This document summarizes a new soft magnetic composite material called FlakeComposite that is suitable for high frequency power modules. FlakeComposite has higher permeability than conventional metal composites at MHz switching frequencies, enabling thinner and more flexible inductors. Prototypes of PCB-embedded inductors using FlakeComposite demonstrated tight inductance tolerances and self-resonant frequencies up to 400MHz. Testing showed FlakeComposite has comparable magnetic properties to ferrites, such as permeability and core loss, but with improved temperature tolerance and saturation properties. FlakeComposite is expected to enable further miniaturization of electronic circuits, especially in DC/DC converters and wireless power transfer systems.

1. © TOKIN 2019
Soft magnetic Metal-flake Composite Material
Suitable for High Frequiency Power Modules
19 Mar. 2019
Ken’ichi Chata’ni
TOKIN Corporation

2. © TOKIN 2019
Ken’ichi Chata’ni,
Ph.D.(Physics)
Manager,
Advanced Materials R&D Division
TOKIN Corporation
kenichichatani@kemet.com

3. © TOKIN 2019
Demands: Shorten the distance from DC/DC converter to the load.
Higher DC current / Higher switching frequency
Motivation
Back surface mount
Processer
Inductor Inductor
Inductor
Processer
PCB embedding
Processer
3D mount
Processer
Conventional
 Spread of GaN
 Integratable L, C
 Low-profiled inductor for integrated DC/DC converter is required.
 PCB embed enabling magnetic material will also be required in future.
Inductor

4. © TOKIN 2019
FlakeCompositeConventional
Metal composite
Permeability 300
(Same as ferrite)
< 40
Metal-flake
Compacting
Technology
Thickness >0.5mm
Brittle
>50μm
Flexible
Heat durability <200℃
Organic binder
>200℃
Inorganic binder
Enable PCB Embedding
Suitable for Automotive
Smaller component's volume
What is FlakeCompositeTM?

5. © TOKIN 2019
Conventional
metal composite
0.0
0.5
1.0
1.5
2.0
100 100010
Bs(T)
MnZn
NiZn
CoZrO(film)
CoZrTa(film)
CoＮｉFe(film)
Fe nano
crystal
Permalloy
FeSiAl
FeSi
Fe
amorphous
Permeability
(1MHz)
Low permeability
ferrite
Deposited Film
Brittle
Difficult to increase
the core volume.
PCB embedded
Magnetic Material
High permeability (300 at 1 MHz.)
50m to 2mm thickness
Thin, Flexible(Rigid)
FlakeComposite
Comparison of Magnetic Materials for PCB Embedding

6. © TOKIN 2019
0
100
200
300
400
0.1 1 10 100
Permeability(Re,Im)
Frequency(MHz)
NiZn ferrite
FlakeComposite
μ’// = 300
μ≦ 5
 Comparable to NiZn ferrite for MHz power
application.
Frequency dispersion of complex permeability
Limitation
Lower Out-plane
permeability.
Permeability(Re,Im)
Frequency (MHz)
Permeability vs Frequency

7. © TOKIN 2019
0
500
1000
1500
-50 -25 0 25 50 75 100 125 150 175
Pcv(mW/cc,1MHzBm25mT)
Temp (℃)
0
1000
2000
0 1 2 3 4 5
Pcv(mW/cc)
f(MHz)
f×Bm=25MHz・mT
23℃
 Core loss of FlakeComposite is comparable to NiZn ferrite,
but much larger than MnZn ferrite.
NiZn ferrite
MnZn ferrite
Conventional
Metal Composite
Core Loss vs Temp.
FlakeComposite
FlakeComposite
Core Loss

8. © TOKIN 2019
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 2000 4000 6000 8000
B(T)
H (A/m)
 Soft-saturation in FlakeComposite.
 Smaller drop of saturated magnetic moment against
temperature, comparing to MnZn ferrite.
125℃
25℃
MnZn ferrite
FlakeComposite
Conventional
Metal Composite
Magnetic Saturation (BH curve)

9. © TOKIN 2019
0
10
20
30
40
50
60
70
80
0 2000 4000 6000 8000
Permeability
Hdc(A/m)
125℃
25℃
MnZn ferrite
FlakeComposite
Conventional
Metal Composite
 In metals, permeability under DC-bias field is insensitive to temperature.
 In metals, permeability survives under high DC-bias field.
In MnZn ferrite and FlakeComposite, effective
permeability under zero bias field is tuned to be 70 by
corresponding demagnetizing coefficient, i.e, air-gap.
N=0.01384
N=0.01091
N=0
Permeability under DC-bias Field

10. © TOKIN 2019
0
50
100
150
200
250
300
0.1 1 10 100
Permeability(Re,Im)
Frequency(MHz)
0
10
20
30
40
50
60
70
80
90
100
0 500 1000
PermeabilityChange(%)
Plane Pressure(kgf/cm2)
 Only 7.6％ permeability decrease
under 1000kgf/cm2 compression.
Plane Pressure(kgf/cm2)
-7.6%
FlakeComposite
 Apply 1000kgf/cm2 plane pressure
on the toroidal core.
After 1000kgf/cm2
compression
Initial
 Only 2.7% permeability decrease
after 1000kgf/cm2 compression.
 No apparent damage was found.
Effect of Plane Compression

11. © TOKIN 2019
10
100
1000
10000
0 200 400 600
Permeability(25℃)
Curie Temperature(℃)
 Higher Curie temperature than ferrites.
NiZn ferrite
MnZn ferrite
FlakeComposite
0
50
100
150
200
250
300
-50 0 50 100 150
RealPermeability
Temp(℃)
FlakeComposite
Curie Temperature

12. © TOKIN 2019
Material characteristics of FlakeCompositeTM ,
in comparison with existing magnetic materials.
-Permeability, magnetic saturation, core loss, etc.
Inductor performance benchmarking.
PCB embedded inductor test fabrication result.

13. © TOKIN 2019
Qiang Li, Fred C. Lee, “High Inductance Density Low-Profile Inductor Structure for Integrated Point-of-Load Converter”, 2009 IEEE Applied
Power Electronics Conference and Exposition (APEC), Washington, District of Columbia, Feb. 15 – 19, 2009, pp. 1011 – 1017.
Dongbin Hou, Yipeng Su, Qiang Li, Fred C. Lee, “Improving the
Efficiency and Dynamics of 3D Integrated POL”, IEEE Applied
Power Electronics Conference and Exposition (APEC), 2015,
pp. 1011 – 1017.
 FlakeComposite is suitable to
demonstrate the proposed advantage
of “Lateral flux” inductor design.
 As inductor goes thinner, the
advantage of “Lateral flux” inductor
structure should be more prominent.
Lateral Flux Inductor Structure

14. © TOKIN 2019
0
10000
20000
30000
0 1 2 3 4 5 6
LxImax/DCR(nH･A/mΩ)
Inductor Height(mm)
Imax≧20A
FlakeComposite
Lateral flux
 The advantage of FlakeComposite Lateral flux inductor
becomes prominent as the inductor height goes lower.
Benchmarking Result

15. © TOKIN 2019
Storage Result (N=22)
-50℃ 1000h Pass
150℃ 1000h Pass
Unbiased Hast
With MSL 3
Pre-Conditioning
130℃85% 96h
Pass
33.3psia(2.3atm)
JESD22-A119 JESD22-A103 Condition B
Heat Cycle
-65⇔150℃ 500cycle Pass
JESD22-A104 Condition C Soak Mode 4
JESD22-A118
MSL test (Level 1)
Pre-bake 125℃ 24h
PassMoisture Soak 85℃85%RH 192h
Reflow 260℃ x 3
J-STD-020E
Sample Structure
・Tin plated lead frame and Cu pins
(without insulation coating) are attached
on the FlakeComposite core. Image
Hi Temp and Humidity
85℃85% 1000h Pass
MIL-STD-202 Method 103
• Acceptance Criteria:
・ Change of Ls, Rs and
DCR<10% pre-test to post-test.
・ No cracks, chips or
discoloration
 AEC-Q200 compatible.
(RoHS2.0, Halogen free, REACH compliant.)
13mm
Reliability Test Example (On samples to CPES)

16. © TOKIN 2019
PCB embedded inductor to minimize:
- PCB board area.
- parasitic inductance of Cu trace.
Power Inductors
Ferrite FlakeCompositeTM
40% height reduction with
FlakeComposite inductor.
Embedded noise shielding layer
Flexible shielding layer (for WPT)
- Combined with PCB embedding technology.
FlexSuppressor® Flex "Embedded"
Suppressor
Magnetic Sheets
Application Target

17. © TOKIN 2019
Material characteristics of FlakeCompositeTM ,
in comparison with existing magnetic materials.
-Permeability, magnetic saturation, core loss, etc.
Inductor performance benchmarking.
PCB embedded inductor test fabrication result.

18. © TOKIN 2019
Y. Su, W. Zhang, Q. Li, F. C. Lee, and M. Mu, "High frequency integrated Point of Load
(POL) module with PCB embedded inductor substrate," in Energy Conversion Congress
and Exposition (ECCE), 2013 IEEE, 2013, pp. 1243-1250.
 Under the testing of similar prototypes.
PCB Embedded Inductor Demonstrated by CPES

19. © TOKIN 2019
2 turn
Upside Downside
DCR
2.8mΩ
3 turn
Upside Downside
DCR
4.4mΩ
With inserted
pins
0.8mΩ
With inserted
pins
2.1mΩ
0
50
100
150
200
250
300
350
0 10 20 30 40
L(nH)@1MHz
Idc(A)
2 turn
3 turn
t2.5mm
12mm
Embedded core size
9 x 8 x t1.5mm
PCB Embedded Inductor Prototype

20. © TOKIN 2019
0
10
20
30
235 255 275 295 315
Count
L(nH, 1MHz)
0
10
20
30
105 115 125 135 145
Count
L(nH, 1MHz)
0
25
50
75
100
125
150
1 10 100 1000
L(nH)
Frequency(MHz)
1
10
100
1000
1 10 100 1000
|Z|(Ω)
Frequency(MHz)
0
100
200
300
1 10 100 1000
L(nH)
Frequency(MHz)
1
10
100
1000
1 10 100 1000
|Z|(Ω)
Frequency(MHz)
2 turn (n=100)
3 turn (n=100)
－10%
±3σ
±3σ
+10%
Ave.
125nH
Ave.
277nH
－10% +10%
SRF=400MHz
SRF=250MHz
 Tight tolerance of inductance is readily achieved in test fabrication.
Dispersion of Inductance , |Z|

21. © TOKIN 2019
 FlakeCompositeTM is:
-Thin, Flexible, PCB-embed-enabling,
-High permeability at multi-MHz swithcing frequency,
-High-saturated magnetic moment than ferrite,
-High temperature tolerant
soft magnetic material for power supply application.
 We believe this material will contribute to the miniturization of
electronic circuits, especially in:
- DC/DC converters,
- Wireless Power Transfer system.
 We are continuing to scale-up this technology for use in
several applications.
Summary

22. © TOKIN 2019
Thank you very much for your attention.

23. © TOKIN 2019
Back Ups

24. © TOKIN 2019
Applied Power Electronics Conference and Exposition (APEC),
2015 Thirtieth Annual IEEE, 2015, pp. 140-145.