Ceramic Component Ni Diffusion Barrier for Lead-Free Soldering
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Solution Overview
Problem
Ceramic electronic components face issues with solder leach and decreased bonding strength when a Cu ground electrode layer is directly coated with lead-free solder, leading to potential failures in dielectric voltage isolation and time-consuming thickening processes.
Innovation Solution
A ceramic electronic component with a ground electrode layer formed by firing, covered by a lead-free solder layer based on Sn—Ag—Cu—Ni—Ge, and a diffusion layer of Ni formed between the ground electrode layer and the solder layer, which acts as a barrier to prevent solder leach and fragile intermetallic compound growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a Cu ground electrode layer is directly coated with lead-free solder having high Sn content, then the bonding process is simplified and productivity is improved, but solder leach of Cu occurs leading to disappearance of the ground electrode layer and decreased reliability
Solution Approach 1:
A Ni diffusion layer is introduced as an intermediary between the Cu ground electrode layer and the Sn-based solder layer. This Ni layer prevents direct contact between Cu and Sn, thereby suppressing solder leach and preventing the formation of fragile intermetallic compounds, while still allowing effective bonding to occur.
Solution Approach 2:
The Ni diffusion layer is formed in-situ during the soldering process itself, without requiring a separate plating step. The Ni diffuses from the solder alloy into the Cu ground electrode layer during heating, automatically creating the protective barrier layer as part of the bonding process.
2Reliability
If the Cu ground electrode layer is thickened to prevent solder leach, then reliability is improved, but the manufacturing time is excessively increased
Solution Approach 1:
The protective Ni diffusion layer is formed automatically during the soldering process without requiring separate thickening operations. The Ni diffuses into the Cu layer during the heating cycle, creating an effective barrier against solder leach within the existing manufacturing time frame.
Solution Approach 2:
The solution changes the chemical composition parameters of the solder alloy by incorporating Ni (0.1-5.0 wt%) and Ge (0.01-1.0 wt%), which enables the formation of the protective Ni diffusion layer during normal soldering conditions, eliminating the need for extended processing times.
3Reliability
If Ni and Sn are plated on the Cu ground electrode layer to prevent solder leach, then reliability is improved, but the process complexity and manufacturing cost are increased
Solution Approach 1:
The Ni diffusion layer serves as an intermediary barrier between Cu and Sn, preventing direct interaction that causes solder leach. This single-layer diffusion approach replaces complex multi-layer plating processes while achieving the same protective function.
Solution Approach 2:
The Ni diffusion layer is formed self-organically during the soldering process itself, eliminating the need for separate plating equipment and processes. The Ni diffuses from the solder alloy into the Cu substrate, automatically creating the protective barrier.
4Manufacturing precision
If vapor deposition is used to form the Cu ground electrode layer, then manufacturing precision is improved, but the time required to achieve sufficient thickness is excessively increased
Solution Approach 1:
The Ni diffusion layer is formed automatically during the soldering process without requiring separate deposition operations. The diffusion occurs in-situ during heating, creating the protective barrier within the existing process cycle.
Solution Approach 2:
The solder alloy composition is modified to include Ni and Ge, which enables the formation of the protective diffusion layer through controlled diffusion during standard soldering temperatures and times, replacing time-consuming deposition processes.
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 allows for direct coating of the Cu ground electrode layer with lead-free solder without reliability issues, maintaining bonding strength and enabling faster thickening of the electrode layer, while preventing solder leach and intermetallic compound growth.
Implementation Method 1
a diffusion layer having been formed by the diffusion of Ni between the ground electrode layer and the solder layer
Implementation Method 2
the diffusion layer, which functions as a barrier layer, can suppress the solder leach of Cu from the ground electrode layer. The diffusion layer of Ni can also suppress the growth of the fragile intermetallic compounds of Sn—Cu
Data Source
AI summary
There are provided a ceramic electronic component and a method for producing the ceramic electronic component, where a ground electrode layer can be directly coated with lead-free solder without lowering reliabilities. Terminal electrode 3 is provided with a ground electrode layer 21 of Cu having been formed by firing, a solder layer 22 formed of a lead-free solder based on five elements of Sn—Ag—Cu—Ni—Ge, and a diffusion layer 23 having been formed by the diffusion of Ni between the ground electrode layer 21 and the solder layer 22. Because the diffusion layer 23 of Ni is formed between the ground electrode layer 21 and the solder layer 22, the diffusion layer 23, which functions as a barrier layer, suppresses the solder leach of Cu from the ground electrode layer 21. The diffusion layer 23 of Ni can also suppress the growth of fragile intermetallic compounds of Sn—Cu. Therefore, a decrease in the bonding strength between the ground electrode layer 21 and the solder layer 22 can be prevented.