Multilayer Ceramic Capacitor Ni-Cu Plating Adhesion
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Solution Overview
Problem
Multilayer ceramic capacitors face issues with moisture resistance due to peeling between underlying Ni and Cu plating electrode layers, leading to impaired characteristics, and existing countermeasures either compromise moisture resistance or are cumbersome in manufacturing.
Innovation Solution
A multilayer ceramic capacitor design featuring a Ni underlying electrode layer, a Cu plating electrode layer with a Ni diffused region closer to the underlying layer and a non-Ni diffused region, and an additional plating electrode layer, optimized for thickness and diffusion to enhance adhesion and moisture resistance without excessive heat treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Cu plating electrode layer is formed on an underlying Ni electrode layer to enhance moisture resistance, then moisture resistance is improved, but adhesion between layers deteriorates causing peeling
Solution Approach 1:
The Cu plating electrode layer is segmented into multiple sub-layers with different thicknesses. The first Cu plating sub-layer (3-12 μm) provides moisture resistance, while the second Cu plating sub-layer (0.5-2 μm) forms an intermediate layer that enhances adhesion. This segmentation allows each sub-layer to perform its specific function optimally without causing peeling between layers.
2Strength
If heat treatment is performed to diffuse Ni into Cu plating electrode layer to enhance adhesion, then adhesion is improved, but moisture resistance deteriorates due to gap formation
Solution Approach 1:
The Cu plating electrode layer is divided into multiple sub-layers where only the first Cu plating sub-layer undergoes heat treatment for Ni diffusion. The second Cu plating sub-layer remains untreated, preserving its integrity and moisture resistance function. This selective segmentation allows adhesion enhancement without compromising the moisture barrier.
Solution Approach 2:
Heat treatment for Ni diffusion is applied locally only to the first Cu plating sub-layer that is in direct contact with the Ni underlying electrode layer. The second Cu plating sub-layer maintains its original properties and serves as a protective moisture barrier. This local application of heat treatment resolves the contradiction by enhancing adhesion where needed while preserving moisture resistance where required.
3Strength
If excessive heat treatment is performed to improve adhesion, then adhesion between Ni and Cu layers is enhanced, but manufacturing complexity increases and moisture resistance is compromised
Solution Approach 1:
The Cu plating electrode layer is segmented into multiple sub-layers with different heat treatment requirements. Only the first Cu plating sub-layer requires heat treatment for Ni diffusion, while the second sub-layer does not. This segmentation reduces the overall heat treatment complexity and time compared to treating the entire Cu plating layer, while still achieving sufficient adhesion enhancement.
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 provides improved moisture resistance and strength to the external electrodes while maintaining sufficient capacitance, as confirmed by the moisture resistance load test, with no defective samples in the preferred embodiment.
Implementation Method 1
performing a heat treatment to diffuse a metal (for example, Ni) in the underlying electrode layer into the Cu plating electrode layer
Implementation Method 2
performing a heat treatment to diffuse a metal (for example, Ni) in the underlying electrode layer into the Cu plating electrode layer
Data Source
AI summary
A multilayer ceramic capacitor includes a capacitive element including ceramic layers and internal electrodes, and external electrodes on the capacitive element. The external electrodes include a Ni underlying electrode layer mainly made of Ni, a Cu plating electrode layer, and at least one second plating electrode layer. The Cu plating electrode layer includes a Ni diffused Cu plating electrode layer on a side closer to the Ni underlying electrode layer and including Ni diffused therein and a non-Ni diffused Cu plating electrode layer on a side closer to the second plating electrode layer and not including Ni diffused therein. The Cu plating electrode layer has a thickness of about 3 μm or more and about 12 μm or less and the non-Ni diffused Cu plating electrode layer has a thickness of about 0.5 μm or more.