Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2000-04-10
2001-08-28
Tolin, Gerald (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C029S843000, C257S720000, C361S719000
Reexamination Certificate
active
06282094
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to integrated circuit (IC) packages, and more particularly, to a BGA (Ball-Grid Array) IC package with an unembedded type of heat-dissipation structure.
2. Description of Related Art
The BGA IC packaging technology allows an IC package to be made very small in size while nevertheless providing highly integrated functionality from a single IC package. During the operation of the IC chip, however, a large amount of heat would be generated from the internal circuitry of the IC chip. Therefore, it is required to provide heat-dissipating means on the IC package for heat dissipation during operation. To allow a BGA IC package to dissipate the IC-produced heat during operation, a conventional solution is to arrange a heat sink or a heat slug in the package structure.
The U.S. Pat. No. 5,285,352 discloses a BGA IC package configuration that utilizes a heat sink for heat dissipation, whose structure is illustrated in FIG.
4
. As shown, the BGA IC package configuration
110
includes an IC chip
112
mounted on a substrate
114
by means of silver paste
116
, and is characterized in that a heat sink
128
is embedded in an opening
130
formed in the substrate
114
and beneath the IC chip
112
. The heat sink
128
has a top side abutted on the bottom side of the IC chip
112
and a bottom side exposed to the atmosphere from the bottom side of the substrate
114
. The IC-produced heat during operation can be dissipated through this heat sink
128
to the outside of the package body.
Moreover, the U.S. Pat. No. 5,642,261 discloses a BGA IC package configuration that utilizes a heat slug for heat dissipation, whose structure is illustrated in FIG.
5
. As shown, the BGA IC package configuration includes an IC chip
70
mounted on a substrate
74
, and is characterized in that a heat slug
72
is arranged beneath the IC chip
70
. The heat slug
72
has a top side abutted on the bottom side of the IC chip
70
and a bottom side exposed to the atmosphere from the bottom side of the substrate
74
. The IC-produced heat during operation can be dissipated through this heat slug
72
to the outside of the package body.
In addition, the U.S. Pat. No. 5,583,377 discloses a BGA IC package configuration that utilizes a heat sink for heat dissipation, whose structure is illustrated in FIG.
6
. As shown, the BGA IC package configuration includes an IC chip
213
and a substrate
212
, and is characterized in the use of a heat sink
222
having a base portion
224
, a sidewall portion
226
, and a flange portion
228
. The heat sink
222
is embedded in an opening
220
formed in the substrate
212
, and its flange portion
228
is fixed on the rim of the opening
220
on the top surface of the substrate
212
. The IC chip
213
is mounted by means of silver paste
230
on the base portion
224
within the space defined by the sidewall portion
226
. The IC-produced heat during operation can be dissipated through this heat sink
222
to the outside of the package body.
The foregoing patented package structures, however, have the following draw-backs.
First, since the heat slug or heat sink is embedded in the substrate and is different in coefficient of thermal expansion (CTE) from the substrate, the substrate would be easily subjected to compressive stress resulted from the heat slug or heat sink when undergoing a temperature change during the molding process, and thus easily deformed or broken.
Second, since the embedding of the heat slug or heat sink in the opening of the substrate would hardly achieve absolute airtightness, it would easily allow ambient moisture to enter into the inside of the package body. If the inside of the package body contains moisture, it would easily explode during the solder reflow process, resulting in the so-called popcorn effect, which can break up the entire package body.
Third, since it is required to form an opening in the substrate, it would make the overall manufacture process more complex, thus increasing the overall manufacture cost. In addition, the making of the heat slug and heat sink would require precise machining so as to allow the heat slug or heat sink to be fitted snuggly to the opening, which is also hard to achieve, thus resulting in poor quality of the manufactured IC package.
Fourth, since the heat slug or heat sink is typically made of metal, it would considerably increase the overall weight of the entire IC package, thus undesirably making the manufactured IC package heavier to handle.
SUMMARY OF THE INVENTION
It is therefore an objective of this invention to provide a BGA IC package configuration with an unembedded type of heat-dissipation structure, which can be manufactured using existing equipment and process.
It is another objective of this invention to provide a BGA IC package configuration with an unembedded type of heat-dissipation structure, which can prevent ambient moisture from entering into the inside of the package body.
It is still another objective of this invention to provide a BGA IC package configuration with an unembedded type of heat-dissipation structure, which can be manufactured easily through a simplified process so as to reduce manufacture cost.
In accordance with the foregoing and other objectives, the invention proposes a novel BGA IC package configuration that comes with an unembedded type of heat-dissipation structure.
The BGA IC package configuration of the invention includes: a substrate having a front surface and a back surface, with the front surface having a central part being defined as a die-attachment area; an IC chip mounted on the die-attachment area of the substrate; a first electrically-conductive trace formed over the front surface of the substrate, which is electrically connected to the IC chip; a plurality of electrically-conductive vias formed in the substrate and extending from the front surface to the back surface of the substrate; a plurality of electrically-conductive devices arranged on the back surface of the substrate and bonded to the electrically-conductive vias; a plurality of thermally-conductive vias formed in the die-attachment area of the substrate and extending from the front surface to the back surface of the substrate; a plurality of thermally-conductive devices arranged on the back surface of the substrate and bonded to the thermally-conductive vias; and a thermally-conductive layer spreading over the area where the thermally-conductive devices are arranged.
The thermally-conductive layer can help increase the exposed area of the overall heat-dissipation structure to the atmosphere, so that the overall heat-dissipation efficiency can be increased. Moreover, the unembedded manner of integration requires no openings to be formed in the substrate that would otherwise allow ambient moisture to enter into the inside of the package body as in the case of the prior art, and also allows the heat-dissipation structure to be more easily integrated to the package configuration, allowing the overall manufacture process to be more simplified and thus more cost-effective to carry out, making the invention more advantageous to use than the prior art.
REFERENCES:
patent: 5285352 (1994-02-01), Pastore et al.
patent: 5583377 (1996-12-01), Higgins, III
patent: 5642261 (1997-06-01), Bond et al.
patent: 5741729 (1998-04-01), Selna
patent: 5825628 (1998-10-01), Garbelli
patent: 5942795 (1999-08-01), Hoang
patent: 5959356 (1999-09-01), Oh
patent: 6008536 (1999-12-01), Mertol
patent: 6023098 (2000-02-01), Higashiguchi
patent: 6034427 (2000-03-01), Lan
patent: 6038137 (2000-03-01), Bhatt
patent: 6117705 (2000-09-01), Glenn
patent: 6125042 (2000-09-01), Verdi
Ho Tzong-Da
Ko Eric
Lai Jeng Yuan
Lo Randy H. Y.
Corless Peter F.
Edwards & Angell LLP
Siliconware Precision Industries Co. Ltd.
Tolin Gerald
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