U.S. patent application number 09/846363 was filed with the patent office on 2002-02-21 for semiconductor device having heat radiating member.
Invention is credited to Fukatsu, Akihiro, Harada, Yoshiharu, Kinouchi, Kan, Saito, Mitsuhiro.
Application Number | 20020021553 09/846363 |
Document ID | / |
Family ID | 26591802 |
Filed Date | 2002-02-21 |
United States Patent
Application |
20020021553 |
Kind Code |
A1 |
Fukatsu, Akihiro ; et
al. |
February 21, 2002 |
Semiconductor device having heat radiating member
Abstract
A semiconductor device has a case, a printed circuit board, a
fin, and a ceramic substrate mounting a semiconductor element
thereon. The case contains the printed circuit board, the ceramic
substrate and the fin. The fin and the case radiate heat
transmitted from the ceramic substrate. The fin has protrusions on
a contact face facing a contact face of the case. The fin contacts
the case though the protrusions when the fin is fixed to the case.
The protrusions serve as heat radiating path.
Inventors: |
Fukatsu, Akihiro;
(Anjo-city, JP) ; Kinouchi, Kan; (Okazaki-city,
JP) ; Saito, Mitsuhiro; (Obu-city, JP) ;
Harada, Yoshiharu; (Okazaki-city, JP) |
Correspondence
Address: |
LAW OFFICE OF DAVID G POSZ
2000 L STREET, N.W.
SUITE 200
WASHINGTON
DC
20036
US
|
Family ID: |
26591802 |
Appl. No.: |
09/846363 |
Filed: |
May 2, 2001 |
Current U.S.
Class: |
361/688 ;
257/E23.105 |
Current CPC
Class: |
H05K 7/20445 20130101;
H01L 2924/0002 20130101; H01L 2924/0002 20130101; H01L 23/3677
20130101; H01L 2924/00 20130101 |
Class at
Publication: |
361/688 |
International
Class: |
H05K 007/20 |
Foreign Application Data
Date |
Code |
Application Number |
May 12, 2000 |
JP |
2000-140554 |
Mar 14, 2001 |
JP |
2001-72444 |
Claims
What is claimed is:
1. A semiconductor device comprising: a substrate having a
semiconductor element; a heat radiating member for radiating heat
transmitted from the substrate; a body member supporting the
substrate and the heat radiating member; protrusions formed on one
of contact surfaces of the heat radiating member and the body
member facing each other; wherein the heat radiating member
contacts the body member through the protrusions.
2. A semiconductor device according to claim 1, wherein: the one of
the contact surfaces is formed in a saw blade-like shape having
concavity portions and convexity portions, wherein the convexity
portions correspond to the protrusions.
3. A semiconductor device according to claim 1, wherein: tip
portions of the protrusions are deformed when the heat radiating
member is fixed to the body member.
4. A semiconductor device according to claim 1, wherein: tip
portions of the protrusions are stuck into another one of the
contact surfaces when the heat radiating member is fixed to the
body member.
5. A semiconductor device according to claim 1, wherein the heat
radiating member is fixed to the body member by use of a screw.
6. A semiconductor device according to claim 1, wherein the
semiconductor element is mounted on the substrate.
7. A semiconductor device according to claim 1, wherein the body
member is a case containing the substrate and the heat radiating
member.
8. A semiconductor device according to claim 1, wherein the
protrusions extend from the one of contact surfaces.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon Japanese Patent Application
Nos. 2000-140554 filed on May 12, 2000, and 2001-72444 filed on
Mar. 14, 2001, the contents of which are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to a semiconductor device having a
ceramic substrate on which a semiconductor element is disposed, and
a heat radiating member which is fixed to the ceramic substrate so
that the heat radiating member radiates heat transferred through
the ceramic substrate.
[0004] 2. Description of the Related Art
[0005] Recently, semiconductor devices have been required to
satisfy high performance, for example, large scale integration and
application of high power thereto. Accordingly, power consumption
in the semiconductor devices may increase with the large scale
integration and the high power application.
[0006] On the other hand, while a base plate on which a
semiconductor element is disposed and a case in which the
semiconductor element is contained are required to be
miniaturized.
[0007] Therefore, it is difficult to radiate heat from the
semiconductor device sufficiently because of the increase of the
power consumption and a decrease of a radiating heat area in the
device based on the miniaturization.
[0008] A prototype as shown in FIGS. 7A to 7C was studied to solve
the above-mentioned problem. FIG. 7A shows a cross sectional view
of a ECU (Electric Controlling Unit) for a vehicle as the
semiconductor device. FIG. 7B is a cross sectional view taken along
line VIIB-VIIB in FIG. 7A.
[0009] A ceramic substrate 21 constituting a hybrid IC (Integrated
Circuit) that includes an LSI and a high power IC is disposed on a
printed circuit board 25 through lead terminals 29 which
electrically connect the hybrid IC and the printed circuit board
25. Moreover, the ceramic substrate 21 is fixed to a fin (heat
radiating member) 23 directly. The ceramic substrate 21, the
printed circuit board 25, and the fin 23 are collectively disposed
in a case 24.
[0010] In this structure, heat radiation can be improved by fixing
the ceramic substrate having the hybrid IC directly to the heat
radiating fin 23.
[0011] Incidentally, the printed circuit board 25 is fixed to the
case 24 by using screws 26. Similarly, the fin 23 is fixed to the
case 24 and the printed circuit board 25 by using screws 27, 28.
Accordingly, the heat radiating fin 23 contacts an inner wall of
the case 24 when the fin 23 is fixed to the case 24 as shown in
FIGS. 7A and 7B. Therefore, heat generated in the ceramic substrate
21 by semiconductor elements in the power IC is externally radiated
from the case 4 through the fin 23. In addition, even when the case
24 holds several ceramic substrates, a whole dimension of the case
24 can be miniaturized by fixing the several ceramic substrates to
the fin 23 in common.
[0012] Usually, a surface of the printed circuit board and each
electrically connecting portion are covered and protected by a
moisture-proof material such as a humid-sealing. The portion which
needs a moisture-proof described above is covered by the
moisture-proof material that is coated by spray and the like after
the ceramic substrate 21 and the fin 23 are mounted on the printed
circuit board 25. Then, the printed circuit board 25 is put in the
case 24. Therefore, the moisture-poof material adheres to the fin
23 or the case 24 occasionally. FIG. 7C is a enlarged view showing
a portion around a contacting interface between the case 24 and the
fin 23.
[0013] Usually, moisture-proof material has a heat insulating
characteristic. Therefore, in the case that a moisture-proof
material K0 adheres to the interface between the case 24 and the
fin 23, heat radiation of the device becomes worse because heat
resistance between the case 24 and the fin 23 increases by the
moisture-proof material K0.
[0014] To avoid adhering of the moisture-proof material to the
interface between the case 24 and the fin 23, a rigorous process
control or special structure is required. Thus, it may take much
time to assemble the printed circuit board 25 and the case 24, or
structure of the fin 23 or the case 24 becomes complicated.
[0015] In addition, the heat radiation of the device also become
worse in the case that a contact surface of the case 24 or the fin
23 is deformed by an error in process, that is, in the case that
the contact surface is not flat. This is because a contact area
between the case 24 and the fin 23 is reduced. Thus, accuracy in
processing of the case 24 and the fin 23 is required to make the
contact surface flat.
SUMMARY OF THE INVENTION
[0016] This invention has been conceived in view of the background
as described above and an object of the invention is to provide a
semiconductor device in which heat radiating path is secured.
[0017] According to the invention, protrusions are formed on at
least one of surfaces of a body member of a semiconductor device
such as a case and a heat radiating member fixed to the body
member. The heat radiating member contacts the body member through
the protrusions. The protrusions serve as a heat radiating
path.
[0018] Other objects, features and advantages of the present
invention will become more apparent from the following detailed
description made with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a schematic plan view showing a semiconductor
device of a first embodiment;
[0020] FIG. 2A is a schematic cross sectional view showing the
semiconductor device taken along line IIA-IIA in FIG. 1;
[0021] FIG. 2B is a schematic cross sectional view showing the
semiconductor device taken along line IIB-IIB in FIG. 1;
[0022] FIG. 3A is an enlarged sectional view showing a portion of
an interface between a case 4 and a fin 3 of the semiconductor
device;
[0023] FIG. 3B is an enlarged sectional view showing a portion of
an interface between a case 4 and a fin 3 of the semiconductor
device;
[0024] FIG. 4 is an enlarged sectional view showing a portion of an
interface between a case 4 and a fin 3 of the semiconductor
device;
[0025] FIG. 5 is a graph showing a relationship between contact
rate between the case 4 and the fin 3 and thermal resistance
between the case 4 and the fin 3;
[0026] FIGS. 6A and 6B are other examples showing protrusions of
the case or the fin;
[0027] FIG. 7A is a schematic cross sectional view of a
semiconductor device as a prototype;
[0028] FIG. 7B is a schematic cross sectional view showing the
semiconductor device taken along line IIVB-IIVB in FIG. 7A; and
[0029] FIG. 7C is an enlarged sectional view showing a portion of
an interface between a case 4 and a fin 3 of the semiconductor
device.
DESCRIPTION OF THE EMBODIMENTS
[0030] Specific embodiments of the present invention will now be
described hereinafter with reference to the accompanying drawings
in which the same or similar component parts are designated by the
same or similar reference numerals.
[0031] Referring to FIGS. 1, 2A and 2B, a semiconductor device 100
is utilized for an ECU for a vehicle, for example.
[0032] A ceramic substrate 1, which is made of alumina or the like
having a good heat radiating characteristic, constitutes a hybrid
IC (HIC). Electric parts such as semiconductor elements, resistors
or capacitors (not shown) are mounted on or formed on the ceramic
substrate 1. The ceramic substrate 1 is fixed to a fin (heat
radiating member) 3 having a block shape with an adhesion 2 made of
silicone rubber and the like. The fin 3 is made of a metal having a
good heat radiating characteristic, such as aluminum.
[0033] The ceramic substrate 1 and the fin 3 are put in a case 4
which is made of a metal having a good heat radiating
characteristic, such as aluminum. A printed circuit board 5 is also
put in the case 4. The printed circuit board 5 is supported by the
case 4 at supporting portions 4a. Screws 6 fix the printed circuit
board 5 to the case 4.
[0034] The fin 3 is pinched between the inner wall of the case 4
and the printed circuit board 5, and is fixed to the case 4 and the
printed circuit board 5 respectively with a screw 8 and a screw 7.
Accordingly, the fin 3 is fixed to the case 4 in contact with the
inner wall of the case 4.
[0035] The ceramic substrate 1 fixed to the fin 3 is electrically
connected to the printed circuit board 5 through plural lead
terminals 9. A connecter 10, which is electrically connected to an
external device (not shown), is provided with the case 4 so that
the connecter 10 penetrates a wall of the case 4. The connecter 10
is electrically connected to the printed circuit board 5 through a
lead portion 10a thereof disposed in the case 4.
[0036] The semiconductor device 100 includes the ceramic substrate
1, the fin 3 and the printed circuit board 5 electrically connected
to the ceramic substrate 100 in the case 4. Moreover, the fin 3
contacts and is fixed to the case 4. In this semiconductor device
100, heat generated by the semiconductor elements and the like or
by the ceramic substrate 1 is transmitted by fin 3 to the case 4,
and is radiated from the case 4.
[0037] The semiconductor device 100 is assembled as follows.
[0038] First, the fin 3 mounted on the ceramic substrate 1 is fixed
to the printed circuit board 5 by the screw 7. Next, the ceramic
substrate land the connecter 10 are electrically connected to the
printed circuit board 5. Next, the printed circuit board 5 and
electrical connecting portions are protected by a moisture-proof
material such as a humid-sealing that is sprayed to the surface of
the printed circuit board 5. Then, the printed circuit board 5 on
which the parts such as the fin 3 is mounted and to which the
moisture-proof material is applied is put in the case 4, and the
printed circuit board 5 and the fin 3 are fixed to the case 4 by
the screws 6 and 8 respectively, so that the semiconductor device
100 is assembled.
[0039] FIGS. 3A and 3B show an interface between the case 4 and the
fin 3. Especially, FIG. 3A shows a state before the fin 3 is fixed
to the case 4 by the screw 8, while FIG. 3B shows a state after the
fin 3 is fixed to the case 4 by the screw 8. A contact face of the
fin 3 (heat radiating member) contacting the case 4 is formed in
concavity and convexity shape like a saw blade. That is, the
contact face of the fin 3 has protrusions 11 as convex portions
protruded from the contact surface of the fin 3. In other words,
the protrusions 11 extend from the contact surface of the fin 3.
Incidentally, the protrusions 11 are formed by a cutting process or
a die process. In other words, the protrusions 11 are made of
material the same as that of fin 3.
[0040] Moreover, the protrusions 11 have tip portions that are
sharp toward the case 4.
[0041] The protrusions 11 contact a contact face of the case 4 so
that the sharp tip portions of are deformed by screwing up the fin
3. A moisture-proof material K1 may be adhered to the contact face
of the fin 3 or the case 4 when the moisture-proof material is
applied to the printed circuit board 5 and the electrical
connecting portions, or when the printed circuit board 5 is put in
the case 4.
[0042] However, even if the moisture-proof material K1 is disposed
on the contact face, the protrusions 11 thrust the moisture-proof
material K1 away to contact the case 4 sufficiently. Namely, the
tip portions of the protrusions 11 contact the case 4 by deforming
themselves. Even if the contact face of the fin 3 or the case 4 has
an undulation, that is, even if the contact face of the fin 3 or
the case 4 is not flat, the contact area is secured because the fin
3 comes in contact with the case 4 with deforming the tip portions
of the protrusions 11.
[0043] In other words, the contact area between the fin 3 and the
case 4 becomes enough to radiate the heat by approximately
controlling a number and a size or a degree of deforming of the
protrusions 11. In this embodiment, a heat radiating path between
the fin 3 and the case 4 is secured by a simple structure such as
the protrusions 11 extending from the contact face of the fin 3.
Incidentally, protrusions are also formed on the contact face of
the case 4 instead of the contact face of the fin 3 by the cutting
process or the die process.
[0044] In addition, as shown in FIG. 4, the tip portions of the
protrusions 11 may be stuck into the contact face of the case 4 to
contact the case 4. In this case, the contact area is secured by
the tip portions stuck into the contact face of the case 4. The tip
portions of the protrusions 11 can be stuck into the case 4 when
the fin 3 is harder than the case 4 (in the case that the case 4 is
made of resin, for example).
[0045] FIG. 5 shows a relationship between heat resistance
generated between the case 4 and the fin 3, and a contact rate
between the case 4 and the fin 3. Here, the contact rate represents
a ratio of an area of the tip portions of the protrusions 11 (a
height of the protrusions is, for example, 0.3 mm) contacting the
contact face of the case 4 with respect to an entire area of the
contact face of the fin 3.
[0046] When the contact rate is 10%, the heat resistance is reduced
by about 50% in comparison with the case that the contact rate is
5%. It is preferable that the contact rate is approximately 10% or
more to secure heat radiating characteristic in practical use.
[0047] In addition, since heat radiating characteristic of the
semiconductor device 100 is improved by the protrusions 11, the
ceramic substrate 1 and the fin 3 can be disposed in the vicinity
of the connecter 10 in the ECU, for example. Thus, wiring
resistance in the semiconductor device 100 can be reduced, so that
power saving can be achieved in the semiconductor device 100.
Moreover, it becomes possible to miniaturize the printed circuit
board 5, the heat radiating area in the semiconductor device 100,
and the dimensions of the semiconductor device 100
conclusively.
[0048] Incidentally, each protrusion 12 may have a pointed tip
portion or a flat tip portion. Namely, a shape of the each
protrusion 12 may be a pencil-like shape or in a rectangular shape
as shown in FIGS. 6A and 6B. In other words, the protrusions 12 may
be a member extending from the contact surface of the fin 3 or the
case 4 and having a point, or a member extending from the contact
surface of the fin 3 or the case 4 and having a flat top.
[0049] In the case that tip portions of the protrusions 11 shown in
FIGS. 6A and 6B contact the contact face of the fin 3 or the case 4
by being deformed or stuck into the contact face when the fin 3 is
attached to the case 4, the heat radiating path is secured between
the fin 3 and the case 4.
[0050] Incidentally, the fin 3 may be fixed to the case 4 by
another manner except a screw.
[0051] Such changes and modifications are to be understood as being
within the scope of the present invention as defined by the
appended claims.
* * * * *