Coil Component Outer Electrode Grain Size Control
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Solution Overview
Problem
Existing coil components face issues with electrochemical migration of silver (Ag) in outer electrodes, leading to potential short circuits, especially when the distance between electrodes decreases, causing reliability concerns.
Innovation Solution
A coil component design featuring an outer electrode with a silver-containing layer having an average grain size of 4.2 μm to 15 μm, reduced grain boundaries, and a plating layer of Ni and Sn, which suppresses electrochemical migration by minimizing Ag ionization and moisture penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If outer electrodes contain Ag with fine grain size (0.5 to 0.9 μm) to form dense and thick electrodes, then electrode density and thickness are improved, but electrochemical migration of Ag occurs leading to short circuits
Solution Approach 1:
The patent changes the grain size parameter of Ag from fine (0.5-0.9 μm) to coarse (3 μm to 15 μm). This parameter change reduces the grain boundary area, thereby suppressing electrochemical migration while maintaining electrode density and thickness, thus resolving the contradiction between manufacturing precision and reliability
Solution Approach 2:
The patent creates a composite outer electrode structure combining Ag particles with glass frit and organic vehicle. The glass frit acts as a barrier matrix that restricts Ag ion migration pathways, while the organic vehicle ensures proper paste formulation. This composite approach maintains electrode density while preventing electrochemical migration, resolving the reliability issue
2Volume of moving object
If coil components are reduced in size to decrease distance between outer electrodes, then miniaturization is achieved, but electrochemical migration becomes more likely
Solution Approach 1:
The patent changes the Ag grain size parameter to coarse (3-15 μm), which reduces grain boundary area and suppresses electrochemical migration. This allows miniaturization of the component while maintaining resistance to electrochemical migration, as the coarse grain structure is less susceptible to migration regardless of electrode spacing
Solution Approach 2:
The composite structure of Ag particles embedded in glass frit creates a more stable electrode material that resists electrochemical migration even when electrode spacing is reduced. The glass frit matrix provides physical barriers to ion migration, enabling miniaturization without compromising reliability
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 reduces the occurrence of electrochemical migration and short circuits, enhancing the reliability and durability of the coil component by controlling grain size and adding a protective plating layer.
Implementation Method 1
there is a possibility that the potential difference between the two coil conductors will cause electrochemical migration of Ag contained in the outer electrodes
Implementation Method 2
since the average grain size of Ag grains contained in the outer electrode is 4.2 μm to 15 μm, grain boundaries of Ag grains are reduced, and thus Ag ionization reaction can be suppressed
Implementation Method 3
the outer electrode may further include a plating layer disposed on the Ag-containing layer... suppressing electrochemical migration by minimizing Ag ionization and moisture penetration
Data Source
AI summary
A coil component includes a device main body composed of an insulator, a coil conductor which is disposed inside or on a surface of the device main body, and an outer electrode which is disposed on a surface of the device main body and electrically connected to the coil conductor. The outer electrode includes a Ag-containing layer containing Ag grains with an average grain size of 4.2 to 15 μm.