U.S. patent application number 13/122145 was filed with the patent office on 2011-07-28 for method of manufacturing electronic component for rf applications by sintering.
Invention is credited to Won Ki Ahn, Byung Hoon Ryou, Won Mo Sung.
Application Number | 20110182763 13/122145 |
Document ID | / |
Family ID | 42073993 |
Filed Date | 2011-07-28 |
United States Patent
Application |
20110182763 |
Kind Code |
A1 |
Ryou; Byung Hoon ; et
al. |
July 28, 2011 |
METHOD OF MANUFACTURING ELECTRONIC COMPONENT FOR RF APPLICATIONS BY
SINTERING
Abstract
Disclosed herein is a method for manufacturing an electronic
component comprising a ferrite by sintering. The method comprises
the steps of: adding 3 wt% of ammonium alginate to a ferrite to
form a mixture, and stirring the mixture while adding water thereto
to form a gel; drying the gel at a temperature ranging from 85
.degree. C to 95 .degree. C to form a dried material; grinding the
dried material to produce a ferrite powder coated with the ammonium
alginate; subjecting the ferrite powder to compression molding; and
sintering the compression-molded ferrite powder. According to the
method, by adding ammonium alginate to the ferrite, the cohesion of
the ferrite can be enhanced to facilitate the molding of the
ferrite. Also, the magnetic loss tangent of the ferrite can be
reduced and the permeability thereof can be increased, thus
increasing the efficiency of the ferrite.
Inventors: |
Ryou; Byung Hoon; (Seoul,
KR) ; Sung; Won Mo; (Siheung-si, KR) ; Ahn;
Won Ki; (Anyang-si, KR) |
Family ID: |
42073993 |
Appl. No.: |
13/122145 |
Filed: |
September 28, 2009 |
PCT Filed: |
September 28, 2009 |
PCT NO: |
PCT/KR09/05517 |
371 Date: |
March 31, 2011 |
Current U.S.
Class: |
419/10 |
Current CPC
Class: |
C04B 35/2683 20130101;
C04B 35/2666 20130101; C04B 2235/3206 20130101; C04B 35/628
20130101; C04B 35/636 20130101; H01F 41/0246 20130101; C04B
2235/3275 20130101; H01F 1/344 20130101 |
Class at
Publication: |
419/10 |
International
Class: |
B22F 3/12 20060101
B22F003/12; B22F 3/10 20060101 B22F003/10 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 1, 2008 |
KR |
10-2008-0096601 |
Claims
1. A method for manufacturing an electronic component for RF
applications comprising a ferrite by sintering, wherein ammonium
alginate is added to the ferrite before the ferrite is
sintered.
2. The method of claim 1, wherein the ferrite has a spinel
structure.
3. The method of claim 1, wherein the ammonium alginate is added to
the ferrite in an amount of 3 wt%.
4. The method of claim 1, wherein the ferrite is sintered at a
temperature ranging from 600 .degree. C to 1400 .degree. C.
5. A method of manufacturing an electronic component for RF
applications by sintering, the method comprising: adding 3 wt% of
ammonium alginate to a ferrite to form a mixture, and stirring the
mixture while adding water thereto to form a gel; drying the gel at
a temperature ranging from 85 .degree. C to 95 .degree. C to form a
dried material; grinding the dried material to produce a ferrite
powder coated with the ammonium alginate; subjecting the ferrite
powder to compression molding; and sintering the compression-molded
ferrite powder.
6. The method of claim 5, wherein the ferrite is a spinel ferrite
having a composition of MXFe(3.times.X)O4, wherein M is at least
one of Mg and Co, and X is an integer of 1 or 2.
7. The method of claim 5, wherein the compression-molding operation
is carried out by compressing the ferrite powder with a load of 2-6
tons.
8. The method of claim 5, wherein the sintering step operation is
carried out at a temperature ranging from 600 .degree. C. to 1400
.degree. C.
Description
TECHNICAL FIELD
[0001] The present invention relates to a method of manufacturing
an electronic component for RF applications comprising a ferrite by
sintering, and more particularly to a method of manufacturing an
electronic component for RF applications by sintering, in which
ammonium alginate is added to the ferrite so that the cohesion of
the ferrite can be enhanced to facilitate the molding of the
ferrite, the magnetic loss tangent of the ferrite can be reduced
and the permeability thereof can be increased.
BACKGROUND ART
[0002] In general, the term "wireless device" refers to any device
capable of transmitting and receiving information anywhere
regardless of location, including mobile phones, palm PCs or PDAs
(Personal Digital Assistants), or HPCs (Hand-Held Pet). In such
wireless devices, antennas for transmitting and receiving
electronic information through wireless communication are placed.
In such antennas, RF (Radio Frequency) magnetic devices for
wireless transmission and reception of information are placed.
[0003] The term "electromagnetic wave" refers to a phenomenon where
electromagnetic waves with periodically changing intensities are
propagated through space.
[0004] Electromagnetic waves are classified, according to their
frequency or wavelength, into low-frequency, high-frequency,
short-wavelength, and long-wavelength electromagnetic waves. These
electromagnetic waves have various electromagnetic properties, and
thus are used in various fields and applications, including
electrical devices, electronic devices, and communication
devices.
[0005] The effect of electromagnetic waves on the human body can be
seen through various syndromes found to be caused by
electromagnetic waves, such as the thermal effects caused by
microwaves used in electronic ranges, mobile phones and the like,
or video display terminal syndromes indicating syndromes, such as
headaches or sight disturbance, which are caused by electromagnetic
waves. In addition, there are a number of study results, such as an
increase in the cancer development of residents in the vicinity of
power transmission lines, or an attack of brain tumor in long-term
users of mobile phones.
[0006] In particular, due to the development of mobile
communication technology and the public use of personal mobile
communication, there are continued studies on the possibility of
adverse effects on the human body and the suggestion of problems,
for example, the defenseless exposure of users to high-frequency
electromagnetic waves generated from mobile communication devices,
such as mobile phones, and an increase in body temperature at
cranial sites during the use of such mobile communication devices.
For this reason, in highly developed countries where personal
mobile communication is commonly used, the standards for the
protection of the human body from electromagnetic waves are made
and provided as recommendation standards by private organizations,
such as associations or societies, on the assumption that
electromagnetic waves are harmful to the human body. In some
countries, these standards are in force. Also, the recognition of
consumers is spread that judges not only the function of products
but also the non-harmfulness of products to the human body as
important quality factors. As concern and consciousness about the
harmfulness of electromagnetic waves to the human body are
increased as described above, research and development on
electrical/electronic devices with minimized generation of
electromagnetic waves or materials for absorbing generated
electromagnetic waves are now actively conducted. Particularly,
various forms of electromagnetic wave-absorbing materials, which
are attached to various electrical/electronic devices so as to
absorb the generated harmful electromagnetic waves, are developed
and applied as internal or external parts in antennas or
monitors.
[0007] The electromagnetic wave-absorbing material can be typically
exemplified by a ferrite. As used herein, the term "ferrite" refers
to a solid solution in which allaying elements or impurities melt
in iron having a body-centered cubic crystalline structure, which
is stable at a temperature of 900 .degree. C or below. The ferrite
is manufactured into an electromagnetic wave-absorbing material,
mainly by sintering. This ferrite electromagnetic wave-absorbing
material manufactured by sintering has a shortcoming in that it is
weak against impact, and thus is likely to undergo brittle
fracture. Also, the electromagnetic wave-absorbing material
manufactured using the ferrite disadvantageously has low
dimensional stability due to a shrinkage phenomenon occurring in a
sintering process in which ferrite powder is placed and molded in a
mold under pressure, followed by heating. Furthermore, the mold
should be manufactured in view of shrinkage rate, thus making the
molding process difficult. In addition, the characteristics of the
sintering process make it difficult to apply a mold of complex
shape, thus reducing the formability of the ferrite.
[0008] Particularly, in view of the fact that the electromagnetic
wave-absorbing material is most frequently used for various mobile
electrical/electronic devices, such as mobile phone antennas, the
electromagnetic wave-absorbing material is likely to be exposed to
vibration or impact when it is carried, and thus the weakness of
the electromagnetic wave-absorbing material against impact can be
considered as a serious problem. In addition, an increase in
production cost due to low formability and dimensional stability
can be seen as a serious disadvantage when considering a rapidly
increasing demand for the electromagnetic wave-absorbing
material.
[0009] Binders which are generally added to increase the
formability of the ferrite during a process of molding the ferrite
include polyvinyl alcohol (PVA). However, PVA is difficult to grind
and mix in a dried state and results in a non-uniform molded body.
For this reason, a method of forming and drying a binder solution
and molding the dried material is used, but this method involves a
relatively complex process.
DISCLOSURE
Technical Problem
[0010] Accordingly, the present invention has been made in order to
solve the above-described problems occurring in the prior art, and
it is an object of the present invention to provide a method of
manufacturing an electronic component for RF applications by
sintering, which can reduce the magnetic loss tangent of the
electronic component and increase the permeability of the
electronic component.
[0011] Another object of the present invention is to provide a
method of manufacturing an electronic component by sintering, which
can enhance the cohesion of a ferrite to facilitate the molding of
the ferrite.
Technical Solution
[0012] To achieve the above objects, according to a preferred
embodiment of the present invention, there is provided a method of
manufacturing an electronic component for RF applications
comprising a ferrite by sintering, wherein ammonium alginate is
added to the ferrite before the ferrite is sintered.
[0013] In the method of the present invention, the ferrite
preferably has a spinel structure, and the ammonium alginate is
preferably added to the ferrite in an amount of 3 wt%.
[0014] Also, the ferrite is preferably is sintered at a temperature
ranging from 600 .degree. C to 1400 1 .degree. C.
[0015] According to another preferred embodiment of the present
invention, there is provided a method of manufacturing an
electronic component for RF applications by sintering, the method
comprising the steps of: adding 3 wt% of ammonium alginate to a
ferrite to form a mixture, and stirring the mixture while adding
water thereto to form a gel; drying the gel at a temperature
ranging from 85 .degree. C to 95 .degree. C to form a dried
material; grinding the dried material to produce a ferrite powder
coated with the ammonium alginate; subjecting the ferrite powder to
compression molding; and sintering the compression-molded ferrite
powder.
[0016] In the method of the present invention, the ferrite
preferably is a spinel ferrite having a composition of
M.sub.XFe.sub.(3-X)O.sub.4, wherein M is at least one of Mg and Co,
and X is an integer of 1 or 2.
[0017] Also, the compression-molding step is preferably carried out
by compressing the ferrite powder with a load of 2-6 tons.
[0018] In addition, the sintering step is preferably carried out at
a temperature ranging from 600 .degree. C to 1400 .degree. C.
Advantageous Effects
[0019] The present invention can reduce the magnetic loss tangent
of the ferrite molded material and increase permeability of the
ferrite molded material, thus increasing the efficiency of the
ferrite molded material.
[0020] Also, by adding ammonium alginate to the ferrite, the
cohesion of the ferrite can be enhanced, thus facilitating the
molding of the ferrite.
[0021] For this reason, the density of the ferrite molded material
can be maintained at a relatively uniform level, and thus the
magnetic loss tangent and permeability of the ferrite molded
material can be maintained at constant levels.
[0022] Also, because the binder PVA is not used in the process of
molding the ferrite in the present invention, a process of
preparing a solution of the binder can be omitted, thus making the
mixing process simple. Accordingly, the ferrite can be molded using
a simple process.
BRIEF DESCRIPTION OF DRAWINGS
[0023] FIG. 1 is a process flow chart showing a method of
manufacturing an electronic component for RF applications
comprising a ferrite by sintering according to a preferred
embodiment of the present invention.
[0024] FIG. 2 is a graphic diagram showing the permeability and
magnetic loss tangent of an electronic component for RF
applications manufactured according to a conventional method.
[0025] FIG. 3 is a graphic diagram showing the permeability and
magnetic loss tangent of an electronic component for RF
applications manufactured according to a preferred embodiment of
the present invention.
BEST MODE
[0026] Hereinafter, a preferred embodiment of the present invention
will be described in detail with reference to the accompanying
drawings, but the scope of the present invention is not limited by
the embodiment. For reference, like reference numerals designate
like elements throughout the specification.
[0027] A method of manufacturing an electronic component for RF
applications by sintering according to a preferred embodiment of
the present invention will now be described.
[0028] A method of manufacturing an electronic component for RF
applications comprising a ferrite will be described as a typical
example.
[0029] The electronic component for RF applications is manufactured
by adding ammonium alginate to the ferrite and sintering the
ferrite.
[0030] Alginate is a polysaccharide material that is contained in
algae and bacterial in large amounts. It is a polymer of .beta.-1,
4-D-manuronic acid and .beta.-1, 4-L-glucuronic acid, extracted
from algae, and when it comes into contact with divalent or
higher-valent metal ions, such as Ca and Al (excluding Mg), it will
be easily gelled. The carboxyl group of manuronic acid or
glucuronic acid is crosslinked by chelation with miltivalent metal
ions. Because alginate is harmless to the human body and gelled at
room temperature, it is frequently used for the immobilization of
animal cells.
[0031] In microbial culture, alginate allows the metabolic activity
of microorganisms to be maintained for a long period, and thus is
mainly used as an immobilization agent. Also, an immobilization
process that uses alginate is very simple and relatively
inexpensive.
[0032] Also, ammonium alginate is a white or light yellow fibrous
grain, granule or powder, is substantially odorless and tasteless
and has a chemical formula of
(C.sub.6H.sub.7O.sub.6NH.sub.4).sub.n. Generally, it is a milky
powder, very easily dissolves in water, and becomes a highly
viscous gel even when a small amount of water is added thereto. It
becomes a viscous solution when being dissolved in water, and
slowly dissolves in sodium carbonate, sodium hydroxide and sodium
phosphate.
[0033] As described above, the ferrite is a metal oxide which is
subjected to a heat-treatment process (i.e., sintering process) at
a temperature of about 600-1400 .degree. C, and the sintered metal
oxide powder has low cohesion, and thus does not provide a molded
material in a process of molding the ferrite. For this reason,
according to the present invention, ammonium alginate is added to
the ferrite in order to increase the formability of the
ferrite.
[0034] Namely, the binder PVA is not used in the process of molding
the ferrite in the present invention, so that a process of
preparing a solution of the binder can be omitted, thus making the
mixing process simple. Accordingly, the ferrite can be molded using
a simple process.
[0035] The ammonium alginate is added to the ferrite in an amount
of 3 wt%, and water is added thereto while the mixture is stirred.
Then, due to the above-described properties of the ammonium
alginate, the ferrite can be dried and molded. The method of
manufacturing the electronic component for RF allocations
comprising the ferrite will now be described in further detail with
reference to FIG. 1. FIG. 1 is a process flow chart showing a
method of manufacturing an electronic component for RF applications
comprising a ferrite by sintering according to a preferred
embodiment of the present invention.
[0036] As shown therein, ammonium alginate is added to a ferrite to
form a mixture, and water is added thereto while the mixture is
stirred to form a gel (S1). As described above, the ammonium
alginate is added to the ferrite in an amount of 3 wt%.
[0037] The ferrite that is used in the present invention is a
spinel ferrite having a composition of M.sub.XFe.sub.(3-X)O.sub.4,
wherein M is at least one of Mg and Co, and X is an integer of 1 or
2.
[0038] The spinel ferrite is a ferrite having a spinel structure
that is a crystalline structure which can be seen in an oxide
represented by a chemical formula of XYA, similar to spinel
(MgAl.sub.2O.sub.4). The spinel structures are divided into a
normal spinel structure and an inverse spinel structure and
generally exhibit ferromagnetic or ferromagnetic properties.
[0039] In the normal spinel structure, X.sup.2+ metal ions occupy
tetrahedral sites and Y.sup.3+ metal ions occupy octahedral sites
in a matrix composed of cubic closed-packed oxygen ions. On the
other hand, in the inverse spinel structure, the tetrahedral sites
are occupied by Y.sup.3+, and the octahedral sites are occupied by
half X.sup.2+ and half Y.sup.3+.
[0040] The normal spinel structure and the inverse spinel structure
comprise eight formula units XY.sub.2O.sub.4 per unit cell, and
crystals having this structure generally exhibit ferromagnetic or
ferromagnetic properties.
[0041] Then, a step (S2) of drying the gel to form a dried material
is carried out. In this step, the gel is preferably dried at a
temperature between 85 .degree. C and 95 .degree. C. More
preferably, the gel is dried at a temperature of 90 .degree. C. The
drying step yields the dried material in which the ferrite and the
ammonium alginate remain and from which the water has been
removed.
[0042] Then, a step (S3) of grinding the dried material to produce
a ferrite powder coated with the ammonium alginate is carried
out.
[0043] Then, a step (S4) of subjecting the ferrite powder to
compression molding is carried out. As described above, it is
difficult to mold a general ferrite, because the ferrite has a
relatively low cohesion; however, according to the present
invention, the ferrite powder can be easily molded due to the
ammonium alginate.
[0044] The step of subjecting the ferrite powder to compression
molding is preferably carried out by compressing the ferrite powder
with a load of 2-6 tons.
[0045] Then, a step (S5) of sintering the compression-molded
ferrite powder is carried out, thereby manufacturing an electronic
component for RF applications.
[0046] The efficiency of an antenna among electronic components for
RF applications is greatly influenced by the magnetic loss tangent
and permeability thereof. Particularly, a decrease in the magnetic
loss tangent of the antenna leads to a very great increase in the
efficiency thereof, and an increase in the permeability of the
antenna leads to an increase in the aspect ratio thereof,
indicating that a more miniaturized antenna can also be
manufactured.
[0047] Table 1 below shows the change in efficiency of the ferrite
according to the dielectric loss tangent and magnetic loss tangent
of the ferrite.
TABLE-US-00001 TABLE 1 Dielectric Loss Tangent Efficiency 0.001
0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.01 Magnetic 0.01
0.85 0.84 0.83 0.82 0.81 0.80 0.79 0.78 0.78 0.76 Loss 0.02 0.74
0.73 0.72 0.72 0.71 0.69 0.69 0.68 0.68 0.67 Tangent 0.03 0.65 0.64
0.64 0.63 0.62 0.61 0.61 0.60 0.60 0.59 0.04 0.57 0.57 0.56 0.56
0.55 0.55 0.54 0.54 0.53 0.52 0.05 0.51 0.50 0.50 0.49 0.49 0.48
0.48 0.47 0.47 0.47 0.06 0.46 0.45 0.45 0.44 0.44 0.43 0.43 0.43
0.42 0.42 0.07 0.41 0.40 0.40 0.40 0.39 0.39 0.39 0.38 0.38 0.37
0.08 0.37 0.36 0.36 0.36 0.35 0.35 0.35 0.35 0.34 0.34 0.09 0.33
0.33 0.33 0.32 0.32 0.32 0.32 0.31 0.31 0.31 0.1 0.30 0.29 0.29
0.29 0.29 0.29 0.28 0.28 0.28 0.28
[0048] As can be seen in Table 1 above, as each of the dielectric
loss tangent and magnetic loss tangent of the ferrite having a
permeability of 10 and a permittivity of 10 increases, the
efficiency of the ferrite greatly decreases.
[0049] FIGS. 2 and 3 show a comparison of permeability and magnetic
loss tangent between an electronic component for RF applications
manufactured according to the method of a preferred embodiment of
the present invention and an electronic component for RF
applications manufactured according to a conventional method.
Specifically, FIG. 2 is a graphic diagram showing the permeability
and magnetic loss tangent of an electronic component for RF
applications manufactured according to a conventional method, and
FIG. 3 is a graphic diagram showing the permeability and magnetic
loss tangent of an electronic component for RF applications
manufactured according to the method of a preferred embodiment of
the present invention. For reference, the electronic component
manufactured according to the conventional method indicates the
ferrite molded using PVA as a binder, and the electronic component
for RF applications manufactured by the method of the preferred
embodiment of the present invention indicates the ferrite to which
ammonium alginate has been added.
[0050] As can be seen in FIGS. 2 and 3, the ferrite molded
according to the preferred embodiment of the present invention has
a low magnetic loss tangent and a high permeability compared to the
ferrite molded using PVA according to the conventional method.
[0051] As used herein, the term "permeability" is a coefficient
indicating the ratio, in any substance, of the magnetic flux
density (B) to the magnetic field strength (H), and is expressed by
p.
[0052] More specifically, the permeability is a coefficient
indicating how the magnetic flux easily passes. Thus, as the
permeability (.mu.) increases, the magnetic flux more easily
passes. Accordingly, when the external magnetic flux comes in, as
the permeability increases, the magnetization more easily
occurs.
[0053] The magnetic flux has the same meaning as the current of
electric force and means the degree of operation as a magnetic
material. In the electronic component for RF applications, the term
"magnetic material" is not frequently used, but in the case in
which a ferrite is used, the permeability of the ferrite should be
considered.
[0054] As used herein, the magnetic loss tangent, that is, tangent
delta as graphically shown in FIGS. 2 and 3, is an indicator of
dielectric loss. The tan 5 which is expressed by the ratio of the
imaginary part to the real part of the complex permittivity of
dielectric material is often called "loss tangent".
[0055] Namely, when the permeability (i.e., real part) is assumed
as .mu..sub.1, the imaginary part is expressed as .mu..sub.2, and
the magnetic loss tangent is expressed as the ratio of .mu..sub.2
to .mu..sub.1.
[0056] Accordingly, the magnetic loss tangent of the electronic
component for RF applications according to the preferred embodiment
of the present invention is 0.03 which is lower than that (0.06) of
the ferrite molded using PVA according to the conventional method.
Namely, the present invention can reduce the magnetic loss tangent
of the ferrite by about 50% compared to the conventional method. In
addition, according to the present invention, the permeability of
the ferrite is increased from 7 to 9, indicating that the present
invention increases the permeability by about 30% compared to the
conventional method.
[0057] Although the preferred embodiment of the present invention
has been described for illustrative purposes, those skilled in the
art will appreciate that various modifications, additions and
substitutions are possible, without departing from the scope and
spirit of the invention as disclosed in the accompanying
claims.
* * * * *