Stacked-die package structure

Details Stacked-die package structure Stacked-die package structure

2000-08-02

2003-07-15

Nelms, David (Department: 2818)

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

Combined with electrical contact or lead

Chip mounted on chip

C257S668000, C257S676000, C257S686000, C257S723000, C257S784000

Reexamination Certificate

active

06593662

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a stacked-die package structure. More particularly, the present invention relates to a stacked-die package with a ball grid array (BGA) structure.
2. Description of Related Art
Integrated circuits (ICs) significantly influence on every aspect of human's life and have a variety of applications for various fields. In modern era, all products trend towards more small and light for convenient purposes. Accordingly, the ICs also become smaller than ever. Current semiconductor technology is heading towards a 0.18-micron process. For the IC products, three stages are usually required: fabricating silicon wafers, manufacturing IC circuits and packaging the IC dies. Namely, the package is the finally stage for completing the IC products. The package can be provided as a medium for electrically connecting between dies in the package and the printed circuit board (PCB), or between the dies and other elements. In addition, the package can protect the dies therein from damage as well.
FIG. 1
shows a conventional structure of a stacked-die package. Generally, a ball grid array (BGA) structure is usually used for a stacked-die structure. For example, similar memory dies can be packed within one package for increase memory capacity. As shown in
FIG. 1
, a first die
106
is attached to a substrate
102
first, and then a second die
108
is stacked on the first die
106
. Adhesive layers
104
are formed between the substrate
102
and the first die
106
, and between the first die
106
and the second die
108
. Then, a wire bonding process is performed for electrically connecting the first die
106
to the substrate
102
using conductive lines
110
a
, and for electrically connecting the second die
108
to the substrate
102
using conductive lines
110
b
. A mold compound
114
is formed over the substrate
102
to encapsulate the substrate
102
, the dies
106
,
108
, and the conductive lines
110
a
,
110
b
. Finally, solder balls
112
are assembled to the back surface of the substrate
102
.
However, the structure above requires that the first die
106
must larger than the second die
108
, or that a width difference for each side of the two dies
106
,
108
must be greater than 0.3 mm. If the two dies
106
,
108
have the same sizes, the wire bonding process will fail, or the second die will short the conductive lines
110
a.
FIG. 2
shows a top view of a conventional stacked-die structure. A first die
806
is sat on a substrate
802
, and a second die
808
is then stacked on the first die
806
, in which the first die
806
and the second die
808
are perpendicular to each other. There are several bonding pads on the two sides of each die
806
,
808
. For preventing crack or collapse of the second die
808
during wire bonding, spacers
840
are formed under two other sides of the second die
808
for shoring the second die
808
. However, the conventional stacked-die structure is not suitable for dies having bonding pads located on their four peripheral sides.
FIG. 3
shows a conventional structure of a stacked-die package using a lead frame as a carrier. The structure shown in
FIG. 3
is issued to U.S. Pat. No. 5,291,061. A first die
906
and a second die
908
have almost the same sizes. The first die
906
is affixed to the lead frame
902
, and conductive lines
910
a
are electrically connected the first die
906
to the lead frame
902
. A polyimide tape
930
is attached on the first die
906
, and then the second die
908
is stacked on the polyimide tape
930
. Conductive lines
910
b
are then electrically connected the second die
908
to the lead frame
902
. Finally, a mold compound
914
is used for encapsulating the first and second dies
906
,
908
, the conductive lines
910
a
,
910
b
and the lead frame
902
, while pins
932
of the lead frame
902
are exposed. In the prior art structure, the polyimide tape
930
costs high and its thermal conductivity is bad, causing that the second die
908
is not easily to dissipate heat. Furthermore, it requires special tapping machine for taping the polyimide tape
930
between the dies
906
,
908
under a high temperature condition above 400° C., thus increasing cost. In addition, the polyimide tape causes the cushion effect on the second die
908
, affecting the quality and reliability of wire bonding for the second die
908
.
SUMMARY OF THE INVENTION
The present invention provides a stacked-die package structure capable of stacking dies having substantially the same size and bonding pads around the peripheral sides of the dies within one package.
The present invention provides a stacked-die package structure for reducing the cushion effect, which usually occurs in the conventional stacked-die structure.
The present invention provides a stacked-die package structure capable of increasing efficiency of heat dissipation.
The present invention provides a stacked-die package structure for reducing cost and simplifying manufacturing process.
As embodied and broadly described herein, the invention provides a stacked-die package structure. A carrier having an upper surface and a back surface opposite to the upper surface is provided. A number of dies are stacked one by one on the upper surface of the carrier, and a number of bonding pads formed around the peripheral sides of each die. A number of spacers are located between two adjacent dies. Adhesive layers are located between the spacers, the dies, and the carrier for adhering layers therebetween. Conducting lines are used for respectively electrically connecting each of the bonding pads of the dies and the carrier. And, a mold compound is formed over the upper surface of the carrier, for encapsulating the spacers, the dies and the adhesive layers.
The invention also provides a stacked-die package structure. A carrier having an upper surface and a back surface opposite to the upper surface is provided. A number of dies are stacked one by one on the upper surface of the carrier, and a number of bonding pads are formed around the peripheral sides of each die. Spacers are located between two adjacent dies, and one of the spacers, which is located on a top of the stacked dies, has a thermal dissipation surface. Adhesive layers are located between the spacers, the dies, and the carrier for adhering layers therebetween. Conducting lines are used for respectively electrically connecting each of the bonding pads of the dies and the carrier. And a mold compound is formed over the upper surface of the carrier, for encapsulating the spacers, the dies and the adhesive layers, but the heat dissipation surface is exposed.
The invention further provides a stacked-die package structure. A carrier having an upper surface and a back surface opposite to the upper surface is provided. A number of dies are stacked one by one on the upper surface of the carrier, and a number of bonding pads are located around the peripheral sides of each die. A thermal dissipation plate is stacked on the dies, having at least one thermal dissipation surface. A number of spacers are located between two adjacent dies, and between the dies and the thermal dissipation plate. Adhesive layers are located between the spacers, the dies, the thermal dissipation plate and the carrier for adhering layers therebetween. Conducting lines are used for respectively electrically connecting each of the bonding pads of the dies and the carrier. And, a mold compound is formed over the upper surface of the carrier, for encapsulating the spacers, the dies and the adhesive layers, but the heat dissipation surface of thermal dissipation plate is exposed.
Advantageously, the material of the adhesive layers can be silver paste, or paste with thermal conductivity and non-electrical conductivity, such that the adhesive process is not necessary to be performed under a high temperature above 400° C., simplifying the manufacturing process and avoiding crack or collapse of the first and the second dies during the adhesive process under high t

Affiliated with

Also associated with

Rating

Stacked-die package structure does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Stacked-die package structure, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Stacked-die package structure will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3100864