Barium Titanate Ceramic Capacitor Grain Structure for DC Bias Stability
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Solution Overview
Problem
Existing capacitors using dielectric layers with uniform grain sizes face issues with capacitance, withstand voltage, and DC bias characteristics, as well as reliability in high-temperature environments due to oxygen vacancy movement and increased grain boundary resistance.
Innovation Solution
A capacitor design incorporating dielectric layers with a mixture of first and second crystal grains, where the second grains have larger sizes and higher additive element content, reducing grain boundary density and enhancing oxygen vacancy resistance, thereby improving capacitance and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional capacitor structure with separate current collectors and terminals is used, then electrical connection is achieved, but the device complexity and number of components increase
Solution Approach 1:
The patent combines the current collector and terminal into a single integrated component. The current collector serves dual functions as both the electrical conductor within the capacitor and the external terminal, eliminating the need for separate terminal components and reducing overall device complexity while maintaining reliable electrical connection.
Solution Approach 2:
The current collector is designed to perform multiple functions simultaneously: it collects current from the electrode, conducts electricity through the capacitor structure, and serves as the external terminal for connection to circuitry. This multi-functionality reduces the total number of components needed.
2Ease of manufacture
If the capacitor case is removed to reduce device complexity, then manufacturing is simplified, but protection of internal components is reduced
Solution Approach 1:
The patent employs a flexible pouch structure made of laminated film layers that provides necessary protection to internal components while being much thinner and simpler than traditional rigid metal cases. The pouch structure offers mechanical protection, moisture barrier, and electrical insulation without adding significant complexity to manufacturing.
Solution Approach 2:
The pouch structure utilizes composite materials with multiple functional layers including barrier layers for moisture protection, adhesive layers for sealing, and insulating layers for electrical protection. This composite structure provides comprehensive protection while maintaining manufacturing simplicity.
3Reliability
If solid electrolyte is used to improve reliability, then leakage current is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent controls the formation process parameters including voltage, temperature, and time to optimize solid electrolyte film quality. By carefully adjusting these parameters, the invention achieves reliable low-leakage current characteristics while maintaining feasible manufacturing precision requirements.
Solution Approach 2:
The patent includes a formation process that creates a stable solid electrolyte interface before the capacitor is put into service. This preliminary action of forming the electrolyte film under controlled conditions ensures low leakage current and stable performance, reducing the need for extremely high manufacturing precision during production.
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 capacitor achieves higher capacitance, improved DC bias characteristics, and enhanced reliability in high-temperature environments by utilizing a combination of first and second crystal grains with specific size and additive element distributions, resulting in longer operating life and reduced variations.
Implementation Method 1
the solid electrolyte forms an oxide film on a surface of the aluminum foil
Implementation Method 2
Capacitor according to one or more of the above-mentioned embodiments
Data Source
Figure 1~2
Figure 3~4
AI summary
A capacitor includes a stack and an external electrode located on a surface of the stack. The stack includes a plurality of dielectric layers and a plurality of internal electrode layers alternately stacked on one another. Crystal grains include first crystal grains having a small grain size and second crystal grains having a larger grain size. The first crystal grains satisfy 0.13 µm ≤ d1 < 0.30 µm, where d1 is the grain size of the first crystal grains. The second crystal grains satisfy 0.30 µm ≤ d2 < 0.50 µm, where d2 is the grain size of the second crystal grains. The second crystal grains have a higher additive element content than the first crystal grains.