Soft Magnetic Nanocrystalline Materials for Inductors and Shielding Applications Optimized for Higher Frequencies.

MRS-2018 Brazil Sept. 2018 1
Christian Polak
Soft Magnetic Nanocrystalline
Materials for Inductors and
Shielding Applications
Optimized
for Higher Frequencies
Rapid Solidification Technology
VACUUMSCHMELZE GmbH & Co. KG, D-63450 Hanau, Germany
®

VACUUMSCHMELZE
VACUUMSCHMELZE is one of the world's leading manufacturers
of advanced magnetic materials and value added products.
In 1914 the first vacuum melting furnace laid the foundation
for today's VACUUMSCHMELZE. Melting alloys under vacuum
went into production on an industrial scale in 1923.
The Company / Portrait
Vacuum melting furnace
1914 - 1917

VACUUMSCHMELZE
The Company / Portrait
VACUUMSCHMELZE offers the entire range
of magnetic products:
Today VACUUMSCHMELZE
manufactures a broad spectrum
of high quality materials & parts,
components and systems for
numerous markets, from Swiss
watch manufacturers to the
aircraft industry.
Materials and Parts
33 %
Permanent Magnets
31 %
Cores and Components
36 %

VACUUMSCHMELZE
The Company / Locations
VAC worldwide
VACUUMSCHMELZE is present
in more than 50 countries on all
five continents, in order to be able
to provide you with competent
service wherever you are.

VACUUMSCHMELZE
million Euro 2015 2016 2017
Sales 379 363 400
Capital Expenditure 19 16 20
R & D 16 16 17
Employees 4,300 4,300 4,400
The Company / Facts and Figures
Headquarter an R&D Center
located in Hanau, Germany.
Active on a global basis:
with approx. 4,400 employees
in more than 50 countries
annual sales 400 million Euro
Headquarter: Hanau, Germany

Applications of Amorphous and Nanocrystalline Alloys
Established Products:
Industrial applications:
• Chokes, transformers and
power sensors for power
supplies and rectifiers
Transportation:
• Chokes, transformers and
current sensors
The frequency converter permits
efficient control
of motors in which complex semi-
conductor technology is used.
Current-compensated chokes made of
nanocrystalline materials have excellent
attenuation characteristics combined with
high temperature resistance (150 C)
and a smaller volume for the design.

Installation:
• Total current converters for
earth fault current protection
switches
• Current converters for
electronic energy meters
Current sensors using
a magnetic probe provide
high accuracy and excellent
temperature stability.

Installation:Automotive:
• Chokes and transformers for
the power management
• Current-Compensated chokes
• Current sensors
• Flexible antennas, e.g.
Keyless-Entry
Current-compensated chokes made of
nanocrystalline materials have excellent
attenuation characteristics combined with
high temperature resistance (150 C)
and a smaller volume for the design.
Cost-optimised chokes and
transformers for power control
units such as gas or diesel direct injection
systems.
Current sensors using
a magnetic probe provide
high accuracy and excellent
temperature stability.
VAC manufactures transmission
antennas
for 19-kHz KEYLESS-ENTRY-Systems.

Nanocrystalline Alloys - Differentiation
Target:
High Frequency Range:
up to MHz
• Cores
• Planar Inductors
• Shielding material
• Sensors
smaller size
less weight
less electrical losses
improved energy efficiency
high precision
wide range of service temperature
• Energy efficiency and Renewable energy
• Electrical safety and Smart grids
• Automotive and e-Mobility
New Markets and Applications
LED Technology
www.audi.de
Wireless Charging
Brick-Type Converter (DC/DC)

Amorphous Materials – Rapid Solidification Technology
rapid solidification (106K/s)
Amorphous structure
→ no long range order
T70-85M15-30 (at%)
T = Fe, Co, Ni ...
M= Si, B, C, Nb, Mo ...
Typical Composition
• thin ribbon (d ~ 20 m)
• high electrical resistivity
Properties
• mechanically hard
• magnetically soft
Video

•Fe73.5Cu1Nb3Si13.5B9
(Yoshizawa & Yamauchi, 1988)
•Fe86(Cu1)Zr7B6
•Fe84Nb7B9
(Suzuki et al., 1990, 1991)
nanocrystalline state
for special compositions like:
Annealing above TxRapid Solidification (106K/s)
Amorphous structure
→ no long range order Large scale production as:
• FINEMET® (Hitachi)
• VITROPERM® (Vacuumschmelze)
• AT&M
VITROPERM® (nanocrystalline)
Bs high; ⇒⇒⇒⇒ low and high
brittle; Tapp ≤≤≤≤ 200°C;
Nanocrystalline Materials – Rapid Solidification Technology

Alloy System Nano-Crystalline
Fe74.5Cu1Nb3Si15.5B7
basic ferromagnetic
properties
glass forming
elements
enhances nucleation
of bcc-FeSi crystallites
•impedes grain growth
alternatives:
Au, Ag (?) Cr < V < Mo < Nb ≈≈≈≈ Ta < Zr, Hf
•inhibits formation of
Fe-B compounds

magneto-crystalline
10
102
103
104
J/m3
excellent soft magnetic
properties
properties
Magnetic Anisotropies with regard to Annealing Process customizing magnetic properties
HEATTREATMENT
nanocrystalline Fe-based alloys
Lex
D
K1
1K
K
N
=
Hc
(A/m)
1nm 1µm 1mm
0.1
1
10
100
1 000
10 000
perm-
alloy
50NiFe
FeSi6.5
Grain Size, D
Fe-base
amorphous
Co-base
1/D
crystalline
nano-
crystalline
D6
Herzer, G.,1997, Handbook of Magnetic Materials, Vol.10, Capter 3

Tailoring Hysteresis Loop: Induced Magnetic Anisotropies
annealing induced
⇒ Magnetic
Field Annealing
10
102
103
104
J/m3
HA
H
B
F
Z
HA [A/cm] µ
0.096 100 000
0.32 30 000
HA [A/cm] µ
0.096 100 000
0.32 30 000
2
u02µ
sB
µ
K
=
transverse
anisotropy
H
B
Ku
magnetization rotation
applied magnetic field H
applied magnetic field H
( )u
Fe
3/ 2
ˆK
P
f B
∆ ∝
⋅
H
B
longitudinal
anisotropy
domain wall
displacement
properties
properties

Nanocrystalline Alloys – NEW Products
longitudinal
transverse
perpendicular
NEW Products:
for the higher frequency range:
up to MHz
• Cores & Components
• Planar Inductors
• Shielding material
• Sensors
LED Technology
www.audi.de
Photovoltaic Battery Charger
Brick-Type Converter (DC/DC)
Wireless Charging
DC/DC Converter
Tape wound Cores
Low permeability material
for DC/DC Converter
(e.g. Ćuk – Converter)
M.Christoph, C. Dick,
RWTH Aachen
Low permeability material
for CT’s
(current transformer for
electronic watt hour meter)
Flux guiding and shielding foils
(wirleless charging, NFC, RFID)
E. Waffenschmidt, PHILIPS Research
®

1. Topic: Shielding & Flux Guiding
Wireless Charging
Requirements:
Highly soft magnetic material
Flux guiding: high power transfer efficiency
@ 120 …200 kHz 13.6 MHz
Shielding: protection of electronics and battery from
inductive heating
Shape: as thin as possible consumer electronic market
Materials:
Competitive material: Hard and Flexible Ferrites
Thin and flexible 2/4 layered Composite Material of
nanocrystalline VITROPERM®
of mobile electronic devices…
PET foil + adhesive (20 m)
VP 800 (20 m)
VP 800 (20 m)
adhesive (15 m)
2-layered composite VITROPERM®
Prof. E. Waffenschmidt, PHILIPS Research,
Fachhochschule Köln – Elektrische Netze

Wireless Power Transmission Systems
Application:
Technology & Electrical Circuit
Prof. E. Waffenschmidt, PHILIPS Research, Fachhochschule Köln – Elektrische Netze
Principle & Background

Shielding / Flux Guiding ?
ReceiverTransmitter
mobile device electronic, battery pack, metallic cover …
eddy current “free” area
shielding material
flux guide
Advantages:
• more closed magnetic circuit
• higher coupling factor k ⇒ 1
• reduced losses and heat generation in all
other metallic parts
• improved electro-magnetic compatibility (EMC)
Required material:
• High quality factor Q
• Ability of creating a higher coupling factor k
• Low losses at high frequencies: up to MHz
shielding / flux guiding material

Optimization Process for Efficiency
Responsible for efficiency for wireless power transmission ࢑ ∙ ࡽ
Our consideration: optimize the product of coupling factor k and the average quality factor Q
Inductance L: characteristic of assembly of coil + shielding material
Quality factor Q: indicator of energy loss
Coupling factor k: indicator of energy transfer
Power loss: no suitable indicator of performance
Parameters
[1] C.P. Dick, C. Polak, and E. Waffenschmidt.
Proposal of a Figure of Merit for the characterization
of soft-magnetic shielding material used in inductive wireless
power transmission systems
IEEE Journal of Emerging and Selected Topics in Power
Electronics 2015, Vol 3, Page 272
[2] C.P. Dick, A.Krause, E. Waffenschmidt and C. Polak.
Qualification of Soft-Magnetic Shielding Materials Used in
Inductive Wireless Power Transmission Systems
APEC 2015: Applied Power Electronics Conference and
Exposition 2015, Proceedings of; Charlotte, North Carolina,
USA; 15-19 Mar 2015

Shielding / Flux Guiding Material - Optimization
sheets and packetssheets and packets
planar windings
Sheet,
e.g. nanocrystalline material
Measurement of
Quality Factor Q
)(
)(
fµ
fµ
Q
imag
real
=
imagreal iµµµ +=
flossesµimag @∝
in amorphous and nanocrystalline
alloys power losses are mainly
determined by excess losses:
2/3
)(BfKu∝
Example of a planar coil
used in electronic power
transfer systems

“Zero” Anisotropy ⇒⇒⇒⇒ Planar Inductivities
sheets and packetssheets and packets
planar windings
Sheet,
e.g. nanocrystalline material
0
10
20
30
40
50
60
10 100 1000 10000
Frequency, f [kHz]
QualityFactor,Q[1]
amorphous material
VITROPERM® Fe73.5 Cu1Nb3Si15.5B7
nanocrystalline material; almost completely
reduced anisotropies
≈≈≈≈ isotropic
higher Q, lower losses
theory: Q ⇑ for ⇓ anisotropy
(excess losses: )
VITROPERM® Fe73.5 Cu1Nb3Si15.5B7
nanocrystalline material; almost completely
reduced anisotropies
≈≈≈≈ isotropic
higher Q, lower losses
theory: Q ⇑ for ⇓ anisotropy
(excess losses: )( ) 2/3
BfKu∝
Measurement of
Quality Factor Q
VITROPERM®®®® (nanocrystalline)
⇒ preferred material
Further Quality Enhancement:
(loss reduction)
by structuring
by inducing small, directed anisotropies

Composite layered Structure - Samples
VP 800 (20 m)
VP 800 (20 m)
adhesive (15 m)
2-layered composite VITROPERM®
Nanocrystalline
VITROPERM®
Samples of homogeneous VITROPERM® sheet:
„disc“ shaped and rectangular
Samples of slit VITROPERM® sheet (2mm strips):
„disc“ shaped and rectangular

Cracked / Crashed – Samples, Flake – Samples
Samples: VITROPERM® sheet cracked / crashed material: rectangular
cracks
Samples: VITROPERM® Flakes on adhesive: rectangular
450 m
185 m

Planar Inductivities – Measurement of Quality Factor
0
10
20
30
40
50
60
70
80
90
100
10 100 1000 10000
Frequency f [kHz]
QualityFactorQ[1]
VITROPERM® sheet
cracked / crashed
2 layers, 30x30mm
VITROPERM® sheet:
homogeneous
2 layers, 30x30mm
VITROPERM® sheet:
Slit (2mm)
2 layers, 30x30mm
VITROPERM® Flakes
on adhesive
30x30mm

Loss Reduction by Structuring
Domain structure determined by
magneto-optical Kerr microscopy
100 µµµµm
planar windings
nanocrystalline material
sample: VITROPERM® „R“
nanocrystalline, 20 x 20 mm
sample: VITROPERM® „R“
nanocrystalline, 20 x 20 mm
domain width: 220 µmdomain width: 220 µm
100 µµµµm
domain width: 50 µmdomain width: 50 µm
0
10
20
30
40
50
60
10 100 1000 10000
Frequency, f [kHz]
QualityFactor,Q[1]
structured
un-structured
wall displacement
eddy
currents
eddy current field
external magnetic field

2. Topic: High induced Anisotropy - Cores for DC/DC Converters or CT’s
tape wound corestape wound cores
high frequencies ....
10
100
1000
10000
100000
Frequency, f [MHz]
Permeability,µ'
0.001 0.01 0.1 1 10 100
µDC fg [MHz]
100 000 0.03
30 000 0.1
d = 20 µm
ρel = 120 µΩcm
30 kHz
fg
µ‘
µ‘VAC:
conventional cores
and components
VAC:
conventional cores
and components
Limitation of High Permeability Materials
2
0
4
d
f
DC
el
g
µµ
ρ
π
=

Limitation of High Permeability Materials
2
0
4
d
f
DC
el
g
µµ
ρ
π
=
DCelQ µρ /∝
high frequencies ....
10
100
1000
10000
100000
Frequency, f [MHz]
Permeability,µ'
0.001 0.01 0.1 1 10 100
µDC fg [MHz]
100 000 0.03
10 000 0.3
1 000 3
100 30
d = 20 µm
ρel = 120 µΩcm
3 MHz
30 MHz
fg fg
µ‘
µ‘

H
B
0.5 1.0 1.5
10
3
10
4
10
5
10
6
nanocrystalline
(Fe-base)
amorphous
(Co-base)
permalloys
MnZn-
Ferrites
Permeability,µi
Saturation Induction, Bs
(T)
µ
2
u02
sB
µ
K
=
µ
2
u02
sB
µ
K
=
WANTED
nanocrystalline
Fe-base alloy
low
- Alloy
- Mech. Processing
- Heat Treatment
Typical Permeabilities after Transverse Field Annealing of Tape Wound Cores

Low Permeability Solution: Stress Annealing
Annealing under Tensile Stress (1999)
ribbon
tensile stress σa
kg
weight
furnace
annealing
furnace
supply reel tensile force
control
winding unitinline control
furnace
Annealing under Tensile Stress (2011)
Reel-to-Reel Process
σa
First experiments:
G. Herzer, Nanocrystalline soft magnetic alloys, Handbook of Magnetic Materials Vol 10
©1999 Elsevier Science

10
102
103
104
J/m3
annealing induced
⇒ stress annealing
(without magnetic field)
H
J
HA
Ku= HAJs/2
(induced anisotropy)
HA [A/cm] µ
3.21 3 000
9.63 1 000
96.3 100
HA [A/cm] µ
3.21 3 000
9.63 1 000
96.3 100
Induced Magnetic Anisotropies

VITROPERM®, Fe73.5Cu1Nb3Si15.5B7
0
2
4
6
8
10
12
14
0 200 400 600 800
InducedAnisotropy,Ku(kJ/m
3
)
Annealing Stress, σa (MPa)
stress annealed
4s 600°C
4s 655°C
4s 690°C
field annealed
K1 (Fe80Si20)
furnace
ribbon tensile
stress σa
Induced Anisotropy vs. Annealing Stress, Hystereses, Magnetostriction
Herzer, Budinsky, Polak,
2011 J. Phys.: Conf. Ser. 266 012010

Nano-Crystallization under Tensile Stress: Domain Structure and Coercivity Field
zigzag
domain walls
10 µm
Kerr sensitivity
Herzer, Budinsy, Polak,
2011 J. Phys.: Conf. Ser. 266 012010
easy magnetic plain
Herzer, Budinsy, Polak, 2011 J. Phys.: Conf. Ser. 266 012010
Herzer, Budinsy, Polak, 2011 J. Phys.: Conf.
Ser. 266 012010
0
2
4
6
8
10
0 5 10 15
Induced Anisotropy, K u (kJ/m3
)
Coercivity,Hc(A/m)
K1 (Fe80Si20)K1/3
4s 600°C
4s 655°C
4s 690°C
field annealed
stress annealedFe73.5Cu1Nb3Si15.5B7
∝c uH K

Industrial Production Process
Creep Induced Anisotropy
Advantages:
… continuous process
highly linear hysteresis loops
permeability: 3000 to 100 (60)
vanishing magnetostriction (λs ≈ 0)
positive temperature coefficient of
permeability (Tk > 0)
very good aging stability
-200
-150
-100
-50
0
50
100
150
200
-20 -15 -10 -5 0 5 10 15 20
Magnetic Field H [A/cm]
MagneticFluxΦΦΦΦ[nVs]
annealing
600°C to 700°C magnetic
measurement
tensile stress
along the
ribbon axis

“Stress” Annealing – Production Process
annealing
measurement
tensile stress
along the
ribbon axis
Permeability
= 500
feedback control system
Continuous Process:
Stress-Annealing,
Quality inspection, Core Production
Nanocrystalline,
low permeability,
cores
outstanding low
scattering of
magnetic properties

“Very High” Anisotropy
Requirements:
Highly soft magnetic material
Shape: as flat as possible, height 1mm
Low power losses
Inductivity in the range of H
Quality factor > 20
Applicable at high frequencies (MHz range)
Material & Production Process:
VITROPERM®, VP800 FF, nanocrystalline
Stress Annealing =100
Conventional PCB
Embedded Components
Application of nanocrystalline low permeability cores:
Embedded Tape Wound Cores for DC/DC Converter

Tape Wound Cores: DC-Permeability
-1.5
-1
-0.5
0
0.5
1
1.5
-200 -150 -100 -50 0 50 100 150 200
Magnetic Field, H [A/cm]
Magnetization,J[T]
VITROPERM®, Fe73.5 Cu1Nb3Si15.5B7
nanocrystallization under tensile stress; annealed at 695°C; 4s;
stresses up to 700 MPa
µ ~ 2000
µ ~ 1000
µ ~ 400
µ ~100
µ ~ 60
tape wound cores:
7.5 x 3.5 x 1.0mm
tape wound cores:
7.5 x 3.5 x 1.0mm

Tape Wound Cores: Permeability at high Frequencies
0
0.2
0.4
0.6
0.8
1
1.2
0.01 0.10 1.00 10.00 100.00
Frequency, f [MHz]
NormalizedPermeability,µ'/µ'max
µ ~ 2000
µ ~ 60
µDC d [µm] fg [MHz]
1 750 19.3 1.9
1 070 19.2 3.2
396 18.8 9.1
99 17.8 45.2
58 15.3 95.0
ρel = 120 µΩcm

Recent Developments High Bs Alloys
Coercivity Hc [A/m]
SaturationPolarisation,Js[T]
0.1 1 10 100 1000
0.5
2.0
1.0
2.5
1.5
0.0
50% CoFe
Fe3% SiFe
40-50% NiFe
70-80% NiFe
(Permalloy)
MnZn NiZn
Soft Ferrites
amorphous
Co-base
FeSiAl (Sensust)
amorphous
FeNi-base
amorphous
Fe-base
nano-
crystalline
High Bs
Nano-Crystalline
Fe-base alloys
with high saturation
induction

High Bs Alloys
Fe-content (at.%)
(Liu et al., 2014)
Suzuki et al (1991 – 1993):
Fe84Nb7B9, Fe86Zr7B6Cu1: Js = 1.5 T, λs ~ 0 ppm
Fe91Zr7B2 : Js = 1.7 T, λs ~ - 1 ppm
Older approaches:

High Bs Alloys
Fe-content (at.%)
(Liu et al., 2014)
Older approaches:
Vacuumschmelze (1991 – 2001):
Magnetization:
Magnetostriction: ?

High Bs Alloys
Fe-content (at.%)
(Liu et al., 2014)
Hitachi, Ohta et al 2009:
Fe82.5 Si2 B14 Cu1.5 : Js = 1.85 T, λs ~ 14 ppm
(enhanced Cu content)
IMR, Makino et al 2009:
Fe85.3 Si4 B8 P4 Cu0.7 : Js = 1.80 T, λs ~ 14 ppm
(combined action of Cu+P)
More recent approaches:

Recent Developments
“under development”
• Laboratory Caster
width: 50mm, thickness: 22 m
• Co addition:
improvement of casting
behavior
• Short time, continuous
annealing!
established heat treatments
like batch annealing not
feasible, need for high
heating/cooling rate
• Hc < 10 A/m
• Bs about 1.8T
• λs about 15 to 20ppm
Fe-base Co0 or 4 /Nb free /P high Bs alloy:
annealing
measurement
tensile stress
along the
ribbon axis
M. Kuhnt, M. Marsilius, T. Strache, C. Polak, and G. Herzer,
“Magnetostriction of nanocrystalline (fe,co)-si-b-p-cu alloys,” Scripta Materialia, vol. 130, pp. 46 – 48, 2017

Conclusions: Nanocrystalline Fe-base Alloys
recent developments for high frequency applications
zero induced anisotropy wireless charging
high induced anisotropy Ku (low ) size reduction, CT’s & chokes
high saturation induction (Bs ≈ 1.8 T ) further size reduction
• excellent soft magnetic properties
(due to vanishingly small K1 and near-zero λs )
• customizable to the needs of application
(by annealing induced anisotropies)
• low losses even at high frequencies
(thin ribbons ~20 m, high resistivity ~120 Ωcm, shift fg to high f
growing market
for
nanocrystalline
materials
further progress needs more sophisticated
casting and annealing technologies

Soft Magnetic Nanocrystalline Materials for Inductors and Shielding Applications Optimized for Higher Frequencies.

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