Structure and package of a heat spreader substrate

Details Structure and package of a heat spreader substrate Structure and package of a heat spreader substrate

2001-06-15

2003-09-23

Wilson, Allan R. (Department: 2815)

Active solid-state devices (e.g., transistors, solid-state diode

Encapsulated

With heat sink embedded in encapsulant

C257S738000, C257S783000, C257S784000, C257S693000, C257S710000, C257S712000, C257S706000, C257S707000, C257S708000, C257S709000, C257S711000, C257S713000, C257S714000, C257S715000, C257S716000, C257S717000, C257S718000, C257S719000, C257S720000, C257S722000, C257S721000

Reexamination Certificate

active

06624523

ABSTRACT:

CROSS REFERENCE TO RELATED APPLICATION
This application claims the priority benefit of Taiwan application serial no. 89123557, filed on Nov. 8, 2000.
1. Field of the Invention
The present invention relates to a structure and package of a heat spreader substrate. More specifically, the present invention relates to a cavity down package.
2. Description of the Related Art
With the rapid development in integrated circuits and continuous improvement in semiconductor devices, an important feature of a semiconductor is to have high efficiency, high integration, high speed and to be a multi-functional device. Moreover, the packaging quality of this device is becoming more demanding. For example, high density, high heat diffusion functions and high reliability are very important factors in the development of semiconductor packaging.
FIG. 1
is a schematic cross-sectional view showing a structure of a cavity down ball grid array (BGA). The structure of a cavity down BGA
20
is disclosed in U.S. Pat. No. 5,420,460 and U.S. Pat. No. 5,397,921. The carrier comprises a heat spreader
22
and a substrate
26
. The heat spreader
22
is adhered on the substrate
26
by an adhesive material
28
. A cavity
24
is formed on the middle of the heat spreader
22
and is used to carry a chip
40
. A patterned trace layer and an insulating layer are laminated on the substrate. A mounting pad
30
and a ball pad
32
are formed on the surface of the patterned trace layer, and a solder mask
34
covers the surface of the patterned trace layer. The chip
40
comprises an active surface
40
a
and a backside
40
b.
The backside
40
b
of the chip
40
is adhered on the bottom of the cavity
24
by an adhesive material
36
. A bonding pad
42
, which is formed on the active surface
40
a
of the chip, is connected to the mounting pad
30
of the substrate
26
by gold wires
50
. A molding compound
52
covers the chip
40
, gold wires
50
and the mounting pad
30
. A solder ball
54
is formed on the surface of the ball pad
32
.
FIG. 2
is a schematic, cross-sectional view showing another structure of a cavity down BGA. The cavity down BGA package is disclosed in U.S. Pat. No. 6,020,637. The carrier is made of a heat spreader
102
, a ground plane
104
and a flex substrate
110
. The heat spreader
102
, the ground plane
104
and the flex substrate
110
are stacked on each other with insulating adhesive materials
106
and
108
. A cavity is formed on the middle of the ground plane
104
and the flex substrate
110
to carry a chip
120
. The flex substrate
110
is a flex tape interconnect substrate. A patterned trace layer and a polyimide layer are laminated on the flex tape interconnect substrate. A mounting pad and a ball pad are formed on the surface of the patterned trace layer
112
. A solder mask
114
covers the surface of the patterned trace layer
112
. The chip
120
has an active surface
120
a
and a backside
120
b.
The backside
120
b
of the chip
120
is adhered on the bottom of the cavity by an adhesive material
124
. The bonding pad
122
of the active surface
120
a
is connected to a ground ring
116
of the ground plane
104
and to the mounting pad of the flex substrate
110
. The chip
120
, the gold wires
126
and the mounting pad are encapsulated with a mounting compound
128
. A solder ball
130
is formed on the surface of the ball pad
112
.
According to the above, a heat spreader is the main structure of the carrier. The heat spreader is made of copper, and the copper improves the heat diffusion of the package material.
Referring to
FIG. 1
, the cavity
24
of the heat spreader
22
is formed by an etching process. However, the etching process has a high cost, low throughput and is time consuming. On the other hand, the structure of the heat spreader is limited to its thickness because it is difficult to reduce the thickness by utilizing the conventional method. In
FIG. 2
, the heat spreader is made of two metals, a heat spreader
102
and a ground plane
104
. Although the cavity can be mass produced by a machining method, the structure is still limited to a certain thickness after it is stacked up. Thus, the disadvantage of the conventional method is the lack of control of the thickness of the package.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a heat spreader substrate and the package thereof to reduce the thickness of the packaging.
It is another object of the present invention to provide a machining method and a process for producing a heat spreader substrate and a package to reduce the cost.
According to the present invention, a structure of a heat spreader substrate is provided. A first heat spreader has a first upper surface, a first lower surface and an opening. A second heat spreader has a second upper surface and a second lower surface. A thickness of the second heat spreader is smaller than a thickness of the first heat spreader. The second heat spreader is fit tightly into the opening. The second lower surface of the second heat spreader and the first lower surface of the first heat spreader are coplanar. The upper surface of the second heat spreader is for locating a chip. The substrate is located on the upper surface of the first heat spreader, and the opening is exposed.
To achieve the foregoing and other objects and in accordance with the purpose of the present invention, the second heat spreader of the invention can be designed into various shapes, such as a first portion of the second heat spreader being bigger than a second portion of the second heat spreader. The molding compound is utilized to fill a space between the first heat spreader and the second heat spreader in order to increase the adhesion during the molding process. A groove and a protrusion are formed respectively on a contact portion between the first heat spreader and the second heat spreader.
The purpose of forming the groove and the protrusion is to provide a secure fit for the second heat spreader into the first heat spreader. A chip is located on the cavity surface. A plurality of loop-shaped grooves are formed on the second upper surface.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.


REFERENCES:
patent: 5397921 (1995-03-01), Karnezos
patent: 5420460 (1995-05-01), Massingill
patent: 5909056 (1999-06-01), Mertol
patent: 5952719 (1999-09-01), Robinson et al.
patent: 5972734 (1999-10-01), Carichner et al.
patent: 6020637 (2000-02-01), Karnezos
patent: 6084297 (2000-07-01), Brooks et al.
patent: 6249053 (2001-06-01), Nakata et al.
patent: 406097355 (1994-04-01), None

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