Magnetic Core Solenoid Power Inductors on Organic Substrate for System-in-Package Integrated High-Frequency Voltage Regulators

Abstract

In this paper, the design, modeling, fabrication, and characterization of System-in-Package (SiP) solenoid power inductor using a NiZn ferrite composite magnetic core material is demonstrated. A novel fabrication process has been developed for integrating the inductor into the buck-type integrated voltage regulator (IVR) module. The process uses stencil printing to deposit and pattern the magnetic core material. Photolithography and copper electroplating are used to form the windings. The electrical parameters of the fabricated inductors were extracted from measurements. The inductors had an average dc resistance of 19 $\text{m}\Omega $ , average inductance of 28.3 nH, and average ac resistance of $2.28~\Omega $ at 100 MHz, which is the operating frequency of the IVR. The organic substrate parasitic effect led to an average shunt capacitance of 2.31 pF and an average parasitic conductance of 0.12 mS at 100 MHz. The 10% saturation current was 11.53 A. The electrical parameters of the fabricated inductors were modeled and showed good accuracy with measured data. The inductors showed an inductance to dc resistance ratio of 1613 nH/ $\Omega $ . The area and volume energy densities were 158.4 nJ/mm2 and 283.0 nJ/mm3, respectively. These are the highest reported values for a solenoid magnetic core power inductor at 100 MHz.