Monolithic Ceramic Capacitor ESR Adjustment via External Electrode Oxidation
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Solution Overview
Problem
Monolithic ceramic capacitors struggle to effectively address low-frequency voltage fluctuations due to their low equivalent series resistance (ESR), leading to oscillation and noise generation, and existing methods to adjust ESR are either difficult to implement or inhibit miniaturization of electronic devices.
Innovation Solution
A monolithic ceramic capacitor with external electrodes that include a compound oxide, such as In—Sn compound oxide, and a glass component, allowing for adjustable ESR through variations in the amount of glass component, glass softening point, and electrically conductive metal or insulating oxide, enabling a reliable connection with Ni or Ni alloy internal electrodes without increasing thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a discrete resistance element is connected in series with the monolithic ceramic capacitor, then low-frequency oscillation is suppressed, but mounting area is required which inhibits miniaturization
Solution Approach 1:
The patent merges the resistance element function into the external electrode structure itself. The external electrode is formed with controlled oxidation to create a resistive layer that serves as the series resistance, eliminating the need for separate discrete resistance components and reducing overall mounting area
Solution Approach 2:
The external electrode simultaneously serves as the electrical connection terminal and the resistance element. By controlling the oxidation state and composition of the external electrode material, it provides both low-frequency oscillation suppression and maintains good electrical connectivity, eliminating the need for separate components
2Reliability
If the thickness of the metal oxide film on the external electrode is changed to adjust ESR, then ESR adjustment is possible, but the adjustment process becomes relatively difficult
Solution Approach 1:
Instead of adjusting ESR by changing film thickness through complex processing, the patent changes the compositional parameters of the external electrode material. By controlling the ratio of conductive oxide to insulating oxide, and adjusting sintering conditions (temperature, oxygen partial pressure), ESR can be tuned over a wide range through relatively simple parameter changes in the firing process
3Reliability
If a three-layer external electrode structure with oxidation-resistant metals is used to increase ESR, then ESR is increased, but material costs increase due to noble metals
Solution Approach 1:
The patent uses composite oxide materials for the external electrode layers, combining conductive oxides with insulating oxides. This allows achieving high ESR without relying on thick layers of expensive noble metals. The insulating oxide component provides the resistance, while the conductive oxide ensures connectivity, reducing noble metal content while maintaining performance
Solution Approach 2:
The patent changes the compositional parameters of the external electrode material by controlling the ratio of conductive to insulating oxides, and adjusting sintering conditions. This allows tuning ESR over a wide range without requiring thick noble metal layers, thereby reducing material costs while maintaining adequate ESR
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 precise adjustment of ESR, ensuring reliable electrical connections, improved weather resistance, and miniaturization of the capacitor, while maintaining adequate plating resistance and solderability, thus effectively addressing low-frequency voltage fluctuations.
Implementation Method 1
the external electrode includes a first electrically conductive layer including a compound oxide, which reacts with the Ni or the Ni alloy
Implementation Method 2
adjustable ESR through variations in the amount of glass component, glass softening point
Data Source
AI summary
An external electrode structure for a monolithic ceramic capacitor provided with a function as a resistance element is capable of preventing a reduction of the external electrode due to baking in a reducing atmosphere, so that Ni or a Ni alloy can be used in an internal electrode and a good electrical connection between the internal electrode and the external electrode is achieved. The external electrodes disposed on an outer surface of a capacitor main body include an electrically conductive layer and a metal plating layer disposed thereon, and the electrically conductive layer includes a compound oxide, e.g., an In—Sn compound oxide, which reacts with Ni or the Ni alloy, and a glass component.