Anti-oxidant Electrode Layers in Multi-layer Ceramic Capacitors
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Solution Overview
Problem
Conventional multi-layer ceramic capacitors face issues with oxidization of internal electrodes during sintering at a reducing atmosphere, leading to structural defects like cracks and deteriorated electrical properties, which compromise capacitance reliability.
Innovation Solution
Incorporation of anti-oxidant electrode layers made of nickel, with oxidized portions forming an Mg-Ni-O phase, spaced apart from external electrodes to prevent oxidization of internal electrodes, while maintaining identical or greater width and length to cover layers, effectively inhibiting oxidization and enhancing electrical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sintering is performed at a reducing atmosphere with regulated oxygen partial pressure to prevent internal electrode oxidization, then high-temperature reliability is improved, but oxide layers form on outermost internal electrodes adjacent to thinner cover layers, causing structural defects and electrical property deterioration
Solution Approach 1:
The patent introduces a protective electrode layer as an intermediary between the outermost internal electrode and the reducing atmosphere during sintering. This protective layer acts as a mediator that prevents direct contact between the internal electrode and oxidizing conditions, thereby preventing oxide layer formation while allowing the sintering process to proceed at regulated oxygen partial pressure for improved high-temperature reliability
Solution Approach 2:
The patent creates a locally inert environment by forming a protective electrode layer that isolates the outermost internal electrode from the reducing atmosphere during sintering. This protective layer establishes an inert barrier that prevents oxidization reactions, allowing the bulk sintering atmosphere to maintain regulated oxygen partial pressure for reliability improvement without causing surface oxidization
2Quantity of substance
If the cover layers and outermost internal electrodes are thinned to achieve higher capacitance without size increase, then capacitance density is improved, but the electrical properties of internal electrodes become unstable and oxidization occurs during sintering
Solution Approach 1:
The patent applies local quality by providing differential protection to different regions of the capacitor structure. The protective electrode layer is specifically applied to outermost internal electrodes that are vulnerable to oxidization, while internal electrodes not adjacent to thinner cover layers remain unprotected. This localized approach maintains electrical property stability where needed while preserving the thinned structure for high capacitance density
Solution Approach 2:
The protective electrode layer is formed in advance before the sintering process, preliminarily protecting the outermost internal electrodes from oxidization. This preliminary protective action ensures that when the sintering process occurs at regulated oxygen partial pressure, the vulnerable electrodes are already shielded, preventing instability and oxidization while maintaining the thinned structure for high capacitance
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 anti-oxidant electrode layers significantly reduce defects such as electrical shorts, flash defects, and cover cracks, ensuring stable electrical properties and improved capacitance reliability by preventing oxidization of internal electrodes during sintering.
Implementation Method 1
oxidized portions forming an Mg-Ni-O phase
Implementation Method 2
sintering should be performed at a reducing atmosphere where an oxygen partial pressure is regulated
Data Source
Figure 1
Figure 2A~2B
Figure 3~4A
AI summary
A multi-layer ceramic capacitor (30) including: a ceramic sintered body (31) having cover layers (41a,41b) provided on upper and lower surfaces thereof as outermost layers and a plurality of ceramic layers disposed between the cover layers (41a,41b); first and second internal electrodes (32a,32b) formed on the ceramic layers, the first and second internal electrodes (32a,32b) stacked to interpose one of the ceramic layers; first and second external electrodes (35a,35b) formed on opposing sides of the ceramic sintered body (31) to connect to the first and second internal electrodes(32a,32b), respectively; and anti-oxidant electrode layers (34a,34b) formed between the cover layers (41a,41b) and adjacent ones of the ceramic layers, respectively, the anti-oxidant electrode layers (34a,34b) arranged not to affect capacitance.