Method of making semiconductor package with heat spreader

Details Method of making semiconductor package with heat spreader Method of making semiconductor package with heat spreader

2001-11-15

2002-09-03

Graybill, David E. (Department: 2812)

Semiconductor device manufacturing: process

Packaging or treatment of packaged semiconductor

Insulative housing or support

C438S122000, C438S124000, C438S127000, C257S783000, C257S792000, C257S709000, C257S706000, C257S717000, C257S796000

Reexamination Certificate

active

06444498

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to methods of making semiconductor packages, and more particularly, to a method of making a semiconductor package with a heat spreader, which can enhance heat-dissipating efficiency.
BACKGROUND OF THE INVENTION
How to efficiently dissipate heat generated by a semiconductor chip in operation and to assure lifetime and quality of a semiconductor package having the semiconductor chip encapsulated therein, has always been one critical topic to investigate in semiconductor industry.
Accordingly U.S. Pat. No. 5,726,079 discloses a semiconductor package shown in FIG.
8
. This conventional semiconductor package
1
has a heat spreader
11
directly mounted on a semiconductor chip
10
, with a top surface
110
of the heat spreader
11
being exposed to outside of an encapsulant
12
that encapsulates the chip
10
. Due to the direct attachment of the heat spreader
11
to the chip
10
, and the exposed top surface
110
of the heat spreader
11
in direct in contact with the atmosphere, thus heat generated by the chip
10
can be directly transmitted to the heat spreader
11
for being dissipated to the atmosphere. Such a heat dissipating path needs not to go through the encapsulant
12
, thereby making the semiconductor package
1
good in heat dissipation.
However, there are several drawbacks for fabricating such a semiconductor package
1
. First, when the chip
10
attached with the heat spreader
11
is placed in a molding cavity in a molding process, the top surface
110
of the heat spreader
11
is supposed to abutting a top wall of the molding cavity, so as to avoid the occurrence of flash on the top surface
110
of the heat spreader
11
. If the top surface
110
of the heat spreader
11
cannot closely abut the top wall of the molding cavity with a gap being formed therebetween, thus a molding compound used for forming the encapsulant
12
flashes through the gap on the top surface
110
of the heat spreader
11
. The flashes occurred on the heat spreader
11
not only deteriorate heat dissipating efficiency, but also impair appearance of the fabricated product. As a result, a deflash process is often required subsequently. However, this deflash process is time consuming and cost ineffective, and also possibly damages the fabricated product. On the other hand, if the heat spreader
11
too closely abuts the top wall of the molding cavity, damage to the chip
10
possibly occurs due to excessive abutting force.
Moreover, an adhesive or laminating tape used for adhering the heat spreader
11
to the chip
10
is mostly made of a thermosetting material, and thus appears to be soft prior to being subjected to a curing process. This makes structure of the chip
10
combined with the heat spreader
11
difficult to be controlled in height, thereby resulting in the foregoing problems due to the top surface
110
of the heat spreader
11
not properly coming into contact with the top wall of the molding cavity. As a result, quality of the fabricated product cannot be assured, as well as costs in fabrication cannot be reduced.
Furthermore, since precise height control is required for the combined structure of the heat spreader
11
and the chip
10
, thus the heat spreader
11
cannot be attached to the chip
10
in batch-type manner for fabricating the semiconductor package
1
. In other words, the heat spreader
11
has to be one-by-one deposited on the corresponding chip
10
, and this therefore increases complexity and time consumption in fabrication, which is not favorable in cost reduction and fabrication efficiency improvement.
Besides, the heat dissipating efficiency of the semiconductor package
1
is proportional to surface area of the exposed top surface
110
of the heat spreader
11
; that is, in the case of the semiconductor package
1
remaining intact in size, the heat spreader
11
identical in surface area to the package provides the maximum exposed area, as well as the maximum heat dissipating efficiency. However, when the heat spreader is dimensioned to have the same surface area as the package, edge sides of the heat spreader size needs to be aligned with side walls of the molding cavity. If the heat spreader is oversized due to fabrication inaccuracy, it cannot be successfully placed into the molding cavity; whereas if the heat spreader is undersized, flashes easily occur on the top surface or edge sides thereof. Therefore, such structure is disadvantageous in quality degradation and difficulty in fabrication.
U.S. Pat. No. 5,471,366 discloses another semiconductor package having an exposed heat spreader. In this semiconductor package, the heat spreader is encapsulated by an encapsulant in a molding process; whereas after completing the molding process, part of the encapsulant positioned above the heat spreader is ground until a top surface of the heat spreader being exposed to outside of the encapsulant. Such a disclosure eliminates the foregoing problems in the U.S. Pat. No. 5,726,079, but still have several drawbacks as follows. First, the use of the extra grinding process increases complexity and costs in fabrication for preparing a grinding machine and equipment. Moreover, if warpage occurs in the semi-fabricated package after forming the encapsulant, this degrades planarity of the semi-fabricated package to be ground, thereby making the semi-fabricated package easily damaged in the grinding process, and thus increasing the fabrication cost.
Chinese Patent Application No. 90118118 proposed by the inventor of the present invention discloses a fabrication method of a semiconductor package, so as to effectively improve the foregoing drawbacks in the conventional semiconductor packages having the exposed heat spreaders. This fabrication method comprises the following steps.
First, a heat spreader module plate is attached to a plurality of semiconductor chips mounted on a chip carrier module plate. Then, an interface layer is formed on the heat spreader module plate, allowing adhesion force between the interface layer and an encapsulating compound to be smaller than that between the heat spreader module plate and the encapsulating compound. Subsequently, an encapsulant is formed by the encapsulating compound to entirely encapsulate the chips and the heat spreader module plate. Then, a singulation process is performed to form individual semi-fabricated packages. Finally, residues of the encapsulating compound on the interface layer of the semi-fabricated packages are removed.
However, in the foregoing fabrication method, the interface layer formed on the heat spreader module plate usually has the adhesion force with the encapsulating compound much smaller than that between the heat spreader module plate and the encapsulating compound. When a jig is used to adsorb in vacuum the residues of the encapsulating compound on the interface layer of the semi-fabricated packages in the singulation process, the residues of the encapsulating compound often detach from the semi-fabricated packages under singulation, thereby making the singulated packages dislocated from the jig, and damaging the packages or equipment. Therefore, how to effectively maintain sufficient bonding between the residues of the encapsulating compound and the semiconductor packages during singulation has become a critical problem to solve.
SUMMARY OF THE INVENTION
A primary objective of the present invention is to provide a method of making a semiconductor package with a heat spreader, in which semi-fabricated packages can be held in position on a jig in a singulation process, and the heat spreader is dimensioned to have the maximal exposed area with no concern of flashes occurring thereon, so that heat dissipating efficiency can be improved.
Another objective of the invention is to provide a method of making a semiconductor package with a heat spreader, in which the heat spreader is directly attached to a semiconductor chip so as to increase the heat dissipating efficiency, and the chip can be prevented from being damaged in a molding process, s

Affiliated with

Also associated with

Rating

Method of making semiconductor package with heat spreader does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Method of making semiconductor package with heat spreader, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of making semiconductor package with heat spreader will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2908469