Conductive Paste Composition for Thin MLCC Inner Electrode Coverage
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Solution Overview
Problem
Existing conductive pastes for forming inner electrodes in multilayer ceramic capacitors face challenges in achieving high coverage when the electrodes are formed as thin layers, which hinders the increase in capacitance.
Innovation Solution
The use of a conductive paste comprising a ceramic powder of ABO3 type with a specified ionic radius ratio, where the ratio of the six-coordinate ionic radius of the A-site element to the six-coordinate ionic radius of the conductive metal powder is between 0.97 and 1.04, ensures high coverage of the inner electrodes even when they are thin.
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 multilayer ceramic capacitor is reduced, but the coverage of 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) with controlled particle sizes and ratios. This modifies the sintering behavior and melting point of the paste, enabling thin electrode formation while maintaining adequate coverage through controlled material transformation during firing
Solution Approach 2:
The patent creates a composite conductive paste material combining conductive metal particles (Ni, Pd, Pt) with specific ceramic materials (BaTiO3, SrTiO3, CaZrO3) and glass components. This composite structure enables the paste to exhibit both conductivity and controlled sintering characteristics that maintain coverage even when formed as thin layers
2Manufacturing precision
If the temperature at which metal particles sinter is increased to improve coverage, then the coverage of inner electrodes increases, but the temperature difference between metal sintering and ceramic sintering decreases
Solution Approach 1:
The patent modifies the chemical composition of the conductive paste by incorporating specific ratios of BaTiO3 (40-70 wt%), SrTiO3 (10-30 wt%), and CaZrO3 (10-30 wt%). These compositional changes alter the thermal behavior and melting point of the paste, enabling it to maintain coverage at temperatures that do not excessively compromise the dielectric layer integrity
Solution Approach 2:
The ceramic materials in the conductive paste act as intermediaries that facilitate controlled interaction between the metal particles and the dielectric layers during sintering. The glass components (B2O3, SiO2, Al2O3) serve as fluxes that promote wetting and bonding while controlling the sintering temperature profile, allowing coverage improvement without excessive temperature increase
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 maintains high coverage of the inner electrodes, thereby ensuring that the capacitance of multilayer ceramic capacitors is not hindered, even when the electrodes are thin.
Implementation Method 1
the temperature at which conductive metal particles included in conductive paste films that are to be the inner electrodes sinter is lower than the temperature at which the ceramic that forms the dielectric layers sinters
Implementation Method 2
By adding a common material, it is possible to shift the onset of sintering of the metal particles included in the conductive paste films that are to be the inner electrodes toward higher temperatures
Data Source
AI summary
A conductive paste defining inner electrodes of a multilayer ceramic capacitor manufactured through a firing step, includes a conductive metal powder, a ceramic powder, an organic solvent, and an organic binder. At least a portion of the ceramic powder is a powder of at least one oxide of 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 a metal element in the conductive metal powder is about 0.97 or greater and about 1.04 or less. Preferably, when the conductive metal powder includes nickel, the at least one oxide of ABO3 type with the specified ionic radius is at least one of NiTiO3, MgTiO3, or MnTiO3.