IEEE Power Electronics Magazine - December 2015 - 32

key component, the embedded inductor. Based
Formed
Inserted
on the premise that the
converter inductor can
b e e m b e d de d e it he r
within the processing
chip or within the associated interposer or a
substrate, very fine inductor elements can be
deposited or otherwise
integrated. Intel was the
Plated Connection
Plated
Connection
first to commercialize a
Annular Ring
Surface Mounted
(Active Device)
(Passive Device)
Resistor
in Cavity
granular power supply
Soldered to
Plated
Resistor
Plated
Resistor
Hole Wall
by embedding a number
Resistor Paste
(Thin Film)
(Thick Film)
(Horizontal or Vertical)
in Cavity
of inductors within the
Haswell microprocessor
FIG 1 An example of embedded assembly elements of component embedding: formed passives,
substrate, thus creating
inserted passives, and active devices. (Figure courtesy of the IPC International Technology Road Map.)
a multiphase low-voltage
high-current dc-dc converter.
Since
each
converter
inductor
has a very limited
Inductors for granular Power
current
or
power
capacity,
the
macroconverter
is comA granular power supply is composed of hundreds of small
posed of many miniature converters (depending on the acconverters, all switching in concert with the converter, one
tual product specifications), each having its own inductor.
dc voltage to another dc voltage. Each tiny converter will
The fully integrated voltage regulator (FIVR) inductors
operate in coordination with a group of converters to create
are formed as air-core type, utilizing five layers of a tena phase of a dc-dc converter. Then, the groups are phased
layer substrate, as shown in Figure 4.
on and off to create high efficiency over a wide load range,
Due to the very limited power capacity of formed inmuch the same as modular converters. Each tiny converter
ductors, several forming processes on semiconductor
is integrated into a semiconductor assembly or perhaps an
substrates are presently under development by more than
interposer. The total entity created from the tiny converters
a dozen companies and research entities. The works by
is called a granular power supply because each tiny eleYu et al. [5] and Wang et al. [6] are two examples of these
ment is smaller than a grain of sand.
efforts. They are all seeking to increase the inductance
Over the past five years, there has been a plethora of
and current density by an order of magnitude or more.
development regarding the granular power supply and its
The inductor road map (Figure 5) shows the trends in the
use of materials and materials used to create embedded inductors. First, the presently established materials are well

Y
Wound Power Inductor
with Ferrite Core
(a)

Thin-Film Power Inductor with
Magnetic Metal Material Core
(b)

FIG 2 A comparison of (a) a standard wound inductor and
(b) a TDK plated thin-film inductor.

Flake

Fiber
1-D B

H
1-D Material

3-D

IEEE PowEr ElEctronIcs MagazInE

L10
L9
L8
L7
L6

L5
L4
L3
L2
L1
Haswell i5 4430 Processor Substrate Polished
Cross-Sectional Image (Y Direction)

Interconnect Layers:
L1-L5

H
3-D Material

FIG 3 Principal B-H curves for three ideal compacted materials [4].

Processor Die

Ten-Layer PCB

H
2-D Material

Observation Direction
PCB

Inductor Layers:
L6-L10

Sphere
2-D
1-D

2-D

z December 2015

FIG 4 Conductor layers dedicated to air-core inductors in
Intel's i5-4430 processor FIVR embedded converter. (Figure
courtesy of LTEC Corp.)

Table of Contents for the Digital Edition of IEEE Power Electronics Magazine - December 2015