Multilayer Ceramic Capacitor Outer Electrode Ni-Sn Barrier
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Solution Overview
Problem
Multilayer ceramic electronic components face mechanical and electrical joint failures due to solder leaching, especially in high-temperature environments, where the Ni plating layer's barrier function is compromised, leading to dissolution of base electrode materials and penetration of solder into the component.
Innovation Solution
A multilayer ceramic electronic component with a metal layer structure comprising a Pd layer, an Ni layer, and an Sn layer, where the Ni layer is thick enough (≥0.4 μm) to form a sufficient Ni-Sn intermetallic compound that acts as a strong barrier against solder leaching, even at elevated temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the Ni plating layer is thickened to prevent solder leaching, then the barrier function against solder dissolution is improved, but the total thickness of the outer electrode increases and stress increases causing peeling
Solution Approach 1:
The outer electrode is segmented into multiple functional layers: base electrode layer (Cu or Ag), Ni plating layer (barrier function), and Sn plating layer (wetting function). This segmentation allows each layer to perform its specific function optimally without requiring excessive thickness of any single layer, thus preventing peeling while maintaining barrier effectiveness.
Solution Approach 2:
The outer electrode uses a composite structure combining different materials (Cu/Ag base layer + Ni barrier layer + Sn wetting layer). This composite approach leverages the advantages of each material: Cu/Ag provides electrical conductivity, Ni provides barrier protection against solder leaching, and Sn provides solder wettability, achieving multiple functions without increasing overall thickness excessively.
2Reliability
If the Ni plating layer is thickened to prevent solder leaching, then the barrier function against solder dissolution is improved, but the stress in the Ni plating increases causing peeling at interfaces
Solution Approach 1:
The electrode structure is divided into multiple thin layers (base electrode layer, Ni plating layer, Sn plating layer) rather than one thick layer. This segmentation reduces the stress accumulated in any single layer, preventing peeling at interfaces while maintaining the barrier function through the combined thickness and material properties of all layers.
Solution Approach 2:
The invention optimizes the thickness parameter of the Ni plating layer to be within a specific range (0.01-10 μm, preferably 0.05-5 μm). This parameter optimization ensures sufficient barrier function against solder leaching while keeping the stress and peeling risk within acceptable limits, balancing protection and adhesion.
3Object-affected harmful factors
If lead-free solder with higher melting point is used for mounting, then environmental compatibility is improved, but the temperature at mounting increases causing Ni plating dissolution
Solution Approach 1:
The Ni plating layer is designed as a sacrificial barrier layer that may undergo some dissolution during high-temperature lead-free soldering, but its controlled thickness and strategic placement ensure it protects the more valuable base electrode layer (Cu or Ag) from dissolution. The Ni layer serves its protective function temporarily during mounting.
Solution Approach 2:
The multi-layer composite structure (base electrode layer + Ni plating layer + Sn plating layer) provides progressive protection: the Ni layer acts as the primary barrier against solder leaching at high temperatures, while the Sn layer ensures proper solder wettability. This composite approach enables compatibility with lead-free soldering processes.
4Length of stationary object
If the Ni plating layer is made thin to maintain outer electrode thickness, then the total thickness is controlled, but the barrier function against solder leaching is compromised
Solution Approach 1:
The invention precisely optimizes the Ni plating layer thickness within the range of 0.01-10 μm (preferably 0.05-5 μm). This parameter optimization ensures the layer is thin enough to maintain overall electrode thickness control while thick enough to provide effective barrier protection against solder leaching, achieving the right balance through careful parameter selection.
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 reduces or prevents solder leaching and mechanical/electrical joint failures by maintaining the barrier function of the Ni-Sn intermetallic compound over time, even in high-temperature environments above 175°C, thereby enhancing the reliability and stability of the component.
Implementation Method 1
the Ni layer is thick enough (≥0.4 μm) to form a sufficient Ni-Sn intermetallic compound that acts as a strong barrier against solder leaching
Implementation Method 2
an active dissolution of the Ni plating and Cu or Ag in the base electrode layer into the solder solution occurs
Implementation Method 3
When a multilayer ceramic electronic component is used in such a high-temperature environment, an Ni layer that inhibits solder leaching is exposed to high temperature over time
Data Source
AI summary
A multilayer ceramic capacitor includes a laminate and an outer electrode. The laminate includes a plurality of laminated ceramic layers and a plurality of internal electrode layers. The internal electrode layers are respectively laminated on the ceramic layers. The outer electrode is provided on each end surface of the laminate. Each outer electrode includes a metal layer. The metal layer includes at least a Pd layer, an Ni layer, and an Sn layer laminated from a portion adjacent to or in a vicinity of the laminate in order of the Pd layer, the Ni layer, and the Sn layer. The metal layer is located at an outermost surface of the outer electrode. A thickness of the Ni layer is greater than or equal to about 0.4.