U.S. patent application number 10/960721 was filed with the patent office on 2005-08-18 for electronic part mounting substrate, electronic part, and semiconductor device.
Invention is credited to Deushi, Yuichi, Machida, Masahiro, Noguchi, Takashi, Terui, Makoto.
Application Number | 20050178574 10/960721 |
Document ID | / |
Family ID | 34836186 |
Filed Date | 2005-08-18 |
United States Patent
Application |
20050178574 |
Kind Code |
A1 |
Noguchi, Takashi ; et
al. |
August 18, 2005 |
ELECTRONIC PART MOUNTING SUBSTRATE, ELECTRONIC PART, AND
SEMICONDUCTOR DEVICE
Abstract
An infrared emissive first insulating portion, which radiates
heat transferred from a WCSP corresponding to an electronic part to
a first conductive portion as infrared radiation with high
efficiency, is formed on the first conductive portion lying in a
through hole provided in a printed wiring board with the WCSP
mounted thereon.
Inventors: |
Noguchi, Takashi; (Tokyo,
JP) ; Machida, Masahiro; (Tokyo, JP) ; Terui,
Makoto; (Yamanashi, JP) ; Deushi, Yuichi;
(Tokyo, JP) |
Correspondence
Address: |
RABIN & BERDO, P.C.
Suite 500
1101 14th Street
Washington
DC
20005
US
|
Family ID: |
34836186 |
Appl. No.: |
10/960721 |
Filed: |
October 8, 2004 |
Current U.S.
Class: |
174/535 ;
174/260; 174/264; 174/565; 257/E23.067; 257/E23.105 |
Current CPC
Class: |
H01L 2924/16152
20130101; H05K 2201/099 20130101; H01L 2924/01078 20130101; H01L
2224/05001 20130101; H01L 24/05 20130101; H05K 2201/0959 20130101;
H05K 2201/10977 20130101; H01L 2224/02377 20130101; H01L 2924/01079
20130101; H05K 3/28 20130101; H01L 2924/01019 20130101; H05K 3/3452
20130101; H01L 2224/05569 20130101; H05K 2201/0209 20130101; H01L
2224/05024 20130101; H01L 2224/16 20130101; H05K 2201/10734
20130101; H01L 2224/05008 20130101; H01L 2924/00014 20130101; H01L
2224/05022 20130101; H01L 23/49827 20130101; H05K 1/114 20130101;
H01L 23/3677 20130101; H05K 1/0206 20130101; H01L 2924/00014
20130101; H01L 2224/05599 20130101; H01L 2924/00014 20130101; H01L
2224/05099 20130101 |
Class at
Publication: |
174/052.1 ;
174/260; 174/264 |
International
Class: |
H02G 003/08; H05K
005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 12, 2004 |
JP |
034709/2004 |
Claims
What is claimed is:
1. A substrate for mounting an electronic part thereon, comprising:
a base body having a first main surface and a second main surface
opposite to the first main surface, and a through hole which
penetrates from the first main surface to the second main surface;
a first conductive portion formed on an inner wall surface of the
through hole; and a first insulating portion which is formed on the
first conductive portion and higher in thermal emissivity than the
first conductive portion.
2. A substrate according to claim 1, wherein the first insulating
portion is filled in the through hole.
3. A substrate according to claim 1, further comprising a second
insulating portion higher in thermal emissivity than the first
conductive portion is formed on both or either one of the first
main surface and the second main surface.
4. A substrate according to claim 1, further comprising: a second
conductive portion formed on both or either one of the first main
surface and the second main surface so as to be connected to the
first conductive portion; and a third insulating portion which is
formed on the corresponding second conductive portion and higher in
thermal emissivity than the first and second conductive
portions.
5. A substrate according to claim 4, wherein the second and third
insulating portions are formed on the main surface opposite to the
main surface on which the electronic part is mounted and wherein
the first insulating portion, the second insulating portion and the
third insulating portions are formed continuously.
6. A substrate according to claim 1, wherein the first insulating
portion contains ceramics.
7. A substrate according to claim 6, wherein the ceramics contains
Al.sub.2O.sub.3 as a major component.
8. A semiconductor device, comprising: a base body having a first
main surface and a second main surface opposite to the first main
surface, and a through hole which penetrates from the first main
surface to the second main surface; a first conductive portion
formed on an inner wall surface of the through hole; second
conductive portion formed on the first main surface and the second
main surface so as to be connected to the first conductive portion;
an electronic part mounted on the first main surface, said
electronic part being electrically connected to the second
conductive portion formed on the first main surface; a first
insulating portion which is formed on the first conductive portion
and higher in thermal emissivity than the first conductive portion;
and an external terminal formed on the second conductive portion
provided on the second main surface.
9. A semiconductor device according to claim 8, further comprising
a fourth insulating portion which is formed on the first main
surface so as to cover a surface of the electronic part and is
higher in thermal emissivity than the first and second conductive
portions.
10. A semiconductor device according to claim 8, further comprising
a second insulating portion which is formed on the second main
surface and is higher in thermal emissivity than the first and
second conductive portions.
11. A semiconductor device according to claim 8, further comprising
a third insulating portion which is formed on the second conductive
portion on the second main surface and higher in thermal emissivity
than the first and second conductive portions.
12. A semiconductor device according to claim 8, wherein the
electronic part has protruded conductive portion each electrically
connected to the second conductive portion.
13. A semiconductor device according to claim 12, wherein the
electronic part is a semiconductor chip having circuit
elements.
14. A semiconductor device according to claim 12, wherein the
electronic part is a semiconductor package which includes a
semiconductor chip having circuit elements and has the same outer
size as that of the semiconductor chip.
15. A semiconductor device according to claim 8, wherein the first
insulating portion contains ceramics.
16. A semiconductor device according to claim 15, wherein the
ceramics contains Al.sub.2O.sub.3 as a major component.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an electronic part mounting
substrate, an electronic part, and a semiconductor device in which
an electronic part is mounted on an electronic part mounting
substrate.
[0003] This application is counterpart of Japanese patent
application, Serial Number 34709/2004, filed Feb. 12, 2004, the
subject matter of which is incorporated herein by reference.
[0004] 2. Description of the Related Art
[0005] The development of a technique for radiating heat produced
from an electronic part to the outside with high efficiency has
heretofore been pursued in the field of an electrical
apparatus.
[0006] Thus, a technique for providing a heat radiating part and a
resin high in thermal conductivity on a chip has been known as the
technique for heat radiation (see, for example, the following
patent document 1).
[0007] There is also known a technique for providing a film for
improving thermal emissivity on a chip or a substrate (see, for
example, the following patent document 2).
[0008] Patent Document 1
[0009] Japanese Laid Open Patent Application No. 10-125834
[0010] Patent Document 2
[0011] Japanese Laid Open Patent Application No. 11-67998
[0012] However, the patent document 1 merely discloses that a
material high in thermal conductivity is adopted as a material for
heat radiation.
[0013] Thus, such a configuration is not enough to radiate heat
transferred from the chip into the air with satisfactory
efficiency. There is a fear that heat transferred from the chip to
the substrate in particular is accumulated inside the substrate, so
that the heat is not radiated into the air efficiently.
[0014] Although the patent document 2 has disclosed that the film
high in thermal emissivity is provided on the substrate, a specific
discussion about a heat transfer path from the chip to the film has
not yet been made. Therefore, there is room for improvement if
consideration is given to the fact that the heat is radiated into
the air more efficiently. There is a fear that heat is accumulated
in a heat transfer path set up to attainment of heat produced in
the chip to the film in particular.
SUMMARY OF THE INVENTION
[0015] Therefore, a principal object of the present invention is to
provide an electronic part mounting substrate capable of
efficiently radiating heat produced from an electronic part such as
a chip to the outside, an electronic part and a semiconductor
device in which an electronic part is mounted on an electronic part
mounting substrate.
[0016] According to one aspect of the present invention, there is
provided a substrate for mounting an electronic part thereon, which
includes a base body having a first main surface and a second main
surface opposite to the first main surface, and a through hole
which penetrates from the first main surface to the second main
surface; a first conductive portion formed on an inner wall surface
of the through hole; and a first insulating portion which is formed
on the first conductive portion and higher in thermal emissivity
than the first conductive portion.
[0017] According to the electronic part mounting substrate of the
present invention, an insulating portion higher in thermal
emissivity than a conductive portion formed on an inner wall
surface of a through hole defined in the substrate is formed on the
conductive portion.
[0018] As a result, an insulating portion excellent in thermal
emission, which is provided on a first conductive portion, promotes
the high-efficiency radiation of heat transferred from an
electronic part used as a heat generation source to the first
conductive portion to the outside.
[0019] Thus, an excellent heat radiating effect can be realized by
use of the through hole defined in the substrate without
additionally mounting a radiating part such as a radiating fin.
[0020] According to another aspect of the present invention, there
is provided a semiconductor device which includes a base body
having a first main surface and a second main surface opposite to
the first main surface, and a through hole which penetrates from
the first main surface to the second main surface; a first
conductive portion formed on an inner wall surface of the through
hole; second conductive portion formed on the first main surface
and the second main surface so as to be connected to the first
conductive portion; an electronic part mounted on the first main
surface, said electronic part being electrically connected to the
second conductive portion formed on the first main surface; a first
insulating portion which is formed on the first conductive portion
and higher in thermal emissivity than the first conductive portion;
and an external terminal formed on the second conductive portion
provided on the second main surface.
[0021] According to still another aspect of the present invention,
there is provided an electronic part, mounted on a main surface of
a substrate for mounting the electronic part thereon, which
includes: a protruded conductive portions respectively electrically
connected to conductive portions formed on the main surface of the
substrate; and an auxiliary conductive portion which extends from a
surface of the electronic part different from a surface thereof on
which the protruded conductive portions are formed, to the main
surface of the substrate, said auxiliary conductive portion having
a length provided in the extending direction, which is set as a
length at which face contact with the main surface of the substrate
is enabled upon mounting of the electronic part.
[0022] According to still another aspect of the present invention,
there is provided a semiconductor device which includes a substrate
for mounting an electronic part thereon; and said electronic part
mounted on a main surface of the substrate, said electronic part
including, protruded conductive portions respectively electrically
connected to conductive portions formed on the main surface of the
substrate; and an auxiliary conductive portion which extends from a
surface of the electronic part different from a surface thereof on
which the protruded conductive portions are formed, to the main
surface of the substrate, said auxiliary conductive portion having
a length provided in the extending direction, which is set as a
length at which face contact with the main surface of the substrate
is enabled upon mounting of the electronic part.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] While the specification concludes with claims particularly
pointing out and distinctly claiming the subject matter which is
regarded as the invention, it is believed that the invention, the
objects and features of the invention and further objects, features
and advantages thereof will be better understood from the following
description taken in connection with the accompanying drawings in
which:
[0024] FIG. 1 is a schematic cross-sectional view for describing a
first embodiment of the present invention;
[0025] FIG. 2 is a schematic view (part 1) for describing the
outline of a method of measuring a thermal resistance value,
according to the first embodiment of the present invention;
[0026] FIG. 3 is a schematic view (part 2) for describing the
outline of the method of measuring the thermal resistance value,
according to the first embodiment of the present invention;
[0027] FIG. 4 is a view showing the result of measurement of
thermal resistance values, which is obtained in the first
embodiment of the present invention;
[0028] FIG. 5 is a schematic cross-sectional view for describing a
second embodiment of the present invention;
[0029] FIG. 6 is a schematic cross-sectional view for describing a
third embodiment of the present invention;
[0030] FIG. 7 is a view (part 1) for describing metal support
sections employed in the third embodiment of the present invention;
and
[0031] FIG. 8 is a view (part 2) for describing the metal support
sections employed in the third embodiment of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] Preferred embodiments of the present invention will
hereinafter be described with reference to FIGS. 1 through 8.
Incidentally, the drawings merely schematically show the size,
shape and positional relationships of respective components to such
a degree that the present invention can be understood. Thus, the
present invention is by no means limited to the illustrated
examples. In order to make it easy to understand the drawings, some
hatching indicative of cross-sections are omitted except for parts.
Incidentally, embodiments to be described below are simply
preferred examples and illustrated numerical conditions are by no
means limited to them. Similar components illustrated in the
respective drawings are respectively identified by the same
reference numerals, and the description of certain common
components might be omitted.
First Embodiment
[0033] FIG. 1 is a schematic cross-sectional view showing a
packaging structure on which an electronic part or component used
as a heat generation source according to the present embodiment is
mounted (or called also "packaged"). The present embodiment will
explain, as an example, a case in which the electronic component
used as the heat generation source is configured as a WCSP
(Waterlevel Chip Size Package) 30 corresponding to a semiconductor
package having substantially the same outer size as that of a
semiconductor chip, and a heat radiation mechanism is provided in a
printed wiring board 20. Incidentally, the term "substantially the
same" means that such a configuration that the outer size of the
package assumes a size increased up to about 20% with respect to
the outer size of the semiconductor chip as well as such a
configuration that the outer size of the package is just the same
size as the outer size of the semiconductor chip.
[0034] Of CSP having a package size substantially identical to the
outer size of the semiconductor chip, the WCSP is called one of
those fractionalized by dicing or the like after the completion of
all up to an external terminal forming process while remaining in a
wafer state. The printed wiring board is called one in which on the
basis of predetermined circuit design, conductor patterns are
formed on the surface of an insulating base material or conductor
wirings are formed on the surface thereof and thereinside by
patterning. Incidentally, a BGA (Ball Grid Array) or the like may
be used as an electronic part mounted over the printed wiring board
20. This can be selected suitably at random.
[0035] As shown in FIG. 1, the WCSP 30 is mounted over the printed
wiring board 20. Described specifically, second conductive portion
27 provided in the printed wiring board 20 and solder balls 39 each
corresponding to a first protruded conductive portion are
electrically connected to one another in contact with one
another.
[0036] The WCSP 30 corresponding to the electronic part will first
be explained. Since the conventionally known structure can be
applied to the WCSP 30 used herein, its structure example will be
explained below in brief.
[0037] As shown in FIG. 1, a passivation film 34 and a protective
film 35 are sequentially provided on a semiconductor chip 32
provided with circuit elements (not shown) so as to expose the
surface of each of electrode pads 33 each electrically connected to
its corresponding circuit element. The passivation film 34 is
formed of, for example, a silicon oxide film (SiO.sub.2). The
protective film 35 is formed of a film material low in hardness
such as a polyimide resin and suppresses shock against the
semiconductor chip 32 and peeling due to stress between the
semiconductor chip 32 and an encapsulating or sealing film 38 to be
described later. Wiring layers (called also "redistribution wiring
layers") 36 respectively extend in the direction of the center of
the semiconductor chip 32 over the protective film 35. The
electrode pads 33 are electrically individually connected to their
corresponding post portions 37 through the wiring layers 36. The
solder balls 39 corresponding to the protruded conductive portions,
which are formed on their corresponding end faces (or top faces) of
the post portions 37, can be relocated from positions directly
above the electrode pads 33 to desired positions on the upper side
of the semiconductor chip 32 by means of the wiring layers 36.
[0038] The printed wiring board 20 with the WCSP 30 mounted thereon
will be explained subsequently.
[0039] In the printed wiring board 20 employed in the present
embodiment, as shown in FIG. 1, the second conductive portions 27
are formed by patterning on the obverse and reverse surfaces of a
glass epoxy base material 22 used as a base body, i.e., a first
main surface 22a and a second main surface 22b. The second
conductive portions 27 are respectively conductor wirings made of
copper foil (Cu).
[0040] An extend-through hole (called also "viaholes or through
holes") 22c, which extends or penetrates between the obverse and
reverse surfaces (22a and 22b) of the base material 22, is defined
in the base material 22 of the printed wiring board 20. A first
conductive portion 26 is formed on an inner wall surface 22d of the
through hole so as to be continuous with its corresponding second
conductive portions 27. The first conductive portion 26 serves as a
thermal via portion which shares the use of a conductor wiring. As
shown in FIG. 1, stoppers 21 may be formed of a resist material or
the like at the peripheral edge of the through hole 22c on the
second conductive portion 27 connected to its corresponding solder
ball 39. The stoppers 21 have the function of preventing solder to
flow into the through hole 22c upon mounting of the WCSP 30.
[0041] The first conductive portion 26 can be provided by forming
the through hole (indicates by a dotted line in FIG. 1) 22c in the
base material 22 with a drill or the like and thereafter forming
and providing copper on the inner wall surface 22d by plating. The
formation of the first conductive portion 26 is performed before
the second conductive portions 27 are formed on the surface layer
of the base material 22 by patterning.
[0042] Incidentally, the first conductive portion 26 and its
corresponding solder ball 39 may be configured so as to be directly
connected to each other. However, owing to the placement of the
solder ball 39 on the second conductive portion 27 as shown in FIG.
1, alignment accuracy at the mounting of the WCSP 30 can preferably
be relaxed. Since the second conductive portion 27 is formed over
the second main surface 22b as well as inside the through hole 22c
as in the present configurational example, heat can preferably be
transferred to the back surface 22b of the printed wiring board 20
reliably in terms of thermal radiation.
[0043] In the present embodiment, its principal feature resides in
that a first insulating portion 25 higher in thermal emissivity
than the first conductive portion 26 is formed on the first
conductive portion 26 lying in the through hole 22c.
[0044] In the present embodiment, the first insulating portion 25
higher in thermal emissivity than the first conductive portion has
such a structure as to fill up the interior of a hollow portion
defined by the first conductive portion 26 formed on the inner wall
surface of the through hole 22c.
[0045] For instance, a coating material containing ceramics may
preferably be used as the material for the first insulating portion
25. This is used because the coating material containing ceramics
has a high thermal emissivity of 90% or more in most cases as well
as thermal conduction and is capable of realizing high-efficiency
heat radiation. Described specifically, alumina ceramics or the
like containing Al.sub.2O.sub.3 as a major component can be used.
One or the like containing such ceramics as described in, for
example, Japanese Laid Open Patent Application No. 10-279845 can be
suitably used at random. Ceramics or the like added with black
pigments for improving the thermal emissivity may be used.
[0046] When the heat radiation is carried out by only the first
conductive portion 26 that shares the use of the thermal via
portion (inclusive of such a structure that the first conductive
portion 26 fills up the interior of the through hole 22c), a rise
in the ambient temperature around the thermal via portion due to
heat transfer by convention is unavoidable.
[0047] Since, however, the first insulating portion 25 is provided
as in the present embodiment, the heat transferred from the WCSP 30
to the first conductive portion 26 can be thermally radiated (or
called also "emitted") from the first insulating portion 25 to the
outside as infrared radiation.
[0048] As a result, the rise in the ambient temperature around the
thermal via portion 26 can be suppressed and efficient thermal
radiation can be realized.
[0049] Described specifically, thermal conductivity and thermal
emissivity at the time that the through hole 22c is filled with
only copper used for the first conductive portion 26, are
respectively given as about 137 W/m.multidot.K and about 0.03. On
the other hand, as in the present configurational example, thermal
conductivity and thermal emissivity in the case of such a
configuration that the through hole 22c is filled with the alumina
ceramics used for the first insulating portion 25, reach about 161
W/m.multidot.K and about 0.92 respectively.
[0050] Owing to the provision of the first insulating portion in
the through hole 22c, as is apparent from this point of view, the
heat transferred from the electronic part such as the chip can
efficiently be radiated outside.
[0051] Incidentally, the first insulating portion 25 may be formed
on the first conductive portion 26 lying in the through hole 22c
with a predetermined film thickness. As in the present
configurational example, however, a heat radiating effect can
preferably be further promoted by filling up the through hole 22c
with the first insulating portion 25, i.e., embedding the first
insulating portion 25 in the through hole 22c.
[0052] In the present embodiment, a second insulating portion 28
higher in thermal emissivity that the first conductive portion 26
is formed on the second main surface 22b, and a third insulating
portion 29 higher in thermal emissivity than the first conductive
portion 26 is formed on the second main surface 22b with the second
conductive portion 27 interposed therebetween. These are formed so
as to be continuous with the first insulating portion 25. Thus,
higher-efficiency heat radiation can be realized. Incidentally,
each of the second and third insulating portions (28 and 29) used
here is also a coating material containing ceramics in a manner
similar to the first insulating portion 25.
[0053] Such first, second and third insulating portions (25, 28 and
29) can be formed by, for example, applying a liquid
infrared-emissive insulator coating material to a predetermined
area by a spray method and thermally curing it.
[0054] From the above description, the printed wiring board 20
employed in the present embodiment combines a function used as a
wiring board and a function used as an excellent radiating plate,
which makes it possible to carry out high-efficiency heat radiation
by the infrared emissive insulator.
[0055] Subsequently, the verification of the radiating effect of
the printed wiring board 20 having the above-described structure
was done by measuring a "thermal resistance value (.theta.ja)" used
as an index of the radiating effect.
[0056] A summary of a method of measuring thermal resistance values
where electronic parts are set as a WCSP 30 and a BGA 50, will
first be explained with reference to FIG. 2.
[0057] FIG. 2(A) is a schematic view for describing a summary of
the method of measuring the thermal resistance value where the
electronic part is configured as the WCSP 30. The
P-VFLGA48-0606-0.8 manufactured by Oki Electric Industry Co., Ltd.
was used as for the WCSP 30 used here. Incidentally, since the
structure of the WCSP 30 is substantially identical to the
already-described WCSP 30, the description thereof will be omitted.
In the present embodiment, the temperature at the boundary between
the semiconductor chip 32 and the passivation film 34 bonded to the
semiconductor chip 32 was set as a junction temperature (Tj), and
the temperature at a position spaced a predetermined distance away
from the WCSP 30 was set as a reference point temperature (Ta).
[0058] FIG. 2(B) is a schematic cross-sectional view for describing
the summary of the method of measuring the thermal resistance value
where the electronic part is configured as the BGA 50. The
P-BGA352-3535-1.27 manufactured by Oki Electric Industry Co., Ltd.
was used as for the BGA 50 used here. Incidentally, since the
structure of the BGA 50 is substantially similar to the
conventional known wire bonding system, its structure will be
explained below in brief.
[0059] As shown in FIG. 2(B), a semiconductor chip 53 is mounted on
an insulated board 52 with a circuit element (not shown) forming
surface set as the upper side. Electrode pads 54 connected to their
corresponding circuit elements are connected to their corresponding
conductor patterns 55 on the insulated board 52 by wires 56. Thus,
a predetermined circuit element is electrically connected to its
corresponding solder ball 58 corresponding to an external terminal
via a contact 57 provided so as to penetrate between the obverse
and reverse surfaces of the insulated board 52. A resin sealing or
encapsulating film 59, which buries and seals the semiconductor
chip 53, is formed on the insulated board 52. The semiconductor
patterns 55 shown here are formed of copper and the wires 56 are
formed of gold (Au). In the present embodiment, the temperature at
the boundary between the semiconductor chip 53 and the resin
encapsulating film 59 bonded to the semiconductor chip 53 was set
as a junction temperature (Tj), and the temperature at a position
spaced a predetermined distance away from the BGA 50 was set as a
reference point temperature (Ta).
[0060] A specific method of measuring a thermal resistance value
will be explained subsequently with reference to FIG. 2(C).
[0061] As shown in FIG. 2(C), a constant voltage power supply 81
applies a power of 1 W to a resistor R provided in the neighborhood
of a position where a junction temperature (Tj) of each of the
semiconductor chips (32 and 53) is measured, to thereby generate
heat, whereby a thermal saturated state (or called also "thermal
equilibrium state") is formed. Incidentally, the constant voltage
power supply 81 is fine-adjusted by reference to an ammeter 82 and
a voltmeter 83 to supply the power (1 W).
[0062] Then, a constant current power supply 84 is activated to
cause current to flow in a diode D provided in the semiconductor
chip near the resistor R, and a voltage value obtained at this time
is measured by the voltmeter 85, whereby the above junction
temperature (Tj) is calculated. A reference point temperature (Ta)
is measured by means of a thermocouple (not shown) or the like.
[0063] Further, in the present configurational example, measuring
samples different in the insulating portion forming area were
prepared to examine the influence of infrared emissive insulating
portions on thermal resistance values as shown in FIG. 3. Although
a description will be made of a case in which an electronic part is
set as a WCSP, BGA is also similar to it.
[0064] Sample (1): no infrared emissive insulating portion is
formed (see FIG. 3(A)). Incidentally, the sample (1) might be
called plank (1) below.
[0065] Sample (2): an infrared emissive fourth insulating portion
24 is formed from the whole surface of a WCSP to over a first main
surface 22a (see FIG. 3(B)). Incidentally, the insulating portion
is set to a thickness of about 1.times.10.sup.-4 m at this
time.
[0066] Sample (3): infrared emissive first through third insulating
portions (25, 28 and 29) are formed on a second main surface 22b
and inside a through hole 22c in addition to the area described in
the sample (2) (see FIG. 3(C)). Incidentally, the insulating
portions are set to a thickness of about 1.times.10.sup.-4 m and
the corresponding insulating portion is charged into the through
hole 22c.
[0067] A thermal resistance value Oja can be calculated from the
following expression (1) according to the various parameters
obtained in this way:
.theta.ja[.degree. C./W]=(Tj.multidot.Ta) [.degree. C.]/Power [W]
(1)
[0068] Incidentally, the method of measuring the thermal resistance
value is not limited to only the above methods. Measurement
conditions for the parameters (Tj and Ta) are set based on, for
example, JEDEC (Joint Electron Device Engineering Council) standard
or the like. In addition, arbitrary and suitable methods and
measurement conditions can be selected according to purpose and
design.
[0069] FIG. 4 shows the result of measurement of thermal resistance
values Oja. FIG. 4(A) is the result of measurement thereof where
the electronic part is set as a WCSP, and FIG. 4(B) is the result
of measurement thereof where the electronic part is set as a BGA.
In the present embodiment, thermal resistance values placed under
respective conditions with the thermal resistance value of the
plank (1) as a reference value are illustrated as bar graphs.
Further, reduction rates (%) relative to the thermal resistance
value of the plank (1) are described together in addition.
[0070] It was confirmed from the results of measurements shown in
FIGS. 4(A) and 4(B) that even when the electronic part was either
the WCSP or the BGA, the thermal resistance values were
respectively reduced at rates of 6.3% to 12.9% and 4.0% to 6.5%
owing to the provision of the infrared 2o emissive insulating
portions.
[0071] It is understood from this point of view that an improvement
in the efficiency of thermal radiation of the electronic part can
be realized without additionally mounting a radiating part such as
a radiating fin.
[0072] Judging from the result of the sample (2), a satisfactory
heat 25 radiating effect can be obtained even by the structure that
the whole surface of the electronic part is covered with the
corresponding infrared emissive insulating portion. It was further
confirmed that a heat radiating effect was further promoted owing
to the provision of the same insulating portion on the conductive
portion in the through hole and the back surface of the board as in
the sample (3).
[0073] According to the present embodiment as is apparent from the
above description, an insulating portion higher in thermal
emissivity than a conductive portion is formed on the conductive
portion formed on an inner wall surface of a through hole defined
in a printed wiring board or the like on which an electronic part
is mounted.
[0074] As a result, heat transferred from the electronic part to
the insulating portion via the conductive portion can be highly
efficiently radiated from the insulating portion as infrared
radiation. Therefore, a heat radiating effect can be promoted
without additionally mounting a radiating part such as a radiating
fin.
Second Embodiment
[0075] A second embodiment of the present invention will be
explained with reference to FIG. 5.
[0076] While the infrared emissive insulating portions for
promoting the heat radiating effect are being formed on the
substrate for the motherboard with the package mounted thereon in
the first embodiment, the present embodiment is principally
different from the first embodiment in that infrared emissive
insulating portions similar to those employed in the first
embodiment are formed on an interposer board packageable on the
substrate for the motherboard, and a heat radiating insulating
portion is formed on the whole surface of the interposer board so
as to cover an outer surface of an electronic part or component.
Incidentally, the same elements of structure as those already
described in the first embodiment are respectively identified by
the same reference numerals, and their specific description will
therefore be omitted (respective embodiments to be described below
are also similar).
[0077] The present embodiment will explain, as an example, a board
or substrate for an MCM (Multi Chip Module) as a package's
interposer board. The MCM is one obtained by mounting, for example,
a plurality of packages and their peripheral parts and the like on
one high density board and bringing them into module form.
Incidentally, one having a structure with a bare chip mounted
thereon is included in MCM boards in addition to the above.
[0078] Described specifically, as shown in FIG. 5, a plurality of
WCSPs each used as a constituent or component parts such as a flash
memory are formed on an MCM board 70. Incidentally, since the
structure of the WSCP has already been described in the first
embodiment, its description will be omitted.
[0079] In the MCM board 70 employed in the present embodiment,
second conductive portions 77 are formed by patterning on the
obverse and reverse surfaces of a glass epoxy base material 72,
i.e., a first main surface 72a and a second main surface 72b.
[0080] A through hole 72c, which penetrates between the obverse and
reverse surfaces (72a and 72b) of the base material 72, is defined
in the base material 72 of the MCM board 70. A first conductive
portion 76, which serves as a thermal via portion that shares the
use of a conductor wiring, is formed on an inner wall surface 72d
of the through hole. Also the first conductive portion 76 is formed
so as to be continuous with its corresponding second conductive
portions 77 on the first and second main surfaces (72a and
72b).
[0081] Then, a first insulating portion 75 higher in thermal
emissivity than the first conductive portion 76, is formed on the
first conductive portion 76 lying in the through hole 72c. In a
manner similar to the first embodiment even here, the first
insulating portion 75 has a structure in which it fills up, i.e.,
buries the interior of a hollow portion defined by the first
conductive portion 76 on the inner wall surface of the through hole
72c. A second insulating portion 78 higher in thermal emissivity
than the first conductive portion 76 is formed on the second main
surface 72b, and a third insulating section 79 higher in thermal
emissivity than the first conductive portion 76 is formed on the
second main surface 72b with the corresponding second conductive
portion 77 interposed therebetween. They are formed continuous with
the first insulating portion 75.
[0082] In the present configurational example, a heat radiating
fourth insulating portion 74 is formed on the whole area of the
second main surface 72a of the MCM board 70 so as to cover an
electronic part 30.
[0083] Further, in the present embodiment, solder balls 80 each
used as a second protruded conductive portion, which are mountable
on a board or substrate 88 for the motherboard with the MCM board
70 mountable thereon, are formed on the second main surface 72b
side of the MCM board 70.
[0084] According to the present configuration, the solder ball 80
is connected to its corresponding solder ball 39 through a second
conductive portion 77 provided on a main surface 72b of the MCM
board 70, a first conductive portion (not shown) provided within a
through hole (not shown) of the MCM board 70 and electrically
connected to the second conductive portion 77, and a second
conductive portion 77 provided on a first main surface 72a and
electrically connected to the first conductive portion.
[0085] In a manner similar to the first embodiment, the materials
for the first, second and third insulating portions (75, 78 and 79)
used here may preferably use a coating material containing
ceramics, for example. This is because the coating material
containing ceramics has a high thermal emissivity of 90% or more in
most cases as well as thermal conduction and is capable of
realizing high-efficiency heat radiation. Described specifically,
alumina ceramics or the like containing Al.sub.2O.sub.3 as a major
component can be used. One or the like containing such ceramics as
described in, for example, Japanese Unexamined Patent Publication
No. Hei 10(1998)-279845 can be suitably used at random. Ceramics or
the like added with black pigments for improving the thermal
emissivity may be used.
[0086] According to the present embodiment, as is apparent from the
above description, an effect similar to the first embodiment can be
obtained.
[0087] Further, in the present embodiment, the board having such a
heat radiating effect can be applied to an interposer board such as
an MCM board capable of mounting other substrate thereon.
[0088] Furthermore, according to the present embodiment, the heat
radiating insulating portion is formed over the whole surface on
the interposer board 70 so as to cover the electronic part. As a
result, higher-efficiency heat radiation toward the outside can be
realized.
Third Embodiment
[0089] A third embodiment of the present invention will be
explained with reference to FIG. 6.
[0090] The present embodiment is principally different from the
first embodiment in that processing for promoting a heat radiating
effect is mainly effected on the electronic part side.
[0091] As shown in FIG. 6, a principal feature resides in that an
electronic part 40 according to the present embodiment includes an
auxiliary conductive portion (hereinafter might be called "metal
support section") for efficiently transferring heat from the
electronic part 40 to a substrate or board 60 with the electronic
part 40 mounted thereon. Incidentally, a material such as copper
excellent in thermal conduction can be suitably selected at random
as for the metal support section 45.
[0092] The present embodiment will explain, by way of example, a
case in which the electronic part 40 is configured as a WCSP
provided with solder balls 39 each used as a substrate mounting
protruded conductive portion and the substrate 60 is configured as
a printed wiring board.
[0093] In the present embodiment, a first feature resides in that
as shown in FIG. 6, the metal support section 45 extends from over
the surface of the WCSP 40, which is different from the surface on
which the solder balls 39 are formed, to a main surface 60a of the
substrate, and the length of the metal support section 45 as viewed
in its extending direction is equivalent to the length brought into
face contact with the main surface 60a of the substrate.
[0094] Incidentally, the ends of the metal support section 45 as
viewed in the extending direction of the metal support section 45
employed in the present embodiment have shapes bent in the
direction non-opposite to the WCSP 40, i.e., in the direction away
outside from the WCSP. However, the shapes of the ends thereof are
not limited to such shapes. The ends thereof may have portions
brought into contact with the main surface 60a of the substrate.
Thus, the length of the metal support section 45 as viewed in its
extending direction may be such a length or the like that the metal
support section 45 extends through the main surface 60a of the
substrate 60 and is embedded in the substrate 60. Various shapes
can be suitably selected at random according to purpose and design
(the details thereof will be described later).
[0095] At this time, the metal support section 45 may be provided
so as to cover a wide area on an exposed surface of a silicon (Si)
substrate 32 constituting a semiconductor chip 32, of the surface
of the WCSP 40. This is because heat generated from a silicon
surface including a circuit element that serves as a heat
generation source can efficiently be transferred to an insulating
portion 47 and the substrate 60.
[0096] Owing to the provision of such a metal support section
excellent in thermal conduction, heat on the back surface (i.e.,
back surface 32b of the semiconductor chip) and side surfaces
(i.e., side surfaces 32c of the semiconductor chip) of the WCSP 40
are promptly transferred to the insulating portion 47 and further
transferred even to the substrate 60 promptly. That is, since heat
transfer paths between the WCSP 40 and the insulating portion 47
and between the WCSP 40 and the substrate 60 can be reinforced, the
heat from the WCSP 40 can reliably be transferred to the substrate
60.
[0097] Further, in the present embodiment, a second feature resides
in that the infrared emissive insulating portion 47 is formed on
the metal support section 45.
[0098] In the present configurational example, the infrared
emissive insulating portion 47 covers the whole surface of the WCSP
40 including over the metal support section 45 and is formed over
the main surface 60a of the substrate 60. The insulating portion 47
may take a configuration in which it is formed on the metal support
section 45 with a predetermined film thickness. Since, however, the
insulating portion is provided in a wide-ranging region including
over the metal support section 45 in this way, the area of heat
radiation is made larger, thereby making it possible to further
promote a heat radiating effect.
[0099] In a manner similar to the first embodiment, the material
for the insulating portion 47 employed in the present embodiment
may also preferably use a coating material containing ceramics, for
example. This is because the coating material containing ceramics
has a high thermal emissivity of 90% or more in most cases as well
as thermal conduction and is capable of realizing high-efficiency
heat radiation. Described specifically, alumina ceramics or the
like containing Al.sub.2O.sub.3 as a major component can be used.
One or the like containing such ceramics as described in, for
example, Japanese Unexamined Patent Publication No. Hei
10(1998)-279845 can be suitably used at random. Ceramics or the
like added with black pigments for improving the thermal emissivity
may be used.
[0100] The insulating portion 47 can be formed by applying a liquid
infrared-emissive insulator coating material to a predetermined
area from the main surface 60a side of the substrate by, for
example, a spray method after the formation of the metal support
section 45 on the WCSP 40, and thermally curing it.
[0101] Thus, the heat from the WCSP 40, which has been reliably
transferred to the substrate 60 through the metal support section
45, can be converted to infrared radiation with high heat
emissivity by means of the insulating portion 47 and emitted
outside, thereby making it possible to promote a heat radiating
effect.
[0102] Specific examples each illustrative of the shape of the
metal support section 45 will be explained subsequently with
reference to FIG. 7. Each of lower stages of FIGS. 7(A) through
7(C) is a schematic cross-sectional view of the structure shown in
FIG. 6 as viewed from the direction indicated by arrow P in the
figure. Upper stages thereof are developed views of the metal
support sections 45 corresponding to the lower stages.
Illustrations of infrared emissive insulating portions 47 are
omitted here. For the purpose of fixing the metal support section
45 to be described below to the WCSP 40, arbitrary suitable methods
such as a method of heating a molded metal support section 45 at a
predetermined temperature and welding it to the WCSP 40, etc. can
be used.
[0103] The metal support section 451 shown in FIG. 7(A) has such a
shape as to fully cover the whole surface of the WCSP 40. Although
there is a fear of stress concentration due to such a shape, heat
generated from the silicon surface can be reliably transferred to
the corresponding substrate 60 side. Incidentally, such a shape can
be formed by means of an etching process or the like.
[0104] The metal support section 452 shown in FIG. 7(B) is
different from the metal support section 451 shown in FIG. 7(A) in
that it has such a shape as to cover the whole area of a back
surface 32b of a semiconductor chip 32. Owing to the provision of
such a shape, heat generated from the surface of a silicon
substrate constituting the semiconductor chip can be transferred to
the corresponding substrate 60 with efficiency. Incidentally, such
a shape can be formed by means of an etching process or the
like.
[0105] The metal support section 453 shown in FIG. 7(C) has such a
shape as to cover the back surface and side surfaces of a WCSP 40
in a mesh fashion. Since there are formed slits 49 which extend
from a main surface 60a of a substrate to the WCSP 40, the
concentration of stress due to the difference in thermal expansion
coefficient, which occurs in the boundary between the substrate 60
and the WCSP 40, can be relaxed. Since such a flat or plate-shaped
copper plate including mesh patterns can be relatively easily
molded through the use of a die or the like, it is excellent in
manufacturing cost.
[0106] Specific examples of the shapes of the ends of the metal
support sections 45 (451, 452 and 453 (see FIG. 7) or the like),
i.e., the ends thereof brought into contact with main surfaces 60a
of substrates will be explained subsequently with reference to FIG.
8.
[0107] In FIG. 8(A), connecting pins 65, which extend through a
main surface 60a of the substrate and are embedded in the substrate
60, are formed at their corresponding ends of the metal support
section 45. Owing to the provision of such connecting pins 65, a
WCSP 40 mounted on the substrate 60 can be prevented from causing
its position displacement due to external shock and maintained in a
stable mounted state. The metal support section at this time can be
fabricated by, for example, welding connecting pins 65 separately
formed of copper to the ends (positions indicated by Q in FIG.
7(A), for example) of the flat copper plate so as to become normal
to the copper plate. Then, the connecting pins 65 may be fitted in
and fixed to their corresponding pores of the substrate 60, which
has previously been formed by, for example, a drill or the
like.
[0108] FIG. 8(B) is different from FIG. 8(A) in that the ends per
se of the metal support section 45 are respectively connecting pins
67. Since there is no need to weld the connecting pins separately
in the case of such a shape, the present example is excellent in
manufacturing cost. The support section at this time can be
fabricated by processing a flat copper plate in advance in
consideration of portions embedded in the substrate 60, which serve
as connecting pins. In a manner similar to FIG. 8(A), a stable
mounted state can suitably be maintained.
[0109] In FIG. 8(C), the ends of the metal support section 45 are
respectively bent in the direction opposite to the WCSP 40.
Therefore, the present example is excellent in that the suppression
of the degree of freedom of wiring design due to the placement of
the connecting pins does not occur as compared with the structure
that the connecting pins serving as the conductors are embedded
therein.
[0110] Incidentally, the shapes of the infrared emissive insulating
portion and the metal support section are not limited to only the
above-described shapes but can be formed in various ways according
to purpose and design.
[0111] According to the present embodiment, as is apparent from the
above description, since a heat transfer path between an electronic
part and a substrate can be reinforced owing to the provision of a
metal support section, heat produced from the electronic part can
reliably be transferred to the substrate.
[0112] As a result, the heat reliably transferred to the substrate
side can highly efficiently be converted into infrared radiation by
the infrared emissive insulating portion 47, followed by being
radiated, thereby making it possible to promote a heat radiating
effect.
[0113] As mentioned above, the present invention is not limited to
the aforementioned embodiment alone. Thus, the present invention
can be applied by utilizing the above conditions in combination
suitably at random.
[0114] While the present invention has been described with
reference to the illustrative embodiments, this description is not
intended to be construed in a limiting sense. Various modifications
of the illustrative embodiments, as well as other embodiments of
the invention, will be apparent to those skilled in the art on
reference to this description. It is therefore contemplated that
the appended claims will cover any such modifications or
embodiments as fall within the true scope of the invention.
* * * * *