Ni-Mn-Zn Ferrite Co-Firing with Copper Conductors
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Solution Overview
Problem
Ceramic multi-layer substrates face challenges with high material costs and inferior productivity due to the use of Au, Pt, Ag—Pd alloys, and Ag—Pt alloys for coil conductors, and Ag's tendency to cause migration, leading to reduced moisture resistance and size limitations, while co-firing with Cu poses oxidation and resistivity issues.
Innovation Solution
A ferrite ceramic composition with specific molar content ranges of Fe, Mn, Ni, and Zn, allowing co-firing with Cu to achieve favorable insulation and electrical characteristics, reducing the gap between coil and via electrodes, and suppressing migration, with Cu molar content up to 5 mol% and Zn content between 6-33 mol%, ensuring reliable operation at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Cu is used for coil conductors and co-firing is performed in a reducing atmosphere to avoid Cu oxidation, then Cu oxidation is prevented, but Fe2O3 is reduced to Fe3O4 causing decreased resistivity and degraded electrical characteristics
Solution Approach 1:
The patent changes the compositional parameters of the ferrite ceramic by controlling the molar ratios of Fe2O3, Mn2O3, ZnO, and NiO within specific ranges. This compositional adjustment allows the material to maintain high resistivity (ρ≥107Ω·cm) even when subjected to reducing atmosphere during co-firing with Cu, thereby preventing Fe2O3 reduction to Fe3O4 and maintaining electrical characteristics while allowing Cu to remain in metallic state for moisture resistance
Solution Approach 2:
The patent creates a composite ferrite system combining multiple metal oxides (Fe2O3, Mn2O3, ZnO, NiO) with specific molar ratios. This composite composition synergistically enhances the material's ability to resist reduction of Fe2O3 during co-firing with Cu, maintaining both electrical insulation properties and enabling Cu to function effectively for moisture resistance without oxidation
2Manufacturing precision
If firing is performed in an oxidizing atmosphere to maintain Fe2O3 state, then electrical characteristics are maintained, but Cu is oxidized to Cu2O causing decreased moisture resistance
Solution Approach 1:
The patent modifies the chemical composition parameters of the ferrite ceramic, specifically controlling the molar content of Fe2O3 (30-50 mol%), Mn2O3 (5-15 mol%), ZnO (20-40 mol%), and NiO (10-30 mol%) within defined ranges. This compositional optimization enables the material to maintain high resistivity and electrical characteristics while allowing Cu to remain unreduced during co-firing, thus maintaining moisture resistance
Solution Approach 2:
The patent introduces Mn2O3 and ZnO as intermediary components that mediate the interaction between Fe2O3 and Cu during co-firing. These intermediaries help maintain the oxidizing environment locally around Fe2O3 while protecting Cu from oxidation, enabling both materials to coexist in their desired states without direct harmful interaction
3Quantity of substance
If Ag is used for coil conductors, then material cost is reduced compared to Au, Pt, Ag—Pd alloys, but Ag causes migration leading to reduced moisture resistance and size limitations
Solution Approach 1:
The patent replaces expensive noble metals (Au, Pt, Ag—Pd alloys) with Cu, which is cheaper and does not suffer from migration issues. By optimizing the ferrite ceramic composition, the patent makes Cu a viable long-term solution rather than a short-lived alternative, achieving both cost reduction and maintained reliability
Solution Approach 2:
The patent uses the optimized ferrite ceramic composition as an intermediary medium that prevents Ag migration and enables Cu to function effectively. The specific composition acts as a barrier and stabilizing environment that eliminates the migration problem associated with Ag while allowing Cu to provide both electrical conductivity and moisture resistance
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 ceramic composition ensures desired insulation and electrical characteristics, reduces substrate size, and enhances reliability and ESD protection functions by maintaining Cu and Fe2O3 stability during co-firing, avoiding oxidation and resistivity degradation.
Implementation Method 1
when firing is carried out with the oxygen partial pressure set in such an oxidizing atmosphere that maintains the state of Fe2O3, Cu is also oxidized to produce Cu2O
Implementation Method 2
when firing is carried out with the oxygen partial pressure set in a reducing atmosphere that maintains the state of Cu metal, Fe2O3 is reduced to produce Fe3O4
Data Source
AI summary
A coil conductor and a via electrode placed away from the coil conductor are embedded in a magnetic layer. The magnetic layer is sandwiched between a pair of non-magnetic layers. The coil conductor and the via electrode are formed from a conductive material containing Cu as its main constituent, and the magnetic layer is formed from Ni—Mn—Zn ferrite where the CuO molar content is 5 mol % or less, and (x, y) falls within the range of A (25, 1), B (47, 1), C (47, 7.5), D (45, 7.5), E (45, 10), F (35, 10), G (35, 7.5), and H (25, 7.5) when the molar content x of Fe2O3 and the molar content y of Mn2O3 are represented by (x, y). Thus, insulation properties can be ensured, favorable electrical characteristics can be achieved, and a ceramic electronic component is achieved which is able to be reduced in size.