Multilayer Ceramic Electrode Composition for Stronger End-Terminal Bonding
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Solution Overview
Problem
The challenge in ceramic electronic devices, such as multilayer ceramic capacitors, is the degradation of bondability between internal electrode layers and external electrodes due to differences in densification temperature ranges during the firing process, leading to poor electrical conductivity and desired characteristics not being achieved.
Innovation Solution
The solution involves alternately stacking dielectric and internal electrode layers with a higher concentration of a sub-metal element in internal electrode layers and external electrodes, using a manufacturing method that includes forming ceramic multilayer structures with internal electrode patterns containing Ni and a co-material, and applying a metal paste with a higher concentration of the sub-metal element on the external electrodes, thereby improving the bondability through delayed sintering and diffusion of the additive metal element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If internal electrode layers and external electrodes are formed with the same metal composition during firing, then the manufacturing process is simple, but bondability degrades due to differences in densification temperature ranges
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of the sub-metal element (Cu, Ag, or Au) within the external electrode structure. The sub-metal element concentration is higher in the portion adjacent to the internal electrode layers and decreases toward the outer surface. This localized compositional variation optimizes bondability at the interface while maintaining manufacturing feasibility through a single paste formulation.
Solution Approach 2:
The patent changes the compositional parameter of the external electrode by incorporating a sub-metal element (Cu, Ag, or Au) at specific concentrations (0.1-10 wt%). This parameter change modifies the sintering characteristics of the external electrode, enabling it to match the densification temperature range of the internal electrode layers and improve bondability.
2Strength
If the concentration of sub-metal element in external electrodes is increased to improve bondability, then bonding strength improves, but manufacturing complexity increases due to precise concentration control requirements
Solution Approach 1:
The patent establishes specific parameter ranges for the sub-metal element concentration (0.1-10 wt%) and the ratio between sub-metal element and Ni (0.01-1.0). These parameter definitions provide clear manufacturing targets that balance bondability improvement with manufacturing feasibility, reducing the complexity of concentration control.
Solution Approach 2:
The patent specifies that the sub-metal element concentration should be higher in the portion of the external electrode adjacent to the internal electrode layers. This local quality requirement focuses the complexity of concentration control only where it is most needed (at the bonding interface) rather than requiring uniform precision throughout the entire electrode structure.
3Manufacturing precision
If densification temperature ranges of internal electrode layers and external electrodes are made different, then sintering control becomes difficult, but uniform densification is achieved
Solution Approach 1:
The patent changes the compositional parameters of the external electrode by adding sub-metal elements (Cu, Ag, Au) to modify its sintering characteristics. This enables the external electrode's densification temperature range to overlap with that of the internal electrode layers, achieving uniform densification while maintaining relatively simple sintering control through a single-step firing process.
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
This configuration enhances the continuity modulus of internal electrode layers, improves bondability, and suppresses capacity decrease due to poor connections, achieving desired electrical characteristics and reliability.
Implementation Method 1
a concentration of the sub metal element in the plurality of internal electrode layers is higher than that in the external electrodes
Implementation Method 2
firing the ceramic multilayer structure so that a concentration of the sub metal element in internal electrode layers formed from the plurality of internal electrode patterns is higher than that in external electrodes formed from the metal paste
Data Source
AI summary
A ceramic electronic device includes a multilayer chip in which each of a plurality of dielectric layers of which a main component is a ceramic and each of a plurality of internal electrode layers including Ni as a main component are alternately stacked, the multilayer chip having a rectangular parallelepiped shape, each of the plurality of internal electrode layers being exposed to two end faces opposite to each other; and external electrodes that are respectively provided on the two end faces and have a main component of Ni. The plurality of internal electrode layers include a sub metal element other than Ni, and co-materials. A concentration of the sub metal element in the plurality of internal electrode layers is higher than that in the external electrodes.