U.S. patent application number 10/831428 was filed with the patent office on 2004-10-14 for forming method of magnetic body, magnetic body, and printed circuit board.
Invention is credited to Kawai, Hideharu, Matsuzaki, Toru.
Application Number | 20040201134 10/831428 |
Document ID | / |
Family ID | 19065320 |
Filed Date | 2004-10-14 |
United States Patent
Application |
20040201134 |
Kind Code |
A1 |
Kawai, Hideharu ; et
al. |
October 14, 2004 |
Forming method of magnetic body, magnetic body, and printed circuit
board
Abstract
A method of forming a magnetic body, alternative to a ferrite
core, on a printed circuit board is provided. A printed circuit
board is set in a mold and injection molding is conducted. The mold
comprises a fixed plate, an intermediate plate and a movable plate.
A cavity in the intermediate plate is filled with a melted material
(i.e., mixture of resin and magnetic filler) supplied via a sprue
and a runner. A cavity in the movable plate is also filled with the
material supplied to the cavity in the intermediate plate through a
hole in the printed circuit board. When a magnetic body for noise
control is directly injection molded onto the printed circuit board
in such a way, no gap appears between the magnetic body and the
printed circuit board. As a result, the magnetic body functions
well as desired.
Inventors: |
Kawai, Hideharu;
(Nagoya-shi, JP) ; Matsuzaki, Toru; (Nagoya-shi,
JP) |
Correspondence
Address: |
DAVIS & BUJOLD, P.L.L.C.
FOURTH FLOOR
500 N. COMMERCIAL STREET
MANCHESTER
NH
03101-1151
US
|
Family ID: |
19065320 |
Appl. No.: |
10/831428 |
Filed: |
April 23, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10831428 |
Apr 23, 2004 |
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10209394 |
Jul 30, 2002 |
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6758999 |
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Current U.S.
Class: |
264/267 |
Current CPC
Class: |
H01F 27/2804 20130101;
H05K 2203/1327 20130101; H01F 17/0006 20130101; H01F 41/0246
20130101; H05K 1/0233 20130101; H01F 2017/065 20130101; Y10T
428/24917 20150115; H05K 2201/086 20130101; H05K 1/165 20130101;
H01F 17/06 20130101 |
Class at
Publication: |
264/267 |
International
Class: |
H01F 005/00; B29C
031/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 1, 2001 |
JP |
2001-233559 |
Claims
1-8. (CANCELED).
9. A printed circuit board on which a magnetic body is formed by a
method of: preparing a melted material by mixing and melting at
least a magnetic filler and a binder including at least one resin,
setting the printed circuit board into a mold, and performing
molding to the printed circuit board using the melted material,
wherein the magnetic body is formed on at least one side of the
printed circuit board, and the magnetic body is formed to cover at
least a portion of a circuit pattern on the printed circuit
board.
10. The printed circuit board according to claim 9, wherein said
magnetic body is formed such that the magnetic body is appressed to
said printed circuit board.
11. The printed circuit board according to claim 9, wherein said
performing molding step includes an injection molding.
12. The printed circuit board according to claim 11, wherein a
gate, used as an inflow opening for supplying said melted material
to a cavity of said mold during the injection molding step, is one
of a pin gate, a side gate and a submarine gate.
13. The printed circuit board according to claim 9, wherein: the
printed circuit board further comprises; at least one through hole,
a first surface side, and a second surface side, wherein the
through hole forms a passageway for the melted material to
communicate with both the first surface side and the second surface
side of the printed circuit board, and the magnetic body is formed
on both sides of the printed circuit board.
14. The printed circuit board according to claim 9, wherein said
magnetic body is formed from one soft ferrite, hard ferrite,
amorphous in Fe, Fe--Si, Fe--Si--Al, Fe--Se--Cr, Fe--Ni, Fe--Cr and
Co system, and Fe-based nanocrystal.
15. The printed circuit board according to claim 9, wherein said
binder is selected from thermoplastic resin such as EVA
(Ethylene-Vinyl acetate copolymer), EVOH (Ethylene-Vinyl
alcohol-Copolymer, PVC (PolyVinylChloride), CPE (Chlorinated
polyethylene), CA (Cellulose-Acetate), POM (PolyOxyMethylene), PA
(PolyAmide), PAR (Polyarylate), TPU (Thermoplastic Polyurethane),
TPE (Thermoplastic-Elastomer), LCP (Liquid Crystal Plymer0, PEEK
(PolyEtherEtherKetone), PSU (Polysulphone), PES
(PolyEtherSulphone), LLDPE (Linear Low Density Polyethylene), PET
(PolyEthylene Terephthalate), PC 9PolyCarbonate0, PS 9PolyStyrene0,
PPE (PolyPhenyleneEther), PPO (PolyPhenyleneOxide), PPS
(PolyPhenyleneSulfide), PBD (PolyButadiene), PBT (PolyButhylene
Terephthalate), PP (PolyPropylene), PMMA (PolyMethylMethAcrylate),
PMP (Polymethylpentene) and BP (Butyl Phthalate), thermosetting
resin such as EP (Epoxy resin), PDAP (Polydiallyl Phthalate), SI
(Silicone), PF (Phenol-Formaldehyde), UP (Unsaturated Polyseter0,
PI (Polyimide), PUR (Polyurethane0, MF (Melamine-Formaldehyde) and
UF (Urea-Formaldehyde), vulcanized rubber such as SBR
(Styrene-Butadiene Rubber0, NBR (Nitril-Butadiene Rubber), IIR
(Isobutylene-Isoprene Rubber), EPDM (Ethylene-Propylene-Diene
Methylene linkage), CSM (CholroSulfonated Polyethylene), AR
(Acrylic rubber), FR (Fluorine Rubber), VMQ (Silicone Rubber), ECO
(Epichlorhydrin Rubber) and EU (PolyeterUrethane rubber),
polyurethane or silicone thermoplastic rubber, liquid rubber and
elastomer.
16. The printed circuit board according to claim 9, wherein said
circuit pattern is one of a signal line pattern, a power line
pattern, a ground line pattern, a transformer circuit patter and a
choke coil pattern.
17. The printed circuit board according to claim 9, further
comprising: at least one magnetic plate, wherein the at least one
magnetic plate is inserted into the mold containing the printed
circuit board prior to molding a melted material, and the melted
material covers at least a portion of the magnetic plate and the
circuit pattern of the printed circuit board.
18. The printed circuit board according to claim 17, wherein the
magnetic plate is at least one of a sintered ferrite plate and a
magnetic metal plate.
19. A printed circuit board on which a magnetic body is formed by a
method of: preparing a melted material by mixing and melting at
least a magnetic filler and a binder including at least one resin,
setting the printed circuit board into a mold, and performing
molding to the printed circuit board using the melted material,
wherein the magnetic body is formed on at least one side of the
printed circuit board, and the magnetic body is formed to cover at
least a portion of an electronic component on the printed circuit
board.
20. The printed circuit board according to claim 19, wherein said
magnetic body is formed such that the magnetic body is appressed to
said printed circuit board.
21. The printed circuit board according to claim 19, wherein said
performing molding step includes an injection molding.
22. The printed circuit board according to claim 21, wherein a
gate, used as an inflow opening for supplying said melted material
to a cavity of said mold during the injection molding step, is one
of a pin gate, a side gate and a submarine gate.
23. The printed circuit board according to claim 19, wherein: the
printed circuit board further comprises; at least one through hole,
a first surface side, and a second surface side, wherein the
through hole forms a passageway for the melted material to
communicate with both the first and second surface side of the
printed circuit board, and the magnetic body is formed on both
sides of the printed circuit board.
24. The printed circuit board according to claim 19, wherein said
magnetic body is formed from one of the soft ferrite, hard ferrite,
amorphous in Fe, Fe--Si, Fe--Si--Al, Fe--Si--Cr, Fe--Ni, Fe--Cr and
Co system, and Fe-based nanocrystal.
25. The printed circuit board according to claim 19, wherein said
binder is selected from thermoplastic resin such as (EVA
(Ethylene-Vinyl acetate copolymer), EVOH (Ethylene-Vinyl
alcohol-Copolymer), PVC (PolyVinylChloride), CPE (Chlorinated
polyethylene), CA (Cellulose-Acetate), Pom (PolyOxyMethylene), PA
(PoluAmide), PAR (Polyarylate), TPU (Thermoplastic Polyurethane),
TPE (thermoplastic-Elastomer), LCP (Liquid Crystal Polymer), PEEK
(PolyEtherEtherKetone), PSU (Polysulphone), PES (PolyEtherSulfone),
HDPE (High Density Polyethylene), LDPE (Low Density Polyethylene),
LLDPE (Linear Low Density Polyethylene), PPE (PolyPhenyleneEther),
PPO (PolyPhenyleneOxide), PPS (PolyPhenyleneSulfide), PBD
(PolyButadiene), PBT (PolyButhylene Terephthalate), PP
(PolyPropylene), PMMA (PolyMethylMethAcrylate), PMP
(Polymethylpentene) and BP (Butyl Phthalate), thermosetting resin
such as EP (Epoxy resin), PDAP (Polydiallyl Phthalate), SI
(Silicone), PF (Phenol-Formaldehyde), UP (Unsaturated Polyester),
PI (Polyimide), PUR (Polyurethane), MF (Melamine-Formaldehyde) and
UF (Urea-Formaldehyde), vulcanized rubber such as SBR
(Styrene-Butadiene Rubber), NBR (Nitril-Butadiene Rubber), IR
(Isoprene Rubber, CR (Chloroprene-Rubber), BR (Butadiene Rubber),
IIR (Isobutylene-Isoprene Rubber), EPDM, Ethylene-Propylene-Diene
Methylene linkage), CSM (ChloroSulfonated Polyethylene), AR
(Acrylic rubber), FR (Fluorine Rubber0, VMQ (Silicone Rubber), ECO
(Epichlorhydrin Rubber) and EU (PolyeterUrethane rubber),
polyurethane or silicone thermoplastic rubber, liquid rubber and
elastomer.
26. The printed circuit board according to claim 19, wherein the
electronic component is one of a pin, a resistance, and a
condenser.
Description
FIELD OF THE INVENTION
[0001] This invention relates to a method of forming a magnetic
body, such as a choke or transformer core, on a printed circuit
board, the magnetic body, and the printed circuit board on which
the magnetic body is formed.
BACKGROUND OF THE INVENTION
[0002] FIG. 4A shows a conventional method for providing a ferrite
core and the like on a printed circuit board, for noise control or
for use in transformer and choke coil. In this case, a ferrite core
is formed and split into two pieces in advance. The split ferrite
core pieces 51a, 51b are then attached to a printed circuit board
3, respectively, from both sides and glued to each other via
attachment holes 5, 5 created beforehand.
[0003] However, since a ferrite core is typically molded from
compacted ferrite material by a sintering molding process, it is
difficult to form the core to the desired measurements and shape.
Thus, it is necessary to grind the sinter molded ferrite core to
the desired dimensions after the core is sintered. Also, if the
maximum tolerances of the sintered ferrite core are too great, the
distances to adjacent electronic components on a printed circuit
board must be at least as great as the tolerances, and this could
prevent high density packaging. Moreover, a ferrite core which is
made too thin is likely to break or get chipped when dropped or in
transit.
[0004] Additionally, if the ferrite core pieces 51a, 51b are
attached as above, gaps 57 are likely to appear between the
respective ferrite core pieces 51a, 51b and a circuit pattern 6 on
the printed circuit board 3 as illustrated in FIG. 4B. A gap 57
between the circuit pattern 6 and the ferrite core pieces 51a, 51b
causes a decline in magnetic properties of the ferrite core, which
increases rapidly as the gap 57 increases.
SUMMARY OF THE INVENTION
[0005] An object of the present invention is to provide a magnetic
body, and a manufacturing method thereof, as an alternative to a
ferrite core or similar shape, for noise control and for use in
transformers and choke coils.
[0006] In order to attain the above object, the present invention
discloses a method of forming a magnetic body by preparing a
magnetic material by mixing and melting at least a magnetic filler
and a binder containing one or more kinds of resin, setting a
printed circuit board in a mold, and injection molding to or around
the printed circuit board using the magnetic material, by which the
magnetic body is formed to cover a circuit pattern on the printed
circuit board.
[0007] According to such a forming method, the magnetic body
includes resin as binder, and is thereby more resistant to shocks
than ferrite alone. Owing to injection molding of the body, the
molding tolerances are reduced to 10% of that of the case of
sintering molding. Accordingly, there is no need to grind the
magnetic body after it is formed. Also, it is possible to arrange
the magnetic body close to other electronic components which are
generally provided on a printed circuit board (including a flexible
board). Thus, high density packaging is realized.
[0008] In another aspect of the present invention, the magnetic
body is formed in such a manner that it is appressed to the printed
circuit board as a result of the injection molding process. Wherein
the term "appressed" means that a magnetic body 7 is formed as a
single, unitary body without unwanted gaps therein or unwanted gaps
between the magnetic body and the printed circuit board.
[0009] In this way, a decline in magnetic properties which results
from gaps between the printed circuit board and the magnetic body
is prevented.
[0010] With injection molding, it is easy to have the magnetic body
appressed to the printed circuit board.
[0011] In further aspect of the present invention, a gate for
supplying the melted material to a cavity of the mold is in the
form of pin gate.
[0012] In this case, a cross section of the gate becomes small and
a trace of the gate on the molded magnetic body is not obtrusive,
or clearly distinct. Therefore, the gate can be provided at any
desired position, even when two magnetic bodies (or a magnetic body
and another member) are molded adjacently.
[0013] In another aspect of the present invention, the printed
circuit board has at least one through-hole in an area where the
magnetic body is formed, and material is supplied to form the
magnetic body on both sides of the printed circuit board via the
through-hole.
[0014] In this way, the magnetic body is formed on both sides of
the printed circuit board at one time, and it is not necessary to
use adhesives and the like to hold the magnetic body fast to the
printed circuit board.
[0015] In another aspect of the present invention, the magnetic
body is formed to cover an electronic component mounted on the
printed circuit board.
[0016] The covered electronic component is protected from noise.
The electronic component to be covered may be a pin, resistance or
condenser. Other electronic components can be covered as well.
[0017] As explained above, such a magnetic body can function to the
full extent, and it does not need be ground after formed.
[0018] Additionally, the magnetic body may be formed on only one
side of the printed circuit board.
[0019] On such a printed circuit as well, the magnetic body can be
set adjacent to other electronic components, and high density
packaging can be attained.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
[0020] The invention will now be described, by way of example, with
reference to the accompanying drawing, in which:
[0021] FIGS. 1A-1C are explanatory views which illustrate the
forming of a magnetic body 7 for noise control or for use as a
transformer or choke coil on a printed circuit board 3 according to
the present invention.
[0022] FIGS. 2A and 2B are explanatory views which illustrate
forming of the magnetic body 7 in a mold.
[0023] FIGS. 3A-3D are explanatory views of a magnetic body 43 for
use in transformer, formed according to the present invention.
[0024] FIGS. 4A and 4B are explanatory views of prior art using
ferrite core pieces 51a, 51b for noise control.
[0025] FIGS. 5A-5C are explanatory views of an experiment which
measures effect by making a magnetic body fast to a printed circuit
board.
DETAILED DESCRIPTION OF THE INVENTION
[0026] FIGS. 1A-1C, 2A and 2B show how a printed circuit board 3
according to the present invention is produced. With regard to
components in those figures, the same reference numbers as those in
FIGS. 4A and 4B are used to represent the same components, so far
as such use of the same numbers does not cause unnecessary
confusion. As an example, a case is described in which a magnetic
body for noise control is provided in a position X on the printed
circuit board 3 of FIG. 1A. As in the prior art, attachment holes
5, 5 are created in the printed circuit board 3 in advance. The
printed circuit board 3 is then set in a mold 11 as shown in FIG.
2A to perform the injection molding process. This mold 11 comprises
a fixed plate 11a, an intermediate plate 11b and a movable plate
11c. A melted material 11d comprised of a magnetic material filler
and a binder is filled into a cavity 17b via a sprue 13, a runner
15 and a gate 16.
[0027] FIG. 2B is a sectional view taken along the line B-B in FIG.
2A. The cavity 17b on the intermediate plate 11b communicates to a
cavity 17c on the movable plate 11c via one or more holes 5 in the
printed circuit board 3. The material 11d supplied to the cavity
17b reaches and fills the cavity 17c through one or more holes 5,
5. With regard to components of the material 11d to be filled, soft
ferrite is used as a magnetic filler, and PA12 is used as binder.
In this example, the gate 16, which is an inflow opening which
supplies the material to the cavity 17b, is in the form of pin
gate. However, the gate 16 may be in the form of side gate or
submarine gate.
[0028] FIG. 1B shows a portion of the printed circuit board 3 after
direct injection molding by which, for example, a magnetic body 7
for noise control is formed on the printed circuit board 3. The
magnetic body 7 appears similar to conventional ferrite cores
pieces 51a, 51b. However, as can be seen in FIG. 1C which is a
sectional view taken along the line A-A in FIG. 1B, no gap 57
appears in the magnetic body 7 or between the magnetic body 7 and
the printed circuit board 3. Consequently, the magnetic body 7 for
noise control can function well and without degradation of its
magnetic properties.
[0029] An experiment was conducted on respective cases in which the
magnetic body 7 is appressed to the printed circuit board 3 by the
method of the present invention and in which the magnetic body 7 is
not appressed to the printed circuit board 3. FIG. 5A shows the
case in which the magnetic body 7 is appressed to the printed
circuit board in accordance with the present invention. As shown, a
magnetic body mixed resin and ferrite is appressed to and around a
measuring cable 21. FIG. 5B shows the case in which the magnetic
body is not appressed to the printed circuit board according to the
present invention and gaps 57 of 0.5 mm are formed between the
measuring cable 21 and respective pieces of the magnetic body 23.
FIG. 5C is a graph showing the result of measurement by impedance
analyzer 25 of impedance frequency characteristics in both cases. A
lateral axis represents frequency and a longitudinal axis
represents impedance. A full line shows the case of having no gap
(FIG. 5A), and a dotted line shows the case of having gaps (FIG.
5B). As can be seen from this graph, when the magnetic body mixed
resin 23 is appressed to the measuring cable 21 by the method of
the present invention, superior impedance frequency characteristics
were achieved.
[0030] In other words, from this graph, it is understood that
higher impedance is achieved at any frequency in the case of having
no gap compared to the case of having gaps. The higher the
impedance is, the higher and superior the noise absorption is.
[0031] A magnetic body 7 of the present invention is also break
resistant since PA12 is used as binder. Accordingly, the magnetic
body 7 does not easily break or get chipped, unlike the ferrite
core pieces 51a, 51b, which break easily. In addition, since the
magnetic body 7 is formed as a single, unitary body extending to
both sides of the printed circuit board 3, gluing is not necessary,
as in the case of ferrite core pieces 51a, 51b. Also, since the
forming tolerance is reduced to 10% of that of the case in using a
sintered product, post-forming processing like grinding becomes
unnecessary, and thus it is possible to simplify the manufacturing
process. By the same reason, the distances to adjacent electronic
components can be made smaller, and thus high density packaging can
be realized.
[0032] In the above, an embodiment of the present invention is
described. However, the present invention is not limited to the
above embodiment, and other modifications and variations are
possible within the scope of the present invention.
[0033] For instance, in the present embodiment, soft ferrite is
used for magnetic material. However, other materials such as hard
ferrite, amorphous in Fe, Fe--Si, Fe--Si--Al, Fe--Si--Cr, Fe--Ni,
Fe--Cr, and Co system, Fe-based nanocrystal can be used. In
addition, the magnetic filler made from such magnetic materials can
be formed in any shape, such as round, flat, etc.
[0034] Also, the binder can be thermoplastic resin such as EVA
(Ethylen-Vinylacetate copolymer), EVOH
(Ethylene-Vinylalcohol-Copolymer), PVC (PlyVinylChloride), CPE
(Chlorinated polyethylene), CA (Cellulose-Acetate), POM
(PolyOxyMethylene), PA (PolyAmide), PAR (Polyarylate), TPU
(Thermoplastic Polyurethane), TPE (Thermoplastic-Elastomer), LCP
(Liquid Crystal Polymer), PEEK (PolyEtherEtherKetone), PSU
(Polysulphone), PES (PolyEtherSulfone), HDPE (High Density
Polyethylene), LDPE (Low Density Polyethylene), LLDPE (Linear Low
Density Polyethylene), PET (PolyEthylene Terephthalate), PC
(PolyCarbonate), PS (PolyStyrene), PPE (PolyPhenyleneEther), PPO
(PolyPhenyleneOxide), PPS (PolyPhenyleneSulfide), PBD
(PolyButadiene), PBT (PolyButhylene Terephthalate), PP
(PolyPropylene), PMMA (PolyMethylMethAcrylate), PMP
(Polymethylpentene) and BP (Butyl Phthalate), thermosetting resin
such as EP (Epoxy resin), PDAP (Polydiallyl Phthalate), SI
(Silicone), PF (Phenol-Formaldehyde), UP (Unsaturated Polyester),
PI (Polyimide), PUR (Polyurethane), MF (Melamine-Formaldehyde) and
UF (Urea-Formaldehyde), vulcanized rubber such as SBR
(Styrene-Butadiene Rubber), NBR (Nitril-Butadiene Rubber), IR
(Isoprene Rubber), CR (Chloroprene-Rubber), BR (Butadiene Rubber),
IIR (Isobutylene-Isoprene Rubber), EPDM (Ethylene-Propylene-Diene
Methylene linkage), CSM (ChloroSulfonated Polyethylene), AR
(Acrylic rubber), FR (Fluorine Rubber), VMQ (Silicone Rubber), ECO
(Epichlorhydrin Rubber) and EU (PolyeterUrethane rubber),
polyurethane or silicone thermoplastic rubber, liquid rubber or
elastomer.
[0035] In addition, and for example, a magnetic transformer body
43, as shown in FIG. 3B, may be formed on the printed circuit board
3 on which three attachment holes 41 are created as shown in FIG.
3A. In this case as well, the magnetic transformer body 43 having
an 8-shaped cross section as shown in FIG. 3C can be formed
appressed to the printed circuit board 3. Furthermore, when setting
the printed circuit board 3 in the mold, it is possible to insert a
sintered ferrite plate 45 or a magnetic metal plate 45 in the
cavity before performing the injection molding. Then, it is
possible to form a magnetic body 7 containing a sintered ferrite
plate 45 as shown in FIG. 3D.
[0036] Moreover, a magnetic body 7 for choke coil may be formed on
the printed circuit board 3. It is also possible to form a magnetic
body 7 only on one side of the printed circuit board 3.
Additionally, the circuit pattern 6 can be a signal line, power
line, ground line, transformer circuit pattern or choke coil
pattern.
* * * * *