低温烧结BIT掺杂NiCoZn铁氧体及高频EMI抑制性能研究

高频高Q的NiCoZn铁氧体可作为关键材料应用于EMI(electromagnetic Interference)滤波器,但高烧结温度限制了其与目前主流的LTCC(low temperature Co-fired ceramic)无源集成技术的结合。本文制备了一系列低温烧结(900℃)的Bi4Ti3O12(BIT)掺杂NiCoZn铁氧体,分析了掺杂量变化对关键性能的影响,并与高温烧结(1100℃)的未掺杂NiCoZn铁氧体进行了对比。其中,6%(质量分数)BIT掺杂的铁氧体可以在大幅降低烧结温度的同时得到和高温烧结铁氧体相近的磁导率。进一步,研究了两类铁氧体制作的滤波器的高频EMI抑制性能,发现两种滤波器都能在2~40 MHz的频带内表现出优异的噪声抑制性能。在部分频段,BIT掺杂铁氧体作差模电感的滤波器对差模噪声抑制能力更强,在结合LTCC集成技术开发高性能EMI器件方面表现出很好的潜力。

Investigation on low temperature sintering and high frequency EMI suppression properties of NiCoZn ferrite with BIT doping

The NiCoZn ferrite with high quality factor and applied in high frequency is the key material for the EMI(electromagnetic interference)filters.However,the high sintered temperature is the main restrictive factor that prevents this ferrite from adapting to the mainstream passive integration method-LTCC(low temperature co-fired ceramic)technology.In this paper,a series of low fired(900℃)Bi4Ti3O12(BIT)doped NiCoZn ferrites were prepared,and the influence of BIT amount on the magnetic properties was analyzed.A comparison of the important properties between BIT doped ferrites and high fired(1100℃)undoped ferrite was also carried out.It can be found that a similar value of permeability was also obtained in 6 wt%BIT doped ferrite in contrast with undoped ferrite while the sintered temperature was greatly reduced.Further,the high frequency EMI suppression properties of two filters fabricated by two kinds of ferrites were investigated.The both two filters showed excellent noise suppression performance in the frequency band of 2-40 MHz.In some frequency band,the filter using BIT doped ferrite as differential-mode inductance showed better differential-mode noise suppression ability,and had good potential to be applied in EMI devices development with LTCC technology.