Conductive Paste Composition for Multilayer Ceramic Capacitor Electrodes
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Solution Overview
Problem
Conventional multilayer ceramic capacitors face issues with low density conductive layers, leading to reduced reliability due to moisture and high-temperature sensitivity, as well as cracking caused by diffusion between copper and nickel internal electrode layers, which affects mechanical strength and capacitance.
Innovation Solution
A conductive paste composition combining flake-shaped and spherical copper powders with two types of glass frits and an anti-oxidation agent, optimized for improved density, adhesion, and oxidation resistance, allowing for sintering at low temperatures to prevent cracking and enhance capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional conductive paste is used to form a conductive layer, then the manufacturing process is simple, but the density of the conductive layer is low leading to reduced reliability
Solution Approach 1:
The conductive paste uses a composite structure combining flake-shaped copper powder and spherical copper powder in specific size ranges. The flake-shaped powder (D50: 2.0-4.0 μm) provides structural framework while spherical powder (D50: 0.3-1.5 μm) fills gaps, creating a dense composite conductive layer with improved reliability and moisture resistance
Solution Approach 2:
The invention optimizes specific parameters including particle size distribution (flake-shaped D50: 2.0-4.0 μm, spherical D50: 0.3-1.5 μm), glass frit composition (SiO2, SrCO3, BaCO3, Li2SO4, K2SO4, V2O5, ZnO, Al2O3, Y2O3), and sintering temperature (900-1100°C) to achieve high density conductive layer formation
2Reliability
If copper powder is used for the conductive layer with nickel internal electrode, then conductivity is improved, but cracks occur due to diffusion and alloy formation between Cu and Ni
Solution Approach 1:
The invention controls the sintering temperature parameter (900-1100°C) to be below the temperature where significant Cu-Ni diffusion and alloy formation occurs. This parameter control prevents the harmful diffusion process while maintaining conductive layer density and electrical conductivity
Solution Approach 2:
The conductive layer uses locally optimized particle distribution with flake-shaped copper powder forming the structural framework and spherical powder filling interstices. This local structural optimization creates a dense network that resists crack propagation and prevents diffusion pathways
3Reliability
If the conductive layer density is increased to improve reliability, then moisture resistance improves, but the manufacturing complexity increases
Solution Approach 1:
The conductive paste employs a composite of flake-shaped and spherical copper powders with specific size distributions. This composite material design achieves high density conductive layer formation through simple screen printing and sintering processes, improving moisture resistance without significantly increasing manufacturing complexity
Solution Approach 2:
The dual-component particle system self-organizes during sintering, with flake-shaped particles forming the structural framework and spherical particles naturally filling the void spaces. This self-assembly behavior achieves high density without complex processing steps
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 composition achieves dense and reliable conductive layers with improved adhesion and oxidation resistance, preventing cracking and ensuring high capacitance and mechanical strength, even under high-temperature and moisture conditions.
Implementation Method 1
sintering at low temperatures, which prevents deterioration of reliability
Implementation Method 2
uses two different types of glass frit to improve shrinkage or contact properties
Implementation Method 3
an anti-oxidation agent as an additive to increase oxidation resistance
Implementation Method 4
prevents deterioration of reliability associated with mechanical strengths or moisture resistance through occurrence of cracks, which is normally caused when using Cu for the conductive powder and Ni for the internal electrode layer in such a manner that Cu particles diffuse throughout the internal electrode layer
Data Source
AI summary
Provided is a conductive paste composition for an external electrode of a multilayer ceramic capacitor that includes a conductive base material, an organic solvent, a binder resin, and a dispersing agent. The conductive base material includes a flake-shaped conductive powder, a spherical conductive powder, and first and second glass frits. The flake-shaped conductive powder has a larger size D50 than the spherical conductive powder. The first glass frit includes SiO2, SrCO3, BaCO3, Li2SO4, K2SO4, V2O5, ZnO, Al2O3, and Y2O3, and the second glass frit includes SiO2, SrCO3, BaCO3, CaF, ZnO, Al2O3, Y2O3, and L2O3.