Study On The Magnetic Alloy Films Of Embedded Inductor In Printed Circuit Board Deposited By Electroless Plating

With the increase of the working frequency of some communication devices,the printed circuit board is developing towards integration and miniaturization,at the same time,the structure and performance of the inductor will inevitably face a great challenge.At present,it is easy to produce large parasitic capacitance and eddy current loss due to the existence of sandwich structure inductors in high frequency working conditions.Starting from the structure of the inductor and the magnetic core material,aiming at eliminating all kinds of losses and parasitic capacitance and improving the inductance,the double reducing agent is selected to deposit the magnetic film on the surface of the plane spiral copper coil by the electroless plating method,so as to design the embedded inductor.In this paper,the core material is deposited directly on the surface of the PCB embedded inductor copper coil,and the structure of the core coating coil is formed to increase the inductance.?1?Firstly,by changing the formulation and pretreatment technology of plating bath,we use metallographic microscope,scanning electron microscope,vibrating sample magnetometer,X ray diffraction,impedance tester to explore the optimal process and bath formulation using single factor experiment method.The problem of plating on the superfluous area can be solved by using double reductant of sodium hypophosphite and two methyl amine borane.In order to obtain a better magnetic core film with better inductance,the best salt of the bath are nickel sulfate and cobalt sulfate.The study shows that the inductance of the magnetic core film prepared by the optimized process and formula is 11%higher than that of the unplated.?2?The inductance performance was explored in detail by changing the plating conditions,plating bath components and heat treatment after plating NiCoP core coating.The optimum condition is determined:1)the ratio of Co²⁺/(Co²⁺+Ni²⁺)is 0.45⁰.6;2)the ratio of 16:1 of sodium hypophosphite and two methyl amine borane has a higher sense of value;3)When DL-malic acid is used as complexing agent,the inductance is increased by 11.8%,which has the best effect;4)the temperature and time of heat treatment are 800? and 30 minutes,respectively.5)the plating temperature is about70?,the value of pH is about 9,the plating time is 1.5h²h.?3?The effect of Fe₃O₄-NiCoP composite coating,NiCo PW and NiCoZnP two kinds of four element alloy films on the properties of the magnetic core coating is also studied.The effects of Fe₃O₄,Na₂WO₄ and ZnSO₄ on the magnetic core deposition were discussed.It is shown that the inductance has the maximum inductance when the amount of the added Fe₃O₄ is greater than or equal to 2.4g.NiCoPW alloy thin film has good inductance performance because of the good effect of sodium tungstate on the deposition of magnetic core,but the NiCoZnP alloy thin film prepared by zinc sulfate can not increase the inductance value.That's because zinc is anti–magnetic element,and its addition is not effective for the experiment.