Substrate Embedded Thin-Film Inductors With Magnetic Cores for Integrated Voltage Regulators

High-density and high-frequency inductors (>5 MHz) enable miniaturization of power modules, and also integration of voltage regulator modules into the processor packages for higher efficiency and switching frequencies. Several advances in magnetic materials and substrate process integration are needed to meet the performance, size, and cost requirements. This paper highlights two substrate-embedded inductor approaches using magnetic paste and pre-fabricated magnetic thick laminate sheets. An innovative cavity-filling process using paste printing and hot pressing is developed to integrate magnetic paste with high magnetic filler loading into the core of standard organic laminate substrates. The hot-pressed metal/polymer composite magnetic cores showed a permeability of ~55 at 10 MHz. The other approach utilizes pre-fabricated thick magnetic sheets with a permeability of ~93 at 10 MHz. Standard panel-scale processes are adapted for high-volume manufacturing at low cost. The electrical performance of the inductors from both approaches showed good correlation between the simulated and measured data. Compared with air-core inductors with the same structure, the advanced thin-film inductors with magnetic sheet showed nine times improvement in inductance. Both these approaches can be scaled to higher frequencies with further innovation in magnetic composites.