Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – With provision for cooling the housing or its contents
Reexamination Certificate
2003-06-18
2004-06-22
Trinh, Michael (Department: 2822)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
With provision for cooling the housing or its contents
C257S720000, C257S717000
Reexamination Certificate
active
06753602
ABSTRACT:
FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION
A conventional BGA (Ball Grid Array) semiconductor package with a heat-dissipating device is illustrated in
FIG. 5
, as designated by the reference numeral
1
. In the drawing, this semiconductor package
1
includes a substrate
10
having a first side
10
A and a second side
10
B, with a semiconductor chip
12
mounted on the first side
10
A and electrically connected to the substrate
10
via gold wires
11
. Further, a heat sink
13
is attached to the first side
10
A of the substrate
10
by means of an adhesive
16
. The heat sink
13
is composed of a flat section
130
and supporting sections
131
used to support the flat section
130
to be positioned above the chip
12
at a predetermined height. A receiving space
132
defined by the flat section
130
, the supporting sections
131
and the first side
10
A of the substrate
10
is used to receive the chip
12
and the gold wires
11
therein. Moreover, an encapsulant
14
is formed through a molding process to hermetically enclose the chip
12
, the gold wires
11
, the heat sink
13
and the first side
10
A of the substrate
10
, with an upper side
130
A of the flat section
130
of the heat sink
13
exposed to the atmosphere. Finally, a plurality of solder balls
15
are mounted on the second side
10
B of the substrate
10
.
One drawback to the foregoing BGA semiconductor package
1
, however, is that the heat sink
13
may be attached to the substrate
10
in a slant manner, due to failure in accurately controlling the amount of the adhesive
16
applied to the supporting sections
131
, as shown in FIG.
5
. As a result, a portion
130
C of the flat section
130
slants downwardly and a spacing is then formed between an encapsulating mold (not shown) for forming the encapsulant
14
and the portion
130
C during the molding process, allowing flash of a molding resin used for making the encapsulant
14
to form on the portion
130
C; when the upper side
130
A of the flat section
130
of the heat sink
13
for heat-dissipation is partly covered by the flash of the molding resin, the area of the upper side
130
A directly exposed to the atmosphere is decreased and the heat-dissipating efficiency thereof is reduced. Accordingly, another portion
130
D of the flat section
130
is upwardly slanted in response to the downward slant of the portion
130
C, which leads to damage to the substrate
10
resulting from the clamping force generated by the encapsulating mold for forming the encapsulant
14
. Therefore, quality and appearance of the semiconductor package
1
are degraded.
Another drawback to the aforementioned semiconductor package
1
is that, the heat sink
13
can not be positioned precisely on the substrate
10
by using the adhesive
16
for attachment thereof. If the heat sink
13
is not disposed in a predetermined position, the package appearance may be damaged, and short circuit may occur, due to accidental contact of the supporting section
131
with the gold wires
11
used for electrically connecting the chip
12
to the substrate
10
.
In conclusion, it is disadvantageous to manufacture a semiconductor package with planarity and positioning of a heat sink mounted therein unable to be assured, and it is also cost-ineffective and a waste of resources to discard those unqualified products. In addition, a complex process, e.g. stamping, is required for the manufacture of the heat sink with the desired flat section and supporting sections, and thus the manufacturing cost is increased.
SUMMARY OF THE INVENTION
It is therefore an objective of the present invention to provide a semiconductor package with a heat-dissipating structure and the method for making the same, which assure the planarity and positioning of the heat-dissipating structure on a substrate on which the heat-dissipating structure is mounted so as to enhance the quality and yield of the manufactured package and to lower the manufacturing cost.
It is another objective of the invention to provide a semiconductor package with a heat-dissipating structure and the method for making the same, which simplify the manufacturing process and reduce the manufacturing cost thereof, due to the attachment of the heat dissipating structure to the substrate being free of the use of any adhesive.
It is still another objective of the invention to provide a semiconductor package with a heat-dissipating structure and the method for making the same, which help prevent flash from contaminating the surface of the heat-dissipating structure exposed to the atmosphere.
It is yet another objective of the invention to provide a semiconductor package with a heat-dissipating structure and the method for making the same, which help increase the heat-dissipating efficiency by forming a protrusion on the heat-dissipating structure toward the semiconductor chip.
In accordance with the foregoing and other objectives of the invention, a semiconductor package with a heat-dissipating structure and the method for making the same are proposed. The semiconductor package of the invention includes a substrate having a first side and a second side; a semiconductor chip attached to and electrically connected to the first side of the substrate; a heat-dissipating structure comprising a heat sink having a first surface and a second surface and a plurality of solder columns attached to the second surface of the heat sink, so that the heat sink is elevated to a predetermined height above the semiconductor chip via the solder columns when the heat-dissipating structure is mounted on the first side of the substrate via the solder columns; an encapsulant formed on the first side of the substrate so as to encapsulate the semiconductor chip and the heat-dissipating structure in a manner that the first surface of the heat sink is exposed to the exterior of the encapsulant; and a plurality of conductive elements attached to the second side of the substrate.
The method for making the semiconductor package of the invention comprises the steps of: providing a heat sink having a first surface and a second surface; forming a plurality of concaves at preset positions on the second surface of the heat sink, the concaves being arranged in position not to interfere with electrical connection between a semiconductor chip and a substrate for carrying the semiconductor chip and the heat sink; attaching a plurality of solder columns to the concaves on the second surface of the heat sink respectively to form a heat-dissipating structure; providing a substrate having a first side and a second side; forming on the first side of the substrate a plurality of connecting pads for attaching the solder columns; mounting at least one semiconductor chip on the first side of the substrate and electrically connecting the semiconductor chip to the substrate; attaching the heat-dissipating structure to the first side of the substrate by reflowing the solder columns to the connecting pads on the substrate; forming an encapsulant on the first side of the substrate to encapsulate the semiconductor chip and the heat-dissipating structure, while allowing the first side of the heat sink to be exposed to the atmosphere; and mounting a plurality of conductive elements on the second side of the substrate.
Alternatively, the manufacture of the semiconductor package of the invention may further comprise a step of encapsulating the semiconductor chip mounted on the substrate, prior to the step of attaching the heat-dissipating structure to the substrate by reflowing the solder columns to the connecting pads of the substrate.
The concaves on the second surface of the heat sink may be formed by etching solder mask coated on the heat sink.
The solder columns are made of material having a melting point lower than that of the heat sink, such that the solder columns are flexible in nature and capable of acting as a cushion between the heat sink and the substrate to thereby prevent the substrate from being damaged during a molding process for forming the encapsulant. The materia
Corless Peter F.
Edwards & Angell LLP
Jensen Steven M.
Siliconware Precision Industries Co. Ltd.
Trinh Michael
LandOfFree
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