U.S. patent application number 09/730016 was filed with the patent office on 2001-11-08 for semiconductor device mounting structure and feeding-side charger with heat radiating unit.
Invention is credited to Kajiura, Katsuyuki.
Application Number | 20010038526 09/730016 |
Document ID | / |
Family ID | 18421668 |
Filed Date | 2001-11-08 |
United States Patent
Application |
20010038526 |
Kind Code |
A1 |
Kajiura, Katsuyuki |
November 8, 2001 |
Semiconductor device mounting structure and feeding-side charger
with heat radiating unit
Abstract
In a feeding-side charger, a heat transfer unit (23), which
comes into contact with a heat radiating duct (16) fixed with a
power circuit board (18), is fixed to the power circuit board (18)
in which a power conversion circuit is formed. Each main body (22)
of a plurality of MOSFETs (21) mounted on the power circuit board
(18) comes into contact with the heat transfer unit (23) with a
silicone sheet (24) being interposed therebetween.
Inventors: |
Kajiura, Katsuyuki;
(Kariya-shi, JP) |
Correspondence
Address: |
WOODCOCK WASHBURN KURTZ
MACKIEWICZ & NORRIS LLP
46th Floor
One Liberty Place
Philadelphia
PA
19103
US
|
Family ID: |
18421668 |
Appl. No.: |
09/730016 |
Filed: |
December 5, 2000 |
Current U.S.
Class: |
361/700 |
Current CPC
Class: |
H01L 2924/0002 20130101;
H01L 2924/0002 20130101; H05K 7/20909 20130101; H01L 2924/00
20130101 |
Class at
Publication: |
361/700 |
International
Class: |
H05K 007/20 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 10, 1999 |
JP |
11-352082 |
Claims
1. A semiconductor device mounting structure, wherein a heat
transfer unit is fixed to a circuit board on which semiconductor
devices are mounted, said heat transfer unit coming into contact
with a heat radiating unit provided contiguous with said circuit
board, and wherein main bodies of said semiconductor devices
mounted on said circuit board come into contact with said heat
transfer unit.
2. A semiconductor device mounting structure, as set forth in claim
1, wherein an insulation sheet having thermal conductivity is
interposed between said heat transfer unit and said semiconductor
devices.
3. A semiconductor device mounting structure, as set forth in claim
1, wherein said semiconductor devices are those of a molded type
and come into contact with said heat transfer unit in a state, in
which said main bodies are pressed against said heat transfer unit
by means of a fixing member that is fixed to said heat transfer
unit.
4. A semiconductor device mounting structure, as set forth in claim
3, wherein said heat transfer unit is formed into a rectangular
prism-like shape extending along said circuit board and has
longitudinally parallel side faces thereof, contiguous with a
fixing face which comes into contact with said circuit board, to be
abutment faces for said semiconductor devices, and wherein same
numbers of said semiconductor devices come into contact with each
of said abutment faces respectively.
5. A feeding-side charger, comprising: said power circuit board, in
which a power conversion circuit that converts a commercial
alternating current into a high-frequency alternating current is
formed; and a heat radiating duct as said heat radiating unit,
wherein said power circuit board is disposed so as to be parallel
with one side of said heat radiating duct, wherein power
semiconductor devices incorporated into said power conversion
circuit are mounted on said power circuit board in accordance with
said semiconductor device mounting structure as set forth in claim
1.
6. A semiconductor device mounting structure, as set forth in claim
2, wherein said semiconductor devices are those of a molded type
and come into contact with said heat transfer unit in a state, in
which said main bodies are pressed against said heat transfer unit
by means of a fixing member that is fixed to said heat transfer
unit.
7. A semiconductor device mounting structure, as set forth in claim
6, wherein said heat transfer unit is formed into a rectangular
prism-like shape extending along said circuit board and has
longitudinally parallel side faces thereof, contiguous with a
fixing face which comes into contact with said circuit board, to be
abutment faces for said semiconductor devices, and wherein same
numbers of said semiconductor devices come into contact with each
of said abutment faces respectively.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a mounting structure for
semiconductor devices such as power MOSFETs and a feeding-side
charger comprising the semiconductor device mounting structure.
[0003] 2. Description of the Prior Art
[0004] A conventional electromagnetic induction system feeding-side
charger, such as one used to charge a battery of an electric
automobile, comprises a power circuit board having formed therein a
power conversion circuit for converting a commercial alternating
current to a high-voltage high-frequency alternating current. The
power conversion circuit comprises, for example, a
rectification/power factor improving circuit and a resonance
converter. The resonance converter is constituted by four (4) or
eight (8) bridge connected power MOSFETs.
[0005] As is known, MOSFETs generate much heat when they are in
operation. Therefore the MOSFETs are mounted on a heat radiating
unit fixed on a circuit board. The heat radiating unit is made of,
for example, an aluminum alloy and is provided with heat radiating
fins for radiating heat, transferred from the MOSFETs, to the
atmosphere. The radiating unit continues to cool the MOSFETs by
radiating heat transferred from the MOSFETs to the atmosphere. In
order to secure a sufficient heat radiating capacity from heat
radiating fins, the mounting area of a heat radiating unit is
designed to be remarkably larger than the mounting area of the
MOSFET main bodies.
[0006] On the other hand, since smaller feeding-side chargers have
been demanded, there is now a demand for smaller power circuit
boards which govern the size of a feeding-side charger. This has
triggered a demand for the reduction in mounting area of the heat
radiating unit of MOSFETs whose mounting area occupies a large
portion on a circuit board.
[0007] However, when a heat radiating unit having a smaller
mounting area is used, the MOSFETs mounted thereon cannot be cooled
sufficiently, and the mounting density of the MOSFETs cannot be
increased. Due to this, the mounting area of the power MOSFETs
cannot be reduced. These problems apply not only to a case where a
plurality of MOSFETs are mounted but also to a case where a single
power semiconductor device is mounted.
SUMMARY OF THE INVENTION
[0008] The present invention was made with a view to solving the
above problems and the object thereof is to provide a semiconductor
device mounting structure which can improve the cooling efficiency
of semiconductor devices, relative to the mounting area thereof on
a circuit board, so as to increase the mounting density of
semiconductor devices, and a feeding-side charger provided with the
same mounting structure of a semiconductor device.
[0009] With a view to solving the above problems, according to a
first aspect of the present invention, there is provided a
semiconductor device mounting structure wherein a heat transfer
unit, which comes into contact with a heat radiating unit installed
contiguously with the circuit board, is fixed to a circuit board on
which semiconductor devices are mounted, and wherein the main
bodies of the semiconductor devices mounted on the circuit board
come into contact with the heat transfer unit.
[0010] According to the first aspect of the present invention, heat
generated in the main bodies of the semiconductor devices when they
are put in operation is transferred to the heat transfer unit, with
which the main bodies of the semiconductor devices come into
contact, and is then transferred therefrom to the heat radiating
unit for radiation therefrom. Thus, when compared with the
conventional mounting structure, in which heat from semiconductor
devices is radiated by a heat radiating unit directly connected on
a circuit board, since heat from semiconductor devices according to
the mounting structure of the present invention is radiated by the
heat radiating unit having a great heat radiating capacity, which
can be provided irrespective of the mounting area on a circuit
board, the heat radiating capacity per mounting area for mounting
the heat transfer unit replacing the conventional heat radiating
unit, on a circuit board, can be increased.
[0011] The present invention may be more fully understood from the
description of the preferred embodiments of the invention, which
will be described below, together with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] In the drawings;
[0013] FIG. 1 is a diagrammatic perspective view showing a typical
mounting structure for MOSFETs.
[0014] FIG. 2 is a perspective view showing a typical feeding-side
charger.
[0015] FIG. 3 is a diagrammatic perspective view showing the
interior of a main body of the same charger.
[0016] FIG. 4 is an exploded perspective view showing a MOSFET
mounting structure.
[0017] FIG. 5 is a front view showing an assembling process of the
MOSFET mounting structure.
[0018] FIG. 6 is similarly a front view showing the assembling
process.
[0019] FIG. 7 is similarly a front view showing the assembling
process.
[0020] FIG. 8 is similarly a front view showing the assembling
process.
[0021] FIG. 9 is similarly a front view showing the assembling
process.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] Referring to FIGS. 1 to 9, an embodiment of the present
invention will be described, below, in which the present invention
is embodied into a power semiconductor device mounted on a power
circuit board provided in an electromagnetic induction system
feeding-side charger.
[0023] The electromagnetic induction system charger comprises, as
shown in FIG. 2, a feeding-side charger 10 installed in a specified
charging area and a receiving-side charger installed in a vehicle
and not shown. The feeding-side charger 10 converts a commercial
alternating current to an alternating current of high voltage and
high frequency and supplies electricity to the receiving-side
charger by electromagnetic induction. The receiving-side charger
converts an alternating current of high frequency, supplied from
the feeding-side charger by electromagnetic induction, to a direct
current and charges batteries.
[0024] As shown in FIG. 2, the main body of a feeding-side charger
10 is constituted by a lower frame 11 and a main body cover 12
adapted to cover an upper portion of the lower frame 11. The
feeding-side charger 10 comprises a feeding coupler 13 adapted to
connect to a receiving-side charger. A coupler accommodating
portion 15 covered with a coupler cover 14 is provided on a side
face of the main body.
[0025] As shown in FIG. 3, a heat radiating duct 16 as a vertically
extending heat radiating unit is fixed to a rear part of a bottom
face of the lower frame 11 in the interior of the main body of the
feeding-side charger 10. The heat radiating duct 16, inside which a
plurality of heat radiating fins 16a (shown in FIG. 1) are
provided, is made of an aluminum alloy. The lower end opening of
the heat radiating duct 16 communicates with the outside through an
exhaust opening, which is provided in the bottom of the lower frame
11 and is not shown, and electric fans 17 are provided on an upper
end opening thereof to supply air into the heat radiating duct
16.
[0026] The electric fans 17 introduce outside air into the main
body cover 12 from an intake opening, which is not shown and is
provided in a front part of the bottom of the lower frame 11, and
the outside air passes through the outside of a front face 16b of
the heat radiating duct 16 and then is supplied into the heat
radiating duct 16.
[0027] A power circuit board 18 is fixed to the front side of the
heat radiating duct 16. A power conversion circuit, which converts
a commercial alternating current into an alternating current of
high voltage and high frequency, is provided on the power circuit
board 18. The power conversion circuit has a rectification/power
factor improving circuit and a resonant converter. The
rectification/power factor improving circuit comprises a smoothing
electrolytic condenser 19. The resonance converter comprises a
bridge circuit comprising power MOSFETs 21 (shown in FIGS. 1, 4),
as semiconductor devices and power semiconductor devices, which are
connected to each other in parallel, and resonance coils 20. The
smoothing electrolytic condenser 19 and the resonance coils 20 are
fixed to a side face 16c of the heat radiating duct 16. As shown in
FIG. 1, respective electronic components other than the smoothing
electrolytic condenser 19 of the rectification/power factor
improving circuit are mounted on a front face 18a of the power
circuit board 18.
[0028] As shown in FIG. 1, the eight (8) MOSFETs 21 constituting
the bridge circuit are of a molded type and are mounted on a back
face 18b of the power circuit board 18. To be specific, the
respective MOSFETs 21 are mounted by soldering the terminals 21a
thereof to the board 18 so that main bodies 22 of the respective
MOSFETs 21 are erect on the back face 18b of the power circuit
board 18. Note that respective electronic components of the power
conversion circuit other than the resonance coils 20 and the
respective MOSFETs 21 are mounted on a front face 18a of the power
circuit board 18.
[0029] A heat transfer unit 23 is fixed to the area of the back
face 18b side of the power circuit board 18, on which the
respective MOSFETs 21 are mounted, with a silicone sheet 24
functioning as an insulation sheet being interposed therebetween.
As shown in FIG. 4, the heat transfer unit 23 is made of a block of
aluminum alloy and formed into a rectangular prism-like
configuration extending along the power circuit board 18. A second
fixing face 23b of the heat transfer unit 23, which is opposite to
a first fixing face 23a that functions as a fixing face coming into
contact with the back face 18b of the power circuit board 18, comes
into contact with the front face 16b of the heat radiating duct 16.
Further, provided in the first fixing face 23a are a pair of first
fixing holes 23c and a pair of second fixing holes 23d.
[0030] Furthermore, each four (4) main bodies 22 of the respective
MOSFETs 21 come into contact with each of both abutment faces 23e
of the heat transfer unit 23, which are contiguous with and
parallel in a longitudinal direction to the first fixing face 23a
of the heat transfer unit 23, via the silicone sheet 24. To be
specific, heat radiating portions 22a (shown in FIG. 4) provided on
the main bodies 22 of the respective MOSFETs 21 come into contact
with the heat transfer unit 23 with the silicone sheet 24 being
interposed therebetween. Note that no MOSFET 21 comes into contact
with both side faces 23f orthogonal to the longitudinal direction
of the heat transfer unit 23 and the power circuit board 18.
[0031] The main bodies 22 of the respective MOSFETs 21 are pressed
and fixed to the heat transfer unit 23 by means of angle materials
25 as a fixing material with the silicone sheet 24 being interposed
therebetween. To be specific, heat radiating portions 22a provided
in the main bodies 22 of the respective MOSFETs 21 come into
contact with the angle materials 25 with the silicone sheet 24
being interposed therebetween. The angle materials 25 are made of
an aluminum alloy similar to the heat transfer unit 23 and, as
shown in FIG. 4, are formed into longitudinally elongate bodies
having an L-shaped consistent cross section. The angle materials 25
are then fixed to the heat transfer unit 23 without coming into
contact with the front face 16b of the heat radiating duct 16.
[0032] The silicone sheet 24, which is interposed between the
respective MOSFETs 21 and the heat transfer unit 23 and between the
heat transfer unit 23 and the power circuit board 18, is an
insulation sheet having high thermal conductivity (for example, a
heat radiating sheet commercially available from SHINETSU
CHEMICALS). As shown in FIG. 4, the silicone sheet 24 comprises a
rectangular central portion 26 sized so as to cover the first
fixing face 23a of the heat transfer unit 23, longer-side wing
portions 27 provided along longer sides of the central portion 26
and shorter-side wing portions 28 provided similarly along shorter
sides of the central portion 26.
[0033] Provided in the central portion 26 are first through holes
26a corresponding to the first fixing holes 23c in the heat
transfer unit 23 and second through holes 26b corresponding to
second fixing holes 23d in the heat transfer unit 23.
[0034] The respective longer-side wing portions 27 comprise a first
wing portions 27a, a second wing portions 27b and a third wing
portions 27c from the central portion 26 toward the outside in that
order. In addition, the respective shorter-side wing portions 28
are provided with folded portions 28a on both sides thereof.
[0035] Referring to FIGS. 5 to 9, an assembling process of the
MOSFET mounting structure will be described below.
[0036] As shown in FIG. 5, in mounting a MOSFET 21, first the
central portion 26 of the silicone sheet 24 disposed on the back
face 18b of the power circuit board 18 is fixed to the back face
18b of the circuit board 18 by inserting a first fixing member 29,
which comes into contact with the front face 18a of the power
circuit board 18, into a second fixing member 30 adapted to be
inserted into each of the second fixing holes 23d in the heat
transfer unit 23.
[0037] Next, as shown in FIG. 6, as well as the second fixing
member 30 being inserted into each of the second fixing holes 23d
in the heat transfer unit 23, a fixing screw 32 penetrating through
the first fixing member 29 fixed to the power circuit board 18 and
the second fixing member 30 is then screwed into each of
female-threaded holes formed in bottom faces of the respective
second fixing holes 23d, so that the heat transfer unit 23 is fixed
to the back face 18b of the circuit boar 18 with the central
portion 26 of the silicone sheet 24 being interposed
therebetween.
[0038] Next, as shown in FIG. 7, with the respective longer-side
wing portions 27 of the silicone sheet 24 being folded downward so
as to enable the first wing portions 27a to come into contact with
the respective abutment faces 23e of the heat transfer unit 23, the
respective MOSFETs 21 are mounted to the back face 18b of the power
circuit board 18 by soldering the terminals 21a thereof. Thus, the
main bodies 22 of the respective MOSFETs 21 come into contact with
the respective abutment faces 23e of the heat transfer unit 23 via
the first wing portions 27a.
[0039] Next, as shown in FIG. 8, with the respective longer-side
wing portions 27 being folded back upward so that the second wing
portions 27b are interposed between the respective MOSFETs 21 and
the angle materials 25, the respective angle materials 25 are fixed
to the heat transfer unit 23 by fixing screws which screw into the
heat transfer unit 23. When this occurs, the main bodies 22 of the
respective MOSFETs 21 come into contact with abutment sides 23e of
the heat transfer unit 23 via the first wing portions 27 in a state
in which the main bodies 22 of the respective MOSFETs 21 are
pressed against the angle materials 25 via the second wing portions
27b upwardly folded back.
[0040] Next, as shown in FIG. 9, each shorter-side wing portions 28
of the silicone sheet 24 are folded downward and are then fixed
with fixing screws 34 which are screwed into respective side faces
23f of the heat transfer unit 23. Furthermore, the respective
longer-side wing portions 27 are then folded back downward and the
third wing portions 27c come into contact with the external faces
25a of the angle materials 25 as well as the respective folded
portions 28a of the respective shorter-side wing portions 28 come
into contact with an external faces 25a of the angle materials 25
from the outside of the third wing portions 27c. Then, the folded
portions 28a and the third wing portions 27c superposed on the
external faces 25a of the angle members 25 are interposed together
with the second wing portions 27b, which come into contact with an
internal faces 25b of the angle materials 25, with nylon rivets 35
penetrating through the angle materials 25. Finally, the second
fixing face 23b of the heat transfer unit 23 is pressed to contact
with the front face 16b of the heat radiating duct 16 by screwing
fixing screws 36, inserted from holes 18c formed in the power
circuit board 18 through into the respective first fixing holes 23c
of the heat transfer unit 23 into the heat radiating duct 16.
[0041] Next, the function and effects of the semiconductor mounting
structure constructed as described above will be described.
[0042] (1) Heat generated at the main bodies 22 of the respective
MOSFETs 21 is transferred to the heat transfer unit 23 via the
silicon sheet 24 and then to the heat radiating duct 16, against
which the heat transfer unit 23 is brought into press contact,
whereby the heat so transferred is then radiated. Thus, when
compared with the conventional mounting structure where heat from
MOSFETs is radiated by a heat radiating unit directly connected
onto the power circuit board 18, since in the present invention the
heat from the MOSFETs 21 is radiated by means of the heat radiating
duct 16 which can be provided irrespective of the mounting area on
the power circuit board 18 and has a large heat radiating capacity,
the heat radiating capacity per mounting area for mounting the heat
transfer unit 23 on the power circuit board 18, which replaces the
conventional heat radiating units, becomes higher.
[0043] As a result of this, the cooling efficiency of the
respective MOSFETs 21 relative to the mounting area on the power
circuit board 18 can be improved, whereby the respective MOSFETs 21
can be further cooled or, by increasing the mounting density of a
plurality of MOSFETs 21, it is possible to miniaturize the power
circuit boards 18.
[0044] In addition, in the feeding-side charger 10 electromagnetic
induction system, the main body of the charger can be miniaturized
by miniaturizing the power circuit board 18.
[0045] (2) When there occurs a failure in a main bodies 22 of the
MOSFETs 21, the respective MOSFETs 21 are insulated from the heat
radiating duct 16 with the silicone sheet 24 having insulating
properties and interposed between the respective MOSFETs 21 and the
heat transfer unit 23. Therefore, even if there occurs a failure in
the MOSFET 21, no electric current is allowed to flow through the
heat radiating duct 16.
[0046] (3) The silicone sheet 24 interposed between the heat
transfer unit 23, with which the main bodies 22 of the respective
MOSFETs 21 come into contact, and the angle material 25 are
provided so as to come into contact with the abutment face 23e of
the heat transfer unit 23 and the internal face of the angle
material 25 over a more sufficiently wide area range than the area
range of the contact areas of the main bodies 22. Therefore, the
shortest creepage distance along the surface of the silicone sheet
24 between the respective MOSFETs 21 and the heat transfer unit 23
and between the respective MOSFETs 21 and the angle materials 25
becomes remarkably longer than the shortest distances between the
respective MOSFETs 21 and the heat transfer unit 23 and between the
respective MOSFETs 21 and the angle materials 25. As a result of
this, if there occurs a failure in the MOSFET 21, surface discharge
via the silicone sheet 24 hardly occurs, so that it is difficult
for electric current to flow through the heat radiating duct 16 or
the angle material 25. Due to this, even if the mounting density of
the respective MOSFETs 21 on the power circuit board 18 is
increased, superior insulating properties can be secured.
[0047] (4) Heat generated in the main bodies 22 of molded type
MOSFETs is efficiently transferred, to the heat transfer unit 23,
from the main bodies 22 which are pressed against the heat transfer
unit 23 by the angle material 25 fixed to the heat transfer unit 23
and come into contact with the heat transfer unit 23. Thus, in a
case where molded type MOSFETs are used, the heat radiating
capacity per mounting area for mounting the heat transfer unit 23
on the power circuit board 18 can be increased.
[0048] (5) The plurality of molded type MOSFETs in the same numbers
are arranged to come into contact with each of the longitudinally
parallel abutment faces 23e, respectively, which are contiguous
with the first fixing face 23a of the rectangular prism-like heat
transfer unit 23 extending along the power circuit board 18. In
this case, the mounting area of the heat transfer unit relative to
the cooling capacity of the respective MOSFETs 21 becomes smaller
than in a case where a plurality of MOSFETs 21 are arranged to come
into contact with respective side faces orthogonal to the power
circuit board 18 in a disk-like or regular polygonal heat transfer
unit with a center axis perpendicular to the power circuit board
18. Thus, the combined mounting areas of those of the plurality of
MOSFETs 21 plus the heat transfer unit 23 become smaller. As a
result of this, a plurality of MOSFETs 21 can be mounted within a
minimized mounting area.
[0049] Embodiments other than those described above, embodying the
present invention, are listed below.
[0050] In the above embodiment, the heat transfer unit is not
limited to the rectangular prism-like heat transfer unit on which
the main bodies of the plurality of molded type semiconductor come
into contact with the respective longitudinally parallel side
faces. Alternatively, for example, a heat transfer unit may be
formed into shapes such as a disk-like or regular polygonal shape
having a central axis perpendicular to the power circuit board 18,
in which main bodies of a plurality of molded type semiconductors
may come into contact with respective peripheral faces orthogonal
to the power circuit board 18. In this case, also, the cooling
efficiency of the molded type semiconductor devices can be
improved.
[0051] The semiconductors are not limited to power MOSFETs but it
may be possible to use power semiconductor devices such as bi-polar
power transistors, IGBTs, rectifier devices, thyristors, GTO
thyristors, light-triggered thyristors, TRIACs and SITS. In
addition, the present invention may be applied to a mounting
structure for semiconductor devices other than power semiconductor
devices.
[0052] The present invention may not only be applied to the
mounting structure of molded type semiconductor devices, but also
applied to those of can-type semiconductor devices.
[0053] The circuit board applied to the semiconductor mounting
structure of the invention, in the electromagnetic induction system
feeding-type charger, is not limited to the power circuit board 18
in which the power conversion circuit for converting a commercial
alternating current into a high frequency alternating current is
provided. The present invention may be applied to a mounting
structure for any circuit board with semiconductor devices mounted,
such as a mounting structure for power semiconductor devices in a
power circuit board in which a three-phase inverter circuit is
included for generating an alternating current of a predetermined
frequency from a direct current in a forklift truck adapted to run
or perform loading and unloading operations with a direct current
power source fed from batteries.
[0054] According to the first to fifth aspects of the present
invention, the cooling efficiency of semiconductor devices relative
to the mounting area on the circuit board can be improved so as to
increase the mounting density.
[0055] In addition, according to the second to fifth aspects of the
present invention, no electric current is allowed to flow to the
heat radiating unit side when there occurs a failure in the
semiconductor device and, moreover, the superior insulating
properties can be secured even if the mounting density is
increased.
[0056] In addition, according to the fifth aspect of the present
invention, the entirety of the charger can be miniaturized by
miniaturizing the circuit board.
[0057] While the invention has been described by reference to
specific embodiments chosen for the purposes of illustration, it
should be apparent that numerous modifications could be made
thereto by those skilled in the art without departing from the
basic concept and scope of the invention.
* * * * *