Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – With provision for cooling the housing or its contents
Reexamination Certificate
1998-08-31
2001-12-04
Picardat, Kevin M. (Department: 2822)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
With provision for cooling the housing or its contents
C257S675000, C257S713000, C257S796000
Reexamination Certificate
active
06326686
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a vertical semiconductor device package having a printed circuit board and heat spreader, and a module containing the packages. More particularly, the invention relates to a vertical semiconductor device package having a heat spreader which is directly attached to a semiconductor chip or the printed circuit board which comprises multiple metal layers, and a module having a plurality of the packages and a heat sink.
2. Description of the Related Arts
In the field of electronics, as power consumption increases due to higher speed transmission and processing of data, the amount of heat generation from the semiconductor increases. Accordingly, poor heat dissipation capability of a semiconductor package can adversely affect the reliability and the lifetime of the electronic device. For example, a junction temperature increase of approximately 10° C. can reduce the lifetime of the device by about 50%. Therefore, in case of the high power package, the importance of the heat dissipation capability of the package has become greater than ever. Particularly, in memory devices such as DRAMs and SRAMs requiring fast data transmission speed, as well as in non-memory devices such as logic chips and power transistors, effective heat dissipation is an important issue.
The data processing speed of a memory chip being slower than that of the CPU (central processing unit) creates a bottleneck for data transmission. In DRAMs, data storage capacity has greatly increased generation after generation, but their speed to input and output the data has not improved enough to match that of the CPUs.
Recently, Rambus DRAM, which enhances the data transmission speed by removing the data bottleneck created by conventional DRAM, was developed and introduced by Rambus Inc. in the U.S. Rambus DRAMs may achieve high performance and high speed for synchronous imaging and three dimensional graphics by providing high speed data processing capability.
It is known that Rambus DRAM adopts a “bus type technique”, in which the complicated data transmitting networks are simplified by arranging them in parallel.
Since I/O pads of the Rambus DRAM chip are aligned on the active front side of the chip along one edge, the corresponding leads or the corresponding pins of the package naturally protrude from only one edge of the package. Accordingly, Rambus DRAMs are packaged in two types of packages: SVPs (Surface Vertical Packages) and SHPs (Surface Horizontal Packages).
In an SVP, the leads protrude from one edge of the package and are perpendicularly bent outward, and the package is vertically mounted on a motherboard so that the bent portions of the leads are attached to the motherboard. However, the mounting area of an SVP on the motherboard is very small, for example, {fraction (1/7)} of the mounting area of a conventional surface mount type package such as an SOJ (Small Outline J-lead Package), or ⅓ of the mounting area of a ZIP (Zigzag Inline Package). For secure mounting of the SVP on the motherboard, the unbent pins from both ends of the package are inserted in the holes in the motherboard, and dummy pins formed on both ends of the package are alternately bent in opposite directions to support the package.
The SHP has a similar structure to that of a TSOP (Thin Small Outline Package) and is mounted on the motherboard by functional pins, which are formed along one edge, and dummy pins, which are formed along the opposite edge for mounting the package. The mounting height of an SVP on the motherboard is greater than that of a SHP.
Although a 16-Mbit or a 18-Mbit Rambus DRAM can be packaged with leadframes as described above, 64 Mbit or larger Rambus DRAMs, which have greater electrical demands, are packaged on printed circuit boards which have multiple circuit layers. At this time, the maximum operational electric power of the Rambus DRAM is approximately 2.0~2.1 W, which may cause heat dissipation problem.
FIG.
1
and
FIG. 2
show a conventional vertical semiconductor device package using a PCB (printed circuit board)
16
. Referring to FIG.
1
and
FIG. 2
, a semiconductor chip
12
is attached to a front side of the PCB
16
, on which copper wirings
22
are formed, by interposing a thermally conductive and electrically dielectric adhesive
24
. Chip pads
14
, which are formed on a front side of the chip
12
, are connected to respective board pads
18
of the PCB
16
by metal wires
26
for the electrical connection with external circuitry. The board pads
18
are connected to respective connection pads
20
, which are formed on one edge of the PCB
16
, via the copper wirings
22
, and the connection pads
20
of the PCB
16
are inserted into a slot on a motherboard
40
. The chip
12
is encapsulated with a molding compound
28
to protect chip
12
from external environmental stress. A heat spreader
30
is attached to the back side of the PCB
16
.
The heat dissipation route of the vertical semiconductor device package
10
is as follows. Heat generated from the front side of the chip
12
is transferred to the external surface of the package
10
through the molding compound
28
, the PCB
16
, and the heat spreader
30
, and heat that reaches the external surface of the package
10
is dissipated to the surrounding environment by convection and radiation.
FIG. 3
shows the results of a computer simulation of heat dissipation from the device of
FIGS. 1 and 2
and shows a temperature gradient distribution. As shown in
FIG. 3
, since the molding compound and the PCB have the low thermal conductivity, the heat generated in the chip may not be effectively dissipated. This ineffective heat dissipation raises the junction temperature in the chip, and can cause a decrease in the data processing speed, erroneous operation, and electrical failure of semiconductor devices.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a vertical semiconductor device package comprising a heat spreader to enhance the heat dissipation capability of the package.
Another object of the present invention is to provide a vertical semiconductor device package comprising a printed circuit board to improve the electrical characteristics of the package.
Still another object of the present invention is to provide a package module having a plurality of vertical semiconductor device packages, which are vertically mounted on a circuit board with an additional heat sink on the top of the packages.
A further object of the present invention is to provide a Rambus DRAM chip package having enhanced heat dissipation capability and excellent electrical characteristics.
In order to achieve these and other objects, the present invention provides a vertical semiconductor device package comprising a printed circuit board(PCB) and a heat spreader. The vertical semiconductor device package of the present invention comprises a semiconductor chip, and chip pads are formed on a front side of the chip along one edge of the chip. The heat spreader, which is made of metal, is attached to a back side of the chip. The PCB has a plurality of board pads, which are formed on one edge of the PCB for connection to the chip pads, and a plurality of connection pads, which are connected to a respective one of the corresponding board pads by circuit wirings. The chip pads are electrically connected to a respective one of the corresponding board pads by a plurality of metal wires, and the semiconductor chip, the metal wires, and the board pads are encapsulated with a molding compound.
The vertical semiconductor device package of the present invention may comprise a Rambus DRAM chip. Even with a 64-Mbit or larger Rambus DRAM chip, the present invention provides enhanced heat dissipation capability and excellent electrical characteristics. It is preferable that the size of the heat spreader be greater than that of the chip. Herein, the PCB is coplanar and adjacent to the chip, and the back side of the PCB is partially attached to the
Baek Joong Hyun
Cho Chang Ho
Jung Il Gyu
Lee Tae Koo
Heid David W.
Picardat Kevin M.
Samsung Electronics Co,. Ltd.
Skjerven Morrill & MacPherson LLP
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