Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2002-03-05
2003-08-05
Nelms, David (Department: 2818)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S612000, C438S666000, C029S840000, C029S832000, C257S784000, C257S786000
Reexamination Certificate
active
06602778
ABSTRACT:
TECHNICAL FIELD
The present invention relates to methods and apparatuses for electrically coupling bond pads of a microelectronic device.
BACKGROUND OF THE INVENTION
Computers and other electronic devices typically include a number of interconnected semiconductor devices. The semiconductor devices include a semiconductor chip or die containing internal circuitry. The dies are generally mounted in a package and connected to other semiconductor devices through external pins or contacts. However, the dies may also be connected directly to other circuitry, including another semiconductor die.
FIG. 1A
is a side elevation view of a portion of a semiconductor die
20
having two bond pads
21
(shown as
21
a
and
21
b
) on a surface of the die. The bond pads
21
may be coupled to each other with circuitry
53
that is internal to the semiconductor die
20
, as shown schematically in FIG.
1
A. One bond pad
21
a
is electrically coupled with a wire
50
to a lead finger
43
of a conductive lead frame
40
. In one conventional arrangement, one end of the wire
50
is bonded to the bond pad
21
a
with a “ball bond”
60
and the other end of the wire
50
is bonded to the lead finger
43
with a “wedge bond”
70
. The semiconductor die
20
and the lead frame
40
may then be encapsulated in a plastic material (not shown) and ends
42
of adjacent lead fingers
43
(one of which is shown in
FIG. 1A
) may be bent downward to form connection pins. The pins may be inserted into corresponding sockets of another device (not shown) to couple the semiconductor die with the other device.
FIG. 1B
is an enlarged side elevation view of a portion of the semiconductor die
20
shown in
FIG. 1A
, as the wire
50
is being attached to the bond pad
21
a
. The wire
50
can be attached with a wire bonding tool
30
(shown in
FIG. 1B
as a ball/wedge bonder
30
a
) by feeding the wire
50
downwardly through an aperture
31
of the ball/wedge bonder
30
a
and forming a wire ball
51
at the end of the wire
50
. The ball/wedge bonder
30
a
then presses the wire ball
51
against the bond pad
21
a
while the remainder of the wire
50
extends approximately normal to the bond pad
21
a
. The bonder
30
a
then applies heat and/or pressure to the wire
50
at the wire ball
51
to bond the wire to the bond pad
21
a
, forming the ball bond
60
shown in FIG.
1
A. For example, the bonder
30
a
can use a thermosonic or thermocompression process to apply both heat and pressure to the wire
50
. The bonder
30
a
then moves along the wire
50
to the lead finger
43
and presses the wire
50
against the lead finger
43
. The bonder again applies heat and/or pressure to the wire
50
to both bond the wire
50
to the lead frame
40
(forming the wedge bond
70
shown in FIG.
1
A), and separate the bonded portion of the wire
50
from a remaining portion of the wire.
FIG. 2A
is a side elevation view of the semiconductor die
20
having the wire
50
connected between the bond pad
21
a
and the lead finger
43
in accordance with another conventional arrangement in which a first wedge bond
70
a
is formed at the bond pad
21
a
and a second wedge bond
70
b
is formed at the lead finger
43
.
FIG. 2B
is an enlarged side elevation view of a portion of the semiconductor die
20
shown in
FIG. 2A
as the wire
50
is being attached to the bond pad
21
a.
Referring to
FIG. 2B
, the wire
50
can be attached to the bond pad
21
a
with a wedge/wedge bonder
30
b
by feeding the wire
50
through an aperture
31
a
of the wedge/wedge bonder
30
b
and pressing the wire
50
against the bond pad
21
a
. The wedge/wedge bonder
30
b
then applies heat and/or pressure to the wire
50
to bond the wire to the bond pad
21
a
, forming the first wedge bond
70
a
shown in FIG.
2
A. The bonder
30
b
then moves along the wire
50
to the lead finger
43
and presses the wire against the lead finger
43
. The bonder
30
b
again applies heat and/or pressure to the wire to bond the wire
50
to the lead finger
43
, forming the second wedge bond
70
b
shown in FIG.
2
A. In one conventional arrangement, the bonder
30
b
can apply sufficient heat and/or pressure to both bond the wire
50
to the lead frame
40
and separate the bonded wire from the remaining supply of wire. In another conventional arrangement, the bonded wire can be separated from the remaining wire by clipping the wire next to the second wedge bond
70
b.
As discussed above, two or more bond pads
21
may be connected within the die
20
by internal circuitry
53
. The internal circuitry
53
may include very small conductive lines. One drawback with this arrangement is that the conductive lines may have a high resistance, increasing the current necessary to transmit signals between the bond pads, and increasing the heat generated by each semiconductor die. In addition, internal circuitry
53
is inaccessible once the die has been manufactured. Accordingly, another drawback with conventional arrangements is that they may lack the flexibility for interconnecting bond pads that are not connected by the internal circuitry at the time of manufacture.
Yet a further drawback with the conventional methods and devices discussed above is that it may be difficult to route wires between the lead frame
40
and bond pads that are not proximate to the lead frame
40
. For example, if one or more of the wires
50
is particularly long, so as to reach a particular bond pad, the wire may be more likely to break or contact other adjacent wires, creating a short circuit that can affect the operation of the semiconductor device.
SUMMARY OF THE INVENTION
The present invention is directed toward methods and apparatuses for electrically coupling bond pads of a microelectronic device. In one aspect of the invention, the apparatus can include first and second spaced apart bond pads on a surface of a microelectronic device. The microelectronic device can further include a conductive member connected to and extending between the first and second bond pads. The conductive member can be positioned on or above the surface of the microelectronic device. In one aspect of the invention, the conductive member can include a wire, and, in another aspect of the invention, the conductive member can include a flowable conductive material, such as a conductive epoxy. In still another aspect of the invention, the microelectronic device can include an insulating material between the conductive member and the surface of the microelectronic device.
In yet another aspect of the invention, the apparatus can include a microelectronic device having at least one bond pad for receiving wire connections. The microelectronic device can further include two wires connected to the same bond pad, for example, a first wire connected at one end to the bond pad with a first bond and a second wire connected at one end to the first bond with a second bond. Either or both of the first and second bonds can be a wedge bond or a ball bond, and the opposite ends of the first and second wires can be connected to other bond pads of the microelectronic device, or to external structures.
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Ball Michael B.
Manning Troy A.
Dorsey & Whitney LLP
Le D
Nelms David
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