Key Technologies and materials for new generation ferrite-metal composite multilayer power inductive devices

• Applicant: Professor Dr. Jörg Töpfer
• Subject Area: Glass, Ceramics and Derived Composites
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 383431924

Due to the advances in mobile communications, not only the electronic devices are getting smaller, but also their function is upgraded continuously. Discrete components cannot completely meet the requirements of miniaturization. Moreover, portable devices continue to develop toward low-profile and multi-functionality, which results in the diversification of operating voltages. Portable devices are often powered by batteries and DC-DC converters are used to convert battery energy to supply power for microprocessors and integrated circuits. Portable electronic devices are required to be compact and, hence, space for converters is very limited. Therefore, the demand for integrating individual components into modules to reduce the size and increase the power density of DC-DC converters is increasing. To achieve this goal, improved inductive components are required. New concepts include the fabrication of ferrite-metal-composite inductors. The ceramic multilayer technology and the LTCC technology (Low-temperature Ceramic Cofiring) are modern technologies that are frequently used to fabricate planar passives used in complex multilayer modules. LTCC technology is a promising technology for passive fabrication and 3-D integration. Ferrite tapes and paste and low-k capacitor tapes are used to fabricate planar embedded passives and they can be easily integrated into LTCC dielectric substrates to form complex modules. Based on the previous discussion, we are aiming at developing materials and processes for the fabrication of Ni(Cu)Zn ferrite-metal-composite multilayer inductors. This includes (1) the investigation of electric and magnetic properties of the Ni(Cu)Zn ferrites sintered under reducing atmosphere (2) the development of cofiring of Ni(Cu)Zn ferrite and base metal electrode (copper), and (3) the investigation of pressure-assisted constrained sintering technologies for Ni(Cu)Zn ferrite and FeSiCr alloy tapes as multilayer components under reducing atmosphere. This includes investigation on the stability of ferrite materials under low oxygen partial pressure conditions, and of correlations between composition, sintering behavior, microstructure, cation distribution, and functional properties of these ferrite materials, which are sintered at low temperature (900°C) and low pO2. Ni(Cu)Zn power ferrites with superior DC-bias superposition characteristics and metal components will be integrated using multilayer ceramic processing and low-pressure assisted constrained sintering technologies.This project is planned as cooperation between Prof. JörgTöpfer (University of Applied Sciences Jena, Germany) and Prof. Hsing-I Hsiang (National Cheng Kung University, Taiwan). The German group will focus on the investigation of the solid state chemistry and ferrite sintering under reducing conditions, whereas the Taiwanese group concentrates on the metal alloy components and their implementation into the multilayer process.

• DFG Programme: Research Grants
• International Connection: Taiwan
• Partner Organisation: National Science and Technology Council (NSTC)
• Cooperation Partner: Professor Dr. Hsing-I Hsiang