Multilayer Ceramic Component Electrode Structure for Crack Resistance
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Solution Overview
Problem
Multilayer ceramic capacitors face issues such as cracks, reduced capacitance, insulation resistance, and connection strength due to stress from substrate deflection and temperature changes, with existing conductive resin layers having insufficient bonding strength and moisture ingress leading to insulation resistance decrease.
Innovation Solution
A multilayer ceramic electronic component with external electrodes comprising a base layer, a first Ni layer, a metal layer with lower Young's modulus than Ni, a second Ni layer, and a surface layer, where the metal layer relaxes stress and inhibits cracking, and the Ni layers enhance adhesion and solder wettability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conductive resin layer is used as part of the external electrode to relax stress, then crack occurrence is inhibited, but bonding strength between different materials is insufficient causing peeling
Solution Approach 1:
The patent uses a composite structure consisting of a base layer, first Ni layer, metal layer with lower Young's modulus, second Ni layer, and surface layer. This composite structure combines materials with different properties: the metal layer with lower Young's modulus provides stress relaxation and crack resistance, while the Ni layers provide strong bonding and adhesion, resolving the contradiction between crack resistance and bonding strength.
Solution Approach 2:
Different layers of the external electrode are assigned different local functions: the metal layer with lower Young's modulus is specifically positioned to provide stress relaxation and inhibit cracks, while the Ni layers are positioned to provide bonding strength and adhesion. This local differentiation of material properties resolves the contradiction by assigning each function to the most suitable material in the appropriate location.
2Reliability
If the conductive resin layer is used to relax stress, then crack occurrence is inhibited, but moisture resistance deteriorates due to peeling
Solution Approach 1:
The composite electrode structure with multiple layers (base layer, Ni layers, metal layer with lower Young's modulus, surface layer) provides both crack resistance through the flexible metal layer and moisture resistance through the intact multi-layer structure. The strong bonding between layers prevents peeling and moisture ingress while maintaining stress relaxation capabilities.
Solution Approach 2:
The Ni layers act as intermediary layers between the base layer and the metal layer with lower Young's modulus, providing strong adhesion and preventing direct contact between materials that might cause peeling. This intermediary structure maintains both crack resistance and moisture resistance by ensuring intimate bonding throughout the electrode structure.
3Strength
If heat treatment is performed to form external electrodes, then adhesion is improved, but surface oxidation occurs
Solution Approach 1:
The patent forms the metal layer with lower Young's modulus on the first Ni layer before performing heat treatment. This preliminary formation of the stress-relaxing metal layer allows the heat treatment to improve adhesion of subsequent layers without causing oxidation of the final surface, as the surface layer is formed after heat treatment completes.
Solution Approach 2:
The external electrode is segmented into multiple layers formed at different stages: the metal layer with lower Young's modulus is formed first to provide stress relaxation, then heat treatment is performed to improve adhesion, and finally the surface layer is formed to provide oxidation resistance. This segmentation of the formation process allows each function to be optimized independently.
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 configuration improves the reliability by reducing the occurrence of cracks and maintaining moisture resistance, ensuring the integrity of the structure, and enhancing the adhesion and solderability, thus preventing cracks and maintaining high insulation resistance.
Implementation Method 1
the metal layer acts to relax the stress applied to the ceramic body and the external electrodes, thereby inhibiting occurrence of cracks
Implementation Method 2
the first Ni layer has a recrystallized structure with fewer dislocations and fewer lattice defects than the second Ni layer
Implementation Method 3
by forming the second Ni layer after the heat treatment, the adhesion of the surface layer and high solder wettability during substrate mounting can be obtained on the surface of the second Ni layer
Data Source
AI summary
A multilayer ceramic electronic component includes a ceramic body having internal electrodes stacked in a direction of a first axis, and end surfaces perpendicular to a second axis orthogonal to the first axis, and external electrodes covering the end surfaces of the ceramic body, respectively, wherein each of the external electrodes includes a base layer formed on a corresponding one of the end surfaces and connected to the plurality of internal electrodes that are led out to the corresponding end surface, a first Ni layer formed on the base layer, a second Ni layer formed on the first Ni layer, a surface layer formed on the second Ni layer, and a metal layer that is formed between the first Ni layer and the second Ni layer and contains a metal having a Young's modulus lower than that of Ni, as a main component.