Flip chip package of monolithic microwave integrated circuit

Details Flip chip package of monolithic microwave integrated circuit Flip chip package of monolithic microwave integrated circuit

2001-08-09

2002-12-17

Williams, Alexander O. (Department: 2826)

Active solid-state devices (e.g., transistors, solid-state diode

Housing or package

For high frequency device

C257S778000, C257S734000, C257S737000, C257S738000, C257S724000, C257S725000, C257S691000, C257S774000, C257S684000, C257S796000

Reexamination Certificate

active

06495915

ABSTRACT:

FIELD OF THE INVENTION
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
In our modem 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.
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.
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.
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
.
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.
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.
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.
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
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:
1. The undesired impedance matching and the self-resonant problems resulted from the parasitic capacitance and parasitic inductance generated by the bonding wires.
2. The inability problem to undertake automation on the production of the chip-and-wire package.
3. The inertly heat-dissipative problem of the chip of gallium arsenide (GaAs) commonly used by the RF, microwave, and milli-wave.
4. The inability to have a compact package since the size of the package becomes large after the packaging process.
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 dispos

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