基于磁芯化学包覆的集成平面电感研究及其在板级封装中的应用

Inductor integration in printed circuit board (PCB) becomes the research point under the driving of the integration transfer from IC SoC (System on Chip) to PCB and further miniaturization for PCB. This project proposes a new structure inductor with magnetic core cladding planar coils based on the previous research results and electromagnetic theories. Through the cladding of the magnetic core, the magnetization efficiency of the magnetic core in the inductive coil is greatly improved and meanwhile the proximity effect between the coils is reduced. Consequently, the inductance between the coils is improved, and the loss between the coil and the coil and the parasitic capacitance are reduced. The magnetic core cladding realization was developed by fabricating an ultra-thin and high-mechanical dielectric layer (between coil and core layer) on copper coil surfaces to achieve high magnetization efficiency, and this layer crystalizes the electroless-deposition of magnetic core. Among this method, the magnetic material coordinating depositing method is optimized under criterion of comprehensive performance of magnetic core. To eliminate the high loss and capacitance under ultra-thin dielectric layer, magnetic core introduced the reverse current or voltage is designed with the aid of theoretically electromagnetic calculating. The theoretical model and related equations are deduced based on Maxwell's equations and therefore demonstrates the electromagnetic and electric field distribution model by HFSS. It accordingly guides the further optimization of the structured inductor and its design in PCB. Moreover, we also explore the practical application of our proposed inductor.

芯片中电感系统级封装的外溢与有机树脂电路板电感的集成需求促使电感的板级封装成为行业关注的焦点和发展方向。项目基于前期研究成果与电磁理论体系，突破现有磁芯电感的结构限制，提出磁芯包覆平面电感的新型结构。通过磁芯的包覆，提高磁芯在电感线圈的受磁效率，减少线圈间“邻近效应”，提高线圈之间感值，降低线圈与线圈之间损耗和寄生电容。开发与结构融合的超薄高机械强度的介质层（线圈与磁芯层）制作方法，并以此作为催化层优选磁芯沉积材料与方法，实施磁芯的化学包覆，形成超薄介质磁芯包覆电感线圈的高受磁结构。通过电磁理论计算磁芯感应电流，引入感应反向电流或电压降低引入超薄介质层导致的磁芯损耗和磁芯与线圈间寄生电容，从而达到提感、降损、降容，提高电感的高频适用性的目的。基于麦克斯韦方程组推导本结构电磁理论关系式，利用HFSS模拟电磁、电场的分布模型，指导磁芯电感的进一步优化与该结构电感的设计，并探索该产品的实际应用。

芯片中电感系统级封装的外溢与有机树脂电路板电感的集成需求促使电感的板级封装成为行业关注的焦点和发展方向。开发出高感值、高品质因子的集成磁芯电感一直以来都是解决电感器集成难题的重要手段。项目研究中设计并完善了磁芯包覆电感结构，建立了磁芯包覆平面电感的电磁理论模型，制作了磁芯实物样品并进行测试。研究内容包括：1）探究了不同磁芯集成磁芯的方式对平面螺旋电感的影响。相比现有的几种结构，全包覆型磁芯电感结构是提高电感最有效，并保障品质因子Q值的结构。全包覆型磁芯电感的感值是空心结构的3.4倍，即提高了2.4倍。在100MHz频段以下，全包覆型电感的品质因子Q优于空心电感。2）探究了包覆型磁芯电感结构与其他结构的磁芯电感寄生电容的问题。研究结果表明，全包覆型磁芯电感的寄生电容在200fF左右，与空心电感相当，比三明治等结构小。因此磁芯包覆结构并未增加结构的寄生效应。3）探究了包覆型磁芯电感结构开口时对平面螺旋磁芯电感的影响。开口尺寸，即绝缘层厚度增加会降低电感器的感值。因此，绝缘层薄型化有利于提高电感性能。4）实施了磁芯包覆平面电感制作技术研究。研究了化学沉积平面电感磁芯层的方案，即设计改性绝缘催化胶，利用催化胶催化生长磁芯层，从而实现磁芯化学包覆电感线圈的目的。测试结果表明，实物测试感值和品质因子与仿真结构吻合，证明了磁芯包覆结构的优越性。