Thermosetting Conductive Paste for Multilayer Ceramic Capacitor Electrodes
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Solution Overview
Problem
Existing methods for forming external electrodes in multilayer ceramic capacitors face issues such as cracking, poor bonding between internal and external electrodes, and reliability problems due to diffusion of glass frit, low curing temperatures, and humidity sensitivity, which affect electrostatic capacity and insulation resistance.
Innovation Solution
A thermosetting conductive paste comprising metal powders with melting points of 700°C or higher and between 300°C to 700°C, combined with a thermosetting resin, is used to form external electrodes, enabling solid phase diffusion and improved bonding between internal and external electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a calcination type conductive paste is used and calcined at high temperature (500-900°C), then the external electrode can be formed, but glass frit diffuses into the capacitor device causing cracks during mounting and plating solution penetration leading to reliability problems
Solution Approach 1:
The patent changes the temperature parameter from high-temperature calcination (500-900°C) to low-temperature thermal curing (150-250°C), and changes the chemical composition by replacing glass frit with thermosetting resin, thereby eliminating glass frit diffusion and its harmful effects while maintaining electrode formation capability
Solution Approach 2:
The patent extracts and removes the glass frit component from the conductive paste formulation, replacing it with thermosetting resin, thereby eliminating the source of diffusion problems while preserving the bonding and conductive functions
2Object-generated harmful factors
If a thermosetting conductive paste is used with low curing temperature (150-250°C), then glass frit diffusion is avoided, but solid phase diffusion does not proceed between conductive particles and internal electrode resulting in poor bonding and unsatisfactory electric properties
Solution Approach 1:
The patent optimizes the curing temperature parameter to a specific range (150-250°C) that is sufficiently high to enable solid phase diffusion between metal particles and internal electrode, while remaining low enough to prevent glass frit diffusion, achieving both bonding strength and reliability
Solution Approach 2:
The patent uses a composite conductive paste containing both thermosetting resin for low-temperature curing and metal powder for conductivity and bonding, creating a material that achieves both strong bonding through solid phase diffusion and reliability through avoidance of glass frit diffusion
3Temperature
If silver acetate and amine are used in thermosetting conductive paste, then the paste can be thermally cured at moderate temperature, but pot life is shortened and insulation deteriorates due to humidity aging
Solution Approach 1:
The patent replaces the short-lived silver acetate-amine system with a more stable thermosetting resin system that has extended pot life and improved resistance to humidity aging, while maintaining moderate curing temperature capability
Solution Approach 2:
The patent changes the chemical composition parameters by replacing silver acetate and amine with thermosetting resin, thereby improving stability parameters including pot life and insulation resistance while maintaining curing temperature within acceptable ranges
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 solution achieves excellent bonding and electric properties, including enhanced electrostatic capacity and insulation resistance, while being suitable for substrate mounting and plating, thus improving the reliability of multilayer ceramic electronic parts.
Implementation Method 1
solid phase diffusion does not proceed between metals, i.e., the conductive particles, e.g., Ag powder contained in the conductive paste and the internal electrode
Implementation Method 2
thermally cured at a low temperature of 150 to 250° C. to form external electrode
Data Source
AI summary
Disclosed is a thermosetting conductive paste which is advantageous in that an external electrode for multilayer ceramic electronic part formed using the paste exhibits excellent bonding properties with an internal electrode and is suitable for mounting on a substrate or plating, achieving excellent electric properties (electrostatic capacity, tan δ. A thermosetting conductive paste comprising: (A) metal powder having a melting point of 700° C. or higher; (B) metal powder having a melting point of higher than 300 to lower than 700° C.; and (C) a thermosetting resin.