The Study On MEMS-based Integrated Double-layer Planar Inductor With Composite Magnetic Core

It is a basic trend that the electronic products are developed into more miniature,lower cost and more multi-functional.Passive devices are no exception.The active devices are miniaturized continuously and the speed of integration is very fast.Compared with the active devices,the development of the passive devices is lag behind.They take up much effective area in the circuit system.Therefore,the improvement of the integration of passive devices has become the focus of many researches.As one of the three kinds of passive devices,the inductor is widely applied in the integrated circuit systems,especially in the wireless communication system and power circuit module,such as power supply converters,transformers,filters,mixer,oscillator and so on.So the inductors are widely used in this area.DC-DC converter,for example,that in order to improve the conversion efficiency,improve the stability in high frequency,reduce the voltage current ripple,increase the optimum working frequency,there is an urgent need for the micro-inductor with high performance.However,the integration and the manufacture of the inductor with high performance is faced with much more challenges because of the complexity of structure and the material.Not only the micro-inductor is integrated in the system in the form of a discrete device on the board,but also these inductors with high performance still rely on the assembly process of the production.Compared with the other passive components,the micro miniaturization design and integrated manufacturing progress of the inductor is relatively very slow.It is very difficult to adapt to the demand of the rapid development of hardware technology.Therefore,the research and development of the low cost and high performance integrated micro-inductor is necessary.This paper is based on the research progress of micro-inductor design and manufacturing technology,and then puts forward a new type thin film inductor with integrated composite magnetic core.The integrated core is consisted of the patterned permalloy and ferrite-polymer composite materials.Permalloy has a high saturation magnetic induction intensity,which combined with the best pattern can minimize the eddy current loss in the high frequency.At the same time the ferrite-polymer composite material filled in the patterned permalloy,to make up for the part of magnetic flux leakage.The innovative ferrite materials and patterned permalloy formed the integrated composite magnetic core.Based on the requirements of the integrated composite magnetic core,on the premise of compatible with micro processing technology,optimize the key unit manufacture technology,make the core meet the requirement of double-layer planar inductors.Then according to the performance of the soft magnetic materials,the planar inductor with integrated magnetic core was been simulated and analyzed by COMSOL Multiphysics.Different permalloy pattern were simulated to find the laws of the best figure.And the filled ferrite and the integrated composite magnetic core with the double-layer planar inductor were been simulated and analyzed.Then the optimized structure design can be used in the fabrication process.Then,on the basis of multiple compatible integrated manufacturing technology,focus on the development patterned permalloy thin film filled with the soft magnetic ferrite materials,and the sample of the planar inductor with integrated composite magnetic core can be fabricated by a complete manufacturing process.Finally,these samples were tested by using Keysight E4990 A impedance analyzer and 16047 E test port.In the area of the 1.5mm × 1.5mm,the structure of the double-layer planar inductor is a sandwich structure.The coil-part is for a square spiral towards which coil width is 40?m,the coil spacing is 20?m,the thickness of the conductor is 20?m and the single layer is consisted of 13 turns.The up and below magnetic layer is 20?m thick with the best permalloy pattern filled with the ferrite-polymer materials formed the integrated composite magnetic core.At the 1.5MHz,the inductance value of the integrated double-layer planar inductor with integrated composite core is 1.28?H,and the quality factor is 2.81.Under the 5V input voltage,output voltage 1.18 V,output current is 50 mA,the conversion efficiency is 65% in the circuit,the overall volume of 1/8 of the traditional winding coils which can meet the demand of the integrated application of DCDC converter circuit.Compared with the micro-inductor application research,this paper has the very high research significance and application value,has the potential for practical application.The design of magnetic circuit and the manufacturing mode of the integration of soft magnetic metals and ferrite materials make it have huge potential in further improvement of the performance and the cost of the production.The new type of micro inductor has a good practical prospect.