Ceramic Capacitor Electrodes with Conductive Resin Stress Absorption
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Solution Overview
Problem
Ceramic electronic components face stress-induced cracking due to thermal shock and bending of wiring boards, which affects their electrical properties and reliability, particularly when metal sintered compacts are formed at the end surfaces.
Innovation Solution
A ceramic electronic component design featuring first external electrodes made of Cu or B with glass, sintered to lift off from the side surfaces, and covered by a conductive resin layer, with specific ratios of contact length and thickness to absorb and distribute stress, reducing the likelihood of cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a metal layer is formed by printing conductive paste to the end surface of the ceramic electronic component body, then the internal electrodes are connected and the component can be manufactured, but large stress is applied to the metal layer due to thermal shock cycles, resulting in development of cracks in the ceramic component body
Solution Approach 1:
The external electrode is divided into two distinct layers: a metal layer (first external electrode) for electrical connection and a conductive resin layer (second external electrode) for stress absorption. This segmentation allows each layer to perform its specialized function without compromising the other.
Solution Approach 2:
The conductive resin layer is formed to cover the metal layer beforehand, creating a cushioning effect that absorbs thermal stress before it can concentrate on the metal layer and propagate cracks into the ceramic component body.
2Ease of operation
If the metal layer wraps around from the end surface to the side surface of the ceramic component body, then electrical connection is achieved, but stress is concentrated on the end of the metal layer at the side surface, making cracks likely to develop
Solution Approach 1:
The external electrode structure is segmented into a metal layer for electrical connection and a conductive resin layer for stress distribution. The conductive resin layer wraps around the metal layer, preventing stress concentration at the metal layer's end on the side surface.
Solution Approach 2:
The conductive resin layer acts as an intermediary between the metal layer and the ceramic component body, absorbing and distributing stress to prevent concentration at critical points where cracks would otherwise initiate.
3Adaptability or versatility
If the ceramic electronic component is attached to a wiring board, then the component can be mounted and used, but stress increases due to thermal shock from coefficient of thermal expansion difference, causing cracks in the ceramic component body
Solution Approach 1:
The conductive resin layer is formed to cover the metal layer beforehand, creating a protective cushion that absorbs thermal stress generated during mounting and operation, preventing stress transmission to the ceramic component body.
Solution Approach 2:
The external electrode uses a composite structure combining metal (for electrical conductivity) and conductive resin (for stress absorption). This composite material approach allows simultaneous achievement of electrical connection and thermal stress resistance.
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 design effectively absorbs stress from sintering shrinkage and board bending, preventing cracks and maintaining the ceramic component's electrical properties, even under thermal and mechanical strain.
Implementation Method 1
a stress caused by metal sintering shrinkage is concentrated on the end of the metal layer at the side surface of the ceramic electronic component body
Implementation Method 2
the development of cracks in the ceramic component body can be prevented by covering the metal layer with the conductive resin layer to thereby reduce the stress generated in the metal layer
Implementation Method 3
such a stress increases due to the thermal shock cycle by the difference in the coefficient of thermal expansion between the ceramic electronic component and the wiring board
Data Source
AI summary
A ceramic electronic component that is hardly influenced by a stress generated when an external electrode containing a metal sintered compact is formed at the end of the ceramic component body, and a method for manufacturing the same are obtained. A laminated ceramic capacitor 10 contains a ceramic component body 12 and first electrodes 20 to be connected to internal electrodes 14 that are led to the end surfaces are formed. The first external electrodes 20 are formed so that the ends are apart from the side surfaces of the ceramic component body 12. Second external electrodes 22 containing a conductive resin are formed in such a manner as to entirely cover the first electrodes 20 and first and second metal layers 24 and 26 are formed thereon. The first external electrodes 20 are formed by supplying a conductive paste containing conductive metal powder and glass frit having a softening point higher than the sintering starting temperature of the conductive metal powder, and heating the same.