Conductive Paste Composition for Dense MLCC Copper Electrodes
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Solution Overview
Problem
The challenge is to improve the density of sintered electrodes in multilayer ceramic capacitors without increasing the glass content, while maintaining acid resistance and moisture resistance reliability.
Innovation Solution
A conductive paste is developed containing Cu particles and a glass frit with an oxide containing an alkali metal, where the alkali metal content is between 0.16 wt% and 0.35 wt% relative to the total Cu content. This composition enhances the sinterability and density of the electrode layers without excessive glass addition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If the glass component content in the sintered electrode is excessively increased to fill gaps between conductive metal particles, then the density of external electrodes is improved, but gaps between conductive metal particles increase and corrosion resistance to plating solution and moisture-resistance reliability deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters of the glass component by specifying precise ranges: SiO2 (30-70 wt%), B2O3 (5-40 wt%), Al2O3 (5-30 wt%), and controlled amounts of alkali metals (Na2O: 0.1-5 wt%, K2O: 0.1-5 wt%). This parameter optimization allows the glass to fill gaps effectively while maintaining appropriate viscosity and chemical stability, thus improving density without compromising corrosion and moisture resistance.
Solution Approach 2:
The patent creates a composite material system combining conductive metal particles (Cu, Ag, or their alloys) with a specifically formulated glass component. The glass acts as a matrix material that fills interstices between metal particles, providing both density improvement and protective properties. The composite structure leverages the conductivity of metals and the protective, gap-filling properties of glass to achieve both high density and reliability.
2Reliability
If acid-resistant glass containing barium (Ba)-zinc (Zn)-boron (B)-based oxide is used to secure acid resistance, then acid resistance is improved, but wettability with copper (Cu) metal is low causing agglomeration of glass and generation of pores which lowers density
Solution Approach 1:
The patent modifies the glass composition by limiting BaO to 0-10 wt% and ZnO to 0-10 wt%, while emphasizing B2O3 (5-40 wt%) as the primary boron source. The inclusion of Al2O3 (5-30 wt%) and controlled alkali metals further adjusts the glass properties. This balanced composition achieves acid resistance through B2O3 and Al2O3 while preventing excessive agglomeration by optimizing the overall chemical balance and viscosity characteristics.
Solution Approach 2:
The patent applies the concept of local quality by distributing different oxide components throughout the glass matrix to create zones with complementary functions: B2O3-rich zones provide acid resistance, Al2O3-rich zones enhance structural stability and wettability, while controlled amounts of alkali metals localize to provide fluxing action that improves glass flow and reduces agglomeration. This heterogeneous distribution within the homogeneous glass phase optimizes both acid resistance and density.
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 proposed solution effectively improves the density of the electrode layers, thereby enhancing the acid resistance and moisture resistance reliability of the multilayer ceramic capacitors, even when the electrodes are thinned.
Implementation Method 1
A conductive paste includes: a conductive powder containing Cu particles; and a glass frit including an oxide containing an alkali metal
Data Source
AI summary
A conductive paste includes: conductive powder containing Cu particles; and a glass frit including an oxide containing alkali metal, wherein a content of the alkali metal is 0.16 wt % or more and 0.35 wt % or less with respect to a total content of the Cu particles.