Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Flip chip
Reexamination Certificate
2003-05-28
2004-12-07
Thomas, Tom (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Flip chip
C257S680000, C257S706000, C257S782000, C257S783000, C257S796000
Reexamination Certificate
active
06828687
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims the priority benefit of Taiwan application serial no. 91118508, filed Aug. 16, 2002.
BACKGROUND OF INVENTION
1. Field of Invention
The present invention relates to a cavity down ball grid array package structure. More particularly, the present invention relates to a cavity down ball grid array package capable of boosting electrical performance and lowering noise interference.
2. Description of Related Art
As techniques for manufacturing semiconductor devices continue to improve, high-tech electronic products are produced. Electronic products with personalized functions are appearing every day. Most electronic products are now designed to occupy as little space and weigh as little as possible. Yet, the products must be easy to use and feel comfortable. To fabricate a product with all the necessary functions and characteristic properties, the way the product is packaged is very important. Electronic devices are often packaged together inside a dual-in-line package (DIP), a ball grid array (BGA) or a tape automated bonding (TAB). In general, each packaging type has its special characteristics.
Among the conventional types of electronic packages, ball grid array (BGA) is most common. A back of a die is attached to the bonding pad on a substrate using an adhesive tape or other nonconductive adhesive materials. The bonding pads on the die and the contact points on the substrate are electrically connected using conductive wires. An encapsulation encloses the die, the conductive wires, and the contacts. In addition, a plurality of solder balls is planted onto the ball pads on the substrate so that the ball grid array may transmit electrical signals to the external circuit through the solder balls. Since the circuit layout on the BGA package is arranged in the form of an array, the package can accommodate a large number of external contacts.
However, as the size of each die shrinks, the level of integration increases correspondingly so that the amount of heat generated per unit area while the devices are working also increases proportionately. Hence, cooling is also an important consideration for the package designer. In general, a cavity down ball grid array (CDBGA) has a high heat dissipation capacity because the backside of the die is directly attached to a heat spreader. Through the heat spreader, heat generated with the package is directly conducted to the exterior.
FIG. 1
is a schematic cross-sectional view of a conventional cavity down ball grid array package. As shown in
FIG. 1
, the cavity down ball grid array package
100
includes a heat spreader
110
, a substrate
120
, a die
160
, a plurality of conductive wires
170
, an encapsulation
180
and a plurality of solder balls
190
. The substrate
120
has a first surface
122
and a second surface
124
. The first surface
122
of the substrate
120
is attached to the heat spreader
110
through non-conductive glue
192
. The substrate
120
is a stack that includes four metallic layers
132
,
134
,
136
,
138
isolated from each other by alternately positioned insulating layers
142
,
144
and
146
respectively. The substrate
120
has a plurality of through holes
126
,
128
that pass through the substrate
120
. The interior of the through hole
126
contains a metallic layer
131
that links up the four metallic layers
132
,
134
,
136
and
138
electrically. The through hole
128
is wide enough to enclose the die
160
. The substrate
120
further includes two solder mask layers
152
,
154
formed on the first surface
122
and the second surface
124
of the substrate
120
respectively. The solder mask layer
154
has a plurality of openings
156
that exposes a portion of the uppermost metallic layer
132
, thereby forming a number of contacts
130
and
133
. The contacts
133
surround the through hole
128
. In general, the bottom most metallic layer
138
in the substrate
120
also includes a ground plate
139
that serves as an earth connection.
The die
160
has an active surface
162
and a back surface
164
. The active surface
162
of the die
160
has a plurality of bonding pads
166
. The back surface
164
of the die
160
is attached to the heat spreader
110
through an adhesion layer
194
. One end of each conductive wire
170
is bonded to a contact pad
166
while the other end of the conductive wire
170
is bonded to the contact
133
on the substrate
120
. The encapsulation
180
fills up the leftover space within the through hole
128
so that the die
160
, the conductive wires
170
and the contact pads
133
are all enclosed. The solder balls
190
are attached to the contacts
130
on the substrate
120
. Through the solder balls
190
, the substrate
120
connects electrically with an external circuit (not shown).
In the aforementioned cavity down ball grid array package
100
, the ground plate
139
must have a horizontal area smaller than the substrate
120
. If the ground plate
139
is small, noise interference will increase correspondingly. Hence, when the horizontal area of the substrate
120
is reduced due to miniaturization, horizontal area of the ground plate
139
is bound to decrease and noise interference is likely to have a significant effect. In addition, the radiation generated by a radio frequency circuit is likely to increase noise production. Under such circumstance, any decrease in area of the ground plate
139
may lower the noise fighting capacity resulting in the production of several interfering noise sources. Ultimately, logic circuit operations within the die
160
are likely affected.
SUMMARY OF INVENTION
Accordingly, one object of the present invention is to provide a cavity down ball grid array package having an anti-noise interference capacity.
A second object of this invention is to provide a cavity down ball grid array package having superior heat dissipation capacity.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a cavity down ball grid array package. The package includes at least a heat spreader, a substrate, a die, a plurality of conductive wires, an encapsulation and a plurality of solder balls. The substrate has a first surface and a second surface. The first surface of the substrate is attached to the heat spreader. The substrate has a through hole that passes through the substrate and exposes the heat spreader. The substrate and the heat spreader are electrically connected. The die has an active surface and a back surface. The die has a plurality of bonding pads on the active surface. The back surface of the die is attached to the heat spreader inside the through hole. One end of each conductive wire is electrically connected to a bonding pad and the other end of the conductive wire is electrically connected to the substrate. The encapsulation fills the through hole and encloses the die and the conductive wires. The solder balls are attached to the second surface of the substrate.
According to one embodiment of this invention, the first surface of the substrate is attached to the heat spreader through conductive glue. The substrate comprises of a stack of alternately positioned metallic circuit structures and dielectric structures. The dielectric structures have at least an opening that exposes the metallic circuit structures. The conductive glue is applied to the opening so that the conductive glue connects electrically with one of the metallic circuit structures. The heat spreader is made from copper. In addition, a nickel layer is also formed on the surface of the heat spreader. Furthermore, the heat spreader and a ground terminal are electrically connected through the substrate. In other words, the substrate can include a first ground terminal. The heat spreader and the first ground terminal are electrically connected through the conductive glue fills. In addition, the die may also include a second ground terminal and the heat spreader and the second ground te
Advanced Semiconductor Engineering Inc.
Jiang Chyun IP Office
Thomas Tom
Warren Matthew E.
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