Ferrite Composition for Multilayer Chip Coil Stray Capacitance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing multilayer chip coils face challenges in reducing stray capacitance and relative permittivity, especially in high frequency bands, due to the limitations of Ni—Cu—Zn-based ferrites, which affect their practicality and DC bias characteristics.
Innovation Solution
A ferrite composition with a specific range of iron oxide, copper oxide, and zinc oxide, along with silicon, tin, bismuth, and cobalt compounds, is developed to reduce relative permittivity and enhance DC bias characteristics, including crystal grains with higher Sn and Si concentrations on the surface than in the central portion, which helps in minimizing stray capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If Ni—Cu—Zn-based ferrite is used as the device body material, then the material can be fired at the same time with Ag internal electrodes at 900°C, but it is difficult to reduce permittivity and stray capacitance
Solution Approach 1:
The patent modifies the chemical composition parameters of the ferrite material by adding specific amounts of Bi2O3 (0.5-7.0 parts by weight), SiO2 (0.53-11.00 parts by weight), and SnO2 (0.1-12.8 parts by weight) to the Ni-Cu-Zn-based system. These compositional changes enable permittivity reduction while maintaining the ability to be fired at 900°C with Ag internal electrodes, thus resolving the contradiction between manufacturability and stray capacitance reduction.
Solution Approach 2:
The invention creates a composite ferrite material system that combines Ni-Cu-Zn-based ferrite with Bi2O3, SiO2, and SnO2 additives. This composite approach leverages the firing compatibility of the base ferrite while the added compounds contribute to permittivity reduction, achieving both manufacturing ease and reduced stray capacitance simultaneously.
2Object-affected harmful factors
If permittivity is reduced to decrease stray capacitance, then high frequency performance is improved, but DC bias characteristics may deteriorate
Solution Approach 1:
The patent carefully controls the composition parameters within specific ranges: Bi2O3 (0.5-7.0 parts), SiO2 (0.53-11.00 parts), and SnO2 (0.1-12.8 parts) per 100 parts of main component. These controlled parameter changes achieve permittivity reduction for reduced stray capacitance while the specific composition ranges are optimized to maintain DC bias characteristics, resolving the contradiction between high frequency performance and reliability.
Solution Approach 2:
The invention creates local compositional variations by forming crystal grains with higher Sn concentration on the surface side than in the central portion. This local quality differentiation allows the material to exhibit reduced permittivity at the grain boundaries and surfaces where it most affects capacitance, while maintaining the bulk magnetic properties necessary for good DC bias characteristics.
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 ferrite composition effectively reduces stray capacitance and maintains excellent DC bias characteristics, making it suitable for high frequency applications while being sinterable at temperatures compatible with internal electrodes.
Implementation Method 1
A method of reducing the stray capacitance between the electrodes facing each other in the multilayer chip coil is reduction of permittivity between the facing electrodes
Implementation Method 2
a higher frequency band is more widely used recently for a smartphone, a computer, etc. A demand for a noise removal product for a high frequency signal has been increasing
Data Source
AI summary
A ferrite composition comprises a main component and a subcomponent. The main component includes 32.0 to 46.4 mol % of iron oxide in terms of Fe2O3, 4.4 to 14.0 mol % of copper oxide in terms of CuO, and 8.4 to 56.9 mol % of zinc oxide in terms of ZnO. The subcomponent includes 0.53 to 11.00 parts by weight of a silicon compound in terms of SiO2, 0.1 to 12.8 parts by weight of a tin compound in terms of SnO2, and 0.5 to 7.0 parts by weight of a bismuth compound in terms of Bi2O3, with respect to 100 parts by weight of the main component.