Semiconductor assembly without adhesive fillets

Details Semiconductor assembly without adhesive fillets Semiconductor assembly without adhesive fillets

2001-07-23

2003-09-09

Coleman, William David (Department: 2823)

Semiconductor device manufacturing: process

Packaging or treatment of packaged semiconductor

Including adhesive bonding step

C156S060000

Reexamination Certificate

active

06617198

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a structure and method of forming a semiconductor assembly using adhesive materials to secure semiconductor dies to support elements without forming adhesive fillets.
BACKGROUND OF THE INVENTION
In order to reduce the size of semiconductor devices numerous techniques have been developed to vertically stack one semiconductor die, hereinafter “die”, on top of another die.
FIG. 1
illustrates a conventional method of vertically stacking two die
20
,
30
on a support structure
10
, such as a printed circuit board (PCB) or other thin support structure, to form a conventional semiconductor assembly
100
. The first die
20
is shown secured to a support structure
10
by an adhesive material
22
a
using techniques well known in the art. When the first die
20
is pressed against the support structure
10
the adhesive material
22
a
is partially forced outside the die's
20
perimeter
29
and forms an adhesive fillet
24
a
. Likewise, when the second die
30
is secured against the first die
20
by an adhesive material
22
b
a second adhesive fillet
24
b
is also formed.
Both the first die
20
and second die
30
are shown wire bonded
40
to an electrical contact area
18
on the support structure
10
. The first die
20
has an electrical contact area
28
, such as a bonding pad, on its top surface
26
. Because adhesive fillet
24
b
is formed when the second die
30
is secured to the first die
20
, it limits the placement of the first die's
20
electrical contact area
28
. The distance B between the perimeter
39
of the second die
30
and a first die's
20
electrical contact area
28
must be increased by distance A, the width of the adhesive fillet
24
b
, to provide sufficient operating space for the wire bonding equipment. Typical dimensions for distances B are about 428 microns or greater to allow for adhesive fillets
24
b
, which are conventionally about 228 microns in width or greater. Using current wire bonding equipment, distance B between electrical contact area
28
and the perimeter of the fillet
24
b
can be reduced to about 200 microns or less. In other words, adhesive fillet
24
b
requires about 228 microns or more of first die's
20
top surface
26
on each side of the first die
20
. If the adhesive fillet
24
b
were eliminated the space could be used either to increase the size of the second die
30
or to reduce the size of the first die
20
.
An alternative method of stacking dies
20
,
30
to a support structure
10
to form a semiconductor assembly involves using an adhesive film sized and aligned with the respective die
20
,
30
perimeters. Since the adhesive film is cut or dimensioned with the second die's perimeter
39
, no adhesive fillet
24
, as described above, is formed. However, adhesive films are expensive and are difficult to align with the dies
20
,
30
and support structure
10
. Accordingly, there is a need and desire for an easy, low-cost method of securing one or more semiconductor dies
20
,
30
to various support structures
10
to form a semiconductor assembly
100
using adhesive materials
22
such that no adhesive fillets
24
are produced, for example, when a second die
30
is pressed and secured to a first semiconductor die
20
and when a first semiconductor die
20
is pressed and secured to a support structure
10
.
SUMMARY OF THE INVENTION
The present invention provides a method to vertically stack at least one semiconductor die on top of another semiconductor die using an adhesive material without forming an adhesive fillet at the second die's perimeter. An adhesive material is deposited over about 50% to about 90% of the top surface of the first semiconductor die, such that when the second die is secured against the adhesive material and first die no adhesive material extends past the perimeter of the second die. Because no adhesive fillet is formed, the distance between the electrical contact areas on top of the first semiconductor die and the perimeter of the second die can be reduced.


REFERENCES:
patent: 5422435 (1995-06-01), Takiar et al.
patent: 5548091 (1996-08-01), DiStefano et al.
patent: 6107123 (2000-08-01), Distefano et al.
patent: 2001-124395 (2000-04-01), None
patent: 2001-094945 (2001-04-01), None

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