Multilayer Ceramic Capacitor External Electrode Plating Structure
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Solution Overview
Problem
Multilayer ceramic capacitors face challenges in maintaining moisture-resistance reliability, especially with the miniaturization of dielectric and internal electrode thickness, which compromises their performance in various climates and environments.
Innovation Solution
Incorporating a nickel-tin (Ni—Sn) intermetallic compound layer with a thickness of 0.1 μm or more between the nickel and tin plating layers in the external electrodes to enhance the bonding force and improve moisture-resistance reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the dielectric layer and internal electrode thickness are decreased for miniaturization, then the capacitance density is improved, but the moisture-resistance reliability deteriorates
Solution Approach 1:
A nickel-tin (Ni-Sn) intermetallic compound layer is introduced as an intermediary layer between the nickel plating layer and the tin plating layer. This intermediate layer acts as a barrier to prevent moisture penetration and chemical reactions between the nickel and tin layers, thereby maintaining moisture-resistance reliability even when the dielectric layer and internal electrode thickness are reduced for miniaturization.
Solution Approach 2:
The external electrode plating structure is designed as a composite material system consisting of multiple layers: nickel plating layer, nickel-tin intermetallic compound layer, and tin plating layer. This composite structure combines the advantages of each material - nickel provides structural integrity, while the nickel-tin intermetallic compound layer provides moisture barrier properties, and tin provides corrosion resistance, achieving both miniaturization and moisture-resistance reliability.
2Ease of manufacture
If the nickel and tin plating layers are directly plated on the electrode layer, then the manufacturing process is simplified, but the bonding force and moisture-resistance reliability are insufficient
Solution Approach 1:
The nickel-tin intermetallic compound layer serves as an intermediary between the nickel and tin plating layers, creating strong metallurgical bonding through interdiffusion. This intermediate layer enhances the bonding force between the nickel and tin layers, preventing delamination while maintaining a relatively simple three-layer plating structure that can be formed through conventional plating processes followed by heat treatment.
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 effectively secures sufficient moisture-resistance reliability even when the dielectric layer thickness is 0.4 μm or less and the cover portion thickness is 20 μm or less, thereby addressing the degradation of moisture-resistance in miniaturized capacitors.
Implementation Method 1
a nickel-tin (Ni—Sn) intermetallic compound layer having a thickness of 0.1 μm or more, which is formed between the nickel (Ni) plating layer and the tin (Sn) plating layer
Data Source
AI summary
A multilayer ceramic capacitor includes a body including a dielectric layer and an internal electrode and an external electrode disposed on an exterior of the body. The external electrode includes an electrode layer connected to the internal electrode and a plating portion including a nickel (Ni) plating layer, a nickel-tin (Ni—Sn) intermetallic compound layer, and a tin (Sn) plating layer, sequentially disposed on the electrode layer. The Ni—Sn intermetallic compound layer has a thickness of 0.1 μm or more.