Multilayer Ceramic Capacitor Electrodes With Graded Cu Plating
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Solution Overview
Problem
Multilayer ceramic electronic components face cracking due to thermal stress during reflow mounting and moisture penetration issues due to insufficient adhesion and stress distribution of Cu plating electrodes on ceramic bodies, especially as devices miniaturize.
Innovation Solution
A multilayer ceramic electronic component design featuring a Cu plating layer with a lower region of smaller grain diameter for improved adhesion and reduced compressive stress, and an upper region of larger grain diameter for enhanced moisture resistance, using a thin film electrode layer of Ni, Cr, or Ti, and a Ni-Sn plating structure to manage thermal stress and prevent cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat treatment is applied to increase grain size of metal in plating electrode, then adhesion to ceramic body is improved, but compressive stress in plating electrode increases causing cracking under thermal stress
Solution Approach 1:
The plating electrode is segmented into multiple layers with different grain sizes: a lower layer with smaller grain diameter (≤5 μm) for low compressive stress and high adhesion, and an upper layer with larger grain diameter (>5 μm) for high adhesion. This segmentation allows each layer to fulfill different functional requirements simultaneously.
Solution Approach 2:
Different regions of the plating electrode have different grain sizes optimized for their specific functions. The lower layer near the ceramic body has smaller grains for stress management and adhesion, while the upper layer has larger grains for enhanced adhesion. This local quality differentiation resolves the contradiction between adhesion and cracking resistance.
2Volume of moving object
If external electrode thickness is reduced to enable miniaturization, then ceramic body size is maximized increasing internal electrode effective area, but adhesion becomes insufficient and moisture resistance is degraded
Solution Approach 1:
The grain diameter parameter of the plating electrode is changed and distributed differently across layers. The lower layer has grain diameter ≤5 μm while the upper layer has grain diameter >5 μm. This parameter change allows thin electrodes to achieve both good adhesion and moisture resistance without increasing overall thickness.
Solution Approach 2:
The plating electrode is constructed as a composite structure with two distinct layers having different grain size characteristics. This composite approach combines the advantages of fine-grained material (low stress) and coarse-grained material (high adhesion) in a single thin electrode structure.
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 effectively reduces cracking from thermal stress and maintains reliable moisture resistance, ensuring the structural integrity and performance of miniaturized ceramic components.
Implementation Method 1
the Cu plating layer located in the lower layer region having a metal grain diameter smaller than that of the Cu plating layer located in the upper layer region
Implementation Method 2
When thermal stress (for example, ΔT of 230° C. in solder reflow mounting, and ΔT of 140° C. or higher and 180° C. or lower for thermal shock of a product after mounting) is applied in this state
Data Source
AI summary
A multilayer ceramic capacitor includes an external electrode including an underlying electrode layer, a lower plating layer on the underlying electrode layer at a first end surface and a second end surface, and an upper plating layer on the lower plating layer. The underlying electrode layer is a thin film electrode including at least one selected from Ni, Cr, Cu, and Ti. The lower plating layer is a Cu plating layer including a lower layer region located closer to the multilayer body and an upper layer region located between the lower layer region and the upper plating layer, and the Cu plating layer in the lower layer region has a metal grain diameter smaller than that of the Cu plating layer located in the upper layer region.