Active solid-state devices (e.g. – transistors – solid-state diode – Encapsulated – With heat sink embedded in encapsulant
Reexamination Certificate
2001-08-15
2002-11-26
Lee, Eddie (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Encapsulated
With heat sink embedded in encapsulant
C257S687000, C257S706000, C257S710000, C257S712000, C257S787000
Reexamination Certificate
active
06486564
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to an improve structure of a heat dissipation module for BGA (Ball Grid Array) IC (Integrated Circuit) devices, and more specifically to a metal heart dissipation module design for circuit chips encapsulated in an IC device.
2. Related Art
The BGA IC device is a new generation of semiconductor device that has a small volume and many pins. It is made by mounting a cut chip on a substrate with each I/O connecting point of the chip forming electrical communications with the corresponding circuits on the substrate, followed by glue encapsulation and implanting arrayed tin balls on the bottom surface of the substrate. The arrayed tin balls implanted on the bottom of device replace conventional pins. They are formed at designated locations on a circuit board using surface mount technology.
The chip in the foregoing IC device produces a high temperature during operation. The high temperature has to be controlled so that the chip can function normally. In addition to mixing metal materials that help heat conduction into the glue material, another design, shown in
FIG. 4
, encapsulates a metal heat dissipation module
7
, a chip
8
, and a substrate
80
in glue
82
. The heat dissipation module
7
has an annular base
70
installed on the substrate
80
and over the chip
8
. Several supports
71
extending upward from the inner rim of the annular base
70
support a top plate
72
that is higher than wires
81
connecting the I/O connecting points on the chip
8
to those on the substrate
80
. The top plate
72
is outside the glue
82
after encapsulation so that the heat produced by the operating chip
8
can be quickly released to the atmosphere through the large area top plate
72
and good heat conductivity of the metal heat dissipation module
7
.
Even though the heat dissipation module
7
can provide heat conduction and dissipation for the chip
8
, it is hard to make the top plate
72
of the heat dissipation module
7
totally flat as required. Therefore, the module cannot nicely match the mold. Even if the top plate
72
can be made to be exactly flat, it will also deform due to the high temperature. Thus, when the heat dissipation module
7
and the substrate
80
with the chip
8
mounted on the substrate
80
are encapsulated in the mold
83
, the glue
82
is likely to flow onto the outer surface of the top plate
72
, producing so-called glue overflow. This results in bad appearance of the device. If the length or area of the overflown glue exceeds an allowed range, an additional cleaning procedure is needed. This will increase machining costs and difficulty in manufacturing.
Furthermore, since the top plate
72
of the heat dissipation module
7
is simply flat, as shown in
FIG. 5
, the total contact surface between the top plate
72
and the air is not a very large area. Thus, the heat dissipation effect is limited.
SUMMARY OF THE INVENTION
In view of the drawbacks in the foregoing heat dissipation module for IC devices, the heat dissipation module in accordance with the present invention provides an improved structure for heat dissipation modules for BGA IC devices. The top plate dissipation can match with the mold better, thereby reducing the problem of thermal expansion. It can fully solve the glue overflow problem during encapsulation and ensures that each finished product satisfies the standards, avoiding the need for a second machining. The design can also increase the heat dissipation area for better heat dissipation.
To achieve the foregoing objective, the main technique disclosed herein is that the heat dissipation module has an annular base whose inner rim is greater than the area needed for connection between the chip and the substrate. Several supports extend from the inner rim of the annular base upwards to support a top plate. The top plate is higher than the highest point of the electrical connection between the chip and the substrate. By extending at least one protruding ring on the top surface of the top plate, the heat dissipation module can match the mold better during encapsulation, thereby avoiding the glue overflow problem and increasing the total area for heat dissipation.
FIG. 1
is a perspective view of the heat dissipation module in accordance with the present invention;
FIG. 2
is a cross-sectional side plan view of the heat dissipation module in
FIG. 1
used with a BGA IC device;
FIG. 3
is an enlarged cross sectional side plan view of the top plate of the heat dissipation module in
FIG. 2
;
FIG. 4
is a cross-sectional side plan view of a conventional heat dissipation module used with a BGA IC device; and
FIG. 5
is an enlarged cross sectional side plan view of the top plate of the conventional heat dissipation module in FIG.
4
.
REFERENCES:
patent: 5289039 (1994-02-01), Ishida et al.
patent: 6229702 (2001-05-01), Tao et al.
patent: 6246115 (2001-06-01), Tang et al.
patent: 697321 (1994-04-01), None
patent: 697326 (1994-04-01), None
Lee Kuo-Yuan
Liu Wen-Chun
Pan Yi-Hsiang
Dellett and Walters
Lee Eddie
Walsin Advanced Electronics Ltd.
Warren Matthew E.
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