Ultra-Miniaturized Power Converter Modules Using Micromachined Copper Scaffolds

Abstract

This paper presents ultra-miniature (<2 mm 3 ) power converter modules with high power density (77 W/cm 3 ) enabled by micromachined 3D copper scaffolds containing high-inductancedensity (130 nH/mm 2 ) air-core power inductors. The scaffolds are formed by electroplating multiple, 30-!m-thick layers of copper within patterned photoresist molds, yielding freestanding copper traces with >10:1 aspect ratios. After backfilling with a chemically-resistant polymer, the scaffolds are then fully detached from the silicon fabrication wafer by wet-etching an underlying oxide layer. Surface-mount switch/controller chips and capacitors are attached by solder reflow to the copper scaffolds, forming selfcontained converter modules.

Wafer-Level Fabrication of Power Inductors in Silicon for Compact Dc-Dc Converters

“…(4) Polymer based dielectric materials that are regularly used in packaging are chosen as the passivation as well as stress buffering layers. (5) The whole fabrication flow can be done at low temperatures (<150°C) which is compatible with CMOS processes.…”

“…Power System in Packaging (PSiP) and Power System on Chip (PSoC) are two major approaches for passives integration in modern power systems operated at high frequency range (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). For PSiP, power inductors and other passive components are integrated off chip inside a package.…”

“…On the other hand, PSoC is a monolithic integration approach, mostly using MEMS technologies to form power inductors directly on chip. Researchers have reported on-chip inductors employing air cores, sputtered or electroplated magnetic cores, laminated magnetic cores, or composite cores [5][6][7][8][9]. PSoC approaches emphasize on wafer-level batch integration of power inductors, providing minimum sizes and compact interconnections.…”