Ceramic Component Outer Electrode Corrosion Resistance
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Solution Overview
Problem
Ceramic electronic components mounted using conductive adhesive face issues with thermal stress, corrosion, and porosity due to thermal diffusion, leading to reduced moisture resistance and potential metal precipitation when used in high-temperature environments like vehicle ECUs, where exhaust gases can penetrate and corrode the outer electrode layers.
Innovation Solution
A ceramic electronic component design featuring a fired electrode layer with glass content and Ni- and Pd-plated layers, where the Ni-plated layer has a thickness of 3 μm to 8 μm and the Pd-plated layer is 0.025 μm to 1 μm thick, providing a passivation coating that prevents corrosion and maintains structural integrity under thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conductive adhesive is used for mounting a ceramic electronic component, then thermal stress on the ceramic base is reduced, but the outer electrode layers are susceptible to corrosion from exhaust gases in high-temperature environments
Solution Approach 1:
The outer electrode is constructed as a composite structure with multiple layers: a fired electrode layer containing glass, a Ni-plated layer (3-8 μm thick), and a Pd-plated layer (0.025-1 μm thick). This composite structure combines the adhesion benefits of the fired electrode with the corrosion resistance of the plated layers, allowing the component to withstand both thermal stress and corrosive environments like vehicle ECUs
Solution Approach 2:
Different layers of the outer electrode are assigned different functions: the fired electrode layer provides adhesion to the ceramic body, the Ni-plated layer provides bulk corrosion resistance and structural support, and the thin Pd-plated layer provides surface passivation and oxidation resistance. This local differentiation of material properties optimizes both thermal and chemical resistance
2Object-affected harmful factors
If the Ni-plated layer thickness is increased to prevent corrosion, then corrosion resistance improves, but the overall electrode structure becomes more complex and costly
Solution Approach 1:
The patent applies a specific thickness range for the Ni-plated layer (3-8 μm) that provides sufficient corrosion resistance without excessive material use. The Ni layer serves as the primary corrosion barrier in the harsh environment, while the thinner Pd layer (0.025-1 μm) provides surface passivation. This localized optimization of layer thicknesses balances corrosion protection with structural simplicity and cost-effectiveness
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 significantly reduces corrosion and precipitation of the outer electrode, ensuring high reliability and mountability of ceramic electronic components on vehicles by using conductive adhesive, while maintaining the structural integrity and preventing metal exposure.
Implementation Method 1
providing a passivation coating that prevents corrosion and maintains structural integrity under thermal stress
Implementation Method 2
when forming the second metal layer, thermal diffusion may develop between the second metal layer and the first metal layer, which may cause the formation of porosities in the second metal layer due to the Kirkendall effect
Implementation Method 3
cracks are likely to occur in a ceramic base of a ceramic electronic component due to the difference in the thermal expansion coefficient between the ceramic base and an outer terminal electrode
Data Source
AI summary
A ceramic electronic component includes an electronic component body, an inner electrode, and an outer electrode. The outer electrode includes a fired electrode layer and first and second plated layers. The fired electrode layer is disposed on the electronic component body. The first plated layer is disposed on the fired electrode layer. The thickness of the first plated layer is about 3 μm to about 8 μm, for example. The first plated layer contains nickel. The second plated layer is disposed on the first plated layer. The thickness of the second plated layer is about 0.025 μm to about 1 μm, for example. The second plated layer contains lead.