Multilayer Ceramic Capacitor Electrodes for Stronger Cu-AgPd Adhesion
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Solution Overview
Problem
Multilayer ceramic capacitors face issues with substrate bending and increased contact resistance due to high-temperature environments, and existing secondary external electrode structures can experience peel-off phenomena, requiring improved adhesion strength.
Innovation Solution
A multilayer ceramic capacitor design featuring external electrodes with a copper-palladium intermetallic compound formed at the interface between copper and silver-palladium layers, where the silver-palladium layers have varying palladium content to enhance adhesion and prevent substrate warpage during low-temperature mounting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tin soldering is used for mounting, then electrical connection is achieved, but substrate bending and contact resistance increase occur in high-temperature environments
Solution Approach 1:
The patent changes the mounting temperature parameter from conventional high-temperature soldering to low-temperature mounting (below 150°C). This parameter change allows the use of Ag epoxy instead of tin solder, preventing substrate bending and contact resistance issues while maintaining reliable electrical connection
Solution Approach 2:
The patent introduces Ag epoxy as an intermediary material between the capacitor and substrate, replacing direct tin soldering. This intermediary enables low-temperature mounting and prevents the harmful effects of high-temperature soldering on substrate bending and contact resistance
2Reliability
If secondary external electrode structure with Ag epoxy is used, then reliability in high temperature and vibration environment is improved, but peel-off phenomenon occurs between electrodes
Solution Approach 1:
The patent applies local quality by creating a Cu-Pd intermetallic compound layer specifically at the interface between the Cu electrode layer and Ag epoxy. This localized intermetallic compound formation enhances adhesion strength at the critical interface region without affecting other parts of the electrode structure
Solution Approach 2:
The patent creates a composite electrode structure consisting of Cu electrode layer + Cu-Pd intermetallic compound interface layer + Ag epoxy. This composite structure combines the benefits of Cu conductivity with Pd-enhanced adhesion to Ag epoxy, preventing peel-off while maintaining high temperature and vibration resistance
3Ease of manufacture
If conventional single-layer Ag Pd electrode is used, then manufacturing is simple, but adhesion strength is insufficient
Solution Approach 1:
The patent segments the Ag Pd electrode into two distinct layers: a first layer with high Pd content (3-10 wt%) for strong adhesion to Cu electrode, and a second layer with lower Pd content for cost efficiency and overall performance. This segmentation enables optimized adhesion strength while maintaining manufacturing simplicity
Solution Approach 2:
The patent applies local quality by concentrating Pd in the first layer adjacent to the Cu electrode where adhesion is most critical, while using less Pd in the second layer. This localized Pd distribution maximizes adhesion strength at the critical interface while reducing overall material cost
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 provides improved adhesion strength and stability in high-temperature and vibration environments, preventing substrate warpage and ensuring reliable mounting without tin soldering.
Implementation Method 1
a copper-palladium intermetallic compound formed at an interface between the first electrode layer and the second electrode layer
Implementation Method 2
a copper-palladium intermetallic compound formed at an interface between the first electrode layer and the second electrode layer
Implementation Method 3
sintering at 600 to 700° C. for 1 to 2 hours
Data Source
AI summary
A multilayer ceramic capacitor includes a body including a dielectric layer and internal electrodes and external electrodes disposed on one surface of the body, wherein the external electrodes respectively include a first electrode layer connected to the internal electrodes and including copper (Cu); a second electrode layer disposed on the first electrode layer and including silver (Ag) and palladium (Pd); and a copper-palladium intermetallic compound formed at an interface between the first electrode layer and the second electrode layer, wherein the second electrode layer includes a first layer and a second layer formed to be sequentially adjacent to the first electrode layer, and the first layer has a content of palladium higher than a content of palladium of the second layer.