Reinforcing Electrodes in Ceramic Capacitors to Prevent Turnback Cracks
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Solution Overview
Problem
Existing electronic components, such as laminated ceramic capacitors, face issues with crack formation due to stress concentration at the end portions of external electrodes, resulting from residual stress during manufacturing and thermal shocks during mounting.
Innovation Solution
The introduction of reinforcing electrodes within the ceramic body, which are exposed on the surface and have a plated layer covering the thick-film electrode layer, helps distribute stress concentration and improve adhesion, thereby preventing cracks. These electrodes are strategically placed to overlap with internal electrodes and extend onto extraction regions, allowing for effective stress management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external electrodes are formed with thick-film electrode layer and plated films on ceramic sintered body, then solderability and corrosion resistance are improved, but residual stress concentrates at turnback portion end portions causing cracks
Solution Approach 1:
The patent applies different material properties to different regions: the thick-film electrode layer provides solderability and corrosion resistance where needed, while the plated films (Ni and Sn) provide enhanced mechanical strength and stress distribution at the turnback portion end portions. This local differentiation of material properties allows each region to optimize its function without compromising overall reliability.
Solution Approach 2:
The external electrode structure uses a composite material system consisting of multiple layers: thick-film electrode layer (for electrical conductivity and solderability), Ni plated film (for corrosion resistance and intermediate bonding), and Sn plated film (for enhanced solderability). This composite structure distributes stress across multiple interfaces and materials, preventing crack propagation at the turnback portion end portions.
2Ease of operation
If turnback portions extend to top and bottom surfaces for improved mountability, then ease of mounting is improved, but stress concentration at end portions increases leading to ceramic body cracks
Solution Approach 1:
The patent modifies the physical and chemical parameters of the turnback portion by applying multiple plated films with different properties. The Ni layer provides intermediate bonding with controlled adhesion strength, while the Sn layer provides enhanced solderability. These parameter changes allow the turnback portions to extend to the top and bottom surfaces for improved mountability while the multi-layer structure distributes and reduces stress concentration at the end portions.
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 effectively prevents crack formation in the ceramic body by distributing stress and enhancing adhesion, leading to improved reliability and durability of the electronic component.
Implementation Method 1
The introduction of reinforcing electrodes within the ceramic body, which are exposed on the surface and have a plated layer covering the thick-film electrode layer, helps distribute stress concentration and improve adhesion, thereby preventing cracks.
Implementation Method 2
The first external electrode 105 includes a thick-film electrode layer 105a formed by firing conductive paste.
Implementation Method 3
Plated films 105b and 105c are laminated on the thick-film electrode layer 105a. The plated film 105b includes Ni and is provided so as to prevent solder leaching. The plated film 105c includes Sn, for example, and is provided so as to improve solderability.
Data Source
AI summary
An electronic component includes a ceramic body including first to fourth side surfaces, a first external electrode provided on one side surface of the ceramic body, a second external electrode, and a plurality of reinforcing electrodes. Each of the first and second external electrodes includes a thick-film electrode layer including sintered metal, a plated layer arranged so as to cover the thick-film electrode layer, an external electrode main body portion covering the side surface of the ceramic body, and turnback portions extending to the top surface and the bottom surface of the ceramic body. An end portion of at least one reinforcing electrode of the plurality of reinforcing electrodes is exposed on the top surface or the bottom surface of the ceramic body on the center portion of the ceramic body in relation to the thick-film electrode layer in the turnback portion.