Design And Fabrication Of PCB Integrated Power Magnetic Core Inductor

DC-DC converter has the advantages of high-efficiency conversion at different voltages,large current output,and low heat generation,and has always been the focus of research in the field of power modules.In the existing power supply system,discrete inductors occupy a large space and require pin welding,which is not conducive to the development of electronic equipment along the direction of miniaturization.Therefore,the inductor is usually integrated on a PCB（Printed Circuit Board）or a silicon substrate to realize the miniaturization of the inductor device.The on-chip integrated inductor occupies a large amount of precious surface area of the silicon base,and the inductance value is too low to meet the requirements of the switching power supply for the inductance value.The ample space of the printed circuit board（PCB,Printed Circuit Board）can fill the shortage of integrated inductors on the silicon base on the chip,and the manufacturing process is compatible with the PCB process.Therefore,in recent years,it has become an important means of researching the system integration of switching power supplies at home and abroad.Aiming at the problem of low power conversion efficiency due to low inductance density and high DC resistance of integrated inductors on PCB,this thesis proposes a technology and method for integrating planar inductors with clad structure magnetic cores on PCB.The basic theory of printed circuit integrated magnetic core inductor and its application principle in DC-DC converter are studied.With the goal of improving the conversion efficiency of DC-DC power supply,the structure of the coated magnetic core planar inductor was designed and optimized using HFSS software,and the specific structural parameters of the magnetic core inductor were obtained;magnetic composite materials based on nano-amorphous magnetic powder were prepared.After testing,its resistivity is 6.87×10⁸Ω·cm,its magnetic saturation is 440 m T,and its coercive force is only 4.25 Oe.This material can well suppress the eddy current loss of the magnetic core layer in high-frequency application scenarios.Based on the prepared magnetic composite materials,the inductors with single-layer coil and double-layer parallel coil structure were designed and fabricated.In the inductor with a single-layer coil structure,the core inductor with a copper thickness of70μm,when the core thickness is 100μm and 200μm,its L/R_DCis 1.5 n H/mΩand 1.76n H/mΩ,and the peak quality factors are respectively 42.7@36.7 MHz and 50@40.1MHz.In the double-layer parallel coil structure,the L/R_DCof the 70μm copper thick core inductor is 2.49 n H/mΩand 2.92 n H/mΩwhen the magnetic core thickness is 100μm and 200μm,and the peak quality factors are 62.9@10.1 MHz and 72@13.4 MHz.It can be seen that the double-layer parallel coil structure has more performance advantages than the single-layer structure in terms of L/RDC and quality factor.A 70μm copper-thick double-layer parallel coil core inductor was applied to a DC-DC converter with an input voltage of 1.8 V,an output voltage of 0.85 V,and an operating frequency of 100 MHz.After calculation,the inductance efficiency of the output current between 0.1 A and 2 A is above 97.5%,which shows that the magnetic core inductor with double-layer parallel coil structure has excellent performance in improving the conversion efficiency of DC-DC power modules.