacitors.
Implementation Method 1
the sintering temperature of conductive metal particles included in conductive paste films that are to be the inner electrodes is lower than the sintering temperature of the ceramic that forms the dielectric layers, which means that the metal particles included in the inner electrodes are sintered first
Data Source
AI summary
A conductive paste included in inner electrodes of a multilayer ceramic capacitor is fired and includes a conductive metal powder, a ceramic powder, an organic solvent, and an organic binder. The conductive metal powder includes copper, and at least a portion of the ceramic powder is a powder of at least one oxide of an ABO3 type with a specified ionic radius in which a ratio of a six-coordinate ionic radius of an A-site element in ABO3 to a six-coordinate ionic radius of copper is about 0.96 or greater and about 1.04 or less.