U.S. patent application number 11/563029 was filed with the patent office on 2007-04-19 for flip chip package.
This patent application is currently assigned to ADVANCED SEMICONDUCTOR ENGINEERING, INC.. Invention is credited to Yu-Wen Chen, Chi-Hao Chiu, Chih-Ming Chung.
Application Number | 20070085218 11/563029 |
Document ID | / |
Family ID | 33415055 |
Filed Date | 2007-04-19 |
United States Patent
Application |
20070085218 |
Kind Code |
A1 |
Chen; Yu-Wen ; et
al. |
April 19, 2007 |
FLIP CHIP PACKAGE
Abstract
A flip chip package structure is provided. A chip is
electrically connected to a substrate. A heat sink is attached to
the backside of the chip. The heat sink has at least a through hole
located at a peripheral region and laterally adjacent to the chip.
A dispensing process is carried out to deliver an underfill
material via the through hole such that the space between the chip
and the substrate is filled. The underfill material also extends to
cover a portion of the heat sink so that the heat sink and the
substrate are connected together. The underfill material is cured
to fix the heat sink, the substrate and the chip in position.
Inventors: |
Chen; Yu-Wen; (Kaohsiung,
TW) ; Chung; Chih-Ming; (Kaohsiung County, TW)
; Chiu; Chi-Hao; (Pingtung County, TW) |
Correspondence
Address: |
JIANQ CHYUN INTELLECTUAL PROPERTY OFFICE
7 FLOOR-1, NO. 100
ROOSEVELT ROAD, SECTION 2
TAIPEI
100
TW
|
Assignee: |
ADVANCED SEMICONDUCTOR ENGINEERING,
INC.
26, Chin 3rd. Rd., 811, Nantze Export Processing Zone
Kaohsiung
TW
|
Family ID: |
33415055 |
Appl. No.: |
11/563029 |
Filed: |
November 24, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10709588 |
May 17, 2004 |
7163840 |
|
|
11563029 |
Nov 24, 2006 |
|
|
|
Current U.S.
Class: |
257/778 ;
257/E21.503; 257/E23.101 |
Current CPC
Class: |
H01L 2224/73203
20130101; H01L 2924/01029 20130101; H01L 21/563 20130101; H01L
2924/01033 20130101; H01L 24/28 20130101; H01L 2924/3025 20130101;
H01L 2924/00014 20130101; H01L 2224/92125 20130101; H01L 23/36
20130101; H01L 2224/05573 20130101; H01L 2924/16151 20130101; H01L
2924/01013 20130101; H01L 2224/05571 20130101; H01L 2924/01075
20130101; H01L 2224/83102 20130101; H01L 2224/16225 20130101; H01L
2924/3512 20130101; H01L 2924/00 20130101; H01L 2924/00014
20130101; H01L 2224/05599 20130101 |
Class at
Publication: |
257/778 |
International
Class: |
H01L 23/48 20060101
H01L023/48 |
Foreign Application Data
Date |
Code |
Application Number |
May 16, 2003 |
TW |
92113290 |
Claims
1. A flip chip package structure, comprising: a chip having an
active surface and a corresponding backside, wherein the active
surface comprises a plurality of bumps thereon; a substrate,
wherein the substrate is connected to the active surface of the
chip through the bumps; a heat sink attached to the backside of the
chip, wherein the heat sink comprises at least a through hole
located outside a perimeter of the chip; and an underfill material
that fills up a space between the active surface of the chip and
the substrate and connects the heat sink and the substrate.
2. The flip chip package structure of claim 1, wherein the through
hole is positioned outside the perimeter and adjacent to the
chip.
3. The flip chip package structure of claim 1, wherein the heat
sink has a coefficient of thermal expansion comparable to the
substrate.
4. The flip chip package structure of claim 1, wherein the heat
sink has an upper surface and a lower surface, and wherein the
lower surface further comprises at least a stopper on an outer edge
of the through hole.
5. The flip chip package structure of claim 1, further comprising a
thermal conductive layer between the backside of the chip and the
heat sink.
6. The flip chip package structure of claim 1, wherein the
underfill material comprises an epoxy resin.
7. The flip chip package structure of claim 6, wherein the epoxy
resin comprises a thermal-setting epoxy resin.
8. The flip chip package structure of claim 4, wherein the stopper
is downward protruded from the lower surface of the heat sink.
9. The flip chip package structure of claim 4, wherein the stopper
is located outside the perimeter of the chip.
10. The flip chip package structure of claim 1, further comprising
a stiffener connecting the substrate and the heat sink.
11. The flip chip package structure of claim 1, wherein the
underfill material fills the through hole.
12. The flip chip package structure of claim 1, wherein the heat
sink contacts with the substrate.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a divisional application of patent application Ser.
No. 10/709,588, filed on May 17, 2004, which claims the priority
benefit of Taiwan patent application serial no. 92113290, filed May
16, 2003 and is now allowed. The entirety of each of the
above-mentioned patent applications is hereby incorporated by
reference herein and made a part of this specification.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a flip chip package with a
heat sink. More particularly, the present invention relates to a
flip chip package that uses underfill material to firmly fasten a
substrate and a heat sink within the package.
[0004] 2. Description of the Related Art
[0005] Flip chip interconnect technology is a method of bonding a
chip to a substrate as well as connecting the two electrically. To
form a flip chip package, a chip with an array of bonding pads
formed on an active surface is provided. Bumps are formed over the
bonding pads. Thereafter, the chip is flipped over such that the
contacts on a substrate are aligned with the respective bumps on
the chip. Thus, the substrate and the chip are electrically and
mechanically connected via the bumps so that the chip is able to
communicate with an external device through the internal circuits
inside the substrate.
[0006] It is known that the flip chip technology is capable of
producing a chip package having a high pin count while reducing
overall package area and shortening overall signal transmission
pathways at the same time. Consequently, flip chip technique has
been widely adopted in the fabrication of many types of chip
packages. The most common type of flip chip package structure
includes the so-called `flip chip ball grid array` (FC/BGA), for
example. However, as the operational speed of the chip is
increased, more efficient heat-dissipating device must be
accompanied.
[0007] To increase heat-dissipating efficiency, a heat sink is
frequently attached to the backside of a FC/BGA package. In the
conventional technique, a reflow process is carried out after a
chip is flipped over (the active surface facing downward) and
aligned on top of a substrate so that the bumps on the surface of
the chip re-melt and bond with corresponding contacts on the
substrate. Because the substrate and the chip have widely different
coefficient of thermal expansion, considerably stress may build up
between the chip and the bumps under thermo cycles. Ultimately, the
chip may crack or else the package may warp noticeably.
SUMMARY OF THE INVENTION
[0008] Accordingly, one object of the present invention is to
provide a flip chip package having an improved reliability.
[0009] To achieve these and other advantages and in accordance with
the purpose of the invention, as embodied and broadly described
herein, the invention provides a method of forming a flip chip
package structure whose chip and substrate are electrically
connected. The chip has an active surface and a corresponding
backside. The active surface comprises a plurality of bumps. The
chip and the substrate are connected together via the bumps. A heat
sink is attached to the backside of the chip. The heat sink
comprises at least a through hole located in the periphery of the
chip. Via the through hole, a dispensing process is performed by
injecting underfill material not only to fill up the space between
the active surface of the chip and the substrate but also to cover
a portion of the heat sink to connect the heat sink and the
substrate. Thus, the heat sink and the substrate are glued together
by the underfill material. Finally, the underfill material is cured
to fix the heat sink, the substrate and the chip in position.
[0010] The aforementioned dispensing process includes passing a
dispensing needle through the through hole to provide the underfill
material for filling the space between the substrate and the chip
as well as covering a portion of the heat sink to connect the
substrate and the heat sink.
[0011] This invention also provides a flip chip package structure
comprising a chip, a substrate, a heat sink and an underfill
material. The chip has an active surface and a corresponding
backside. The active surface of the chip comprises a plurality of
bumps thereon. The chip and the substrate are boned together
through the bumps on the active surface. The heat sink is attached
to the backside of the chip. The heat sink comprises at least a
through hole disposed around the peripheral region of the chip. The
underfill material not only fills up the space between the active
surface of the chip and the substrate, but also connects the heat
sink with the substrate.
[0012] The aforementioned through hole is positioned around the
peripheral region and laterally adjacent to the chip.
[0013] Furthermore, the heat sink comprises an upper surface and a
lower surface. The lower surface further comprises at least a
stopper just outside the through hole for blocking an outward
expansion of the underfill material so that the injected underfill
material is forced to remain within an area in the neighborhood of
the chip.
[0014] In the aforementioned flip chip package, the underfill
material is an epoxy resin. Preferably, the underfill material is a
thermal-set epoxy resin that can be cured by heating so that the
underfill material is able to fasten the heat sink and the
substrate firmly together.
[0015] It is to be understood that both the foregoing general
description and the following detailed description are exemplary,
and are intended to provide further explanation of the invention as
claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The accompanying drawings are included to provide a further
understanding of the invention, and are incorporated in and
constitute a part of this specification. The drawings illustrate
embodiments of the invention and, together with the description,
serve to explain the principles of the invention.
[0017] FIGS. 1 through 6 are schematic cross-sectional views
showing the progression of steps for fabricating a flip chip
package with a heat sink thereon according to a first embodiment of
this invention.
[0018] FIG. 7 is a planar view of a heat sink according to the
first embodiment of this invention.
[0019] FIG. 8 is a schematic cross-sectional view of a flip chip
package structure according to a second embodiment of this
invention.
[0020] FIG. 9 is a schematic cross-sectional view of a flip chip
package according to a third embodiment of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] Reference will now be made in detail to the present
preferred embodiments of the invention, examples of which are
illustrated in the accompanying drawings. Wherever possible, the
same reference numbers are used in the drawings and the description
to refer to the same or like parts.
The First Embodiment
[0022] FIGS. 1 through 6 are schematic cross-sectional views
showing the progression of steps for fabricating a flip chip
package with a heat sink thereon according to a first embodiment of
this invention. In this embodiment, the fabrication of a flip chip
ball grid array package is used as an example.
[0023] As shown in FIG. 1, a substrate 110 having a plurality of
bonding pads (such as bump pads) on one side and a plurality of
ball pads 114 on the other side is provided.
[0024] As shown in FIG. 2, a chip 102 having an active surface 102a
and a backside 102b is provided. The active surface 102a of the
chip 102 comprises a plurality of bonding pads 104 and each bonding
pad 104 has a bump 106 attached thereon. The chip 102 is flipped
over so that the bumps 106 on the active surface 102a align with
the bump pads 112 on the substrate 110. Thereafter, a reflow
process is performed so that the bumps 106 melt to connect with the
bump pad 112 on the substrate 110.
[0025] As shown in FIG. 3, a stiffener ring 120 is placed on the
substrate 110 around the chip 102. Thereafter, a heat sink 130 is
attached to the backside 102b of the chip 102. The stiffener ring
120 connects the substrate 110 and the heat sink 130. In other
cases, if the heat sink is in a specific shape, for example, a
reversed-U-shape, and the heat sink can be directly attached to the
substrate 110, the stiffener ring 120 can be omitted. FIG. 7 is a
planar view of a heat sink according to the first embodiment of
this invention. The heat sink 130 comprises at least a through hole
132 (four through holes are shown in FIG. 7). The through hole 132
is set in the peripheral region and laterally adjacent to the chip
102. In FIG. 7, the region 150 enclosed by dash lines indicates the
location of the chip 102. Although the through hole 132 is shown to
have a rectangular profile, there is no fixed profile as long the
through hole 132 is formed around and close to the area where the
chip 102 is positioned. There is also no fixed limit on the number
of through holes 132 on the heat sink 130.
[0026] Furthermore, to enhance the heat-dissipating capacity, a
thermal conductive layer 140, for example, made of thermal
conductive glue may be applied to the backside 102b of the chip 102
prior to attaching the heat sink 130 to the chip 102.
[0027] As shown in FIG. 4, a dispensing process is carried out
using a needle 172 of a dispensing nozzle 170. In the dispensing
process, the needle 172 of the dispensing nozzle 170 passes through
the through hole 132 and injects underfill material 160a to fill up
the space between the active surface 102a of the chip 102 and the
substrate 110 through a capillary action. Through the capillary
action, some of the underfill material 160a is able to creep over
the heat sink 130 to form a fillet of underfill layer as shown in
FIG. 5. Preferably, the heat sink 130 has a coefficient of thermal
expansion comparable to the substrate 110 including, for example, a
copper or an aluminum plate. Hence, a sandwiched beam structure
comprising high-strength facial layers (substrate 110 and heat sink
130) and a core layer (underfill material 160a that encloses the
chip 102) is produced.
[0028] Thereafter, the underfill material 160a is cured to fix the
heat sink 130, the substrate 110 and the chip 102 in positions.
With this structural setup, the underfill material 160a that is
regarded as the core layer is able to absorb most of the stress and
relieve the stress at the chip contacts (the bumps 106). In
addition, because the coefficient of thermal expansion of the
substrate 110 and the heat sink 130 which are disposed on each side
of the underfill material 160a are comparable, and therefore
warping or distortion is greatly reduced. Thus, fatigue strength
and reliability of the package can be effectively promoted.
Moreover, the stiffener ring 120 and the underfill material 160a
also provide some resistant when the heat sink 130 is subjected to
an external pressure. Hence, the chip 102 is shielded against most
sources of stress.
[0029] As shown in FIG. 6, an operation is carried out to plant
solder balls 155 to the ball pads 114. Thus, the chip 102 is
electrically connected to the solder balls 155 on the other side of
the substrate 110 through the bumps 106 and the circuits within the
substrate 110.
The Second Embodiment
[0030] FIG. 8 is a schematic cross-sectional view of a flip chip
package structure according to a second embodiment of this
invention. The main difference between the flip chip package
structure 200 in the second embodiment and the first embodiment
(FIG. 6) is that a stopper 134 is added. The stopper 134 is located
beneath the heat sink 130 just outside the through hole 132 for
holding back the underfill material 160a in the neighborhood of the
chip 102. Here, there is no particular restriction on the shape of
the stopper 134. For example, the stopper 134 can be a baffle plate
or extension protruding downward from the lower surface of the heat
sink 130. In general, the stopper 134 is disposed outside the
perimeter of the chip 102, and near or at one side of the through
hole 132 further away from the chip 102.
The Third Embodiment
[0031] FIG. 9 is a schematic cross-sectional view of a flip chip
package according to a third embodiment of this invention. The main
difference between the flip chip package structure 300 in the third
embodiment and the first embodiment (FIG. 6) is that the stiffener
ring 120 is absent. Since all other aspects and advantages of the
third embodiment are identical to the first embodiment, detailed
description is not repeated here.
[0032] Because the underfill material 160a fills the space between
the active surface 102a of the chip 102 and the substrate 100 and
covers a portion of the heats sink 130 to fasten the substrate 100
and the heat sink 130 tightly together, there is little warping in
the flip chip package 300. Hence, with the strengthening underfill
material 160a delivered via the through hole 132, the stiffener
ring 120 (shown in FIG. 6) can be eliminated. Also a heat sink that
directly contacts with the substrate can be used here.
[0033] In all the aforementioned embodiments, a flip chip ball grid
array package is chosen in all the illustrations. However, this
should not limit the scope of the invention as such. In fact, this
invention can be applied to fabricate any flip chip package with a
heat sink.
[0034] Furthermore, the dispensing process performed by way of the
through hole in the heat sink after attaching the heat sink to the
chip not only fixes the chip to the substrate and the heat sink to
the chip but also binds the heat sink to the substrate as well.
Thereafter, the curing process fixes the heat sink and the
substrate. Hence, the overall processing steps for fabricating the
flip chip package according to this invention are simplified.
[0035] In addition, through the injection underfill material via
the through hole and the subsequent curing process, the package is
structurally reinforced. Moreover, the substrate and the heat sink
forming the sides of a sandwiched beam structure are fabricated
using materials having comparable coefficient of thermal expansion.
Therefore, the core layer fabricated using underfill material is
able to absorb most of the stress and reduces the stress acting on
the chip contacts (bumps). Ultimately, warping of the flip chip
package is minimized and reliability of the package is
improved.
[0036] It will be apparent to those skilled in the art that various
modifications and variations can be made to the structure of the
present invention without departing from the scope or spirit of the
invention. In view of the foregoing, it is intended that the
present invention cover modifications and variations of this
invention provided they fall within the scope of the following
claims and their equivalents.
* * * * *