U.S. patent application number 09/927564 was filed with the patent office on 2002-12-05 for flip chip package of monolithic microwave integrated circuit.
Invention is credited to Hsieh, Tsung-Ying, Hsu, Chin-Lien, Hsu, Wen-Rui.
Application Number | 20020180062 09/927564 |
Document ID | / |
Family ID | 21678389 |
Filed Date | 2002-12-05 |
United States Patent
Application |
20020180062 |
Kind Code |
A1 |
Hsieh, Tsung-Ying ; et
al. |
December 5, 2002 |
FLIP CHIP PACKAGE OF MONOLITHIC MICROWAVE INTEGRATED CIRCUIT
Abstract
A flip chip package of monolithic microwave integrated circuit
(MMIC) is disclosed. The MMIC includes a substrate having an top
surface and a bottom surface; a MMIC chip, having an active surface
and having the chip flipped over and covered on the substrate with
the active surface as the contacting surface wherein a central area
of the active surface has one or several active devices; a
plurality of metal strips, provided in a periphery area of the
active surface of the MMIC chip and electrically connected to the
active device; a plurality of solder bumps implanted respectively
on the metal strips on the active surface of the MMIC chip and
electrically connected to the metal strips on the MMIC chip; a
plurality of substrate's top surface metal strips, provided in a
periphery area of the top surface of the substrate and electrically
connected to the solder bumps; a plurality of substrate's bottom
surface metal strips, provided in the periphery area of the bottom
surface of the substrate; a plurality of via holes, penetrating
through the substrate in the periphery area of the upper and bottom
surfaces of the substrate and electrically connected to the metal
strips on the upper and bottom surfaces of the substrate, and
electrically connected to these metal strips thereof; as well as an
underfill, filling all the chinks around the solder bumps and the
plurality of the metal strips connected to the solder bumps on the
substrate's surface, and covering up to a height that is slightly
higher than the thickness of the MMIC chip. Moreover, the MMIC
package for the high power application has a penetration hole
through the substrate in the central area of the upper and bottom
surfaces of the substrate and filled with a heat-dissipative
material in order to obtain a package structure with optimum
heat-dissipative effect.
Inventors: |
Hsieh, Tsung-Ying; (Hsin
Chu, TW) ; Hsu, Chin-Lien; (Hsin Chu, TW) ;
Hsu, Wen-Rui; (Tao Yuan, TW) |
Correspondence
Address: |
MARTINE & PENILLA, LLP
710 LAKEWAY DRIVE
SUITE 170
SUNNYVALE
CA
94085
US
|
Family ID: |
21678389 |
Appl. No.: |
09/927564 |
Filed: |
August 9, 2001 |
Current U.S.
Class: |
257/778 ;
257/E21.511 |
Current CPC
Class: |
H01L 2224/8547 20130101;
H01L 2924/15173 20130101; H01L 2224/13111 20130101; H01L 2224/05573
20130101; H01L 2924/00014 20130101; H01L 2924/01078 20130101; H01L
2924/3011 20130101; H01L 2924/00014 20130101; H01L 2224/45015
20130101; H01L 2924/207 20130101; H01L 2224/05599 20130101; H01L
2924/00012 20130101; H01L 2224/45099 20130101; H01L 2924/00014
20130101; H01L 2924/00014 20130101; H01L 2924/00014 20130101; H01L
2224/85424 20130101; H01L 2924/30107 20130101; H01L 2924/01013
20130101; H01L 2924/01004 20130101; H01L 2924/0105 20130101; H01L
2924/01033 20130101; H01L 2924/014 20130101; H01L 24/48 20130101;
H01L 2224/8547 20130101; H01L 2924/181 20130101; H01L 2924/30105
20130101; H01L 23/66 20130101; H01L 2224/85444 20130101; H01L
2924/01032 20130101; H01L 2924/181 20130101; H01L 2924/10329
20130101; H01L 2224/81801 20130101; H01L 2924/01005 20130101; H01L
2924/01049 20130101; H01L 2924/01079 20130101; H01L 2224/48247
20130101; H01L 2224/85424 20130101; H01L 2924/14 20130101; H01L
2224/85444 20130101; H01L 2924/01006 20130101; H01L 2924/01023
20130101; H01L 2924/00014 20130101; H01L 2924/1423 20130101; H01L
2924/01082 20130101; H01L 2224/45099 20130101; H01L 2224/48091
20130101; H01L 24/81 20130101; H01L 2224/16235 20130101; H01L
2924/00014 20130101; H01L 2924/01029 20130101; H01L 2924/01039
20130101; H01L 2924/00014 20130101; H01L 2924/01047 20130101; H01L
2924/15313 20130101; H01L 2224/05568 20130101; H01L 2224/16
20130101; H01L 2224/48091 20130101 |
Class at
Publication: |
257/778 |
International
Class: |
H01L 023/48; H01L
023/52 |
Foreign Application Data
Date |
Code |
Application Number |
May 30, 2001 |
TW |
90113148 |
Claims
What is claimed is:
1. A flip chip package of monolithic microwave integrated circuit
(MMIC) comprising: a substrate, having an top surface and a bottom
surface, and each of the surfaces is divided respectively into a
periphery area and a central area; an integrated circuit chip (IC
chip), having a first surface and a second surface, and each of the
surfaces being divided respectively into a periphery area and a
central area, and the MMIC package being made by flipping the IC
chip to have its first surface covering on the top surface of the
substrate, and the central area of the first surface having one or
several active devices; a plurality of metal strips, positioned on
the IC chip's first surface and disposed in the periphery area of
the IC chip's first surface, and these metal strips being
electrically connected to the active devices on the first surface
of the IC chip; a plurality of solder bumps, implanted respectively
on and being electrically connected to the first surface's metal
strips of the plurality of IC chips; a plurality of metal strips of
the substrate's top surface, disposed in the periphery area of the
substrate's top surface, and these metal strips being electrically
connected to the plurality of solder bumps; a plurality of metal
strips of the substrate's bottom surface, disposed in the periphery
area of the substrate's bottom surface a plurality of via holes,
penetrating through the substrate and being electrically connected
to the plurality of metal strips on the substrate's top surface and
to the plurality of metal strips on the substrate's bottom surface
respectively; and an underfill, filling the solder bumps and the
plurality of the metal strips which are connected to the solder
bumps and are positioned on the IC chip's first surface, also
filling all the chinks around the top surface's metal strips of the
substrate, and covering the whole IC chip up to a height that is
slightly higher than the thickness of the MMIC chip.
2. The flip chip package of MMIC of claim 1, wherein the plurality
of solder bumps are implanted on and electrically connected to the
top surface's metal strips of the substrate, and also being
electrically connected to the first surface's metal strips of the
IC chip.
3. The flip chip package of MMIC of claim 1, wherein the plurality
of the first surface's metal strips of the IC chip are input/output
(I/O) ports and ground terminals of the IC chip.
4. The flip chip package of MMIC of claim 1, wherein the material
of the plurality of the first surface's metal strips of the IC chip
is selected from the group of metal consisting of gold, copper, and
aluminum.
5. The flip chip package of MMIC of claim 1, wherein the material
of the plurality of the top surface's metal strips and the
plurality of the bottom surface's metal strips of the substrate is
selected from the group of metal consisting of gold, copper, and
aluminum.
6. The flip chip package of MMIC of claim 1, wherein the material
of the IC chip is selected from the group consisting of gallium
arsenide (GaAs) of III-V group compound or silicon (Si).
7. The flip chip package of MMIC of claim 1, wherein the material
of the solder bumps is selected from the group of metal or alloy
consisting of gold (Au), gold-tin (Au--Sn), gold-silicon (Au--Si),
gold-germanium (Au--Ge), tin-lead (Sn--Pb), tin-silver (Sn--Ag),
tin-lead-silver (Sn--Pb--Ag), indium (In), indium-tin (In--Sn),
indium-lead (In--Pb).
8. The flip chip package of MMIC of claim 1, wherein the method for
forming the solder bumps is selected from the group consisting of
deposition, electroplating, stencil printing, wire bonding, solder
ball implanting.
9. The flip chip package of MMIC of claim 1, wherein the material
of the via holes is selected from the group of metal consisting of
gold, silver, copper, and aluminum.
10. The flip chip package of MMIC of claim 1, wherein the forming
method of metal strips on the top and bottom surfaces of the
substrate and on the first surface of the IC chip is etching.
11. The flip chip package of MMIC of claim 1, wherein the number
and disposition of all the metal strips and via holes depend on the
structure and size of the IC chip.
12. The flip chip package of MMIC of claim 1, wherein a penetration
hole is provided in the central areas of the top and bottom
surfaces of the substrate and the material removed by penetrating
the penetration hole is replaced by filling a heat-dissipative
material.
13. The flip chip package of MMIC of claim 12, wherein the
heat-dissipative material is selected from the group consisting of
boron nitride (BN), aluminum nitride (Al N), berylium oxide (Be O),
aluminum oxide (Al.sub.2O.sub.3), silicon carbide (Si C).
14. The flip chip package of MMIC of claim 1, wherein the material
of the underfill is thermosetting resin.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a flip chip package of monolithic
microwave integrated circuit (MMIC), and more particularly, to a
flip chip package of MMIC that has optimum heat-dissipative
characteristic, and that can reduce the effects of parasitic
inductance and parasitic capacitance, for the application in
micro-wave, millimeter-wave and radio-frequency.
BACKGROUND OF THE INVENTION
[0002] In our modern society, internet has become an indispensable
part of our daily life. As the quality demands on the transmitting
speed of the audio, video and data are getting higher and higher,
wide-band network emerges in response to the needs of the
times.
[0003] FIG. 1 is a structural disposition of a microwave integrated
circuit package according to a prior art. As shown in FIG. 1, the
microwave integrated circuit package structure disclosed in patent
No. 69,402 of Taiwan, Republic of China includes a grounded
potential metal surface 112, an IC chip bonding part 113, a
slot-type via hole signal line 115 penetrating through the
substrate, a coplanar waveguide input/output port (I/O port) 121,
and a plurality of circular via holes connecting the top and bottom
metal surfaces of the substrate. The microwave integrated circuit
package provides a grounded potential metal surface to perform
signal transmission between each of the I/O ports and IC circuit.
As far as the disposition of the metal surface on the substrate's
top surface is concerned, the material employed for the metal
surface is any ones that can be performed wire bonding and are
chemically stable. And the metal surface is fabricated by making
use of thick film or thin film or a common IC board's etching
methods, and its attenuation is smaller than that of a micro-strip
since it employs coplanar waveguide.
[0004] FIG. 2 is a cross-sectional view of a microwave integrated
circuit package according to another prior art. The prior art shown
in FIG. 2 is a "small outline integrated circuit (SOIC) package"
which is the most popular IC package technology nowadays. As shown
in FIG. 2, the steps for forming the SOIC package is described as
follows. First of all, a chip 281 is adhered to the paddle 221 of
the lead frame 282 by the surface mounting method. Afterwards, the
wires 283 are bonded, and adhesive material 284 is applied to fix
the package in position. The package is finally formed by mold
injection with encapsulant 285 to protect against the intrusion of
the moisture and the dust that might affect the electrical
characteristic in order to improve the package reliability.
[0005] FIG. 3(a) is a cross-sectional view of a microwave
integrated circuit package according to one other prior art. The
microwave integrated circuit package is disclosed in patent No.
93,511 of Taiwan, Republic of China. As shown in FIG. 3(a), the
microwave integrated circuit package includes an IC chip 363 and a
substrate 361. Wires 331, 332 are employed to connect the I/O ports
341, 342 of the IC to the I/O ports 321, 322 of the substrate's top
surface. They are further connected to the I/O ports 323, 324 of
the substrate's bottom surface through the via holes 315, 316 at
the left and right edges of the substrate. Afterwards, underfill
material 390 is employed to cover the IC chip 363 and bonding wires
331, 332 to fix the IC chip in position. Finally, the package is
formed on the top of the underfill material 390 by mold injection
with encapsulant 391.
[0006] FIG. 3(b) is an isometric top view of a microwave integrated
circuit package according to the one other prior art shown in FIG.
3(a). As shown in FIG. 3(b), the IC chip 416 is flipped over to
have the surface, having signal and ground terminals, facing
downward. In the meantime, metal strip 411, 412 are widen such that
the input signal terminal of the IC chip 416 can contact the metal
strip 411, the output signal terminal can contact the metal strip
412, and the all the grounded terminals can contact the metal strip
415. Moreover, the portion covered by the IC chip 416 is performed
etching to prevent the surface of the IC chip 416 from being
short-circuited.
[0007] Most of the above-mentioned package technology makes use of
bonding wires to connect the IC chip to the I/O ports of the
substrate. Since the bonding wires of this kind of chip-and-wire IC
package will cause significant parasitic inductance effect and
parasitic capacitance effect in the frequency range of micro-wave
and milli-meter wave, the chip-and-wire IC package will affect the
electrical characteristic in the high frequency range and
deteriorate the reliability of the electronic devices. Moreover,
among the MMIC packages, the manufacturing cost of this kind of
chip-and-wire is rather high nowadays, and its mass production is
not feasible. Further, the size of the MMIC made by chip-and-wire
is rather large that does not meet the trend of compact design in
package.
[0008] Currently, in respect of the frequency range of micro-wave
and milli-wave application, although the micro-wave integrated
circuit (MIC) formed by employing bare chip and wire bonding is
widely used, the fabrication process is time consuming and the cost
of manpower is very high, thereby, the price of the MIC package
remains very high. Besides, since the bonding wires currently
employed by the microwave chip package results in parasitic
inductance effect and parasitic capacitance effect, the electrical
performance is deteriorated, consequently, the application of the
wire bonding in milli-wave package is not even feasible.
[0009] On the other hand, a comparison of the invention with the
prior art shown in FIG. 3(b) is made as follows. Since the
invention employs metal strips to connect the IC chip to the
substrate, and since the area of the substrate is only slightly
greater than that of the IC chip, the size of the device after
finishing the packaging process is rather small. Therefore, the
MMIC package of the invention is in accordance with the trend of
the compact design of the package. In addition, since the IC chip
is electrically connected to the substrate through the metal strip
instead of being directly contacted the substrate, the short
circuit phenomenon on the surface of the IC chip can be avoided,
thereby, the yield of the package of the electronic device is
improved.
SUMMARY OF THE INVENTION
[0010] In the light of the above-mentioned disadvantages, and in
order to resolve the problems on the package used in radio
frequency (RF), microwave, and milli-wave devices, an object of the
invention is to have a package that can make use of the common
surface-mounted technology (SMT) to undertake mass production so as
to lower the production cost. The above-mentioned problems are
summarized as follows:
[0011] 1. The undesired impedance matching and the self-resonant
problems resulted from the parasitic capacitance and parasitic
inductance generated by the bonding wires.
[0012] 2. The inability problem to undertake automation on the
production of the chip-and-wire package.
[0013] 3. The inertly heat-dissipative problem of the chip of
gallium arsenide (GaAs) commonly used by the RF, microwave, and
milli-wave.
[0014] 4. The inability to have a compact package since the size of
the package becomes large after the packaging process.
[0015] To attain the object of resolving these problems, the
invention provides a flip chip package of monolithic microwave
integrated circuit (MMIC). The MMIC package of the invention
includes a substrate, having an top surface and a bottom surface,
and each of the surfaces is divided respectively into a periphery
area and a central area; an integrated circuit chip (IC chip),
having a first surface and a second surface, and each of the
surfaces being divided respectively into a periphery area and a
central area, and the MMIC package being made by flipping the IC
chip to have its first surface covering on the top surface of the
substrate, and the central area of the first surface having one or
several active devices; a plurality of metal strips, positioned on
the IC chip's first surface and disposed in the periphery area of
the IC chip's first surface, and these metal strips being
electrically connected to the active devices on the first surface
of the IC chip; a plurality of solder bumps, implanted respectively
on and being electrically connected to the first surface's metal
strips of the plurality of IC chips; a plurality of metal strips of
the substrate's top surface, disposed in the periphery area of the
substrate's top surface, and these metal strips being electrically
connected to the plurality of solder bumps; a plurality of metal
strips of the substrate's bottom surface, disposed in the periphery
area of the substrate's bottom surface; a plurality of via holes,
penetrating through the substrate and being electrically connected
to the plurality of metal strips of the substrate's top surface and
to the plurality of metal strips of the substrate's bottom surface
respectively; and an underfill, filling the solder bumps and the
plurality of the metal strips which are connected to the solder
bumps and are positioned on the IC chip's first surface, also
filling all the chinks around the top surface's metal strips of the
substrate, and covering the whole IC chip up to a height that is
slightly higher than the thickness of the MMIC chip. A penetration
hole is provided in the central areas of the top and bottom
surfaces of the substrate for those high power packages that
require optimum heat-dissipative effect. Moreover, the material
removed by penetrating the penetration hole is replaced by filling
a heat-dissipative material with relatively low dielectric constant
and relatively low dielectric loss.
BRIEF DESCRIPTION OF THE DRAWING
[0016] FIG. 1 is a structural disposition of a microwave integrated
circuit package according to a prior art.
[0017] FIG. 2 is a cross-sectional view of a microwave integrated
circuit package according to another prior art.
[0018] FIG. 3(a) is a cross-sectional view of a microwave
integrated circuit package according to one other prior art.
[0019] FIG. 3(b) is an isometric top view of a microwave integrated
circuit package according to the one other prior art shown in FIG.
3(a).
[0020] FIG. 4 is a flow chart showing the technical content and the
fabrication process of the flip chip package of a monolithic
microwave integrated circuit (MMIC) of the invention.
[0021] FIG. 5(a) is an isometric top view of a flip chip package of
an MMIC of the first embodiment of the invention.
[0022] FIG. 5(b) is a top view of the substrate's top surface of a
flip chip package of an MMIC of the first embodiment of the
invention.
[0023] FIG. 5(c) is a bottom view of the substrate's bottom surface
of an MMIC of the first embodiment of the invention.
[0024] FIG. 5(d) is a top view of the IC chip's bottom surface of a
flip chip package of an MMIC of the first embodiment of the
invention.
[0025] FIG. 6 is an isometric bottom view of a flip chip package of
an MMIC of the first embodiment of the invention.
[0026] FIG. 7 is a cross-sectional view of a flip chip package of
an MMIC of the first embodiment of the invention.
[0027] FIG. 8 is an isometric bottom view of a flip chip package of
an MMIC of the second embodiment of the invention.
[0028] FIG. 9 is a cross-sectional view of a flip chip package of
an MMIC of the second embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] The flip chip packages of the monolithic microwave
integrated circuit are classified into low power packages and high
power packages depending on the required power in their field of
application. The low power packages have their power less that one
milli-Watt (mW) while the high power packages have their power
greater that one milli-Watt (mW). As compared with low power
packages, high power packages require much better heat-dissipative
package structure in order to improve the reliability since the
high power packages contain MMIC that generates relatively high
quantity of heat. The first embodiment of the invention is a low
power package while the second embodiment of the invention is a
high power package.
[0030] The flip chip package of a monolithic microwave integrated
circuit of the first embodiment of the invention is illustrated in
FIG. 5(a), 5(b), 5(c), 5(d), FIG. 6, and FIG. 7. FIG. 5(a) is an
isometric top view of a flip chip package of an MMIC of the first
embodiment of the invention. FIG. 5(b) is a top view of the
substrate's top surface of a flip chip package of an MMIC of the
first embodiment of the invention. FIG. 5(c) is a bottom view of
the substrate's bottom surface of an MMIC of the first embodiment
of the invention. FIG. 5(d) is a top view of the IC chip's bottom
surface of a flip chip package of an MMIC of the first embodiment
of the invention. FIG. 6 is an isometric bottom view of a flip chip
package of an MMIC of the first embodiment of the invention. FIG. 7
is a cross-sectional view of a flip chip package of an MMIC of the
first embodiment of the invention.
[0031] As shown in FIG. 5(a), 5(b), 5(c), 5(d), FIG. 6, FIG. 7, the
flip chip package of a monolithic microwave integrated circuit of
the invention 4 includes a substrate 5, an integrated circuit chip
(IC chip) 6. The substrate 5 has a top surface 501 and a bottom
surface 502, and the IC chip 6 has a first surface 601 and a second
surface 602. The flip chip package of a monolithic microwave
integrated circuit 4 also includes a plurality of first surface
metal strips 641, 642, 643, 644, 645, 646, 647, 648, 649, 650, 671,
672, 673 of the IC chip 6, and a plurality of solder bumps 531,
532, 533, 534, 535, 536, 537, 538, 539, 540, 561, 562, 563
implanting on the plurality of first surface metal strips of the IC
chip 6, a plurality of substrate's top surface metal strips 511,
512, 513, 518, 519, 520, 514, 515, 516, 517, 541, 542, 543, a
plurality of substrate's bottom surface metal strips 571, 572, 573,
574,575, 576, 577, 578, 579, 580, and a plurality of via holes 521,
522, 523, 524, 525, 526, 527, 528, 529, 530.
[0032] Among them, the top surface 501 of the substrate 5 includes
a first side 581, a second surface 582, a third side 583, and a
fourth side 584. Moreover the whole top surface 501 of the
substrate 5 is divided into a periphery area 585 and a central area
586. In the similar way, the bottom surface 502 of the substrate 5
includes a first side 591, a second surface 592, a third side 593,
and a fourth side 594. Moreover, the whole bottom surface 502 of
the substrate 5 is divided into a periphery area 595 and a central
area 596.
[0033] What is more, the first surface 601 of the IC chip 6
includes a first side 611, a second side 612, a third side 613, and
a fourth side 614. Moreover, the whole first surface 601 of the IC
chip 6 is divided into a periphery area 615 and a central area
616.
[0034] FIG. 4 is a flow chart showing the technical content and the
fabrication process of the flip chip package of a monolithic
microwave integrated circuit (MMIC) of the invention. The package
structure and the technical content of the flip chip package of a
monolithic microwave integrated circuit can be understood in
accordance with the flow chart shown in FIG. 4. As shown in FIG. 4,
first of all (step 401, 402), input/output ports (I/O ports) (not
shown), having been connected to external circuit, are disposed on
the top surface 501 of the substrate 5. These I/O ports include
direct current (DC) source terminals, signal terminals, and ground
terminals. Next (step 403), as shown in FIG. 5(b), a plurality of
metal strips (acting as I/O ports) and via holes connected thereof
respectively are provided in the periphery area 585 on the top
surface 501 of the substrate 5. They are metal strips 511, 512, 513
and their corresponding via holes 521, 522, 523 on the first side
581, metal strips 518, 519, 520 and their corresponding via holes
528, 529, 530 on the second side 582, metal strips 514, 515, 516,
517 and their corresponding via holes 527 on the third side 583, as
well as metal strips 541, 542, 543 and their corresponding via
holes 524, 525, 526 on the fourth side 584. Etching method can be
employed for providing these metal strips on the substrate 5, and
the materials employed for these metal strips on both the top
surface 501 and the bottom surface 502 of the substrate 5 can be
gold (Au), copper (Cu), or aluminum (Al). As for the material for
the metal strips on the IC chip 6, gold (Au), copper (Cu), or
aluminum (Al) can also be employed.
[0035] Thereafter, similarly as shown in FIG. 5(c), a plurality of
metal strips and via holes connected thereof respectively are
provided in the periphery area 595 on the bottom surface 502 of the
substrate 5. They are metal strips 571, 572, 573 and their
corresponding via holes 521, 522, 523 on the first side 591, metal
strips 578, 579, 580 and their corresponding via holes 528, 529,
530 on the second side 592, metal strip 577 and its corresponding
via hole 527 on the third side 593, as well as metal strips 574,
575, 576 and their corresponding via holes 524, 525, 526 on the
fourth side 594. The metal strips provided on the bottom surface
502 of the substrate 5 and acting as I/O ports are electrically
connected to the metal strips, also acting as I/O ports, provided
on the top surface 501 of the substrate 5 through these via
holes.
[0036] Subsequently, same way is undertaken as shown in FIG. 5(d).
a plurality of metal strips are provided in the periphery area 615
on the first surface 601 of the IC chip 6. They are metal strips
641, 642, 643 on the first side 611, metal strips 648, 649, 650 on
the second side 612, metal strips 644, 645, 646, 647 on the third
side 613, as well as metal strips 671, 672, 673 on the fourth side
614. Afterwards (step 405), solder bumps are implanted on the
plurality of metal strips provided in the periphery area 615 on the
first surface 601 of the above-mentioned IC chip 6. They are solder
bumps 531, 532, 533 on the metal strips 641, 642, 643 on the first
side 611 of the first surface 601 of the IC chip 6; solder bumps
538, 539, 540 on the metal strip 648, 649, 650 on the second side
612; solder bumps 534, 535, 536, 537 on the metal strips 644, 645,
646, 647 on the third side 613; as well as solder bumps 561, 562,
563 on the metal strip 671, 672, 673 on the fourth side 614. The
metal strips provided on the first surface 601 of the IC chip 6 and
acting as I/O ports are electrically connected to the metal strips,
also acting as I/O ports, provided on the top surface 501 of the
substrate 5 through these solder bumps. The solder bumps are
employed to directly transmit the radio-frequency signals from the
G-S-G or S-G I/O port structure on the MMIC to the G-S-G or S-G I/O
port structure on the substrate where the G-S-D and S-G denote
ground-signal-ground and signal-ground respectively. This method of
the invention does not deteriorate the electrical characteristics
of the MMIC while the conventional chip-and-wire method does. Then
(step 406), the IC chip 6 is flipped over and having its active
surface (the first surface) covered on the substrate 5. Thereafter
(step 407), solder bumps are implanted by placing method and a
reflow process is performed to accomplish the forming of the solder
bumps. In addition to the placing method, the methods of
deposition, electroplating, and stencil printing can also be
employed for forming the solder bumps, and the material for the
solder bumps can be a metal or alloy such as gold (Au), gold-tin
(Au--Sn), gold-silicon (Au--Si), gold-germanium (Au--Ge), tin-lead
(Sn--Pb), tin-silver (Sn--Ag), tin-lead-silver (Sn--Pb--Ag), indium
(In), indium-tin (In--Sn), or indium-lead (In--Pb). It is
worthwhile to mention that the plurality of solder bumps formed in
the periphery area 615 on the first surface 601 of the IC chip 6
can also be implanted on the top surface 501 of the substrate
5.
[0037] In the IC chip 6 of the flip chip package of a monolithic
microwave integrated circuit of the invention, the first surface
601 is the active area provided with electronic device, and the
MMIC package 4 is to have the IC chip 6 flipped over and having its
first surface 601 covering on the top surface 501 of the substrate
5. The circuit on the electronic device is electrically connected
to the metal strips on the first surface 601 through the traces
(not shown) extended from the circuit. The active area becomes the
main source of heat generation since the active area can generate
heat as the active device is operating. The material of the IC chip
can be selected from gallium arsenide (GaAs) of III-V group
compound or silicon (Si).
[0038] From hereon (step 408), underfill 7 is employed to fill
around the solder bumps and the plurality of the metal strips which
are connected to the solder bumps and are positioned on the IC
chip's first surface. The underfill 7 is also employed to fill all
the chinks around the top surface's metal strips of the substrate
5, and to cover the whole IC chip up to a height that is slightly
higher than the thickness of the MMIC chip. Finally (step 409), a
singulating process is performed to the substrate 5, and the
packaging process is accomplished (step 410).
[0039] In the flip chip package of a monolithic microwave
integrated circuit of the invention, the one applicable to the high
power device is the "high power package" of the second embodiment
of the invention. FIG. 8 is an isometric bottom view of a flip chip
package of an MMIC of the second embodiment of the invention, and
FIG. 9 is a cross-sectional view of a flip chip package of an MMIC
of the second embodiment of the invention. Repeated illustration on
the package structure of the flip chip package of an MMIC of the
second embodiment of the invention shown in FIG. 8 and FIG. 9 is
not necessary since the package structure is almost the same as
that of the first embodiment of the invention. The only difference
is a penetration hole 503 provided through the central area 586 of
the top surface 501 and the central area 596 of the bottom surface
502 of the substrate 5. The material removed by penetrating the
penetration hole is replaced by filling a heat-dissipative material
which can be selected from boron nitride (BN), aluminum nitride (Al
N), berylium oxide (BeO), aluminum oxide (Al.sub.2O.sub.3), or
silicon carbide (Si C).
[0040] Among the first and second embodiments of the flip chip
package of a monolithic microwave integrated circuit of the
invention, the number and disposition of the metal strips, solder
bumps, and via holes depends on the structure and dimension of the
IC chip.
[0041] The flip chip package of an MMIC of the invention has the
advantage of low cost, high operation frequency, fast in heat
dissipation. In addition, this MMIC package of the invention can
undertake mass production since the package size become smaller
after the packaging process. What is more, the operation frequency
can be improved since the package of the invention has less
parasitic capacitance and parasitic inductance as the package of
the prior art that has the chip-and-wire package. Therefore, the
invention has the advantages what the package of the conventional
MMIC can not achieve.
[0042] While the invention has been described by way of example and
in terms of a preferred embodiment, it is to be understood that the
invention is not limited to the disclosed embodiment. On the
contrary, it is intended to cover various modifications. Therefore,
the scope of the appended claims should be accorded the broadest
interpretation so as to encompass all such modifications.
* * * * *