U.S. patent application number 09/789557 was filed with the patent office on 2001-12-20 for power module package having insulator type heat sink attached to rear surface of lead frame and manufacturing method thereof.
This patent application is currently assigned to Fairchild Korea Semiconductor Ltd.. Invention is credited to Im, Eul-bin, Jeon, Gi-young, Kim, Byeong Gon, Lee, Eun-ho.
Application Number | 20010052639 09/789557 |
Document ID | / |
Family ID | 19671820 |
Filed Date | 2001-12-20 |
United States Patent
Application |
20010052639 |
Kind Code |
A1 |
Jeon, Gi-young ; et
al. |
December 20, 2001 |
Power module package having insulator type heat sink attached to
rear surface of lead frame and manufacturing method thereof
Abstract
A power module package in which a heat sink made of an
insulating material is attached directly to a second surface of a
lead frame, on which a down set is provided, and exposed to the
outside, and a manufacturing method thereof are provided. A general
rectangular plate or pre-bent plate may be used as the heat sink.
The heat sink may be attached during a sealing process or through a
separate process performed after the sealing process. The power
module package has an improved heat radiation characteristic.
Inventors: |
Jeon, Gi-young;
(Bucheon-city, KR) ; Im, Eul-bin; (Bucheon-city,
KR) ; Kim, Byeong Gon; (Bucheon-city, KR) ;
Lee, Eun-ho; (Bucheon-city, KR) |
Correspondence
Address: |
ROTHWELL, FIGG, ERNST & MANBECK, P.C.
555 13TH STREET, N.W.
SUITE 701, EAST TOWER
WASHINGTON
DC
20004
US
|
Assignee: |
Fairchild Korea Semiconductor
Ltd.
Kyungki-do
KR
|
Family ID: |
19671820 |
Appl. No.: |
09/789557 |
Filed: |
February 22, 2001 |
Current U.S.
Class: |
257/678 ;
257/E23.052; 257/E23.092 |
Current CPC
Class: |
H01L 2924/3511 20130101;
H01L 2924/1815 20130101; H01L 2224/48091 20130101; H01L 2924/00014
20130101; H01L 2924/181 20130101; H01L 2224/45144 20130101; H01L
2224/48247 20130101; H01L 2224/45015 20130101; H01L 2224/45124
20130101; H01L 24/48 20130101; H01L 24/45 20130101; H01L 2924/01079
20130101; H01L 2924/12036 20130101; H01L 23/49575 20130101; H01L
23/4334 20130101; H01L 2224/48137 20130101; H01L 2924/1532
20130101; H01L 2224/48091 20130101; H01L 2924/00014 20130101; H01L
2224/45144 20130101; H01L 2924/00014 20130101; H01L 2224/45124
20130101; H01L 2924/00014 20130101; H01L 2224/45015 20130101; H01L
2924/00 20130101; H01L 2224/45144 20130101; H01L 2924/00015
20130101; H01L 2224/45124 20130101; H01L 2924/00015 20130101; H01L
2924/00014 20130101; H01L 2224/05599 20130101; H01L 2924/12036
20130101; H01L 2924/00 20130101; H01L 2924/181 20130101; H01L
2924/00012 20130101 |
Class at
Publication: |
257/678 |
International
Class: |
H01L 021/44 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 13, 2000 |
KR |
2000-32383 |
Claims
What is claimed is:
1. A power module package comprising: a lead frame having a first
surface, to which components for a power circuit and a control
circuit are attached and on the center of which a down set is
provided, and a second surface, to which a heat sink is attached,
and edges on which external terminals are provided; a heat sink
having one surface attached directly to the second surface of the
lead frame projected by the down set, and the other surface exposed
to the outside of a power module package, the heat sink being
formed of an insulating material having good heat transfer
properties; components for the power circuit which are mounted on a
portion of the first surface of the lead frame on which the down
set is formed; components for the control circuit which are mounted
on the first surface of the lead frame; and an epoxy molding
compound which encapsulates the lead frame and the heat sink
excluding the external terminals of the lead frame and the one side
of the heat sink.
2. The power module package of claim 1 wherein the heat sink formed
of an insulating material having good heat transfer properties is
composed of plastic or ceramic.
3. The power module package of claim 2, wherein the heat sink is
formed by including at least one of Al.sub.2O.sub.3, AIN,
SiO.sub.2, and BeO.
4. The power module package of claim 1, wherein the heat sink is a
pre-bent plate for preventing package warpage.
5. The power module package of claim 4, wherein the heat sink is
pre-bent less than 100 .mu.m.
6. The power module package of claim 1, wherein the heat sink is
protruded slightly more than the epoxy molding compound.
7. The power module package of claim 1, wherein the heat sink is
protruded 0.05-0.1 mm more than the epoxy molding compound.
8. A method of manufacturing a power module package comprising the
steps of: preparing a lead frame on the center of which a down set
is provided and on the edges of which external terminals are
provided; attaching a plurality of chips for serving as a power
circuit and a control circuit to a first surface of the lead frame
and performing wire bonding; positioning the lead frame to a
molding equipment for attaching a heat sink formed of an insulating
material to a bottom mold die; and sealing the lead frame by an
epoxy molding compound in the molding equipment so that the heat
sink may be attached to the second surface of the lead frame on
which the down set is formed, and that the external terminals and a
surface opposing the surface of the heat sink to which the lead
frame is attached may be exposed to the outside.
9. The method of claim 8, wherein a groove for fixing the heat sink
is formed on the bottom mold die of the molding equipment.
10. The method of claim 9, wherein the depth of the groove is
0.05-0.1 mm from the surface of the bottom mold die.
11. The method of claim 8, wherein the heat sink is composed of
plastic or ceramic including one of Al.sub.2O.sub.3, AIN,
SiO.sub.2, and BeO.
12. The method of claim 8, wherein a pre-bent plate is used as the
heat sink.
13. A method of manufacturing a power module package comprising the
steps of: preparing a lead frame on the center of which a down set
is provided and on the edges of which external terminals are
provided; attaching a plurality of chips for serving as a power
circuit and a control circuit to a first surface of the lead frame
and performing wire bonding; positioning the lead frame to a
molding equipment in which a protrusion portion for attaching a
heat sink to a bottom lower die in a subsequent process is formed;
sealing the lead frame by an epoxy molding compound in the molding
equipment so that a recessed surface including the second surface
of the lead frame, on which the down set is provided, and the
external terminals of the lead frame may be exposed; and attaching
the heat sink to the recessed portion including the second surface
of the lead frame exposed to the outside.
14. The method of claim 13, wherein the height of the protrusion
portion is 1-3 mm
15. The method of claim 13, wherein the heat sink is composed of
materials including one selected from the group consisting of
Al.sub.2O.sub.3, AIN, SiO.sub.2, and BeO.
16. The method of claim 13, wherein the heat sink is attached to
the second surface of the lead frame by a liquid epoxy including a
ceramic-based filler.
17. The method of claim 13, wherein a pre-bent plate is used as the
heat sink in order to prevent package warpage.
18. The method of claim 13, wherein the heat sink is comprised of
multiple layers attached by an adhesive.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a semiconductor package,
and more particularly, to a power module package having improved
heat radiating characteristics.
[0003] 2. Description of the Related Art
[0004] In general, a semiconductor package is mounted on a print
circuit board after mounting one or a plurality of semiconductor
chips on a chip pad within a lead frame and sealing with epoxy
molding compound (EMC) to protect the internal part. However, as
high-speed, large scale and highly integrated electronic devices
have been rapidly developed in recent times, techniques that allow
for low cost, miniature, and lightweight manufacturing are also
required for power devices which are applied to automobiles,
industrial equipments and household electric appliances.
Furthermore power devices requires low noise and high reliability.
Thus, power module packages in which a plurality of semiconductor
chips are mounted on one semiconductor package become increasingly
popular.
[0005] FIG. 1 is a cross sectional view of a conventional power
module package. The power module package shown in FIG. 1 is
disclosed in U.S. Pat. No. 5,703,399 for a semiconductor power
module filed on May 15, 1996. Referring to FIG. 1, the power module
package has a structure in which a plurality of semiconductor chips
constituting a power circuit 9 and a control circuit 8 are mounted
on a lead frame 3. Reference numerals 1, 2, 4a, 5a, 5b, 6a, 6b, and
7 denote a heat sink, a resin having good heat transfer properties,
a power circuit chip element, a control circuit chip element, a
resistance element, an aluminum bonding wire, a gold wire, and an
insulating EMC, respectively.
[0006] According to the conventional art, in order to effectively
give off heat which is generated in the power circuit chip element
4a, the highly heat conducting resin 2 is provided beneath the lead
frame 3, and the heat sink 1 made of copper is provided under the
lead frame 3 so that it may be slightly separated from the lead
frame 3. The resin provided on the top of the lead frame is a
general insulating EMC 7 other than the resin 2. In addition, there
are a plurality of embodiments in which the heat sink 1 and the
lead frame 3 are transformed in order to more effectively radiate
heat generated in the power circuit chip element 4a.
[0007] However, the conventional art encounters the following
problems. First, since an EMC still remains filled between the rear
surface of the lead frame 3 and the heat sink 1 made of copper,
there is a restriction of emitting heat generated by the power
circuit chip element 4a to the outside of the power module package.
Second, use of two different resins within one power module package
not only complicates a manufacturing process of the power module
package but also makes automation of the manufacturing process
difficult. Third, use of a heat sink made of copper and the
complicated manufacturing process increases the manufacturing
cost.
SUMMARY OF THE INVENTION
[0008] To solve the above problems, it is an objective of the
present invention to provide a power module package which can
improve heat radiation characteristic, simplify a process, and
lower the manufacturing cost.
[0009] It is another objective of the present invention to provide
a method of manufacturing the power module package.
[0010] Accordingly, to achieve the above objectives, the present
invention provides a power module package including: a lead frame
having a first surface, to which components for a power circuit and
a control circuit are attached and on the center of which a down
set is provided, and a second surface, to which a heat sink is
attached, and edges on which external terminals are provided; a
heat sink having one surface attached directly to the second
surface of the lead frame projected by the down set, and the other
surface exposed to the outside of a power module package, the heat
sink being formed of an insulating material having good heat
transfer properties; components for the power circuit which are
mounted on a portion of the first surface of the lead frame on
which the down set is formed; components for the control circuit
which are mounted on the first surface of the lead frame; and an
epoxy molding compound which encapsulates the lead frame and the
heat sink excluding the external terminals of the lead frame and
the one side of the heat sink.
[0011] Preferably, the heat sink formed of an insulating material
having good heat transfer properties is composed of plastic or
ceramic including at least one of Al.sub.2O.sub.3, AIN, SiO.sub.2,
and BeO.
[0012] Preferably, the heat sink is a pre-bent plate for preventing
package warpage and it is pre-bent to less than 100 .mu.m.
[0013] Preferably, the heat sink is protruded slightly more than
the epoxy molding compound. The heat sink is protruded 0.05-0.1 mm
greater than the epoxy molding compound.
[0014] The present invention provides a method of manufacturing a
power module package. According to the method, a lead frame, on the
center of which a down set is provided and on the edges of which
external terminals are provided, is prepared. A plurality of chips
for serving as a power circuit and a control circuit are attached
to a first surface of the lead frame and then wire bonding is
performed. The lead frame is positioned to a molding equipment for
attaching a heat sink formed of an insulating material to a bottom
mold die. The lead frame is sealed by an epoxy molding compound in
the molding equipment so that the heat sink may be attached to the
second surface of the lead frame on which the down set is formed,
and that the external terminals and a surface opposing the surface
of the heat sink to which the lead frame is attached may be exposed
to the outside. In this case, a groove for fixing the heat sink is
formed to a depth of 0.05-0.1 mm from the surface of the bottom
mold die of the molding equipment.
[0015] The present invention also provides a method of
manufacturing a power module package. According to the method, a
lead frame on the center of which a down set is provided and on the
edges of which external terminals are provided is prepared. A
plurality of chips for serving as a power circuit and a control
circuit are attached to a first surface of the lead frame and wire
bonding is performed. The lead frame is positioned to a molding
equipment, in which a protrusion portion for attaching a heat sink
to a bottom lower die in a subsequent process is formed. The lead
frame is sealed by an epoxy molding compound in the molding
equipment so that a recessed surface including the second surface
of the lead frame, on which the down set is provided, and the
external terminals of the lead frame may be exposed. The heat sink
is attached to the recessed portion including the second surface of
the lead frame exposed to the outside.
[0016] The power module package according to the present invention
can effectively radiate heat generated during its operation through
a heat sink directly attached to the rear surface of a lead frame
on which a down set is formed. Thus, reliability of the power
module package can be guaranteed.
[0017] Furthermore, a sealing process for the power module package
can be performed at one time by using resins having the same
properties, thus simplifying a process and being advantageous to
automation of the process itself.
[0018] Lastly, the power module package uses a low cost heat sink
instead of metal thus lowering the manufacturing cost.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The above objectives and advantages of the present invention
will become more apparent by describing in detail preferred
embodiments thereof with reference to the attached drawings in
which:
[0020] FIG. 1 is a cross sectional view of a conventional power
module package;
[0021] FIG. 2 is a cross sectional view of a power module package
according to the present invention;
[0022] FIG. 3 is a cross sectional view showing the structure of a
bottom mold die in a molding equipment used in a first embodiment
of the present invention;
[0023] FIG. 4 is a cross sectional view showing a sealing process
of a power module package according to a first embodiment of the
present invention; and
[0024] FIG. 5 is a cross sectional view showing a bottom mold die
used in a molding equipment used in a second embodiment of the
present invention;
[0025] FIG. 6 is a cross sectional view showing the power module
package when a sealing process according to the second embodiment
has been completed; and
[0026] FIG. 7 is a cross sectional view of a heat sink used in the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0027] Arrangement of parts of a power circuit and a control
circuit and the structures of a lead frame and a heat sink, which
will be described in this specification, are only examples, and the
present invention will not be restricted to a specific shape as
shown in the accompanying drawings.
[0028] Referring to FIG. 2, a power module package 101 according to
the present invention includes a lead frame 100, a heat sink 140,
power circuit components 110, control circuit components 120 and an
epoxy molding compound (EMC) 150. A down set 130 is formed near the
center of the lead frame 100, thereby effectively radiating heat
generated by a power circuit chip 114 to the outside of the power
module package 101. To this end, the heat sink 140 made of an
insulating material such as plastic or ceramic is directly attached
to a second surface 104, which is the rear surface of the lead
frame 100 on which the down set 130 is formed, so that the heat
sink 140 may be exposed to the outside of the power module package
101.
[0029] Due to the structural characteristics, heat generated in the
power circuit chip 114 can be effectively radiated to the outside,
compared with the conventional method in which the heat sink and
the rear surface of the lead frame contact each other through the
resin. Furthermore, a process can be simplified since there is no
need to use two EMCs having different properties, and the
manufacturing cost can be lowered by using the heat sink 140 made
of low cost ceramic or plastic instead of a heat sink made of
copper.
[0030] The heat sink 140 can be manufactured by including one of
A1.sub.2O.sub.3, AIN, SiO.sub.2, and BeO. For example, in the case
of a ceramic, a heat sink may be formed by including
Al.sub.2O.sub.3, AIN, SiO.sub.2, or BeO in materials of the
ceramic. Furthermore, in the case of plastic, one of
Al.sub.2O.sub.3, AIN, SiO.sub.2, and BeO may be included in a
filler of the plastic.
[0031] Meanwhile, the heat sink 140 is susceptible to thermal
stress that may occur due to a difference in coefficient of thermal
expansion between the adjacent EMC 150 and the lead frame 100.
Thermal stress due to the difference in coefficient of thermal
expansion may induce package warpage. In order to prevent the
possibility of thermal stress-induced warpage, the heat sink 140 of
a rectangular plate shape may be pre-bent less than 100 .mu.m to
compensate for the warpage of the heat sink 140. Furthermore, due
to characteristics in a manufacturing process, the heat sink 140
projects from the top of the power module package 101 less than 0.1
mm.
[0032] The power circuit chip 114 and aluminum bonding wire 116,
which are the power circuit components, are attached to the down
set 130 of the lead frame 100 for ease of heat radiation. Reference
numerals 102 and 104, respectively, denote a first surface which is
the front side of the lead frame 100, and a second surface 104
which is a rear surface of the lead frame 100. Reference numerals
124 and 126, respectively, denote a control circuit chip and a gold
wire.
Method of Manufacturing Power Module Package According to First
Embodiment
[0033] FIG. 3 is a cross sectional view showing the structure of a
bottom mold die in a molding equipment used in a first embodiment
of the present invention, and FIG. 4 is a cross sectional view
showing a sealing process of a power module package according to a
first embodiment of the present invention. Referring to FIGS. 2-4,
in a first step, a power circuit chip 114 and a control circuit
chip 124 are attached to a first surface 102 of a lead frame 100 by
a die attach process. In this case, the power circuit 114 should be
attached to a region of a down set 130. Subsequently, wire bonding
is performed to properly connect the power circuit chip 114 with
the control circuit chip 124. A gold wire 126 is used as a wire of
the control circuit chip 124. As a wire for the power circuit chip
114 it is desirable to use an aluminum wire 116 having a diameter
of 250-500 .mu.m in order to sufficiently withstand high current
rating. In the wire bonding process, bonding techniques known as
wedge bonding and ball bonding are used. In order to perform wire
bonding smoothly, the aluminum wire 116 is first bonded and then
the gold wire 126 is bonded.
[0034] Next, the heat sink 140 is fixed to a groove 224 formed on
the top of a heat sink block 222 of a bottom mold die 220. The
depth of the groove 224 is preferably 0.05-0.1 mm, and the size
thereof should be sufficient for the heat sink 140 to fit into it.
The heat sink 140 is composed of plastic or ceramic including one
of Al.sub.2O.sub.3, AIN, SiO.sub.2, and BeO. Furthermore, in order
to prevent package warpage, a pre-bent type heat sink, which is
bent less than 100 .mu.m, may be used as the heat sink 140. The
heat sink 140 can be composed of a single layer, but multiple
layers attached by an adhesive having good thermal properties may
possibly be used.
[0035] After wire bonding is complete, the lead frame 100 is
positioned at a molding equipment. In this case, the heat sink 140
remains to be fixed to the groove 224 of the bottom mold die 220.
Then, a top mold die 210 comes down and an EMC is injected through
a gate 230. The EMC remains liquified by heat and pressure, so that
the EMC flows in a direction as depicted by an arrow to evenly fill
the inner space of a mold 200. A transfer molding equipment having
a plurality of gates and runners can be utilized as a molding
equipment. A temperature for sealing is preferably 160-170.degree.
C.
[0036] When the lead frame 100 in which sealing has been complete,
i.e., the power module package 101, is unloaded from the molding
equipment, the heat sink 140 is attached directly to a second
surface of the lead frame 100 on which the down set 130 is
provided, and a surface to which the heatsink is not attached is
protruded and exposed to the outside of the power module package
101. A lead which is an external terminal 106 is exposed to the
outside as well. Then, a usually subsequent process including a
trim & forming process is performed.
Method of Manufacturing Power Module Package According to Second
Embodiment
[0037] FIG. 5 is a cross sectional view showing the structure of a
bottom mold die in a bottom mold die used in a molding equipment
used in a second embodiment of the present invention, and FIG. 6 is
a cross sectional view showing the power module package when a
sealing process according to the second embodiment has been
completed. Referring to FIGS. 2, 5, and 6, in a second embodiment,
a heat sink 140 is attached to a second surface of a lead frame 100
through a separate attaching process after exposing the second
surface 104 of the lead frame 100 on which the down set 130 is
provided, during a sealing process, while, in the first embodiment,
the heat sink is directly attached to the second surface 104 of the
lead frame 100 on which the down set 130 is formed.
[0038] The same process as that in the first embodiment is
performed to mount power circuit components 114 and 116, and
control circuit components 124 and 126 on a first surface of a lead
frame 100 through a die attach process and wire boding process.
After the wire bonding is complete, the lead frame 100 is
positioned to a molding equipment. In this case, a protrusion
portion 226 instead of a groove is formed on a bottom mold die 220
of the molding equipment. The protrusion portion 226 serves to
expose a second surface 104 of the lead frame 100 on which a down
set 130 is formed, to the outside of the power module package 101,
when performing a sealing process.
[0039] Thus, after a sealing process is performed in the molding
equipment as shown in FIG. 4, there exists a second surface 149 of
the lead frame which is exposed to the outside with a step
difference. Then, a separate attaching process is performed to
attach the heat sink 140 to the second surface 149 of the lead
frame 100 is exposed with a step difference to the outside using a
liquid epoxy including a ceramic-based filler. Here, the
ceramic-based filler refers to resin or hardener of a liquid epoxy
in which a ceramic-based material such as Al.sub.2O.sub.3 or
AIN.
[0040] Referring to FIG. 7 which is a cross sectional view of a
heat sink used in the present invention, a rectangular plate can be
used as a heat sink 140, but a pre-bent type heat sink can be used
in order to compensate for package warpage that occurs due to a
difference in coefficient of thermal expansion between the heat
sink 140 and a power module package material adjacent thereto. The
pre-bent type heat sink 140 is less than 100 .mu.m bent. The
pre-bent type heat sink 140 can compensate for warpage of a heat
sink made of an insulating material.
[0041] First, a power module package according to the present
invention can guarantee reliability by effectively radiating heat
generated during operation of the power module package through a
heat sink attached directly to the rear surface of a lead frame on
which a down set is provided. As an example, when the structure and
materials of a heat sink in a power module package under the same
conditions were changed as shown in the present invention, heat
transfer properties, i.e., a junction case R.theta. jc and a
junction ambient R.theta. ja , were 0.15.degree. C./Watt and
2.80.degree. C./Watt respectively, while the correspondent values
were 0.26.degree. C./Watt and 3.02.degree. C./Watt when using the
conventional method. Therefore, the result demonstrated that a heat
radiation characteristic was improved about 20-30% compared with
the conventional art. Here, the junction case R.theta. jc refers to
a temperature difference from a PN junction of the power circuit
chip 114 to a case which is a mold line, and a junction ambient
R.theta. ja refers to a temperature difference from the PN junction
of the power circuit chip 114 to the external atmosphere.
[0042] Second, a process can be simplified and automated by
performing a sealing process on a power module package by use of an
EMC having the same properties at a time.
[0043] Third, the manufacturing cost can be lowered by
manufacturing a power module package having a low cost heat sink
instead of a metallic heat sink and simplifying a process.
[0044] While this invention has been particularly shown and
described with references to preferred embodiments thereof, it will
be understood by those skilled in the art that various changes in
form and details may be made therein without departing from the
spirit and scope of the invention as defined by the appended
claims.
* * * * *