Integrated circuit package with multiple heat dissipation paths

Details Integrated circuit package with multiple heat dissipation paths Integrated circuit package with multiple heat dissipation paths

1999-08-24

2001-02-13

Picard, Leo P. (Department: 2835)

Electricity: electrical systems and devices

Housing or mounting assemblies with diverse electrical...

For electronic systems and devices

C361S704000, C361S707000, C361S718000, C361S719000, C257S706000, C257S717000, C174S016300, C165S080200, C165S080300, C165S185000

Reexamination Certificate

active

06188578

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an integrated circuit package, and more particularly, to an integrated circuit package with a heat spreader to dissipate heat.
2. Description of Related Art
Because the integrated circuit semiconductor device is getting more complicated in function and smaller in size, the flip chip semiconductor device is seeing more wide-spread use, since flip chip mounting permits a high component density and fast accessing time.
FIG. 4
shows a conventional integrated circuit package which is of a well known “flip chip on board” type packaging. By welding the solder bumps
42
of a die
40
to a printed circuit board
41
, the die
40
is electrically connected to the printed circuit board
41
. An underfill
43
is injected between the die
40
and the printed circuit board
41
to securely consolidate the die
40
with the printed circuit board
41
so that the solder joints between the die
40
and the printed circuit board
41
will not be damaged due to different degrees of thermal expansion of the die
40
and the printed circuit board
41
upon thermal excursions, which the integrated circuit semiconductor device experiences during operation.
However, due to the fact that the aforementioned flip chip semiconductor device is of small volume and with high power density, the thermal resistance greatly increases. The major heat dissipation paths are from the backside of the die
40
to the environment and from the lower portion of the die
40
to the printed circuit board
41
. Unfortunately, the underfill filled between the die
40
and the printed circuit board
41
is of an insulating material, such as epoxy resin, whose heat conducting capability is extremely low. Therefore, the heat from the die
40
is difficult to be conducted to the printed circuit board
41
and the heat dissipation capability of such a flip chip semiconductor device is unsatisfactory.
In order to eliminate the aforementioned heat dissipating problem, an additional heat cap or heat spreader may be employed to assist in dissipating heat.
FIG. 5
shows a flip chip integrated circuit package having a die
50
attached to a substrate
53
that is mounted on a printed circuit board
54
. A metal heat sink
51
is further mounted on the top of the die
50
via adhesive
52
such that the heat from the die
50
is dissipated to the heat sink
51
. With such a flip chip packaging structure, the effective heat dissipating area can be increased by using the heat sink
51
. However, the heat sink
51
is secured to the die
50
by adhesive
52
, thus the load on the die
50
is heavy so that the connection between the die
50
and the substrate
53
is likely to be damaged due to stress generated by the heavy load. Therefore, the reliability of such a packaged semiconductor device is difficult to promote.
Alternatively,
FIG. 6
shows a flip chip integrated circuit package, which has a metal heat cap
61
disposed on a substrate
63
to cover a die
60
. The heat cap
61
is adhered to the substrate
63
through epoxy resin
62
. A heat conductive adhesive
64
is filled between the heat cap
61
and the die
60
. Thus, the heat from the die
60
can be dissipated out through the heat cap
61
. With such a packaging structure, the heat cap
61
is adhered to the substrate
63
through the epoxy resin
62
that is unable to transfer heat. Thus, the heat can not be effectively conducted to the substrate
63
to be dissipated. Moreover, the aforementioned heat sink
51
and the heat cap
61
are with large footprints with respect to that of the die
50
,
60
. However, since the density of the electronic package is getting higher and the size of electronic product is getting smaller, adding such large heat dissipation elements to the flip chip device is obviously undesired, as it will greatly increase the space required by the flip chip device. Thus, there is a need for the above integrated circuit packages to be improved.
Among the known patents related to the heat dissipation of a flip chip integrated circuit package, U.S. Pat. No. 5,847,929 granted to Bernier et al. has disclosed the use of an adhesive of silicone or flexible-epoxy to attach a heat sink to a semiconductor chip. U.S. Pat. No. 5,726,079 granted to Johnson has provided a thermally conductive planar member in packaging a flip chip. U.S. Pat. No. 5,650,662 granted to Edwards et al. has disclosed a heat spreader that is directly bonded to an electronic device package. U.S. Pat. No. 5,856,911 granted to Riley has provided an integrated circuit package having a top die attach area and a bottom heat spreader thermally coupled to the die. The above patents are provided to dissipate heat out of integrated circuit packages with only one heat dissipation path which us from the die upward to the environment. Therefore, they can not be used to effectively solve the aforementioned heat dissipation problems.
SUMMARY OF THE INVENTION
Accordingly, the object of the present invention is to provide an integrated circuit package having a heat spreader to dissipate heat generated by a die both from the backside of the die and by conducting to the printed circuit board, so as to improve the heat dissipating effect. Moreover, the installation of the heat spreader will not increase the load of the die.
To achieve the object, an integrated circuit package is provided which has a printed circuit board and a die attached to the printed circuit board. A heat spreader secured to the printed circuit board is provided to cover the die and contact with the backside of the die, so that heat from the die can be transferred upward to the environment and downward to the printed circuit board through the heat spreader. Further, since the heat spreader is secured to the printed circuit board, no additional load is added to the die.


REFERENCES:
patent: 4914551 (1990-04-01), Anschel et al.
patent: 5459352 (1995-10-01), Layton et al.
patent: 5504652 (1996-04-01), Foster et al.
patent: 5710459 (1998-01-01), Teng et al.
patent: 5870285 (1999-02-01), Kosteva et al.
patent: 5898571 (1999-04-01), Mertol
patent: 5920458 (1999-07-01), Azar
patent: 5926371 (1999-07-01), Dolbear
patent: 5933324 (1999-08-01), Barrett
patent: 6008536 (1999-12-01), Mertol
patent: 407106721 (1995-04-01), None

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