Active solid-state devices (e.g. – transistors – solid-state diode – Lead frame – With heat sink means
Reexamination Certificate
1998-06-22
2001-04-24
Thomas, Tom (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Lead frame
With heat sink means
C257S676000
Reexamination Certificate
active
06222258
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to semiconductor devices and methods for producing semiconductor devices, and particularly, to a semiconductor device in which a semiconductor chip (element) is bonded to a plurality of leads by wire-bonding and a method for producing such semiconductor devices.
Recently, semiconductor chips have been highly integrated and the method for producing the semiconductor chips comprises steps which require extremely fine operations. Also, according to progress in the semiconductor industry, semiconductor devices having high power have been developed. Naturally, this results in an increase in the amount of heat generated by the semiconductor devices and some semiconductor devices have a structure in which a heat spreader (heat dissipating plate) is provided in order to improve its heat dissipating ability.
On the other hand, there are demands for a semiconductor having high reliability which may be produced at a low cost. Hence, the development of a semiconductor device having properties which may respond to such various requirements is awaited.
2. Description of the Related Art
A conventional semiconductor device will be explained with reference to
FIGS. 1 and 2
.
FIG. 1
is a diagram showing a cross-sectional view of a conventional semiconductor device
1
and
FIG. 2
is a diagram showing a region of a wiring position of a semiconductor chip (element)
2
shown in
FIG. 1
in a magnified scale.
As shown in
FIG. 1
, the semiconductor device
1
is comprised of the semiconductor chip
2
, a plurality of leads
3
, a heat spreader (heat dissipating plate)
4
, a plurality of wires
5
, adhesive tapes
6
, and sealing resin (resin package)
7
. The numeral
9
indicates an adhesive composition.
The semiconductor chip
2
shown in
FIG. 2
is a so-called bare chip and a plurality of pads
8
are provided on the semiconductor chip
2
. As mentioned above, since high integration and high power are required for the semiconductor device
1
, there is a tendency to increase the number of pins formed on the semiconductor chip
2
and, accordingly, the pitch, P, shown in
FIG. 2
of the pad
3
tends to be decreased.
Also, the number of leads
3
corresponds to the number of pads
8
provided with the semiconductor chip
2
, and hence the number of leads
3
tends to increase. As shown in the figures, an inner lead portion
3
a
of the lead
3
is connected to the corresponding pad
8
, which is provided with the semiconductor chip
2
by the wire
5
, and an outer lead portion
3
b
of the lead
3
, which is formed in a gullwing shape in order to make a surface mounting of the semiconductor device
1
possible, extends outside of the sealing resin
7
.
The heat spreader
4
may be made of a flat-shape member having an excellent thermal conductivity and the semiconductor chip
2
is adhered to substantially the center thereof using the adhesive composition
9
. Also, the inner lead portion
3
a
of the lead
3
is connected to the heat spreader
4
using the adhesive tape
6
which has a structure in which an adhesive composition is applied to an insulative resin film. Moreover, the sealing resin
7
is formed so as to cover at least the semiconductor chip
2
and the wire
5
, and it may be formed using a technique such as a mold technique.
In the above-mentioned configuration of the semiconductor device
1
, the reasons that the inner lead portion
3
a
is connected to the heat spreader
4
using the adhesive tape
6
are as follows.
When the wire
5
is provided between the inner lead portion
3
a
of the lead
3
and the corresponding pad
8
provided on the semiconductor chip
2
, the above-mentioned wire-bonding is carried out and, in general, an ultrasonic bonding method is used for the wire-bonding process. On the other hand, the number of pins used has increased these days and the pitch, P, between each of the pads
3
is reduced, the area of the end portion of the inner lead portion
3
a
(i.e., the bonding position for the wire
5
) is reduced accordingly and its mechanical strength is also decreased.
Therefore, if the wire-bonding is performed such that a space is present between the inner lead portion
3
a
and the heat spreader
4
(i.e., so-called space bonding), the lead
3
and the heat spreader
4
tend to contact each other and there is a danger that an electrical short is caused among a plurality of leads
3
since the heat spreader
4
is generally made of a metal having excellent thermal conductivity. For this reason, the inner lead portion
3
a
is connected to the heat spreader
4
using the adhesive tape
6
in order to achieve an insulation of the inner lead portion
3
a
and the heat spreader
4
as well as increase the mechanical strength of the inner lead portion
3
a.
However, in the conventional semiconductor device having a structure in which the inner lead portion
3
a
is connected to the heat spreader
4
using the adhesive composition
6
, there is a danger that gases are generated from the adhesive tape
6
during a cure (heat) process which is carried out after the inner lead portion
3
a
is connected to the heat spreader
4
and the inner lead portion
3
a
is damaged (corroded, for instance) by the generated gases.
In order to avoid the above problem, the lead
3
may be subjected to a washing process such as a plasma cleaning process before carrying out a wire-bonding process. However, this makes the manufacturing process of the semiconductor device complicated and the cost for producing the semiconductor device is increased.
Also, if the area of the adhesive tape
6
is reduced in order to avoid the problem, it is likely that the inner lead portion
3
a
is bonded to the heat spreader
4
in a state that they are not in contact with each other (i.e., the space bonding), and the electrical short may be caused among a plurality of the leads
3
which, as a result, reduces a reliability as well as yield of the semiconductor device.
SUMMARY OF THE INVENTION
It is a general object of this invention to provide a semiconductor device and a method for producing semiconductor devices in which the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide a semiconductor device, in which a semiconductor chip is bonded to a plurality of leads by wire-bonding, and a method for producing such semiconductor devices, by which reliability in electrical connection of the semiconductor device may be improved at low cost.
It is another object of the present invention to provide a method for producing the semiconductor device by which reliability in electrical connection between the leads and the semiconductor element may be improved.
It is still another object of the present invention to provide a method for producing the semiconductor device by which it is possible to decrease the number of steps required for producing a semiconductor device and to reduce the cost necessary for manufacturing the semiconductor device.
The objects described above are achieved by a method for producing a semiconductor device comprising: a) an attaching process in which a flat-plate member is positioned on a flat-shape lead frame provided with a plurality of leads and a plurality of support bars so that the flat-plate member contacts to at least the plurality of leads, and the flat-plate member is attached to the plurality of support bars; b) an element mounting process in which a semiconductor element is mounted on the flat-plate member attached to a plurality of support bars of the flat-shape lead frame; c) a wire-bonding process in which a wire is bonded between each of the plurality of leads and the semiconductor element; and d) a separating process, performed after completion of the wire-bonding process, in which at least one of the plurality of support bars is deformed so as to separate the flat-plate member and the plurality of leads and electrically disconnect the flat-plate member from the plurality of leads.
According to the above method
Asano Yuichi
Kobayashi Hitoshi
Wako Katsunori
Arent Fox Kintner & Plotkin & Kahn, PLLC
Fujitsu Limited
Hu Shouxiang
Thomas Tom
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