Soft Ferrites and Accessories
Contents
Introduction
Quality
Environmental aspects of soft ferrites
Ordering information
Applications
Literature and reference publications
Ferrite materials survey and specifications
- Ferrite materials survey
- Material specifications and graphs
Page
Specialty ferrites
- Ferrites for particle accelerators (T)
- Ferrite building blocks (BLK)
- Machined ferrites and special shapes
- Ferrites for anechoic chambers (PLT, PLT/H)
E cores and Accessories
EI cores
Planar E cores and Accessories (E, E/R, PLT, PLT/S, PLT/R)
EC cores and Accessories
EFD cores and Accessories
EP cores and Accessories
EPX cores and Accessories
EQ, EQ/LP cores and Accessories (EQ, EQ/R, EQ/LP, PLT, PLT/S)
ER cores
Planar ER cores and Accessories
ETD cores and Accessories
Frame and Bar cores and Accessories (FRM, BAR)
Integrated Inductive Components (IIC)
P, P/I cores and Accessories
PT, PTS, PTS/I cores and Accessories
PH cores
PM cores
PQ cores and Accessories
4
14
15
16
17
54
58
59
62
167
168
174
175
177
179
299
311
369
387
421
455
471
491
503
529
557
573
587
667
693
701
707
RM, RM/I, RM/ILP cores and Accessories
U, I cores and Accessories
UR cores
Ferroxtag RFID transponders
RFID transponder cores (BAR, FAR, TAR)
EMI-suppression products / small products
Ferroxfoil flexible sheet EMI absorber
- Bobbin cores (BC)
- Cable shields (CSA, CSC, CSF, CSU, CST)
- EMI-suppression beads (BD)
- EMI-suppression beads on wire (BDW)
- Miniature balun cores (MHB)
- Multihole cores (MHC, MHB, MHR)
- Multilayer inductors (MLI, MLH)
- Multilayer suppressors (MLS, MLP, MLN)
- Rods (ROD)
- SMD beads (BDS)
- SMD common mode chokes (CMS)
- SMD wideband chokes (WBS, WBSM)
- Tubes (TUB)
- Wideband chokes (WBC)
Gapped ferrite toroids (TN)
Ferrite toroids (T, TC, TN, TX)
Alloy powder toroids (TX)
Iron powder toroids (TN)
741
837
861
865
868
871
873
876
878
885
886
887
889
892
905
916
917
922
929
938
939
943
951
1057
1089
DATA SHEET STATUS DEFINITIONS
DATA SHEET STATUS
Preliminary
specification
Product specification
PRODUCT
STATUS
Development
DEFINITIONS
This data sheet contains preliminary data. Ferroxcube reserves the right to
make changes at any time without notice in order to improve design and
supply the best possible product.
This data sheet contains final specifications. Ferroxcube reserves the right
to make changes at any time without notice in order to improve design and
supply the best possible product.
Production
DISCLAIMER
Life support applications
These products are not designed for use in life support appliances, devices, or systems
where malfunction of these products can reasonably be expected to result in personal injury. Ferroxcube customers using
or selling these products for use in such applications do so at their own risk and agree to fully indemnify Ferroxcube for
any damages resulting from such application.
PRODUCT STATUS DEFINITIONS
STATUS
Prototype
Design-in
Preferred
Support
INDICATION
DEFINITION
These are products that have been made as development samples for the purposes of
technical evaluation only. The data for these types is provisional and is subject to change.
These products are recommended for new designs.
These products are recommended for use in current designs and are available via our
sales channels.
These products are
not
recommended for new designs and may not be available through
all of our sales channels. Customers are advised to check for availability.
Ferroxcube
Soft Ferrites
THE NATURE OF SOFT FERRITES
Composition
Ferrites are dark grey or black ceramic materials. They are
very hard, brittle and chemically inert. Most modern
magnetically soft ferrites have a cubic (spinel) structure.
The general composition of such ferrites is MeFe
2
O
4
where Me represents one or several of the divalent
transition metals such as manganese (Mn), zinc (Zn),
nickel (Ni), cobalt (Co), copper (Cu), iron (Fe) or
magnesium (Mg).
The most popular combinations are manganese and zinc
(MnZn) or nickel and zinc (NiZn). These compounds
exhibit good magnetic properties below a certain
temperature, called the Curie Temperature (T
C
). They can
easily be magnetized and have a rather high intrinsic
resistivity. These materials can be used up to very high
frequencies without laminating, as is the normal
requirement for magnetic metals.
NiZn ferrites have a very high resistivity and are most
suitable for frequencies over 1 MHz, however, MnZn
ferrites exhibit higher permeability (µ
i
) and saturation
induction levels (B
s
) and are suitable up to 3 MHz.
For certain special applications, single crystal ferrites can
be produced, but the majority of ferrites are manufactured
as polycrystalline ceramics.
Manufacturing process
The following description of the production process is
typical for the manufacture of our range of soft ferrites,
which is marketed under the trade name ‘Ferroxcube’.
R
AW MATERIALS
The raw materials used are oxides or carbonates of the
constituent metals. The final material grade determines
the necessary purity of the raw materials used, which, as
a result is reflected in the overall cost.
P
ROPORTIONS OF
THE COMPOSITION
Introduction
P
RE
-
SINTERING
The mixed oxides are calcined at approximately 1 000
°C.
A solid state reaction takes place between the constituents
and, at this stage, a ferrite is already formed.
Pre-sintering is not essential but provides a number of
advantages during the remainder of the production
process.
M
ILLING AND GRANULATION
The pre-sintered material is milled to a specific particle
size, usually in a slurry with water. A small proportion of
organic binder is added, and then the slurry is spray-dried
to form granules suitable for the forming process.
F
ORMING
Most ferrite parts are formed by pressing. The granules are
poured into a suitable die and then compressed. The
organic binder acts in a similar way to an adhesive and a
so-called ‘green’ product is formed. It is still very fragile
and requires sintering to obtain the final ferrite properties.
For some products, for example, long rods or tubes, the
material is mixed into a dough and extruded through a
suitable orifice. The final products are cut to the required
length before or after sintering.
S
INTERING
The ‘green’ cores are loaded on refractory plates and
sintered at a temperature between 1 150
°C
and 1300
°C
depending on the ferrite grade. A linear shrinkage of up to
20% (50% in volume) takes place. The sintering may take
place in tunnel kilns having a fixed temperature and
atmosphere distribution or in box kilns where temperature
and atmosphere are computer controlled as a function of
time. The latter type is more suitable for high grade ferrites
which require a very stringent control in conditions.
F
INISHING
After sintering, the ferrite core has the required magnetic
properties. It can easily be magnetized by an external field
(see Fig.2), exhibiting the well-known hysteresis effect
(see Fig.1). Dimensions are typically within 2% of nominal
due to 10- 20% shrinkage. If this tolerance is too large or if
some surfaces require a smooth finish (e.g. mating faces
between core halves) a grinding operation is necessary.
Usually diamond-coated wheels are used. For high
permeability materials, very smooth, lapped, mating
surfaces are required. If an air-gap is required in the
application, it may be provided by centre pole grinding.
The base materials are weighed into the correct
proportions required for the final composition.
M
IXING
The powders are mixed to obtain a uniform distribution of
the components.
2008 Sep 01
4
Ferroxcube
Soft Ferrites
Magnetism in ferrites
A sintered ferrite consists of small crystals, typically
10 to 20
µm
in dimension. Domains exist within these
crystals (Weiss domains) in which the molecular magnets
are already aligned (ferrimagnetism). When a driving
magnetic field (H) is applied to the material the domains
progressively align with it, as shown in Fig.2.
During this magnetization process energy barriers have to
be overcome. Therefore the magnetization will always lag
behind the field. A so-called hysteresis loop (see Fig.1) is
the result.
If the resistance against magnetization is small, a large
induced flux will result at a given magnetic field. The value
of the permeability is high. The shape of the hysteresis
loop also has a marked influence on other properties, for
example power losses.
handbook, halfpage
Introduction
B
H
MBW424
Fig.1 Hysteresis loop.
handbook, full pagewidth
B
B
H
H
(A)
(B)
H
B
B
H
H
(C)
H
(D)
MBW423
H
Fig.2 Alignment of domains.
2008 Sep 01
5
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