Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor – Making plural separate devices
Reexamination Certificate
2000-09-26
2001-10-30
Picardat, Kevin M. (Department: 2822)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
Making plural separate devices
C438S113000, C438S123000, C438S127000
Reexamination Certificate
active
06309909
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device having a semiconductor chip and electrode terminals molded together with a sealing resin and a method of manufacturing the same.
2. Description of the Prior Art
The semiconductor device of conventional design will be discussed with reference to
FIGS. 30A
to
32
. The semiconductor device
50
a
shown in
FIG. 30A
is disclosed in the Japanese Laid-open Patent Publication No. 3-94459 and is of a structure wherein a semiconductor chip
3
is mounted on a die pad
51
, and wire pads
52
are spaced from the die pad
51
and connected with the semiconductor chip
3
through respective wires
4
, both of said pads
51
and
52
being sealed by a synthetic resin
5
. More specifically, the semiconductor chip
3
is bonded to the die pad
51
by means of a die bond material
2
, and bump
53
are added to the wire pads
52
.
The semiconductor device
5
a
disclosed in the publication No. 3-944459 is manufactured in the following processes. In the first place, as shown in
FIGS. 31A and 31B
, semiconductor chips are mounted on a metallic base substrate provided with die pads and wire pads and manufactured in a manner as shown by the flowchart of FIG.
32
. This is followed by connection of the semiconductor chips with the wire pads with wires made from gold or other materials. Then, the semiconductor chips and the chip carrying surface of the metallic base substrate are sealed by a resinous materials. By doing so, the semiconductor devices are formed on the metallic base substrate
60
as shown in
FIGS. 31A and 31B
. Then a portion of the metallic base substrate
60
other than areas where the semiconductor devices have been formed is subsequently removed by etching to thereby complete fabrication of the individual semiconductor devices
50
a.
The publication No. 3-944459 discloses an alternative method which comprises preparing a transfer film including a base film and a metallic layer of, for example, copper formed on the base film through a peel-off layer intervening therebetween, bonding semiconductor chips to the transfer film by the use of a die bonding material, connecting the semiconductor chips with the metallic layer by resin, through wires such as gold wires, sealing the semiconductor chips and a chip carrying surface of the metallic layer, and removing the base film by etching or peeling to thereby complete the individual semiconductor devices with each having both die and wire pads.
According to the publication No. 3-944459, in view of the fact that during the manufacture the metallic base substrate
60
or the base film is etched off, the metallic base substrate
60
or the base film cannot be reused, resulting in an increase in the cost of manufacture. Also, the etching process requires a relatively long processing time and a relatively high processing cost resulting in lower production levels. In addition, the etching process requires the use of an alkaline solvent and, a flushing of water, accompanied by lowering of the bondability between the sealing resin
5
and the external electrodes
35
. This turn brings about reduction in reliability of the semiconductor device.
Even using the method in which the base film is peeled off, the base film is damaged or otherwise deformed and, therefore, no reuse is possible with the transfer film once used, resulting in an increase in the cost of manufacturing. Moreover, a minute uneven surface of 1 to 2 &mgr;m of an electrolyte copper foil which is the metallic layer on the base film tends to constitute a cause of reduction in bondability between the metallic layer and the sealing resin
5
by an anchoring effect, resulting in reduction in reliability of the semiconductor device.
Furthermore, in the prior method of manufacturing semiconductor, since each of the semiconductor devices
50
a
are sealed to the metallic base substrate
60
, the metallic base substrate
60
needs a proper space
60
between the neighboring semiconductor devices
50
a
, therefore, the number of the semiconductor devices
50
a
that can be manufactured on a given surface area of the metallic base substrate
60
is limited, thereby posing a problem associated with productivity.
Another prior art semiconductor device
50
b
shown in
FIG. 30B
is fabricated according to a method disclosed in, for example, the Japanese Laid-open Patent Publication No. 8-115991. The semiconductor device
50
b
includes a semiconductor chip
3
mounted on a lead frame having inner layers
33
,
34
a
and
34
b
formed of materials such as nickel by the use of a evaporation technique or a plating technique utilizing a metal masking aperture and having a cladding
36
of a solder plating. More specifically, the semiconductor chip
3
is sealed at one side thereof by a resinous material S. The portion of the lead frame where no sealing resin is deposited, and other than an area where external electrodes
35
are formed, is covered by a solder resist
38
.
The publication No. 8-115991 also discloses the lead frame provided with a cladding
36
of solder plating formed by press work.
According to the publication No. 8-115991, in the step of manufacturing semiconductor
50
b
, the formation of the inner layers
33
,
34
a
and
34
b
of, for example, nickel, and the solder plated cladding
36
by the use of the evaporation technique or the plating technique utilizing the metal masking aperture requires a relatively long time, bringing about the problem of a reduction in productivity. Also, the formation of the lead frame by the use of press work requires the use of an expensive mold for each of the eventually fabricated semiconductor devices.
SUMMARY OF THE INVENTION
Therefore, the present invention has been devised to substantially eliminate the above discussed problems inherent in the prior art semiconductor devices. The present invention provides a method of manufacturing a semiconductor with high productivity at a minimized cost and also to provide a reliable semiconductor device manufactured according to such method.
In order to solve the problems, the present invention provides a semiconductor device which includes a semiconductor chip mounted on a die pad, the die pad having first and second surfaces opposite to each other, and the semiconductor chip being mounted on the first surface, at least one electrode terminal spaced a distance from the die pad and electrically connected with the semiconductor chip through a corresponding wire, with the electrode terminal having third and fourth surfaces opposite to each other, and the wire being connected to the third surface, and a sealing resin enclosing the die pad and the electrode terminal, with a surface of the die pad opposite to the surface on which the second and fourth surfaces of the die pad and the electrode terminal, respectively, being exposed to an outside of the sealing resin; the die pad and the electrode terminal being formed of a sintered metal formed by sintering a paste containing a metal powder.
The die pads being formed of the sintered metal is effectively increases the bondability among the die pads, the wire pad, and the sealing resin, resulting in increase of the reliability of the semiconductor device.
The fourth surface of the electrode terminal is preferably formed with an electroconductive protrusion.
The electroconductive protrusion of the electrode terminal is effective to increase the connection between the semiconductor device and outside device.
Preferably, at least a portion of the second surface of the die pad may be formed with an electroconductive protrusion.
The electroconductive protrusion of the die pad effectively increases the efficiency of radiation of heat in the semiconductor device.
If desired, the die pad may be made of a plurality of sintered, wherein the semiconductor chip is mounted on the plural sintered metals.
The semiconductor chip mounted on the plural sintered metals is effective to increase the reliability of the semiconductor device.
Preferably the protrusion m
Mitsubishi Denki & Kabushiki Kaisha
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Picardat Kevin M.
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