Ceramic Electrode Interface Protrusions for Copper Bonding Reliability
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Solution Overview
Problem
Conventional ceramic electronic devices face challenges in bonding external electrodes containing conductors with low ionization tendencies, such as copper, to the element body or glass frit, due to difficulties in oxidation and bonding.
Innovation Solution
The introduction of interface protrusions made of oxide, specifically with a narrow and wide part configuration, enhances the anchor effect and bonding reliability between the external electrode and the ceramic layer, utilizing a constriction formed by the narrow and wide parts and incorporating glass for improved wetting and bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If copper or other metals with low ionization tendency are used as conductors in external electrodes, then electrical conductivity is improved, but bonding reliability with oxide-based element body and glass frit deteriorates
Solution Approach 1:
An oxide layer is introduced as an intermediary substance between the copper conductor and the oxide-based element body/glass frit. This oxide layer serves as a chemical bridge that facilitates bonding: it bonds well with the oxide-based materials while providing a surface for copper adhesion, thereby resolving the incompatibility between low-ionization copper and oxide materials.
Solution Approach 2:
The external electrode is designed as a composite structure consisting of copper conductor particles embedded in a glass frit matrix, with an oxide layer at the interface. This composite approach combines the high electrical conductivity of copper with the bonding capabilities of glass frit and oxide, achieving both electrical performance and reliable bonding.
2Ease of manufacture
If conventional baked electrodes with copper conductor are used, then manufacturing simplicity is maintained, but joint strength between external electrode and element body deteriorates
Solution Approach 1:
The chemical composition parameters of the external electrode paste are modified to include oxide components in addition to copper and glass frit. This parameter change enables the formation of an oxide layer during the baking process, which enhances joint strength while maintaining the conventional one-step baking manufacturing method.
3Power
If copper is used as conductor material, then electrical performance is improved, but oxidation resistance causes difficulty in forming strong bonds with oxide materials
Solution Approach 1:
The oxide layer is formed preliminarily during the electrode application and baking process, before final assembly and use. This preliminary formation of the oxide interface layer ensures that bonding conditions are prepared in advance, making the subsequent bonding process easier and more reliable.
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 significantly improves the joint reliability between the element body and external electrode, as demonstrated by a higher change rate in capacitance during thermal shock tests, ensuring a strong and durable bond even with conductors difficult to oxidize like copper.
Implementation Method 1
the interface protrusion comprises an oxide... the interface protrusion contained in the external electrode is easily jointed with the element body including the ceramic layer (oxide)
Implementation Method 2
the interface protrusion contained in the external electrode is easily jointed with the element body including the ceramic layer (oxide), and the element body and the external electrode can consequently firmly be jointed
Implementation Method 3
the interface protrusion includes: a narrow part having a small width; and a wide part having a larger width than the narrow part and disposed next to the narrow part extending to the inner side of the external electrode from the narrow part... the interface protrusion to exhibit an anchor effect for the external electrode due to the constriction formed by the narrow part and the wide part
Implementation Method 4
incorporating glass for improved wetting and bonding
Data Source
AI summary
A ceramic electronic device includes an element body and an external electrode. The element body is formed by laminating a ceramic layer and an internal electrode layer. The external electrode is electrically connected to at least one end of the internal electrode layer. At least a part of a joint boundary between the electrode layer and the ceramic layer includes an interface protrusion on the external electrode side. The interface protrusion is made of an oxide.