MLCC External Electrode Plating for Soldering and Bend Resistance
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Solution Overview
Problem
Multilayer ceramic capacitors face a trade-off between mechanical strength and soldering reliability due to the thickness of external electrodes, where reducing thickness for increased flexibility can lead to defective soldering and reduced mechanical strength.
Innovation Solution
The multilayer ceramic capacitors incorporate external electrodes with a base electrode layer and plated layers, where the lower plated layers have an average thickness of 2.0 μm to 5.0 μm and include thin layer regions, optimizing solderability and bending resistance by controlling the mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the thickness of the plated layers is reduced to decrease mechanical strength and enhance flexibility, then the ability of the multilayer ceramic capacitor to follow deformation of the mounting substrate is improved, but the likelihood of defective soldering increases
Solution Approach 1:
The plated layer is designed with non-uniform thickness, having a first region with thickness of 1 μm or more and a second region with thickness of 0.1 μm or more but less than the first region. This local variation in thickness allows different portions of the plated layer to serve different functions: the thicker first region provides mechanical strength and soldering reliability, while the thinner second region enhances flexibility and adaptability to substrate deformation.
Solution Approach 2:
The invention changes the thickness parameter of the plated layer from a uniform value to a gradient distribution, where the thickness transitions from a first value (1 μm or more) in the first region to a second value (0.1 μm or more but less than the first value) in the second region. This parameter change enables simultaneous optimization of both mechanical strength and flexibility.
2Adaptability or versatility
If the thickness of the plated layers is reduced to enhance flexibility, then the mechanical strength of the external electrodes is decreased, but defective soldering becomes more likely
Solution Approach 1:
The plated layer incorporates regions of different thicknesses: a first region with thickness of 1 μm or more that ensures soldering quality and manufacturing reliability, and a second region with reduced thickness (0.1 μm or more but less than the first value) that provides enhanced flexibility. This local differentiation resolves the contradiction between flexibility and soldering quality.
Solution Approach 2:
The plated layer is segmented into functionally distinct regions: a first region optimized for soldering (thicker portion) and a second region optimized for flexibility (thinner portion). This segmentation allows each region to independently fulfill its specific function without compromising the other.
Data Source
AI summary
A multilayer ceramic capacitor includes a multilayer body including dielectric layers and internal electrode layers, first and second main surfaces opposed to each other in a lamination direction, first and second lateral surfaces opposed to each other in a width direction, and first and second end surfaces opposed to each other in a length direction, and first and second external electrodes respectively on the first and second end surfaces. Each of the first and second external electrodes includes a base electrode layer, a lower plated layer on the base electrode layer, and an upper plated layer on the lower plated layer. Each of the lower plated layers has an average thickness of about 2.0 μm or more and about 5.0 μm or less, and includes thin layer regions with a thickness smaller than the average thickness of the lower plated layer.