Glass-Free Outer Electrode Sintering for Crack-Resistant Ceramic Chips
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Solution Overview
Problem
Ceramic electronic chip components, such as multilayer ceramic capacitors, face issues with crack formation in the ceramic body due to stress from substrate deflection or heat during solder reflow, leading to impaired functionality and potential electrical short-circuits.
Innovation Solution
The use of a glass-free sintered layer in the outer electrode, formed by applying a conductive paste containing a tin-copper or tin-nickel alloy powder and a thermosetting resin, and subjecting it to heat treatment at a temperature higher than the curing temperature of the resin, results in a layer with lower electrical resistance and improved denseness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resin electrode containing conductive metal powder and thermosetting resin is used as the outer electrode, then the stress causing cracks in the ceramic body is absorbed by delamination or fracture of the resin electrode, but the electrical resistance of the electrode increases due to the dispersed conductive metal powder in the thermosetting resin
Solution Approach 1:
The patent uses a composite material consisting of conductive metal powder (such as silver, copper, or nickel powder) dispersed in a thermosetting resin (such as epoxy resin). This composite structure provides both mechanical stress absorption capability and electrical conductivity, resolving the contradiction between crack prevention and low electrical resistance. The resin matrix absorbs stress through delamination or fracture while the conductive metal powder maintains electrical pathways.
Solution Approach 2:
The patent optimizes parameters including the type and amount of conductive metal powder (5-50 wt%), the kind of thermosetting resin, curing temperature (80-150°C), and curing time (1-24 hours) to achieve the balance between stress absorption and electrical conductivity. By adjusting these parameters, the electrode achieves sufficient mechanical protection while maintaining acceptable electrical resistance for the application.
2Reliability
If a glass-containing sintered layer is formed as an underlying layer to protect the ceramic body, then stress is absorbed and crack formation is prevented, but the electrical resistance increases due to the presence of glass on the surface layer
Solution Approach 1:
The patent extracts the glass component from the electrode structure, using only a resin-based electrode without glass-containing sintered layers. This extraction eliminates the source of high electrical resistance while maintaining the stress absorption function through the resin electrode's delamination and fracture mechanisms. The resin electrode directly contacts the inner conductor to ensure electrical connection without the interference of glass layers.
Solution Approach 2:
The patent applies different material properties to different regions: the resin electrode provides stress absorption at the surface where mechanical stress occurs, while the inner conductor provides electrical connection. This local differentiation of material functions allows the system to achieve both crack protection and low electrical resistance without requiring glass-containing layers.
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 configuration reduces the equivalent series resistance (ESR) of the ceramic electronic chip component, enhances its reliability by preventing crack formation in the ceramic body, and improves moisture resistance and load reliability.
Implementation Method 1
the conductive paste is cured by heat treatment, the maximum temperature is set near the temperature at which the carbonization of the thermosetting resin is initiated
Implementation Method 2
a glass-free sintered layer including an alloy of tin and at least one of copper and nickel, the glass-free sintered layer containing no glass
Data Source
AI summary
An outer electrode includes a glass-free sintered layer containing no glass. A glass-free conductive paste is provided and includes a conductive metal powder and a thermosetting resin, the conductive metal powder including an alloy of tin and at least one of copper and nickel, and the glass-free conductive paste containing no glass. This composition is applied to cover a portion of a surface of a ceramic body. Then the ceramic body to which the glass-free conductive paste has been applied is subjected to heat treatment at a temperature of about 600° C., higher than or equal to a temperature about 400° C. higher than the curing temperature of the thermosetting resin. By the heat treatment, the thermosetting resin is subjected to thermal decomposition or combustion and thus little of the thermosetting resin remains, and the conductive metal powder is sintered to form a unified sintered metal body.