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

由于移动通信技术的进步，不仅电子设备越来越小，而且其功能也在不断升级。离散元件不能完全满足小型化的要求。此外，便携式设备不断向小型化、多功能化方向发展，导致了工作电压的多样化。便携式设备通常由电池供电，DC-DC转换器用于将电池能量转换为微处理器和集成电路供电。便携式电子设备要求紧凑，因此，转换器的空间非常有限。因此，将单个元件集成到模块中以减小DC-DC转换器的尺寸并提高其功率密度的需求正在增加。为了实现这一目标，需要改进电感元件。新概念包括制造铁氧体-金属复合电感器。陶瓷多层技术和低温陶瓷共烧（LTCC）技术是一种常用的现代技术，用于制造复杂多层模块中的平面无源。LTCC技术是一种很有前途的被动制造和三维集成技术。铁氧体带、浆料和低k电容带用于制造平面嵌入式无源器件，它们可以很容易地集成到LTCC介电衬底中，形成复杂的模块。基于前面的讨论，我们的目标是开发制造Ni(Cu)Zn铁氧体-金属复合多层电感的材料和工艺。这包括(1)在还原气氛下烧结的Ni(Cu)Zn铁氧体的电性能和磁性能的研究(2)Ni(Cu)Zn铁氧体和母金属电极（铜）共烧的发展，以及(3)Ni(Cu)Zn铁氧体和FeSiCr合金带作为多层组件在还原气氛下的压力辅助约束烧结技术的研究。这包括研究在低氧分压条件下铁氧体材料的稳定性，以及在低温（900℃）和低pO2条件下烧结的铁氧体材料的成分、烧结行为、微观结构、阳离子分布和功能性能之间的相关性。Ni(Cu)Zn功率铁氧体具有优越的直流偏置叠加特性和金属组件，将使用多层陶瓷加工和低压辅助约束烧结技术进行集成。​德国团队将专注于研究固态化学和还原条件下的铁氧体烧结，而台湾团队则专注于金属合金组件及其在多层工艺中的应用。

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.